resistance to anticoccidial drugs: alternative strategies ... · performed in the natural host, 2/...

Resistance to anticoccidial drugs: alternative strategies to control coccidiosis in broilers

Herman Peek

Utrecht

2010

Resistance to anticoccidial drugs: alternative strategies to control coccidiosis in broilers Herman Peek ISBN : 978-90-393-5272-4 Cover : Marije Brouwer Lay-out : Division Multimedia, Faculty Veterinary Medicine, University Utrecht Printed by : Riddderprint Offsetdrukkerij b.v., Ridderkerk Edited by : Animal Health Service (GD), Deventer

Resistance to anticoccidial drugs: alternative strategies to control coccidiosis in broilers

Resistentie tegen anticoccidiosemiddelen: alternatieve strategieën

voor de controle van coccidiose bij vleeskuikens

(met een samenvatting in het Nederlands)

Proefschrift

ter verkrijging van de graad van doctor aan de Universiteit Utrecht op gezag van de rector magnificus, prof.dr. J.C. Stoof, ingevolge het besluit van het college voor promoties

in het openbaar te verdedigen op donderdag 18 februari 2010

des middags te 2.30 uur

door

Hermanus Wilhelmus Peek

geboren op 2 december 1952 te Harmelen

Promotor: Prof. dr. J.A. Stegeman Co-promotor: Dr. W.J.M. Landman The research was financially supported by the Commodity Board for Poultry and Eggs (PPE), the Commodity Board for Animal Feed (PDV) and the Animal Health Service (GD).

Paranimfs: Brenda Vermeulen Gerda Peek

CONTENTS Chapter 1 Introduction 1

General introduction and aim of the thesis 2 Coccidiosis in poultry: anticoccidial products and alternative prevention strategies (a review) 5

Chapter 2 Anticoccidial drug resistance in the field 105

Resistance to anticoccidial drugs of Dutch avian Eimeria spp. field isolates originating from 1996, 1999 and 2001 106 (Avian Pathology, 32, (2003), pp. 392-401) Anticoccidial drug sensitivity profiles of German, Spanish and Dutch Eimeria spp. field isolates 125 (Tijdschrift voor Diergeneeskunde, 129, (2004), pp. 210-214)

Chapter 3 Influence of ibuprofen, a mucolytic enzyme and a

mannanoligosaccharide preparation (MOS) on a coccidiosis infection in broilers 139 Effect of ibuprofen on coccidiosis in broiler chickens 140 (Avian Diseases, 48, (2004), pp. 68-76) Dietary protease can alleviate negative effects of a coccidiosis infection on production performance in broiler chickens 157 (Animal Feed Science and Technology, 150, (2009), pp. 151-159) The effect of an in-feed mannanoligosaccharide preparation (MOS) on a coccidiosis infection in broilers 171 (Animal Feed Science and Technology, 134, (2007), pp. 347-354)

Chapter 4 Influence of live coccidiosis vaccination on the occurrence

of anticoccidial drug resistance 181 Higher incidence of Eimeria spp. field isolates sensitive for diclazuril and monensin associated with the use of live coccidiosis vaccination with Paracox™-5 in broiler farms 182 (Avian Diseases, 50, (2006), pp. 434-439)

Chapter 5 Improvement of live anticoccidial vaccines 197

Cross protection studies between E. acervulina and E. maxima, and E. tenella (submitted) 198

Chapter 6 Summarizing discussion 215 Samenvatting 227 Dankwoord 239 Curriculum vitae 241 List of publications 243

Chapter 1

Introduction

General introduction Introduction Coccidiosis is a parasitic disease affecting mainly the intestinal tract. It is caused by members of the genera Eimeria and Isospora belonging to the phylum Apicomplexa, and characterized by a complex life cycle. It affects many species of mammals and birds, and is of great economic significance in farm animals, especially poultry. Most animals are parasitized by more than one species of Eimeria, which usually differ in pathogenicity and tissue tropism. Although multiple species of coccidia have been identified, new operational taxonomic units are being discovered regularly.

Most knowledge on coccidiosis has been obtained from poultry, in which the disease has been studied most intensively as in this species the parasite causes the most devastating losses due to the large number of birds per flock and high stock densities The economic importance of coccidiosis can be related to decreased profit caused by higher feed conversion, growth depression, increased mortality and the costs of prevention and treatment. Worldwide the annual costs inflicted by coccidiosis to commercial poultry have been estimated at € 2 billion, stressing the urgent need for more efficient strategies to control the parasite (Williams, 1999; Shirley et al., 2004; Dalloul & Lillehoj, 2006).

The traditional control of coccidiosis mainly relies on chemoprophylaxis which appeared to be effective for the last decades. However the increased occurrence of resistance against all anticoccidial drugs has left the poultry industry with a renewed challenge for coccidiosis prevention and control and propelled the search for alternative strategies amongst which vaccination is of major importance. Aim of the thesis Manuscripts documenting the occurrence of resistance against all commonly used anticoccidial drugs abroad, together with the high incidence of clinical coccidiosis in the field (60-90% of flocks) in the Netherlands, were the reasons to start investigations on the occurrence of resistance of Dutch and other European Eimeria spp. field isolates (Chapter 2). This was preceded by an extensive literature review focusing on anticoccidial products and alternative prevention strategies (Chapter 1). In this review, first, a general overview of coccidial infections with Eimeria spp. in farm and game birds including history, classification, life cycle and the determination and diagnosis of the disease is given. This is followed by an outline on the host and site specificity of Eimeria spp., different commercialized anticoccidial products (categories, mode of action, the occurrence and management of resistance) and the influence of feed (structure, composition, ingredients, toxins and administration) on the course of coccidiosis infections. Additionally, alternative anticoccidial strategies such as biosecurity, management, homeopathy, phytotherapy, aromatherapy, pre- and probiotics and vaccination are presented. The review is finalized with conclusions and future perspectives.

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Based on the literature study one alternative coccidiosis control strategy, namely a mannanoligosaccharide (a prebiotic) was chosen for further experimental studies in broiler chickens. Additionally, two other products i.e. ibuprofen (a non-steroidal anti-inflammatory drug- NSAID) and a mucolytic enzyme (protease) were also used in experimental research aiming at assessing their anticoccidial potential. Ibuprofen was chosen because as cyclooxygenase inhibitor it was expected to reduce the pathology of coccidiosis lesions through impairment of the production of prostaglandins, and because it was reported that another NSAID (indometacin) was able to reduce oocyst shedding (Allen, 2000). The mucolytic enzyme was studied as it was speculated that a protease might impair the attachment of Eimeria to the mucus layer through its degradation (Chapter 3).

In view of the poor anticoccidial effect found in the studies performed with mannanoligosaccharide, ibuprofen and the mucolytic enzyme, further research focused on vaccination against chicken Eimeria, which despite some drawbacks was shown to be highly effective against outbreaks of clinical coccidiosis (Williams, 2002). Another reason to focus on vaccination was the inefficacy of rotation and shuttle programs to solve the coccidiosis resistance problem, which is explained by the fact that resistance is stable even in the absence of drug selection pressure (Gardiner & McLoughlin, 1963; Ball, 1968; Williams, 1969; McLoughlin, 1970; Chapman, 1986). A welcome side effect of vaccination is the improved sensitivity of Eimeria spp. field isolates for anticoccidial drugs reported by some researchers. This phenomenon may play a key role in reducing the anticoccidial drug resistance problem. However, large-scale field studies documenting this were lacking. Therefore, in Chapter 4, the relation between the coccidiosis prevention program (vaccination with a live attenuated anticoccidial vaccine or anticoccidial drugs in feed) and anticoccidial drug sensitivity profiles of Eimeria spp. field isolates for diclazuril and monensin was studied.

Major disadvantages of live anticoccidial vaccines are: 1/ propagation has to be performed in the natural host, 2/ yield of oocysts is lowered for attenuated precocious vaccines due to precocity characteristics and 3/ all relevant Eimeria spp. must be included in the vaccine further increasing production costs. Coccidiosis vaccines could be produced more efficiently if cross protection between Eimeria spp. would be relevant enough to reduce the number of species included in the vaccine and/or reduce the vaccination doses. Therefore, cross protection studies between an E. acervulina vaccine line and E. tenella, and E. maxima were performed in Chapter 5.

The thesis is finalized with a summarizing discussion with conclusions and perspectives for future research.

GENERAL INTRODUCTION

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References Allen, P.C. (2000). Effects of treatment with cyclooxygenase inhibitors on chickens infected with Eimeria

acervulina. Poultry Science, 79, pp. 1251-1258. Ball, S.J. (1968). The stability of resistance to glycarbylamide and 2-chloro-4-nitrobenzamide in Eimeria

tenella in chicks. Research in Veterinary Medicine, 9, pp. 149-151. Chapman, H.D. (1986). Eimeria tenella: stability of resistance to halofuginone, decoquinate and aprinocid

in the chicken. Research Veterinary Science, 40, pp. 139-140. Dalloul, R.A. & Lillehoj, H.S. (2006). Poultry coccidiosis: recent advancements in control measures and

vaccine development. Expert Review of Vaccines, 5, pp.143-163. Gardiner, J.L. & McLoughlin, D.K. (1963). Drug resistance in Eimeria tenella. III. Stability of resistance

to glycarbylamide. Journal of Parasitology, 49, pp. 657-659. McLoughlin, D.K. (1970). Coccidiosis: experimental analysis of drug resistance. Experimental

Parasitology, 28, pp. 129-136. Shirley, M.W., Ivens, A., Gruber, A., Madeira, A.M.B.N., Wan, K.L., Dear, P.H. & Tomley, F.M. (2004).

The Eimeria genome projects: a sequence of events. Trends on Parasitology, 20, pp. 199-201. Williams, R.B. (1969). The persistence of drug resistance in strains of Eimeria species in broiler chickens

following a change in coccidiostat. Research Veterinary Science, 10, pp. 490-492. Williams, R.B. (1999). A compartmentalized model for the estimation of the costs of coccidiosis to the

world’s chicken production industry. International Journal for Parasitology, 28, pp. 1209-1229. Williams, R.B. (2002). Anticoccidial vaccines for broilers chickens: pathway to success. Avian

Pathology, 31, pp. 317-353.

Coccidiosis in poultry: anticoccidial products and alternative prevention strategies (a review) H.W. Peek and W.J.M. Landman Animal Health Service (GD), P.O. Box 9, 7400 AA Deventer, the Netherlands Summary Coccidiosis in poultry is a parasitic disease with great economic significance which has been controlled succesfully for decades using mainly anticoccidial products. However, the increasing occurrence of resistance against all anticoccidial drugs and a possible upcoming ban restricting their use prompted us to review the existing literature on anticoccidial products and alternative coccidiosis prevention and control strategies. In the present review the following subjects are discussed: (1) coccidiosis in poultry: history, classification, Eimeria spp. life cycle, determination and diagnosis; (2) host and site specificty of the coccidia; (3) anticoccidial products: mode of action, the occurrence of resistance and efficious use; (4) the influence of feed structure, composition, toxins and administration on the course of a coccidiosis infection; (5) other preventive strategies against coccidiosis and (6) conclusions and perspectives. In chickens, seven Eimeria spp. are considered of which E. acervulina, E. maxima and E. tenella are of crucial importance as they most frequently affect broilers and these birds form a major part of the poultry industry. The diagnosis of coccidiosis is generally performed at postmortem by identifying the localization, morphology and extent of the intestinal lesions of Eimeria spp. Shortcomings in the traditional diagnosis system are being dealt with by developing new laboratory techniques such as computational analysis of microscopic images of oocysts and various PCR-coupled and other molecular techniques. Particular attention has been given to the usefulness of ITS-1 and -2 markers for the diagnosis and the analysis of genetic variation of Eimeria. Host specificity of coccidia was thought to be very strict; however, research showed that this is only true as far as completion of their life cycle is concerned. Eimeria spp. are able to infect other species of hosts, restrictions being less pronounced the closer host species are genetically related. Regarding site specificity, coccidia invade narrowly defined cell types within a tissue or organ. In chickens, the parasite develops in specifc defined regions of the intestine and this is also the case in foreign hosts. Most anticoccidial products have more than one biochemical effect on a specific stage of the coccidia and despite the lack of detailed knowledge on the selective action, a broad categorization of their mode of action has been performed. Products affecting cofactor synthesis are ethopabate, sulphonamides, pyrimethamines and thiamine analogues like amprolium; products affecting mitochondrial functions are quinolones (buquinolate, decoquinate and nequinate), pyridinols (meticlorpindol), nicarbizin, robenidine and toltrazuril; and products that affect cell membrane function are polyether antibiotics or ionophores (monensin, semduramycin, narasin, salinomycin, lasalocid and

COCCIDIOSIS IN POULTRY

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maduramicin). Products with unknown mode of action are diclazuril and halofuginone. The worldwide use of anticoccidial drugs has led to the development of resistance against all these drugs. In order to minimize the occurrence of resistance, a rotation of various anticoccidial drugs in single and/or shuttle programmes are used. Recently, live anticoccidial vaccines have been incorporated into rotation programmes resulting in increased incidence of anticoccidial drug sensitive Eimeria spp. field isolates. Various feed components seem to affect Eimeria parasites, either directly by distributing the development and multiplication of coccidia or indirectly by stimulating the immune system, influencing the intestinal flora and mucosa, changing the physiology of the digestive tract, etc. Feed components which negatively affect Eimeria parasites directly are ω-3 fatty acids. Development of coccidia is negatively influenced in an indirect fashion by β-glucans, vitamin E, selenium, feed restriction, ω-3 fatty acids, vitamin A, C, K, medium chain fatty acids and NaHCO3. Feed components that have been shown to favour the recovery from a coccidiosis infection are: proteins, vitamin A, C and K. Management and biosecurity measures should aim at avoiding the introduction of the parasite to the poultry premises and infected poultry houses are best sanitated by using a lot of cleaning water and disinfection with a solution of ammonia (5-10%). Phytotherapy has become increasingly popular during the last decade due to a renewed interest in natural medicine. Products showing a direct inhibitory effect on the development of the parasite are arteminsin, citric extracts and some different herb extracts. Herbal products showing an indirect effect on the development of coccidia are oregano, Echinacea, mushrooms (lectin), turmeric and betain. Prebiotic mannanoligosaccharide (MOS) have been reported to act directly on coccidia and either inhibit the development of the parasite or show no effect. Probiotics have an indirect hindering effect on Eimeria parasites by stimulating the humoral immune response. Both, attenuated and non-attenuated live anticoccidial vaccines are becoming increasingly popular as an alternative control strategy against coccidiosis. Nevertheless, high production costs, loss of infectivity with time affecting their expiry and management shortcomings during application have limited their use in practice. Subunit vaccines may circumvent most shortcomings of live vaccines; however, at present these products underperform due to the lack of immunogenicity. It can be concluded that future coccidiosis control is unlikely to be achieved solely by using anticoccidial products as feed additives and/or through feed composition and management. The occurrence of resistance against anticoccidial products will most probably further increase and although some dietary compounds seem capable to reduce directly or indirectly a coccidiosis infection, named compounds alone will not be sufficient to control the disease. In contrast, anticoccidial vaccines offer a much better perspectieve despite a number of drawbacks associated with their production and use. If with time the immunogenicity of subunit vaccines can be improved, they could represent the next generation highly efficient and low cost anticoccidial strategy.

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General introduction Introduction Coccidiosis is a disease caused by parasites of the genus Eimeria and Isopsora belonging to the phylum Apicomplexa with a complex life cycle, affecting mainly the intestinal tract of many species of mammals and birds. It is of great economic significance in farm animals, especially chickens. Most knowledge on coccidiosis has been obtained from chickens, where the disease has been studied most intensively as it is in commercial poultry that this parasite causes the most damage due to the fact that birds are reared together in large numbers and high densities. The economic significance of coccidiosis is attributed to decreased animal production (higher feed conversion, growth depression and increased mortality) and the costs involved in treatment and prevention. Worldwide the annual costs inflicted by coccidiosis to commercial poultry have been estimated at 2 billion €, stressing the urgent need for more efficient strategies to control this parasite.

Traditional coccidiosis control in poultry mainly relies on chemoprophylaxis; however, the increasing occurrence of resistance against all anticoccidial drugs and a possible upcoming ban on the use of these products as feed additives have propelled the search for alternative control strategies for coccidiosis of which vaccination is of major importance. The need for cost-efficient alternative anticoccidial strategies, which lays at the basis of this thesis prompt us to perform an extensive literature review exploring the alternative approaches to control Eimeria in poultry. In the present review the following subjects are discussed: 1. History, classification, Eimeria spp. life cycle, determination and diagnosis

History and classification of the genus Eimeria Eimeria spp. in farm and game birds Life cycle of avian Eimeria spp. Eimeria spp. determination and diagnosis

2. Host and site specificity of the coccidia Host and site specificity of Eimeria spp.

3. Anticoccidial products: mode of action, the occurrence of resistance and efficious use Anticoccidial products, categories and mode of action Anticoccidial product resistance and management of resistance

4. The influence of feed structure, composition, toxins and administration on the course of a coccidiosis infection

Feed structure, Feed composition (ingredients), Toxins and Feed management 5. Other preventive strategies against coccidiosis

Management and biosecurity Alternative coccidiosis control (plant (herb) extracts, pre- and probiotics) Vaccines

6. Conclusions and perspectives 7. References


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1. Coccidiosis in poultry: history, classification, Eimeria spp. life cycle, determination and diagnosis 1.1. Introduction Coccidiosis is a parasitic disease with a complex life cycle, affecting many species of farm and game birds and is of great economic significance, especially in chickens.

Most birds are parasitized by more than one species of Eimeria, which usually differ in pathogenicity. Many species have been identified, although new operational taxonomic units are being discovered regularly.

Traditionally, the diagnosis of coccidiosis is based on postmortem (assessment of macroscopic lesions) and histopathological analysis. Moreover, morphological identification of oocysts in native scrapings is performed using light microscopy. The advent of computer aided oocyst morphology identification systems and molecular techniques are greatly improving the shortcomings of classical diagnostic systems. Especially techniques based on molecular biology may, in a near future, contribute significantly to the understanding of the epidemiology of coccidiosis. 1.2. History and classification of the genus Eimeria The first protozoan seen under the microscope by Antoine van Leeuwenhoek in 1674 was probably an eimerian. At the time what he described as pus globules and hepatic lesions due to tuberculosis, was identified 150 years later as unsporulated oocysts of Eimeria stiedae in the bile duct of a rabbit (Hake, 1839). Eimer described in 1870 the endogen cycles of Gregarina falciformis in the mouse, which was renamed later by Schneider as E. falciformis and proposed as a new genus (Schneider, 1875). The class Sporozoa was established by Leuckart in 1879 and the name Coccidium was introduced as a generic term for the rabbit parasite. Since then and up till now, the taxonomy of coccidia has been further defined and underwent many changes. In the traditional general classification scheme (e.g. Bütschli 1880-1882) the phylum Protozoa was divided into four classes (Mastigophora (flagellates), Sarcodina (amoeboid organism), Infusoria (ciliates) and Sporozoa (a parasitic group)), Coccidia being a subclass of the class Sporozoa. This structure dominated mainly the systematic protozoology from the 1880‘s until the 1980’s and during this era only a few trends modified this Bütschlian view. One trend was the process of a hierarchical increase in the number and rank of taxa. In the early schemes only a single phylum of protozoa was documented and this view was maintained until the 1960’s (Honigberg et al., 1964). Later on, some lifted the protozoa to the Kingdom status because of the increase of number of phyla (Levine et al., 1980; Cavalier-Smith, 1998; Corliss, 1998). However, this increase did not go together with important new information and eventually led to widespread taxonomic dismissal. The end of the protozoa as a phylum was favoured by

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the gradual recognition that the popular Bütschlian view was artificial and out of date, moreover electron microscopy, serial endosymbiosis theory of cell evolution, 16S rRNA sequence data and protein gene sequences further triggered changes in evolutionary protistology, finally coming to a classification in which the four classes of protozoa are no longer present (Patterson, 2002). More recently, integrating ultrastructural data with molecular phylogenetic studies a scheme based on nameless ranked systematics was proposed, in which six clusters of eukaryotes (similar to traditional kingdoms) are recognized. The former genus Eimeria has been allocated within the Coccidiasina (Leuckart, 1879), Conoidasida (Levine, 1988) and Apicomplexa (Levine et al., 1980; Adl et al., 2005), which in turn belongs to the first rank of Alveolata (Cavalier-Smith, 1991). The latter is part of the super-group Chromalveolata of the Eukaryotes (Adl et al., 2005). 1.2.1. Characteristics of Coccidiasina (Adl et al., 2005) Mature gametes develop intracellularly; microgamont typically produces numerous microgametes; syzygy absent; zygote rarely motile; sporocysts usually formed within oocysts. Including the genus Cryptosporidium, Cyclospora, Eimeria and Hepatozoon. 1.3. Eimeria spp. in farm and game birds Great pioneering work on the life cycle of coccidia in different hosts, parasite morphology, studies on host-specificity was performed during the 1920’s and 1930’s amongst others by Edward Tyzzer (Tyzzer, 1929; Tyzzer et al., 1932). He is considered the father of modern coccidiology and produced a series of outstanding papers on monospecific Eimeria infections in chicken, turkey and some game birds. Generally coccidia are highly host organ and tissue-specific. Under normal circumstances, most animals shed small amounts of oocysts in their faeces without clinical signs of coccidiosis. However, coccidiosis can become clinically manifest in case chickens are exposed to large numbers of oocysts instead of low doses typical for trickle infections. The former situation is favoured particularly by husbandry systems with high farm animal density. 1.3.1. Farm birds Eimeria spp. are found in the domestic fowl, turkeys, waterfowl (geese and ducks) and pigeons.


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1.3.1.1. Domestic fowl In chickens nine Eimeria spp. have been described: i.e. E. acervulina (Tyzzer, 1929), E. brunetti (Levine, 1942), E. maxima (Tyzzer, 1929), E. mitis (Tyzzer, 1929), E. mivati (Edgar & Siebold, 1964), E. necatrix (Johnson, 1930), E. praecox (Johnson, 1930), E. tenella (Raillet & Lucet, 1891) and E. hagani (Levine, 1938). However, as the existence of E. hagani and E. mivati is questioned, in practice only seven species are considered. If, no convincing evidence for the existence of E. hagani and E. mivati is delivered in the future, both will be eliminated from the reference list with time (McDougald, 2003; Shirley, 1986). The diagnostic characteristics of Eimeria spp. in chickens have been outlined in Table 1. 1.3.1.2. Turkeys Seven different Eimeria spp. of turkeys have been described but only a few species are considered to be economically important. The most important pathogenic species are E. meleagrimitis, E. adenoeides, E. gallopavonis and E. dispersa. Recently, Matsler and Chapman (2006) have investigated the potential pathogenicity of E. meleagridis and they suggested that the significance of this species as a pathogen should be reconsidered. In another article they also described the selection of a precocious line of E. meleagridis (Matsler & Chapman, 2007). The detection of oocysts (even large numbers) in faeces can only yield a tentative diagnosis for coccidiosis since differentiating the oocysts of the pathogenic species from the less pathogenic or “milder” species is very difficult. Therefore, a satisfactory diagnosis can only be obtained after postmortem examination, although the lesions of some species are poorly described. E. innocua and E. subrotunda have been found so rarely that their existence is questioned. The diagnostic characteristics of Eimeria species in turkeys can be found in Table 2 (McDougald, 2003). More recently a comprehensive review on coccidiosis in turkeys is published by Chapman H.D. (2008) where the biology of the Eimeria spp. of turkeys, host specificity and resistance, immunity, pathology, pathogenicity, diagnosis, prevalence, treatment and prevention are described. 1.3.1.3. Geese Five species of coccidia have been described in domestic and wild geese. Some of which are associated with severe disease and even death. The most prevailing and harmful in commercial flocks are E. truncata, which causes renal coccidiosis, and E. anseris which causes intestinal coccidiosis (Betke & Wilhelm, 1976). E. truncata occurs in the kidney of young goslings and may cause high mortality due to a blockage of the kidney function (Sezen et al., 1981). 1.3.1.4. Ducks Outbreaks of coccidiosis in ducks are sporadic but occur frequently enough in order to draw the attention of veterinarians. Until now, five Eimeria species have been described in ducks (Levine, 1985). Cases of coccidiosis from moderate to severe appear to be very

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common worldwide. These infections can cause high morbidity and mortality as well as poor technical performance. E. danailovi is considered to be one of the most pathogenic species (Gräfner et al., 1965). 1.3.1.5. Pigeons To date two species of coccidia have been reported in pigeons: E. labbeana and E. columbarum. However, it is well possible that it concerns only one species as the sizes of their oocysts overlap and the morphology of both species is similar. E. labbeana is considered to produce the smallest oocysts for those believing that both species exist, moreover it is considered to be the most pathogenic species. All Eimeria species found to date in farm birds are outlined in Table 3. 1.3.2. Game birds (pheasants, partridges, quails and grouse) Coccidiosis occurs in all species of game birds (Norton, 1986). It is mainly a disease of young animals and is characterised by signs of weakness and watery droppings frequently containing blood. Affected birds are listless and show decreased water and feed intake. As the illness progresses moderate to high mortality can occur. 1.4. Life cycle of avian Eimeria spp. Fantham (1910) was the first to describe the entire life cycle of an eimerian parasite in an avian host. Later on, Tyzzer (1929) published detailed descriptions of the life cycle stages of various Eimeria spp. (E. acervulina, E. mitis, E. maxima and E. tenella) in sections of intestines. In 1932, he also described details of the life cycle of E. praecox and E. necatrix (Tyzzer et al., 1932). More recently, the life cycle of avian Eimeria spp. has been well documented by various other authors (Long & Reid, 1982; Fernando, 1990; McDougald, 2003). Although numerous drawings on the life cycle of avian Eimeria spp. have been published, the website of the book “Encyclopedic Reference of Parasitology by Heinz Mehlhorn” (2001) shows a clear and detailed scheme (Figure 1), which can be easily accessed online.

Table 1. Diagnostic characteristics of Eimeria spp. in the chicken

Table 2. Diagnostic characteristics of Eimeria spp. in the turkey

McDougald, L.R. (2003). Coccidiosis. In: Saif, Y.M., Barnes, H.J., Glisson, J.R., Fadly, A.M., McDougald, L.R., & Swayne, D.E. (eds.). Diseases of Poultry 11th edn. (pp. 986). Ames: Iowa State University Press. 2003


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Table 3. Oocyst habitat, morphology and pathogenicity of Eimeria spp. in farm birds (Levine, N.D., 1985) Species Host/Habitat Oocyst size (μm) Shape Pathogenicity Reference Length Width Chickens E. acervulina Small intestine 12-23 9-17 Ovoid Low Tyzzer, 1929 E. brunetti Small intestine,

rectum, caeca, cloaca

14-34 12-26 Ovoid Moderate Levine, 1942

E. hagani Small intestine 16-21 14-19 Ovoid Low Levine, 1942 E. maxima Small intestine 21-42 16-30 Ovoid Low to moderate Tyzzer, 1929 E. mitis Small intestine 10-21 9-18 Subspheric Low Tyzzer, 1929 E. mivati Small, large

intestine 11-20 12-17 Ellipsoid

or ovoid Low to moderate Edgar & Siebold,

1964 E. necatrix Small intestine,

caeca 12-29 11-24 Ovoid High Johnson, 1930

E. praecox Small intestine 20-25 16-20 Ovoid No Johnson, 1930 E. tenella Caeca 14-31 9-25 Ovoid High Raillet & Lucet,

1891 Turkey E. adenoeides Small intestine,

caeca, colon 19-31 13-21 Ellipsoid

or ovoid High Moore & Brown,

1951 E. dispersa Small, large

intestine, 22-31 18-24 Ovoid Low Tyzzer, 1929

E. gallopavonis Large intestine, caeca

22-33 15-19 Ellipsoid Moderate Hawkins, 1952

E. innocua Small intestine 19-26 17-25 Subspheric No Moore & Brown, 1952

E. meleagridis Small intestine, caeca, rectum

19-31 14-23 Ellipsoid No Tyzzer, 1927

E. meleagrimitis Small intestine 16-27 13-22 Subspheric Moderate Tyzzer, 1929 E. subrotunda Small intestine 16-26 14-24 Subspheric No Moore et al., 1954 Geese E. anseris Small intestine 16-24 13-19 Moderate Kotlan, 1932 E. kotlani Large intestine 29-33 23-25 Ovoid Low Gräfner &

Graubman, 1964 E. nocens Small intestine 25-33 7-24 Ovoid Moderate Kotlan, 1933 E. stigmosa Small intestine 23-16 23-17 Ovoid No Klimes, 1963 E. truncate Kidneys 14-27 12-22 Ovoid High Raillet & Lucet,

1891 Ducks E. anatis Small intestine 14-19 11-16 Ovoid ? Scholtyseck, 1955 E. battakhi ? 19-24 16-21 Ovoid to

subspheric Dubey & Pande,

1963 E. danailovi Small intestine 19-23 11-15 Ovoid High Gräfner et al., 1965 E. saitamae Small intestine 17-21 13-15 Ovoid High Inoue, 1967 E. schachdagica ? 16-26 12-20 Ovoid ? Musaev et al., 1966 Pigeons E. columbarum Intestine 19-21 17-20 Ellipsoid Mitra & Das Gupta,

1937 E. labbeana Intestine 15-18 14-16 Subspheric

to spheric Low to mild Pinto, 1928

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Figure 1. Life cycle of Eimeria spp. in chickens 1 After oral uptake of sporulated oocysts the sporozoites hatch in the small intestine from the sporocysts. 2–6 After penetration, multinucleate schizonts are formed (3) inside a parasitophorous vacuole (PV). The schizonts produce motile merozoites (DM, M), which may initiate another generation of schizonts in other intestinal cells (2–5) or become gamonts of different sex (7, 8). 7 Formation of multinucleate microgamonts, which develop many flagellated microgametes (7.1-7.2). 8 Formation of uninucleate macrogamonts, which grow to be macrogametes (8.1) that are characterized by the occurrence of two types of wall-forming bodies (WF1, WF2). 9 After fertilization the young zygote forms the oocyst wall by consecutive fusion of both types of wall-forming bodies (FW). 10 Unsporulated oocysts are set free via faeces. 11–13 Sporulation (outside the host) is temperature dependent and leads to formation of four sporocysts, each containing two sporozoites (SP), which are released when the oocyst is ingested by the next host. DG, developing microgametes; DM, developing merozoite; DW, developing wall-forming bodies; FW, fusion of WF1 to form the outer layer of OW; M, merozoite; N, nucleus; NH, nucleus of host cell; OW, oocyst wall; PB, polar body (granule); PV, parasitophorous vacuole; R, refractile (= reserve) body; SB, sporoblast; SP, sporozoite; SPC, sporocyst; SPO, sporont; WF1, wall-forming bodies I; WF2, wall-forming bodies II; Z, cytoplasm of zygote (= young oocyst) (Mehlhorn, 2001). Reproduced with kind permission of Springer Science and Business Media.


16

1.5. Eimeria spp. determination and diagnosis All Eimeria spp. of the chicken parasitize the intestine and can be differentiated by their morphology, cell tropism and pathogenicity (Long et al., 1976; Long & Reid, 1982). These criteria are adequate enough to identify the five most pathogenic and prevailing species: E. acervulina, E. brunetti, E. maxima, E. necatrix and E. tenella. Their pathogenicity varies from moderate to very severe. The other two species E. praecox and E. mitis do not induce very clear characteristic identifiable lesions and are considered to be benign. However, in experiments performed by Williams (1998), these species caused intestinal (mucous membrane) inflammations, diarrhea and reduced feed conversion. It suggested that they can actually cause economic damage and ought to be controlled as well. Traditionally, the diagnosis of coccidiosis in poultry is performed most accurately during postmortem and histopathology. Macroscopically, this is done by thoroughly examining the location and extents of lesions in the intestines and is complemented by analyzing native intestinal scrapings with light microscopy in order to morphologically identify schizonts and oocysts. Assessment of coccidiosis lesions is performed standard following the scoring system introduced by Johnson and Reid (1970). E. acervulina lesion score 1 features ladder-like white streaks in de duodenal loop (≤ 5/cm2); in lesion score 2 the lesion density is higher but not coalescent; in lesion score 3 the lesions are more numerous and coalesce, while thickening of the intestinal wall is visible, and finally in lesion score 4 the mucosal wall is greyish with lesions completely coalesced. Lesion score 1 of E. maxima is characterised by few small red petechiae in the mid-intestine, in score 2 more numerous petechiae are found and the intestinal content may be orange, in score 3 the intestinal wall might be ballooned and thickened with pinpoint blood clots and mucous filling the intestinal contents. Finally, in lesion score 4 the intestinal wall is thickened and ballooned over most of its length, containing numerous blood clots and digested red blood cells. Lesion score 1 of E. tenella shows few scattered petechiae on the caecal wall, in score 2 noticeable blood can be found in the caecal contents, while the caecal wall is thickened. In lesion score 3 large amounts of blood or caecal cores are present, caecal walls are greatly thickened, and in lesion score 4 caecal walls are enormously distended with blood or large caseous cores. The standard McMaster oocyst counting technique is a widely used laboratory method to monitor coccidiosis infection pressure in chicken houses (Hodgson, 1970). This technique can also be used to determine individual oocyst shedding patterns and to study the effect of anticoccidial drugs. A commonly used modification of the standard oocyst counting technique per gram faeces (OPG) is performed by making a faeces suspension in a salt solution of which a small volume is pipetted into saturated sodium chloride. A portion of the latter suspension is subsequently run into a McMaster chamber and oocysts are counted using a microscope (Peek & Landman, 2003). More recently, other modifications of the standard counting technique have been described (Haug et al., 2006).

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17

1.5.1. Advances in diagnosis 1.5.1.1. Species identification based on morphology Due to the overlap of morphological characteristics of Eimeria spp. oocysts, visual identification of species is far from accurate. Recently, identification of Eimeria oocysts was greatly improved by classification through computational analysis of microscope digital images. Images are pre-processed and the parametric contour of oocyst wall is defined, then, using shape and textural characteristics (oocyst length and width, perimeter, area, curvature, texture and symmetry) they are classified after automated feature extraction. Images can be easily uploaded and the user can easily obtain a real-time electronic diagnosis of the Eimeria spp. concerned at http://puma.icb.usp.br/coccimorph/requirements.html (Castanon et al., 2007). 1.5.1.2. Molecular techniques The first molecular technique used for the identification of Eimeria spp. was the characterization of isoenzyme patterns of oocysts by starch block electrophoresis (Shirley, 1975). However, this method requires large number of parasites, is time-consuming and difficult to perform. Moreover, the low and limited number of variable enzymes and the low level of polymorphism restricted the application of this method (Johnston & Fernando, 1997). In the early 1990’s, it was demonstrated that rRNA and rDNA probes could be used to identify Eimeria spp. through characteristics restriction fragment patterns (Ellis & Bumstead, 1990). Shortly thereafter, the random amplified polymorphic DNA (RAPD) technique was developed, which is based on the amplification of DNA using arbitrary primers (Welsh & McClelland, 1990, Williams et al., 1990). However, despite its broad use, the RAPD technique had a lack of reliability and reproducibility (MacPherson et al., 1993; Schierwater & Ender, 1993). A specific PCR diagnostic assay based on an amplification of the Internal Transcribed Spacer-1 (ITS-1), was then developed (Schnitzler et al., 1998; 1999). This test became a standard for the molecular diagnosis of seven Eimeria spp. and was also used to study the intra-strain variation of Eimeria in chickens (Lew et al., 2003; Su et al., 2003). However, due to the occurrence of variability in the amplification of E. maxima strains due to the polymorphic nature of ITS-1, new markers were sought. A novel RAPD-derived marker, the (Sequence-Characterised Amplified Region) SCAR, that could be amplified under stringent conditions was found (Paran & Michelmore, 1993). These SCAR markers made it even possible to develop a simple multiplex PCR test, which can differentiate in one test between seven Eimeria spp. (Fernandez et al., 2003a, 2003b) and a public relational database was constructed, the Eimeria SCARdb, a free-access database (available at the address: http://puma.fmvz.usp.br/eimeriaScardb) that represents a complete and important source of SCAR markers (Fernandez et al., 2004). Recently, a PCR-coupled capillary electrophoretic approach using genetic markers of the ITS-2 region of nuclear ribosomal DNA has been developed and investigated for its use for the identification and epidemiology of seven Eimeria spp. (Gasser et al., 2005; Morris

http://puma.icb.usp.br/coccimorph/requirements.html

http://puma.fmvz.usp.br/eimeriaScardb


18

& Gasser, 2006). This technique may, in a near future, contribute significantly to the understanding of the epidemiology of each Eimeria spp. This knowledge may be used in formulating and implementing new prevention and control programmes (Morris et al., 2007).

CHAPTER 1

19

2. Host and site specificity of the coccidia 2.1. Introduction Historically it was assumed that host specificity of coccidia was very strict. The term refers to the restriction of a species of parasite to one or limited species of hosts (Levine, 1973; Noble & Noble, 1976). However, further research on basic characteristics of parasite biology brought up evidence questioning the strictness of host specificity, which seems strict only as far as completion of their lifecycle with the production of oocysts is concerned (Duszynski, 1981; Marquardt, 1981; Fayer, 1980; Fernando, 1990). The certainty that Eimeria spp. exclusively invade the intestinal tract has been revoked by the demonstrations of parenteral (extraintestinal) development of some eimerians in mammals and birds (Table 4) and may even be more prevalent than we appreciate (Desser, 1978; Overstreet, 1981; Ball et al., 1989; Novilla & Carpenter, 2004). 2.2. Host specificity of Eimeria spp. Eimeria species include some of the most common and best known protozoan parasites with over 900 different species found in a wide range of animals including annelids, insects, reptiles, amphibians, birds and mammals (Levine, 1973; Noble & Noble, 1976; Pellerdy, 1974). Some hosts have more than one Eimeria spp., but one species rarely occurs in more than one host species although there are some exceptions (Tsunoda & Muraki, 1971; Norton & Pierce, 1971; Tsutsumi, 1972; Marquardt, 1981; Joyner, 1982; Ruff et al., 1984; Ruff, 1985). Host specificity of Eimeria spp. in chicken was probably first demonstrated by Johnson (1923). He was unable to infect turkeys with Eimeria from chickens indicating host specificity. Later on host specificity of Eimeria spp. of various groups was investigated by performing cross-transmission experiments with rodents (Levine & Ivens, 1965), domestic chicken and turkeys (McLoughlin, 1969), lagomorphs (Duszynski & Marquardt, 1969) and ruminants (Levine & Ivens, 1970). A detailed description on the results of cross transmission experiments with Eimeria spp. of chickens and turkeys is outlined in Table 5, which shows some remarkable inconsistencies (McLoughlin, 1969). Discrepancies also occurred in some transmission experiments of Doran (1978) with E. dispersa from the turkey. He was able to induce patent infections in Leghorn chickens, the Chukar partridge, ring-necked pheasant and bobwhite quail and these results were in agreement with previous work of Long & Millard (1979), Tyzzer (1929) and Norton (1979) whereas others have not been able to infect chickens with E. dispersa (Kogut & Long, 1981). Later on, in a survey, concerning the host specificity of the Eimeria spp. of rodents, Levine & Ivens (1988) found that 14 out of 112 attempts were successful in transmitting the Eimeria spp. from one genus of rodents to another and that within the same genus 39 of 49 transmissions of Eimeria spp. between species of hosts were successful.


20

Norton (1967) demonstrated that E. colchici, an Eimeria spp. from the pheasant, could produce coccidial infections in turkeys if large numbers of oocysts was inoculated and Marberry & Marquardt (1973) succeeded in transmissing E. separata from the rat to the mouse. Most species of Eimeria are still considered to be monoxenous (i.e. they complete their life cycle in one host) (strictly host specific) and stenoxenous (each species parasitizes a single host) these characteristics can however no longer be regarded as absolute (Fayer, 1980; Marquardt, 1981; Joyner, 1982) considering the results of cross transmission studies, which strongly suggest that closely related species or subspecies may serve as the most adequate host for transmitting Eimeria spp. In this regard E. chinchillae, a coccidian species which parasitizes the chinchilla (de Vos & van der Westhuizen, 1968) is an exception as it showed a total lack of the normal host specificity characteristics of Eimeria spp. crossing families of hosts (de Vos, 1970). Table 5. Summary of the results of cross transmission experiments with Eimeria spp. of chickens and turkeys (McLoughin, D.K., 1969) Speciesa From (host) To (receiver) Transmission Author Eimeria spp. Turkey Chicken Yes Henry, 1931 Duck " No Tiboldy, 1933 E. acervulina Chicken Quail No Patterson, 1933 " " No Tyzzer, 1929 " Pheasant No Tyzzer, 1929 " Turkey No Steward, 1947 Quail Chicken Yes Henry, 1931 " " No Venard, 1933 E. maxima Chicken Quail No Patterson, 1933 E. mitis Chicken Quail No Patterson, 1933 " Turkey No Tyzzer, 1929 Quail (?) Chicken Yes Henry, 1931 E. tenellab Quail Chicken Yes Henry, 1931 " " Yes Venard, 1933 Chicken Quail No Patterson, 1933 " Turkey No Patterson, 1933 " Duck No Patterson, 1933 " Pheasant No Patterson, 1933 " " Yes Haase, 1939 " Pigeon Yes Hofkampd

" " Yes Nieschulz, 1921 " " Yes Yakimoff & Iwanoff-

Gobzem, 1931 E. avium Grouse Chicken Yes Fantham, 1910 (= E. tenella ?) Chicken Turkey No Johnson, 1923 " Duck No Johnson, 1923 E. adenoeides Turkey Chicken No Moore & Brown, 1951 " Guinea No Moore & Brown, 1951

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21

" Pheasant No Moore & Brown, 1951 " Quail No Moore & Brown, 1951 " Chicken No Clarkson, 1959a, b E. gallopavonis Turkey Partridge Yes Hawkins, 1952 " Pheasant No Hawkins, 1952 " Quail No Hawkins, 1952 " Chicken Yes Gill, 1954 E. meleagridis Turkey Chicken Yes Steward, 1947 " " Yes Gill, 1954 " " No Tyzzer, 1929 " " No Moore et al., 1954c

" " No Clarkson, 1959a, b " Pheasant No Tyzzer, 1929 " Partridge No Hawkins, 1952 " Quail No Tyzzer, 1929 " " No Hawkins, 1952 E. meleagrimitis Turkey Quail No Hawkins, 1952 " Partridge No Hawlins, 1952 " Chicken Yes Gill, 1954 E. innocua Turkey Chicken No Moore & Brown, 1952 " Guinea No Moore & Brown, 1952 " Pheasant No Moore & Brown, 1952 " Quail No Moore & Brown, 1952 E. subrotunda Turkey Chicken No Moore et al., 1954

" Guinea No Moore et al., 1954

" Pheasant No Moore et al., 1954

" Quail No Moore et al., 1954

a Natural infections of E. dispersa in a number of hosts have been reported, therefore studies with this species are not included. b Haase, 1939, also reported E. tenella from quail. c Moore, Brown and Carter, cited by Moore, 1954. d Quoted by Yakimoff & Iwanoff-Gobzem, 1931. The mechanisms responsible for inhibiting the reproduction/multiplication of Eimeria spp. in foreign hosts are currently unknown, undeniably very complex and probably diverse regarding the differences in the degree of host specificity. However, mentioned mechanisms are extremely effective because sporozoites from various Eimeria spp. are able to invade the intestinal mucosa of foreign hosts, indicating that excystation of sporozoites is a non-specific event in most foreign hosts (Joyner, 1982; Kogut & Long, 1984; Sundermann et al., 1987;), but are not able to complete their lifecycle (Marquardt, 1966; Todd et al., 1971; Vetterling, 1976; Long & Millard, 1979; Marquardt, 1981; Joyner, 1982; Mayberry et al., 1982; Rose & Millard, 1985; Naciri, 1986). The basis of the mechanisms, which are responsible for this host specificity, probably lays in many biotic interactions e.g. the parasite biochemistry and nutrition, the host genome and in particular the host immune system.


22

2.2.1. Parasite biochemistry and nutrition After invading the host cells, coccidia are retained within a parasitophorous vacuole membrane (PVM) for the duration of their intracellular phase. Therefore, nutrients and wastes have to cross the parasite membrane, the PVM and the host cell membrane. However, there is still a lack of knowledge on the mechanisms involved in the transport of nutrients through the different membranes, despite the fact that they are interesting drug targets. The PVM is permeable to low molecular solutes by high-capacity channels (Werner-Meier & Entzeroth, 1997). Although not completely characterized to the molecular level, uptake of nutrients by the parasite seems to occur through a combined action of transporters and channels in the parasite membrane and endocytosis (Saliba & Kirk, 2001). A list of nutrients necessary for the development of E. tenella through the second generation merogony was obtained by studying the parasite in vitro. However, the requirements in vivo may be quite different, which is suggested by the lack of host specificity in vitro, indicating that the parasite will only develop in those cases where the nutrient requirements are satisfied. Named nutrients are: p-aminobenzoic acid (PABA), thiamine, glutamine, pyridoxal, biotin, folic acid, ascorbic acid, riboflavin, nicotinamide, pyridoxone, vitamin A, menadione, choline chloride, vitamin B12, calciferol, α-tocopherol and inositol (Warren, 1968; Ryley & Wilson, 1972; Sofield & Strout, 1974; Doran & Augustine, 1978; Latter & Holmes, 1979;). Studying the biochemistry of Eimeria may be of help in understanding their further nutrient requirements. Eimeria spp. are obligate intracellular parasites, which has made biochemical research on their nutritional requirements very difficult. Despite this limitation gathered data indicate that although the coccidia go through complicated life cycles the basic pattern of metabolic activities have not significantly changed (Naciri, 1986). These metabolic activities mainly include consumption of polysaccharides (Wagner & Foerster, 1966), cell division (Hammond, 1973; Ryley, 1973; LaFon & Nelson, 1985), amplification or continuation of polysaccharide storage (Wagner & Foerster, 1966; Fry et al., 1984; Smith & Lee, 1986) and the process of active excitation and invading new host cells. The biochemistry of coccidia has significant differences with that of vertebrates providing a wealth of possibilities for drug-designers. Biochemistry pathways that could be used as anticoccidial drug targets are: plastid-associated activities, energy metabolism, pyrophosphate metabolism and acidocalcisomes, electron transport chain and the acquisition of pyrimidines and purines, polyamine metabolism, proteases and host cell invasion, anti-oxidants, the mannitol cycle, folate metabolism and the newly discovered protein kinases (Coombs & Müller, 2002). So far, knowledge on the biochemistry of Eimeria spp. has yielded a few examples of drugs with proven or potential interest to control coccidiosis infections. Nitrophenide a drug inhibiting the mannitol cycle, effectively reduced oocyst excretion (Schmatz, 1997). Aprinocid was reported to interfere with the hypoxanthine and guanine acquisition by Eimeria (Wang et al., 1979). The enzyme α-difluoromethylornithine (inhibitor of ornithine decarboxilase) has shown

CHAPTER 1

23

activity against E. tenella in chickens and some proteinase inhibitors have also shown to affect coccidia parasites (Coombs et al., 1997). 2.2.2. Genetic makeup of the host Host specificity is believed to be connected to genetic nearness, as phylogenetic closely related hosts are more likely to sustain a familiar parasite (Doran, 1953; Vetterling, 1976). Later studies further supported this view and indicated that resistance to coccidiosis is under genetic control of the host (Mayberry et al., 1982; Bumstead & Millard, 1987; Mathis & McDougald, 1987; Bumstead & Millard, 1992; Bumstead et al., 1995). In resistant hosts the Eimeria infection is probably controlled by an efficient immune response, which in turn is dictated by the genetic makeup. 2.2.3. Host immune system Eimeria parasites have a complicated life cycle with asexual and sexual stages as well as intra- and extracellular phases resulting in an equally complex immune response. Although humoral and cell-mediated immunity are activated after an Eimeria infection besides the participation of non-specific immunity, understanding of Eimeria immunology is still subject of ongoing research. The role of antibodies in controlling coccidiosis infections seems limited as hormonal and chemical bursectomy does not abrogate an efficient host response (Lillehoj, 1987; Rose & Long, 1970; Yun et al., 2000) and further indicates the importance of cell-mediated immunity. This was further evidenced by the fact that abrogation of the T cell function impaired protective immunity against coccidiosis. Extensive research has shown that the antigen-specific and non-specific activation of T lymphocytes and macrophages are of main importance in protective immunity against Eimeria. More specifically, Th 1 responses elicited by IFN-γ seem dominant in the immune response induced by Eimeria (Lowenthal et al., 1997; Lillehoj & Choi, 1998; Lowenthal et al., 1998; Lillehoj et al., 2000). Attempts to identify the genes participating in coccidiosis immunity are ongoing and will in near future enable a better understanding of the immune responses to coccidiosis and the host-parasite interaction. QTL (quantitative trait loci) associated with resistance to coccidiosis were recently mapped with DNA marker technology (Zhu et al., 2003), while using DNA array with EST (Expressed Sequence Tags) from activated T cell library several genes associated with immune responses to E. maxima and E. tenella were identified; most clearly IL-15 and IFN-γ being upregulated (Min et al., 2003). 2.3. Site specificity of Eimeria spp. Although Eimeria spp. parasitize a great diversity of hosts, individual species exhibit a high degree of host specificity, as far as the ability to complete their life cycle with oocyst production is concerned (Levine, 1973; Joyner, 1982), and site specificity. Coccidia


24

invade narrowly defined cell types within a tissue or organ (Table 4, Novilla & Carpenter, 2004). Site specificity for invasion is even so precise that intravenous, intramuscular, or intraperitoneal injections of mammalian or avian Eimeria spp. results in infection in the same area of the intestine as if the animals were infected with the parasite orally. This happens in the natural host but it also occurs in foreign host (Davies & Joyner, 1962; Sharma & Reid, 1962; Long & Rose, 1965; Long & Millard, 1976; Joyner, 1982; Augustine & Danforth, 1986; Augustine & Danforth, 1990; Augustine, 2001). Thus, site specificity for invasion of sporozoites in the intestine may be a result of some characteristics of the intestines that are shared by a number of hosts rather than a unique peculiarity of the natural host. The invasion of host cells by Eimeria sporozoites is, similar to other members of the Apicomplexa, likely largely regulated by the apical complex. Although exact mechanisms have not been elucidated yet, there is evidence that proteinases play a key role in the invasion process: i.e. penetration of the mucus layer as well as attachment and entry to the host cell. Proteinases of other parasites have been characterised and the activity of proteinase inhibitors against them has been demonstrated, suggesting that this is an area that may hold promise for an alternative therapeutic approach for coccidiosis (Coombs & Müller, 2002). Besides proteinases, there is evidence from in vitro studies that specific molecules on intestinal cells act as receptor molecules for attachment and invasion. Some host cell molecules involved in invasion are 22, 31 and 37 kDa antigens, surface membrane glyconjugates and common epitopes. Especially host cell membrane glyconjugates are regarded as potential receptors for parasite lectins (lectin-ligand binding) but also microneme proteins like thrombospondin. However, treatments altering mentioned putative receptors were unable to completely block parasite invasion (Augustine, 2000; 2001), suggesting that other mechanisms may be operational as well. Table 4. Eimeria spp. found in extraintestinal tissues of birds and mammals (Novilla et al., 2004) Species Host(s) Tissue Reference E. stiedai Rabbit Liver Pellerdy, 1969 E. tenella Chicken embryo Liver Long, 1971 E. deblieki Pig, chamois Liver Desser, 1978 E. hiepei Mink Bile ducts Ball et al., 1989 E. adenoeides Turkey Gall bladder Critchley et al., 1986 E. arloingi, christenseni, crandalis

Goat Mesenteric lymph node

Lima, 1979

E. arloingi, faurei, ninakohlyakimovae

Sheep and goat Mesenteric lymph node

Lotze et al., 1964

E. neitzi Impala Uterus McCully et al., 1970 E. gaviae Common loon Kidney Montgomery et al., 1978 E. truncate Goose Kidney Gajadhar et al., 1983 E. boschadis, christiansensi, somateria

Mallard duck, mute swan, eider

Kidney Ball et al., 1989

E. reichenowi, gruis Sandhill crane, whooping crane

Widespread Novilla et al., 1981

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25

3. Anticoccidial products: mode of action, the occurrence of resistance and efficacious use 3.1. Introduction Before the pioneering work on the antibacterial and anticoccidial properties of sulphonamides (Levine, 1939; 1940), which led to the development of numerous other anticoccidial drugs, early treatment of coccidiosis was attempted with flowers of sulphur or other compounds, like dry or liquid skim milk and buttermilk (Beach & Corl, 1925; Beach & Freeborn, 1927; Herrick & Holmes, 1936). Later on, the realization that treatment of clinical diseased birds was less efficient than preventing coccidiosis outbreaks, favoured the emergence of preventive in feed medication, which has been of great significance in the upscaling of today’s poultry industry. Up till now, commercial poultry production still largely relies on preventive in feed medication with anticoccidial drugs in order to avoid disease outbreaks. If despite in feed medication clinical disease occurs, treatment of coccidiosis is used as last resource. 3.2. Anticoccidial products The terms coccidiostat and coccidiocidal (coccidiocide), which have been used extensively and characterize the mode of action of drugs used against coccidia, are frequently confused. Drugs with a coccidiostatic mode of action arrest the development of certain parasite stages in a reversible way and their withdrawal will still lead to the completion of the coccidiosis life cycle. In contrast, coccidiocidal drugs kill or irreversibly damage most parasite stages with no signs of disease relapse after drug withdrawal. On the other hand, some products can have coccidiostatic and coccidiocidal properties at the same time depending on the dose used and exposure time. In order to avoid misuse of terminology and due to the fact that, as said, some products may present both modes of action, the term anticoccidial, which conceals both terms, was introduced by Reid (Reid, 1975). Numerous anticoccidial drugs have been introduced since 1948 (Table 6), when sulfaquinoxaline and nitrofurazone were first approved by the American Food and Drug Administration (FDA) (Chapman, 1997; McDougald, 2003). Most of the anticoccidial products currently approved in different regions of the world for prevention of coccidiosis in birds are listed in Table 7 and an overview of the anticoccidial products recommended for therapeutic treatment is given in Table 10 (Conway & McKenzie, 2007). Some of the drugs mentioned in both tables may not be available in specific countries. Moreover, national regulatory limitations may apply to some products. A number of anticoccidials have been withdrawn overtime because of safety or efficacy issues, nevertheless many drugs are still available and used until today.

Table 6. Historical overview of anticoccidial products, reports on the resistance of Eimeria spp. field isolates and withdrawal periods (Chapman, 1997; McDougald, 2003; Conway & McKenzie, 2007) Generic or chemical name (Manufacturer)

Tradename Year of introduction

Resistance described (Country)

Year Eimeria spp. Withdrawal period (days)

Sulfaquinoxaline, 0.015-0.025% (Merck)

Aviochina, Quinatrol, SQ, Sulquin

1948 Waletsky et al. (USA) 1954 E. tenella 10

Nitrofurazone, 0.0055% (Hess & Clark, Smith-Kline)

Nfz, Amifur, Furacin, Furazol, Nitrofural, Coxistat

1948 Cuckler & Malanga (USA)

1955 Not given 5

Arsanilic acid or sodium arsanilate, 0.04% (Abott)

Pro-Gen, Roxarsone

1949 Unknown 5

Butynorate, 0.0375% for turkeys (Solvay)

Tinostat 1954 Unknown 28

Nicarbazin, 0.0125% (Merck, Sharp and Dohme; Merial)

Nicarb, Nicoxin, Nicrazin 1955 Hemsley (GBR) 1964 E. tenella 4

Furazolidone 0.0055-0.011% (Hess & Clark)

NF-180, Furovag, Furoxane, Furoxone, Giarlam

1957 Unknown 5

Nitromide, 0.025% + sulfanitran, 0.03% + roxarsone, 0.005 (Solvay)

Unistat-3, Tristat, Unistat 1958 Unknown 5

Oxytetracycline, 0.022% (Pfizer)

Terramycin 1959 Unknown 3

Amprolium, 0.0125-0.025% (MSD; Agvet; Merial)

Amprol 1960 Hemsley (GBR) 1964 E. brunetti 0

Chlortetracycline, 0.022% (American Cyanamid)

Aureomycin 1960 Unknown ?

Zoalene, 0.004-0.015% (Solvay)

Zoamix, DOT, DNOT 1960 Hemsley (GBR) 1964 E. tenella E. necatrix

5 5

Amprolium, 0.0125% + ethopabate, 0.0004/0.004% (Merck)

Amprol Plus, Amprol Hi-E 1963 Unknown 0

Clopidol or meticlorpindol, 0.0125-0.025% (A.L. Laboratories)

Coyden 1966 (GBR) Williams 1969 E. acervulina E. maxima E. tenella

0 at 0,0125% 5 at 0,025%

Buquinolate, 0.00825% (Norwich-Eaton)

Bonaid 1967 McManus (USA) 1968 Not given 0

Nequinate (methyl benzoquate ) Statyl 1967 Millard (GBR) 1970 E. tenella Decoquinate, 0.003% (Rhone Poulenc; Rorer)

Deccox 1967 (GBR)

(USA)

Stenorol 1975 Hamet RA)

Avatec 1976

Arpocox 1980

Baycox 1986 1993 Not

Monteban 1988

Maxiban 1989

0

Millard 1970 E. tenella 0

Sulfamethoxine, 0.0125% + ormetoprim, 0.0075% (Hoffmann-La Roche)

Agribon, Albon, Rofenaid 1970 Unknown 5

Monensin, 0.01-0.0121% (Elanco)

Elancoban, Coban, Coxidin

1971 Jeffers 1974b E. maxima 0

Robenidine, 0.0033% (American Cyanamid)

Robenz, Cycostat 1972 Jeffers (USA) 1974b E. maxima 5

Halofuginone 0.0003% (Hoechst-Roussell Agri-Vet)

(F 1986 E. acervulina E. tenella

Lasalocid, 0.0075-0.0125% (Hoffmann-La Roche)

Weppelman et al. (USA)

1977 E. acervulina 3

Aprinocid, 0.006% (Merial)

Chapman (GBR) 1982a E. tenella

Salinomycine, 0.004-0.0066% (Hoechst, Pfizer, Roche, Agri-Bio)

Sacox, Bio-Cox, Coxistac, Salgain, Salocin

1983 Jeffers (USA) 1984 Various species 0

Totrazuril, 7 mg/kg bodyweight (Bayer)

Vertommen Pe(Netherlands)

& ek given 18

Narasin, 0.0054-0.0072% (Elanco)

Weppelman et al. (USA)

1977 E. acervulina E. maxima E. tenella

0

Maduramicin, 0.0005-0.0006% (American Cyanamid)

Cygro 1989 McDougald et al. (USA)

1987a Various 5

Narasin + nicarbazin, 0.0054-0.0090% (Elanco)

Chapman (GBR) 1989. E. tenella 5

Diclazuril, 0.0001% (Janssen Pharmaceutica B.V.)

Clinacox 1990 Kawazoe & Fabio (Brazil)

1994 E. acervulina E. maxima E. tenella

Semduramycin, 0.0025% (Pfizer)

Aviax 1995


28

3.2.1. Categories The anticoccidial products can be classified in three categories according to their origin (Chapman, 1999a, 1999b; Allen & Fetterer, 2002c).

1. Synthetic compounds. These compounds are produced by chemical synthesis and are often referred to as “chemicals”. Synthetic drugs have a specific mode of action against the parasite metabolism. For example, amprolium competes for the absorption of thiamine (vitamin B1) by the parasite.

2. Polyether antibiotics or ionophores. These products are produced by the fermentation of Streptomyces spp. or Actinomadura spp. and destroy coccidia by interfering with the balance of important ions like sodium and potassium. The following groups of ionophores exist:

a. Monovalent ionophores (monensin, narasin, salinomycin) b. Monovalent glycosidic ionophores (maduramicin, semduramycin) c. Divalent ionophores (lasalocid)

3. Mixed products. A few drug mixtures, consisting of either a synthetic compound and ionophore (nicarbazin/narasin (Maxiban®)) or two synthetic compounds (meticlorpindol/methylbenzoquate (Lerbek®)), are also used against coccidiosis.

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Table 7. Contemporary anticoccidial products and recommended doses for prophylactic treatment of coccidiosis in chickens (Conway & McKenzie, 2007) Chemical name Bird type Concentration in feed (ppm) Chemicals Amprolium Broiler, rearing 125-250 Amprolium + ethopabate Broiler, rearing 125-250 + 4 Aprinocid Broiler 60 Clopidol Broiler, rearing 125 Decoquinate Broiler 30 Diclazuril Broiler, rearing 1 Dinitolmide (zoalene) Broiler, rearing 125 Halofuginone Broiler 3 Nequinate (methyl benzoquate) Broiler, rearing 20 Nicarbazin Broiler 125 Robenidine Broiler 33 Polyether ionophores Lasalocid Broiler 75-125 Maduramicin Broiler 5-6 Monensin Broiler, rearing 100-120 Narasin Broiler 60-80 Narasin + nicarbazin Broiler 54-90 (of both drugs) Salinomycin Broiler 44-66 Semduramycin Broiler 25 Products listed are known to be used with some frequency in Europe, Latin America, Asia/Pacific region and/or North America. 3.2.2. Mode of action Most anticoccidial products frequently have more than one biochemical effect upon a specific developmental stage of coccidia. Unfortunately, detailed knowledge on the selective action of these compounds against specific stages of the parasite is frequently lacking (Wang, 1982). Nevertheless, despite these shortcomings, a broad categorization of the mode of action of anticoccidials on the parasite metabolism has been undertaken (Chapman, 1997). A summarizing overview of mode of action of various anticoccidial products is given in Table 8. 3.2.2.1. Products affecting cofactor synthesis Several anticoccidial products influence essential biochemical pathways of the parasitic cell by affecting an important cofactor of named pathway (Greif et al., 2001). Ethopabate, which is often used in combination with amprolium to improve the spectrum of efficacy, is a folate antagonist and blocks a step in the synthesis of PABA and prevents


30

the formation of nuclei acids and the construction of vitamins (Rogers et al., 1964). Ethopabate affects the second generation of schizonts (Reid, 1975) and is most active against E. maxima and E. brunetti. Sulphonamides were the first drugs to be extensively used for the control of coccidiosis and also inhibit the folic acid pathway. Similar to ethopabate, the synthesis of dyhydrofolate is prevented by interfering with the dihydropteroate synthetase reaction, blocking the conjugation of pteridine and PABA. Dihydropteroate synthetase is only present in the parasite. Sulphonamides mainly affect the second generation of schizonts (Reid, 1975). They are very effective against the intestinal species E. brunetti, E. maxima and E. acervulina and to a much lower degree against both caecal species E. tenella and E. necatrix (Ryley & Betts, 1973). A major drawback of sulphonamides is their small safety margin, which easily leads to intoxications especially if they are used as treatment for coccidiosis outbreaks. Sulphonamide toxicity is characterized by decrease in egg production, loss of eggshell pigmentation, immune suppression, bone marrow depression and thrombocytopenia frequently leading to multiple hemorrhages (hemorrhagic syndrome). A third product affecting the folate pathway of coccidia is pyrimethamine by preventing the reduction of dihydrofolate to tetrahydrofolate by inhibiting the enzyme dihydrofolate reductase. Pyrimethamine has a clear synergistic effect with sulphonamides (Kendall & Joyner 1956). Similarly to sulphonamides, they affect the second generation of schizonts (Reid, 1973). Thiamine analogues, like amprolium block the absorption of thiamine completely and have probably an antagonistic effect on the vitamin B1 supply. In vivo thiamine is transformed into thiamine pyrophosphate, an important coenzyme in the carbohydrate metabolism. Amprolium, competitively inhibits the uptake of thiamine, however it can not be transformed into vitamin B1 as it lacks a hydroxyl group necessary for the translation into thiamine pyrophosphate (Rogers, 1962). Amprolium seems especially efficacious during schizogony as then the demand of thiamine is at its highest (James, 1980). There is a difference in sensitivity of the thiamine transport system of host and parasite (more sensitive) to amprolium, rendering the product efficacious against coccidiosis. It affects the first generation of schizonts and to a lesser extent the gametogony (Reid, 1973) allowing immune response to develop. It is most effective against the caecal species E. tenella and E. necatrix and to a lesser degree against E. acervulina, E. maxima and E. brunetti (Kaemmerer, 1965; Ryley & Betts, 1973). 3.2.2.2. Products affecting mitochondrial function Quinolone drugs amongst which buquinolate, decoquinate and nequinate (methyl benzoquate) are listed, show anticoccidial activity at very low concentrations. These products inhibit the respiration of coccidia by blocking the electron transport in their mitochondria (Wang, 1975). Although they are relatively safe and do not influence the egg production, egg quality and feed conversion, resistance is rapidly induced (McManus et al., 1968). This has significantly limited their use in the field. Quinolones arrest the development in the sporozoite stage of the coccidiosis life cycle, impairing the

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development of an adequate immune response (Reid, 1973; Yvoré, 1968). They were found to be effective against E. acervulina, E. brunetti, E. maxima and E. mivati and to a lesser degree to E. necatrix and E. tenella (Ryley & Betts, 1973). Meticlorpindol is the most important compound of the pyridone group. Similar to the quinolones it inhibits electron transport of mitochondria, however possibly at another level as cross resistance with quinolones does not occur. A synergistic effect between meticlorpindol and 4-hydroxiquinolones has been described (Challey & Jeffers, 1973). A widely used pyridone-quinolone combination drug is Lerbek® consisting of meticlorpindol and methyl benzoquate. Pyridones, similar to quinolones, affect early stages of the coccidiosis life cycle of all Eimeria spp. (Reid, 1973; Ryley & Wilson, 1975) and inhibit development of immunity (Bennejean et al., 1970). The true mode of action of nicarbazin (4, 4’-dinitrocarbanilide) is unknown. The product has been shown to inhibit both, the succinate-linked NAD reduction in mitochondria of beef hearts and the energy dependent transhydrogenase and accumulation of Ca2+ ions by rat lever mitochondria (Dougherty, 1974). It is not suitable for layers as it affects negatively the egg production and egg quality. It may cause yolk mottling and eggshell depigmentation. Nicarbazin mainly affects the second generation of schizonts and to a lesser extent the other parasite stages (McLoughlin & Wehr, 1960). It is most effective against E. tenella, E. necatrix and E. acervulina and less to E. maxima and E. brunetti. Development of immunity is not inhibited. Similar to nicarbazin, the exact anticoccidial mechanism of robenidine (a guanidine derivative) is still unknown, however from studies in mammals, where the product has shown to inhibit the oxidative phosphorylation of mitochondria at high concentrations, it is assumed that it also affects this process in the parasite (Wong et al., 1972). It targets the first and second generation of schizonts and allows the development of immune response. Robenidine is highly effective against all Eimeria spp. (Kantor et al., 1970). Another anticoccidial drug possibly affecting mitochondrial function is the triazinetrione compound toltrazuril, which is applied in drinking water for preventive and therapeutic treatment. Harder and Haberkorn (1989), showed that activities of some enzymes of the respiratory chain, such as succinate-cytochrome C reductase, nicotinamide adenine dinucleotide (NADH) oxidase and succinate oxidase from mouse liver, were reduced in the presence of toltrazuril. They also showed an inhibitory effect on the dihydroorotate-cytochrome C reductase from mouse liver. More recently, it has been suggested that toltrazuril might affect plastid-like organelles (Hackstein et al., 1995). Toltrazuril is efficacious against all intracellular stages (schizogony and gametogony) of all important Eimeria spp. in the chicken (Mehlhorn et al., 1984; 1988). It induces cidal changes in the organelles of the parasite at multiple levels, and it does not seem to impair the development of natural immunity (Greif & Haberkorn, 1997; Greif, 2000). 3.2.2.3. Products affecting cell membrane function Polyether antibiotics, commonly known as ionophores, with anticoccidial activity influence the transport of mono- or divalent cations (Na+, K+ en Ca++) across cell membranes inducing osmotic damage (Berger, 1951; Shumard & Callender, 1967). These


32

drugs are accumulated by extracellular stages (like sporozoites and merozoites) of the parasite in the lumen of the intestine (Long & Jeffers, 1982, Mehlhorn et al., 1983). An overview of all ionophores can be found in Table 7. Monensin has a good efficacy against all Eimeria spp. although the efficacy seems to be less against E. tenella (Reid et al., 1972; Folz et al., 1988). Semduramycin showed a good efficacy against all Eimeria spp. and an excellent protection against E. maxima (Logan et al., 1993; Conway et al., 1995). Narasin has a good efficacy against all Eimeria spp. more or less comparatively to monensin (Ruff et al., 1979; Ruff et al., 1980; Walters et al., 1981). Salinomycin has a broad anticoccidial spectrum against all Eimeria spp. comparable to or more effective than monensin and lasalocid (Migaki et al., 1979; Bedrnik, et al., 1980; Greuel & Raether, 1980; McDougald et al., 1981). Fetotoxicity has been described for salinomycin, robenidine, and arprinocid (Atef et al., 1989). Lasalocid shows good efficacy against all Eimeria spp. In efficacy tests it showed a better performance against E. brunetti and E. maxima and lower effect against E. acervulina, E. necatrix and E. tenella in comparison to salinomycin and monensin (Mitrovic & Schildknecht, 1974; Reid et al., 1975; Migaki et al 1979). Maduramicin shows good efficacy against all Eimeria spp. In animal experiments, maduramicin showed a better effect on E. acervulina, E. maxima and E. tenella than monensin and narasin, but comparable to salinomycin (Kantor & Schenkel, 1984; Kantor et al., 1984; McDougald et al., 1984; Schenkel et al., 1984; Wang et al., 1986). In another comparative study with halofuginone, lasalocid, monensin and salinomycin, maduramicin was the least effective against an E. maxima infection (Folz et al, 1988). In general, treatment with ionophore anticoccidials allows some level of infection and consequently the development of immunity against coccidia, however this depends upon the dosage used, the Eimeria spp. and the infection level (Jeffers, 1989; Chapman & Hacker, 1993; Chapman, 1999b). 3.2.2.4. Products with unknown mode of action: diclazuril and halofuginone Diclazuril shows a coccidicidal effect towards all Eimeria spp. of the chicken; however its exact mode of action has not been unraveled yet. It is a nucleoside analogue thought to be involved in acid nucleic synthesis, possibly affecting later phases of coccidia differentiation (Verheyen et al., 1988). It has been shown to affect parasite wall synthesis resulting in the formation of an abnormally thickened, incomplete oocyst wall and zygote necrosis in both, E. brunetti and E. maxima (Verheyen et al., 1989). Halofuginone is a quinazolinone derivative with unknown mode of action effective against all six pathogenic Eimeria spp. of chicken. It affects the sexual stages, particularly the first generation of the schizogony.

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Table 8. Metabolic process affected by anticoccidial products, their mode of action and speed of resistance (Chapman, 1997) Anticoccidial drug Metabolic process Mode of action Speed of resistancea Ionophores (monensin, lasalocid, narasin, salinomycin, maduramicin & semduramycin)

Membrane permeability

Cation transport Slow

Amprolium (Sulfonamides + dihydrofolate reductase (DHFR) inhibitor)

Cofactor synthesis Inhibit thiamine uptake Blocks folate synthesis

Slow Slow

Quinolones (buquinolate, decoquinate & nequinate)

Mitochondrial function

Electron transport Fast

Pyridones (clopidol) (clopindol & mehylclorpindol)

Mitochondrial function

Electron transport Moderate

Nicarbazin Mitochondrial function

? Slow

Robenidine Mitochondrial function

? Moderate

Halofuginone Unknown ? Moderate Diclazuril Unknown ? Moderate a Resistance has been described for all anticoccidial drugs introduced. ? = Unknown. 3.2.3. Antimicrobial & growth promoting properties of anticoccidial products The antimicrobial and growth promoting properties of ionophores have been recognized previously. Besides being active on parasites, they have been found to inhibit gram-positive organisms and mycoplasmas (Shumard & Callender, 1967; Dutta & Devriese, 1984; Stipkovits et al., 1987). Monensin and narasin were shown to inhibit Clostridium perfringens (types A and C) in chickens and turkeys (Elwinger et al., 1992; Vissiennon et al., 2000). Ionophores may therefore have contributed in some cases to the control of necrotizing enteritis (Martel et al., 2004) similar to traditional antibiotic growth promoters (AGPs) like virginiamycin, zinc bacitracin, avoparcin and avilamycin (Elwinger et al., 1998). Due to the occurrence of drug resistant C. perfringens strains (Devriese et al., 1993; Benno et al., 1988), it is not possible to blindly rely on AGPs including ionophores for the control of necrotizing enteritis.


34

As necrotizing enteritis is a multifactorial disease in which coccidiosis may be involved, but also many other factors such as environmental and management conditions, stress and immune suppression, the diet, etc., to conclude that the ban on AGPs will invariably lead to increased outbreaks of necrotizing enteritis is an oversimplification of reality (Van Immerseel et al., 2004, Williams, 2005). On the other hand until recently (before the introduction of Clostridium perfringens vaccines) antibiotic treatment has been found to be the only reliable way to control necrotizing enteritis. Antibiotic candidate replacement treatments including probiotics, prebiotics, organic acids, enzymes, plant extracts, hen egg antibodies, bacteriophages, vaccinations and diet composition (increase feed particle size, corn-based diets, reducing non-starch polysaccharides and reducing proteins of animal origin) might be effective to some extent in controlling necrotizing enteritis although no single non-antibiotic treatment has proved satisfactory (Dahiya et al., 2006). No effect of monensin and nicarbazin on the caecal colonization of Salmonella could be demonstrated experimentally in chickens (Manning et al., 1994). Salinomycin has been shown to reduce the number of resistant coliforms (sulfadiazine) and streptococci (erythromycin and lincomycin) (George et al., 1982). It was also shown that salinomycin seemed to reduce the number of resistant Salmonella Typhimurium bacteria (Ford et al., 1981). 3.2.4. Incompatibilities of anticoccidial products Ionophores are incompatible with some therapeutic antibiotics like tiamulin, chlorampheniol, erythromycin, oleandromycin and certain sulfonamides. Ionophores are also incompatible with some antioxidants (XAX-M, Duokvin, TD) (Umemura et al., 1984; Prohaszka et al., 1987; Dowling, 1992; Von Wendt et al., 1997). 3.2.5. Regulations of anticoccidial products within the European Union (EU) In the EU, the regulation of anticoccidial drugs, which are considered as feed additives, is stipulated in Directive 70/524 since 1970. More recently, Directive 96/51 and the Regulation (EC) 1831/2003 have been added. The main changes put forward by Regulation 1831/2003 are the implication of the European Food Safety Authority (EFSA) in the scientific review of the dossier of products and the call for maximum residue limits. The future status of anticoccidial drugs is uncertain at this moment: their current status as feed additives may be maintained or new legislation and phasing-out of these drugs as feed additives could be proposed. Article 11 of Regulation 1831/2003 called for a report of the Commission on this subject, which should have been made public in January 2008. Actual and forthcoming information of the obtained regulations can be found on the website of the European commission animal nutrition feed additives (http://ec.europa.eu/food/food/animalnutrition/feedadditives/legisl_en.htm).

http://ec.europa.eu/food/food/animalnutrition/feedadditives/legisl_en.htm

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3.2.5.1. Anticoccidial products currently available in the Netherlands In Table 9 a complete list of all authorized anticoccidial products used in the Netherlands is given. Table 9. Authorized anticoccidial products in the Netherlands with registration number, end of authorization, target species, dose and withdrawal period Additive Registration

number End of authorization

Animal species

Dose (ppm) Minimum Maximum

Withdrawal period (d)

Decoquinate E 756 17/07/2014 Broiler 20 40 3 Monensin E 757 30/07/2014 Broiler 100 125 1 30/07/2014 Chicken 100 120 1 30/07/2014 Turkey 60 100 1 Robenidine E 758 29/10/2014 Broiler 30 36 5 29/10/2014 Turkey 30 36 5 Lasalocid E 763 20/08/2014 Broiler 75 125 5 20/08/2014 Chicken 75 125 5 30/09/2009 Turkey 90 125 5 Halofuginone E 764 30/09/2009 Chicken 2 3 5 Narasin E 765 21/08/2014 Broiler 60 70 1 Salinomycin E 766 21/08/2014 Broiler 60 70 1 Maduramicin E 770 30/09/2009 Broiler 5 5 5 15/12/2011 Turkey 5 5 5 Diclazuril E 771 30/09/2009 Broiler 1 1 5 20/01/2013 Chicken 1 1 5 28/02/2011 Turkey 1 1 5 Narasin/ Nicarbazin

E 772 30/09/2009 Broiler 80 100 5

Semduramycin E 773 30/09/2016 Broiler 20 25 5 3.3. Anticoccidial product resistance The World Health Organization defines drug resistance in antimalarial chemotherapy, which can also be applied to coccidiology, as "the ability of a parasite strain to survive and/or multiply despite the administration and absorption of a drug in doses equal to or higher than those usually recommended but within the limits of tolerance of the subject" (World Health Organization, 1965). Generally, drug resistance in coccidia can be complete, in which case increasing doses up the maximum tolerated by the host is ineffective (i.e. diclazuril, nicarbazin). In contrast, relative resistance to anticoccidial drugs is characterized by the fact that increasing doses tolerated by the host still will show efficacy (i.e. ionophores). The worldwide intensive use of anticoccidial drugs to prevent coccidiosis, has inevitably led to the development of resistance to all anticoccidial drugs as long term exposure to any drug will result in loss of sensitivity. The widespread occurrence of resistance has been described in the United States, South America, Europe and China (Jeffers, 1974a, 1974b,


36

1989; Chapman, 1978, 1982b, 1984, 1997; Ryley, 1980; Hamet, 1986; Litjens, 1986; McDougald et al., 1986; 1987b; Zeng & Hu, 1996; Zhou et al., 2000; Peek & Landman, 2003, 2004). In some cases resistance is induced very quickly, as in the case of quinolones and pyridinols, which led to a decline in their use; while in other instances it may take several years, as in the case of the ionophores. Despite the widespread occurrence of resistance, at least in Europe, coccidiosis outbreaks seem to have had limited impact so far. This is explained by the fact that resistance in many cases will have allowed the occurrence of trickle infections, which are essential in the built-up of immunity (Jeffers, 1989; Chapman, 1998; Peek & Landman, 2003). The occurrence of anticoccidial drug resistance in the field and corresponding first reports has been described in Table 6. 3.3.1. Resistance and cross resistance: contributing factors and genetic basis An important contributing factor to the occurrence of resistance is the high reproductive potential of coccidia and subsequent forthcoming genetic variation, which increases the chances for resistant strains to be selected from the parasite population. Also, long-term exposure to anticoccidial drugs will increase the frequency of resistance genes by selection of resistant mutants that will become the dominant phenotype. Additionally, the occurrence of large numbers of asexual haploid stages against which most anticoccidials are effective, will efficiently allow the selection of resistant phenotypes because genetic complexities as found in diploid organisms are not interfering (Jeffers, 1989; Chapman, 1997). Drug resistance of coccidia is based on the occurrence of single mutations or mutations at several loci with subsequent selection of resistant phenotypes. Multiple resistance is believed amongst others to be the result of genetic recombination. Cross resistance between anticoccidial drugs with similar mode of action is likely to occur. This is an important motivation for the alternation of different drugs and drug programmes when it comes to sustainable coccidiosis control in poultry. 3.3.2. Management of resistance The development of resistance to anticoccidial drugs, which is widespread and has been described for all products introduced so far (Chapman, 1986, 1997; Peek & Landman, 2003, 2004), is a major drawback in coccidiosis control. To minimize the occurrence of resistance, rotation (a given anticoccidial product is used during a maximum of two months or two fattening periods) of various anticoccidial drugs or shuttle programmes (two or more anticoccidial drugs are used within a fattening period) are used. The rationale behind this is the fact that, as said previously, the loss of sensitivity is correlated to the length of drug exposure, which should be kept short if possible. Due to the occurrence of cross resistance between anticoccidial drugs, anticoccidial drugs with distinct mode of action should be used within rotation and shuttle programmes.

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In order to optimize the use of prophylactic medication in the field, scientific information on the drug-sensitivity profiles of Eimeria spp. field isolates concerned, is vital. This information can only be obtained by performing an in vivo Anticoccidial Sensitivity Test (AST) in battery cages. Despite the fact that the AST is the only accurate tool to detect anticoccidial drug resistance, the procedure is slow and expensive, isolates frequently originate from disease outbreaks (and may not always be representative for the field) and need to be propagated first in specified pathogen free (SPF) chickens for multiplication (which may result in selection of non-relevant coccidia). Nevertheless, it is generally accepted by the scientific community that ASTs provide valuable information and should be given more attention in coccidiosis prevention programs in order to maintain the efficacy of the steadily decreasing number of available anticoccidial drugs. A more recent development in managing anticoccidial drug resistance is the rotation of anticoccidial drugs with live Eimeria spp. vaccines. Several studies have documented a higher incidence of sensitive Eimeria spp. field isolates when live anticoccidial vaccines and anticoccidial products are rotated. The exact mechanism resulting in an increase of sensitivity of Eimeria spp. field isolates is currently unknown, but it is explained by the fact that chicken houses are seeded with drug-sensitive vaccine oocysts (Jeffers, 1976; Mathis & McDougald, 1989; Chapman, 1994, 1996; Newman & Danforth, 2000; Mathis & Broussard, 2006; Peek & Landman, 2006). This may lead to outgrow of resistant strains by reproductively more advantageous drug-sensitive coccidia, interbreeding between field and vaccine parasites resulting in (more) sensitive interbreeds or a combination of both. Moreover, in case live attenuated coccidiosis vaccines are used, less virulent interbreed field isolates may be produced (Shimura & Isobe, 1994; Williams, 2002a). 3.3.2.1. Anticoccidial programs In order to minimize the occurrence of resistance it is crucial to shorten the exposure time to anticoccidial drugs as much as possible and to alternate compounds with a different mode of action. This has lead to a great variety of coccidiosis control programs. The design of the various programs will depend on the goal of named program. In replacement layer and breeder birds full coccidiosis control is not desired, instead it should be monitored, for instance by regularly determining the mean lesion score in birds, number of oocysts per gram faeces, etc., as the desired development of immunity takes place (Long & Jeffers, 1986). In contrast, in broilers maximal growth and optimum feed conversion with minimum disease of the birds is the main concern. In general the efficacy of anticoccidial drug programs depends on nutritional factors (see section 4) and adequate mixing procedures. Regarding the latter, it is crucial that the levels of anticoccidial drugs meet the required dose. Assessment of mixing procedures by means of chemical analysis of feed samples originating from the field should be performed regularly, although in practice this is rarely done. In single drug programs, a single anticoccidial product is continuously supplied to the birds during successive grow-out periods until its efficiency declines and coccidiosis outbreaks occur.


38

Shuttle programs are characterized by the alternation of anticoccidial compounds within a single grow-out period: i.e. the drug used in the starter feed is different to the one used in grower feed. Frequently, a chemical compound is used in the starter, followed by an ionophore in the grower feed, although sometimes ionophores with distinct mode of action are used. The choice of drugs may depend on a number of factors amongst which the past experience and the season of the year (nicarbazin given in summer increases the chances of heat stress) (Buys & Rasmussen, 1978; McDougald & McQuistion, 1980). Single drug and shuttle programs can be used within rotation programs, which are characterized by the use of distinct anticoccidial drugs between successive grow-out periods. The use of live attenuated coccidiosis vaccines can be included within rotation programs (Chapman et al., 2002; Williams, 2002a). In these cases, a chemical anticoccidial drug is preferably used in the last grow-out period before vaccination especially if during earlier fattening periods ionophores have been used. The chemical drug will then more efficiently control the coccidiosis population including ionophore resistant parasites and favour the repopulation of the poultry house with drug sensitive vaccine oocysts, subsequently increasing the sensitivity of Eimeria spp. field isolates (Jeffers, 1976; Mathis & McDougald, 1989; Chapman, 1994, 1996; Newman & Danforth, 2000; Mathis & Broussard, 2006; Peek & Landman, 2006). Also in rotation programs coccidiosis control can be performed using toltrazuril applied in drinking water during two days (Mathis et al., 2004). Table 10. Anticoccidial products and doses for therapeutic treatment of coccidiosis in chickens (Conway & McKenzie, 2007) Chemical name Application form Used concentration Treatment schedule Amprolium Feed 250 ppm 2 wks Water 0.006% 1-2 weeks Water 0.012-0.24% 3-5 days Sulfadimetoxine Water 0,05% 6 days Sulfaguanidine Feed 10,000-15,000 ppm 5-7 days Sulfamethazine Feed 4,000 ppm 3-5 days Water 0.1% 2 days Water 0.05% 4 days Sulfaquinoxaline Feed 1,000 ppm 2-3 days on,3 days off; then 500

ppm for 2 days on Feed 500 ppm 3 days on, 3 days off, 3 days on Water 0.04% 2-3 days on, 3 days plain water

and then 2 days 0.025% Sulfaquinoxaline + pyrimethamine

Water 0.005% + 0.0015%

2-3 days on, 3 off and 2 days on

Furazolidone Feed 110 ppm 5-7 days on, 2 weeks 55 ppm on Nitrofurazone Feed 110 ppm 5 days Water 0.0082% 5 days Toltrazuril Water 0.0025% 2 days continuous Water 0.0075% 6-8 h/day for 2 days

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4. The influence of feed structure, composition, toxins and administration on the course of a coccidiosis infection 4.1. Introduction Optimal animal health is amongst other factors directly dependent on an adequate supply of dietary nutrients. Nutritional deficiencies can be primary (deficiency of one or more essential nutrients) or secondary (suboptimal use of nutrients by the animal) in nature and have been described extensively by various authors. Besides many reports on specific nutritional deficiencies or diseases resulting from ingestion of toxic of nutrients, there is a wealth on scientific literature describing the direct influence of nutrients and diet composition on the immune competence of animals and humans. Inadequate nutrient supplies, even marginal, frequently result in impaired resistance to infectious diseases, but can also result in reduced growth, deficient egg production and hatchability.

According to the National Research Council (1994), diets of poultry are mostly a mixture of ingredients like cereal grains, soybean meal, animal by-product meal, fats, vitamins and mineral premixes. Together with water these compounds deliver proteins, amino acids, carbohydrates, fats, minerals, vitamins and energy that the birds need to grow, to reproduce and to stay healthy.

Deficiencies of nutrients or energy levels can cause problems with the biochemical processes which depend on the involved nutrient and may result in inadequate performances and even disease. In the field, nutrient deficiencies are often erroneously attributed to management problems and infectious diseases (NRC, 1994).

Changes in feed and feed ingredient quality can often result in health problems of the animals. It is therefore highly desirable to provide diets being stable in nutrient composition, energy content, moisture content, physical structure and texture.

In view of the importance of feed in disease resistance, almost all macronutrients (carbohydrates, proteins and polyunsaturated fatty acids) and micronutrients (minerals, oligo-elements and vitamins) have been investigated for their potential use as dietary supplements for coccidiosis control. Some of these nutrients have a direct beneficial effect on the development of the parasite within the host and are in fact coccidiosis promoting compounds, while others actively enhance the host’s resistance against Eimeria by stimulating the immune system, thus decreasing the pathological effects of a coccidiosis infection. Moreover, nutrients that improve the recovery after an Eimeria infection have also been described (Allen et al., 1998; Crévieu-Gabriel & Naciri, 2001).

In the present section scientific research on the influence of feed structure, feed composition (macro and micro ingredients, special additives) and feed management on coccidiosis is reviewed. The main conclusions obtained in the field of nutrition and coccidiosis control have been summarized in Table 11 and Figure 2 for convenience.


40

4.2. Feed structure Feed structure or texture is partly determined by the feed particle size, which in turn is largely dependent on the presence of cereals and the extent, to which they have been grounded. Processing of feed into pellet or crumb at the factory may further decrease the average particle size of poultry feedstuffs. Describing the particle size of ground feed ingredients involves using a sieve set of specific designation to separate a representative sample of feed into eight size categories. The Modulus of Uniformity (MU) is then used to indicate the percentage of the various filter fractions (coarse, medium and fine), while the Modulus of Fineness is used to reflect the coarseness or fineness of the analyzed feed (http://www.asft.ttu.edu/ansc5001/). The average particle size of a sample is frequently expressed as geometric mean diameter (GMD in mm or µm; <600 µm is fine, 700-900 µm medium and >1000 µm is coarse). Particle size uniformity is described by geometric standard deviation (GSD), a small GSD representing higher uniformity. The physical structure of the feed influences the development of the intestinal tract, the secretion of digestive enzymes and the development of the gastrointestinal flora. Feed mainly consisting of fine particles has a strong inhibiting effect on the contraction and reflux activity of the intestine, and thus on the development of the intestinal tract, in comparison to coarse feeds based on larger particles. This was shown in pigs fed with larger maize grains resulting in higher villi and lamina propria (Healy et al., 1994). Feed particle size also plays a major role in the development of the gizzard: greater gizzards were found in chicks fed medium or coarse particle size diets compared to fine particulate feeds. Feed based on whole cereals improved the motility of the intestinal tract and the health status of the birds; however, studies on the influence of such feeds on the development of a coccidiosis infection have yielded ambivalent results. Birds housed in cages supplied with whole cereals up to 60-70% and high protein concentrations (40%) in their diet, showed reduced oocyst shedding and mortality most prominently for E. tenella but also E. acervulina and E. maxima in a mixed coccidiosis infection model (Cumming, 1987). These results were in agreement with those obtained in floor pen trials (Cumming, 1989; 1992a, b; 1994). In these studies heavier gizzards as well as lower pH in the intestines were found. It was hypothesized that the mechanical function of the better developed gizzards will have destroyed more oocysts, while the lower pH will probably have resulted in a more hostile environment for excysted sporozoites, thus tempering the coccidiosis infection. The promising results presented by Cumming could not be repeated by other European research groups except by Langhout (1999), who reported in a non-peer-reviewed journal lower coccidiosis lesion scores for E. acervulina in broilers fed coarse wheat compared to birds fed fine wheat. However, the coccidiosis inhibiting effect of coarse wheat could not be demonstrated in case of an E. tenella infection. Feed supplemented with whole wheat up to 30%, increased the weight of the gizzard 1.2 to 1.5% of the bodyweight (less than found by Cumming in 1992b), however it had no significant effect on a subclinical (low infection doses) infection with E. tenella or E.

http://www.asft.ttu.edu/ansc5001/

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maxima regarding lesion scores, oocyst shedding and performance (Waldenstedt et al., 1998). In another study, no changes were found in oocyst excretion during an infection with E. acervulina when birds were given feed containing 20% whole wheat compared with feeds containing 20% ground wheat (Banfield et al., 1998). Banfield & Forbes (2001) also failed to demonstrate that neither dilution nor substitution of feeds with whole wheat did influence the E. acervulina infection as measured by oocyst excretion, although whole wheat significantly increased the size of gizzards. Previously, it was shown that the administration of whole wheat may be detrimental instead of beneficial: substitution of 20 and 40% of ground wheat with whole wheat, showed that the oocyst excretion was significantly increased and that significant poorer feed conversion efficiency was achieved in case of an E. acervulina infection. Increased viscosity of the diet did not influence the coccidiosis infection either (Banfield et al., 1999; Waldenstedt et al., 2000a). A detrimental effect of whole wheat supplementation on the performance of broiler chickens during the course of an E. acervulina infection was also shown by Banfield et al. (2002). More recently, a detrimental effect of feeding whole wheat compared to ground wheat on an experimental coccidiosis infection was shown by Gabriel et al. (2006). The whole wheat diet led to lower weight gain in E. acervulina, E. maxima or E. tenella infected birds during the acute phase of infection, although in uninfected birds it lead to a more efficient feed conversion and more beneficial microflora. Further, the oocyst excretion was higher in whole wheat fed birds (x 1.5 for E. maxima and x 10 for E. tenella). These results confirmed previous studies (Gabriel et al., 2003) showing that feeding whole wheat increases the more detrimental effect of Eimeria parasites on the birds during the acute phase of a coccidiosis infection compared to a diet with ground wheat. The conflicting results between the work of Cumming and other research groups was explained by the much higher concentrations of whole wheat used by the former (60-70% compared to 20-40%), which resulted in the largest diet-induced gizzard development. The bigger gizzards will probably have had a bigger mechanical impact on the oocysts, sporocysts and sporozoites resulting in their destruction. In contrast, the limited gizzard development induced by moderate whole wheat diets will have yielded optimal mechanical forces for the breakage of oocysts, resulting in increased coccidiosis infection. Moreover, low-to-moderate whole wheat diets (20-40%) have shown to increase pancreas weight (Banfield et al., 2002; Wu et al., 2004), which may lead to increase production of pancreatic enzymes favourable for excystation (Farr & Doran, 1962) and thus aggravating the clinical signs of a coccidiosis infection. Summarizing, it can be concluded that feed structure and degree of fineness of cereal grains in particular may influence the course of a coccidiosis infection. As cereals form an important basis for today’s poultry diets in Western Europe, these effects and the underlying mechanisms deserve to be further explored.


42

4.3. Feed composition Besides texture, specific nutrients or feed ingredients may have a direct effect on the Eimeria parasite by influencing certain stages of its life cycle, while other components may modulate indirectly a coccidiosis infection by enhancing the immune response or improving the recovery after infection.

4.3.1. Basic ingredients of feed Poultry feeds are most frequently based on wheat or corn as main energy source. Relative few research data on the influence of these ingredients in poultry diets on a coccidiosis infection are available. The effect of natural feedstuffs added to a semi-purified diet on E. tenella, was studied by Colnago et al. (1984b), who showed that corn and corn fermentation solubles contain factors that enhance a clinical E. tenella infection, however soybean meal did not. In contrast, in a later study, where a corn diet was compared to wheat, lower mortality was found in the birds infected with E. tenella given the first diet (Williams, 1992a). More evidence suggesting a beneficial effect of a corn based diet on a coccidiosis infection, was published by Morgan and Catchpole (1996), showing superior growth in E. tenella and E. acervulina infected broilers fed corn compared to wheat. The different effect of corn and wheat on a coccidiosis infection is possibly related to differences in their micronutritive components as suggested by Williams (1992a): while corn is rich in vitamin A (x 1.8) and E (x 1.7) that may boost the immune response, wheat contains about twice as much niacin and x 1.3 riboflavin, which are beneficial to the parasite (Warren, 1968). Moreover, a wheat-based diet may also alter the intestinal flora favouring the development of the parasite. Compared to corn, such a diet has been shown to increase mortality by C. perfringens (Branton et al., 1987). 4.3.2. Macronutrients 4.3.2.1. Carbohydrates Carbohydrates make up the largest portion of a poultry diet, are the primary source of metabolizable energy and influence the intestinal microbial activity. Modulation of the intestinal flora mainly depends upon the type of carbohydrate. In animal feed carbohydrates are usually classified into sugars (mono- (glucose, fructose, galactose) and disaccharides (sucrose, lactose and maltose), oligosaccharides (raffinose, stachyose and verbascose), starch (amylose and amylopectin) and non-starch polysaccharides (NSP) (cellulose, hemicellulose, fructans, galactans, mannans, pectic substances, and gumsand substances)). Except NSP, which need previous fermentation by the intestinal microflora, most sugar fractions are readily digested in the small intestine with the aid of pancreatic enzymes (Trowell et al., 1976). Carbohydrates have been investigated frequently for their influence on a coccidiosis infection; most attention has been given to the non-digestible carbohydrates (i.e. NSP).

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43

Different types of saccharides The influence of various carbohydrate compounds mainly mono- and disaccharides on E. tenella coccidiosis was studied after their in feed administration. The following results were obtained: mannose slightly favours growth and reduces lesions, the latter is also induced by lactose, however does not modify oocyst shedding. Fructose, maltose, saccharose, amylopectin and glucose favour oocyst shedding without enhancing coccidiosis lesions except fructose. Potato starch increased coccidial lesions, while amylose did not influence their occurrence (Matsuzawa, 1979). In general, if the saccharide content exceeds 50% of the diet, the growth of birds is influenced negatively, while the oocyst excretion is enhanced. These effects are explained by the modification of the intestinal flora by the high saccharide content of the diet. NSP (non-starch polysaccharides) or dietary fibre NSP are polysaccharides that cannot be degraded by endogenous enzymes and therefore reach the colon almost indigested where they are fermented by microbes. There are two kinds of NSP: insoluble (cellulose and hemicellulose) and soluble (fructans, galactans, mannans, pectic substances (protopectin, pectin and pectic acid) and gumsand mucilages (β-glucans, xyloglucans and mannoglucans)). Insoluble NSP do not dissolve in water and do not swell in water to form a gel; soluble NSP do not dissolve in water completely but swell to form a gel. The anti-nutritional effects of soluble NSP are related to their viscous properties contributing to a higher viscosity of the aqueous fraction of the intestinal content impairing the efficient transport of nutrients. Also, the diffusion of digestive enzymes may be affected by the increased viscosity. Insoluble NSP do not seem to affect nutrient digestibility, however, they may change the anti-nutritional effect of soluble NSP due to their laxative properties. Most plant foods contain both types NSP although proportions vary. Insoluble NSP can be found in wheat, corn, rice, vegetables and pulses, while soluble NSP are found in apples, citrus fruits, beans, barley, rye and oats. Studies on the effect of the dietary fibre content in poultry diets on coccidiosis infections have yielded conflicting results. Feed with high level of crude fibres (10% instead of 6.5%) aggravated clinical coccidiosis with E. tenella resulting in higher mortality and caecal hemorrhages (Mann, 1947). However, in another study no effect of almost 10% cellulose on E. tenella infection was observed (Koltveit, 1969). More recently, increased fibre content (9%) was shown to reduce oocyst excretion of E. tenella and E. acervulina although lesions remained unaffected (Muir & Bryden, 1992). In contrast, Cumming showed previously (1987) that increased levels of fibre decreased oocysts yields related to a better gizzard development and subsequent oocyst destruction. The increased intestinal viscosity entrained by NSP (through increase of pentosans) could favour the development of coccidiosis. The coccidiosis promoting effect may be lowered by enzymes that reduce viscosity like pentosanases. In chickens infected with E. acervulina and E. tenella, they seemed to diminish the growth retardation (Morgan & Catchpole, 1996). In agreement with previous research, experimental increase of intestinal viscosity with carboxymethylcellulose diminished the feed efficiency of E. acervulina infected chickens, however oocyst shedding was not affected (Banfield et al., 1999).


44

Another study on the influence of intestinal digesta viscosity showed that the performance, lesion scores and C. perfringens counts of E. acervulina and E. praecox infected birds was not affected (Waldenstedt et al., 2000a). NSP derived from barley (containing β-glucans) could have an indirect effect on a coccidiosis infection by their immunoprotective properties. Nevertheless, although zymosan (a product which contains β-glucan a.o.) enhanced the immune responsiveness in mammals (Vadiveloo, 1999; Volman et al., 2005) and it promoted oocyst shedding in E. tenella challenged chickens (Smith & Ovington, 1996). Although NSP seemed to have little or no effect on a coccidiosis infection, more complementary research is needed to determine the effect of these ingredients. 4.3.2.2. Proteins Proteins are essential dietary components vital for growth, maintenance and repair of muscle tissue and energy supply. A protein concentration dependent effect on coccidiosis has been described by various authors (Mann, 1947; Britton et al., 1964; Sharma et al., 1973). In general, low levels of dietary protein (≤ 13%), which are mostly detrimental for growth performance, seem to diminish coccidiosis mortality, oocyst shedding and coccidiosis lesions. This is attributed to a reduction of trypsin activity in the small intestine, thereby limiting sporozoite excystation and subsequent parasite invasion (Britton et al., 1964). High dietary protein may also favour bacterial growth in the intestines and enhances the development of coccidiosis lesions due to E. tenella (Mann, 1947). On the other hand, increased dietary protein (≥ 16%) protects against weight reduction during clinical coccidiosis and stimulates compensatory growth (Sharma et al., 1973). Raw soybeans as protein source have a protective effect against coccidiosis-induced growth retardation and lesions scores by several Eimeria spp., attributed to protease inhibitors limiting excystation. This effect was not seen when continuously feeding raw soybeans as it induced pancreas hypertrophy and hyperfunction (Mathis et al., 1995). In practice, raw soybeans are not used due to the high level of antinutritional factors and the low protein digestibility. 4.3.2.3. Lipids In response to the growing number of lipids expected to be discovered through lipidomics and advances in lipid research, recently a new classification scheme for lipids has been proposed. Lipids are divided into eight primary categories: fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterol lipids, prenol lipids, saccharolipids and polyketides. These categories are based on the functional backbone of the lipid molecule from a chemical standpoint. The categories are further subdivided into classes and subclasses to handle the existing and emerging arrays of lipid structures (http://www.lipidmaps.org/). Lipids are important in poultry feed as source of energy, they are essential components of cellular and subcellular membranes, serve as biological carriers for the absorption of fat-soluble vitamins and yield essential fatty acids.

http://www.lipidmaps.org/

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45

Fatty acyls Unsaturated fatty acids seem to promote clinical and pathological signs of coccidiosis and pathology. Essential fatty acids are required for the development of Eimeria parasites. Chickens fed diets enriched with coconut oil, composed of medium chain saturated fatty acids, showed better performance after an E. acervulina infection than those birds given soy oil (unsaturated fatty acids) (Adams et al., 1996). Similarly, the use of coconut oil in essential fatty acids deficient purified diet reduced the lesions and mortality as a result of a coccidiosis infection (E. tenella and E. mivati) compared to a diet supplemented with corn and soya or corn oil (unsaturated essential fatty acid) (Charney et al., 1971). Regarding performance loss due to coccidiosis, medium chain fatty acids seem advantageous compared to long chain fatty acids. Coconut oil significantly improved fat digestion and performance values during a coccidiosis infection with E. acervulina in comparison with natural long chain saturated fatty acids of animal fat. This is explained by the better digestibility of medium chain fatty acids and their more efficient absorption by the diseased mucosal surface (Babayan, 1987; Adams et al., 1996). In case the intestinal health is compromised, as during coccidiosis infection, the digestibility of lipids (especially long fatty acids) in feed is decreased first. It is probably the consequence of the inactivation of bile salts due to microbiological activity. Bilesalts are essential in the process of lipid emulgation, which is particularly important during the digestion of long chain fatty acids. This provides an explanation for the fact that young chickens suffering from clinical coccidiosis show better performance whenever they are supplied with medium chain fatty acids. Moreover, these type of fatty acids also have antimicrobial properties. Essential fatty acids Essential fatty acids (EFAs) must be obtained from the diet as they cannot be synthesized from other components by any known chemical pathway by land animals except the landsnail. There are two families of EFAs: ω-3 (or omega-3 or n-3 or α-linolenic acid) and ω-6 (omega-6, n-6 or linoleic acid). Both acids form the starting point for the creation of longer and more unsaturated fatty acids, which are also referred to as long chain polyunsaturated fatty acids. Examples of ω-3 fatty acids are eicosapentaenoic acid and docosahexaenoic acid, and of ω-6 fatty acids are gamma-linolenic acid, dihomogamma-linolenic acid and arachidonic acid. EFA ω-3 belonging to the family of polyunsaturated fatty acids can be found abundantly in fish oil, flaxseed oil and whole flaxseed and can be easily supplemented to the feed. In E. tenella infection experiments, lesion scores and growth retardation were significantly reduced in birds supplemented with 2.5, 5 and 10% fish oil and 10% flaxseed oil compared to unsupplemented diets (Allen et al., 1996; 1997a; Korver et al., 1997). The beneficial effect of ω-3 fatty acids was explained by the retarded development of E. tenella (Allen et al., 1996) and ultrastructural changes of both asexual and sexual stages induced by these compounds (Danforth et al., 1997). These results are consistent with reports on the influence of ω-3 fatty acids on other parasites and suggest that a state of


46

oxidative stress is created that is harmful to the parasite (Allen et al., 1998). In agreement herewith, high vitamin E concentrations (35 IU/kg in stead of 4.2-21 IU/kg) added to feed in order to limit the oxidation of unsaturated fatty acids seemed to nullify the positive effect of ω-3 fatty acids on an E. tenella infection (Allen et al., 2000). In contrast to the positive results obtained for E. tenella, dietary flaxseed supplementation showed to be ineffective against moderate and severe E. maxima infections (Allen et al., 1997a). This difference was attributed to differences in intestinal environment of both species (caeca versus less anaerobic mid intestine) making E. maxima less vulnerable to oxidative stress (Allen et al., 1998). Although the immunomodulating and anti-inflammatory effects of ω-3 fatty acids are well documented and these substances are able to dampen the growth depressing effect of coccidiosis, a relation between their anti-inflammatory properties and effect on growth has not been found yet (Korver et al., 1997). 4.3.3. Micronutrients Micronutrients are generally necessary in small amounts for living and include minerals and vitamins. 4.3.3.1. Minerals Dietary minerals form the inorganic part of poultry feed and are needed in order to maintain the osmotic balance, as co-factors for enzymes, for cellular activity and skeleton physiology. They are available for immediate use after absorption and do not require digestion. Given in excess quantities some minerals can be toxic. Minerals that are needed in relatively large quantities such as calcium, salt (sodium and chloride), magnesium and potassium (along with phosphorus and sulfur) are also referred to as macrominerals. In contrast, those consistently needed in small amounts like iron, cobalt, chromium, copper, iodine, manganese, selenium, zinc and molybdenum are designated as microminerals or trace elements. 4.3.3.1.1. Macrominerals Calcium In contrast to a slight (1.5%) calcium overdose (Watkins et al., 1989), high dietary calcium concentrations (approx. 2% or higher) exceeding the optimum required in a poultry diet, consistently had a negative influence on the outcome of coccidiosis infections with both E. tenella or E. acervulina (Holmes et al., 1937; Zucker et al., 1967; Bafundo et al., 1984b). The activation of trypsine (important in excystation) by calcium, may explain the coccidiosis enhancing effect of high dietary calcium. A higher calcium supplementation (even slighty increased (1.5%)) had a negative effect on healthy birds in comparison with coccidiosis infected birds. This effect is probably caused by a reduced absorption of calcium in the coccidiosis infected birds (Watkins et al., 1989).

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47

Dietary buffers (NaHCO3, Al(OH)3, Al(OH)2NaCO3, kaolin, CaCO3, MgO). Fox and co-workers (1987) were the first to test the effect of various dietary buffers (NaHCO3, Al(OH)3, Al(OH)2NaCO3, kaolin, CaCO3, MgO) on an E. acervulina infection. Only NaHCO3 (1%) added to diet at the rate of 1% resulted in an improvement of the weight gain and feed conversion in infected chicks in comparison to uninfected controls. The positive effect of NaHCO3 was attributed to the electrolyte status of the diet and partial alleviation of the coccidiosis-induced acidosis. The effect of dietary NaHCO3 on coccidial challenge with E. acervulina, E. maxima and E. tenella and ionophore coccidiostats was studied by Hooge and others (1999). NaHCO3 levels of 0.2-0.4% yielded improvement in body weight, feed efficiency, coccidial lesion scores, liveability, carcass yield, breast yield and occasionally abdominal fat pad. NaHCO3 potentiated the effect of the ionophores salinomycin and monensin possibly by rapid early induction of immunity triggered by enhanced coccidial invasion of the intestinal wall as found for NaHCO3 and monensin by Augustine in 1997 (Hooge et al., 1999). Magnesium The effect of magnesium on a coccidiosis infection varies according to the form in which it is presented in the feed. An overexposure in the form as carbonate (0.6 or 1.2%) or sulfate (0.3%) did not have an effect on an E. acervulina infection; however, if presented as magnesium oxide (0.3%) it induced a reduction in performance possibly due to its laxative effect (Giraldo et al., 1987; Zucker et al., 1967). 4.3.3.1.2. Microminerals or trace elements Except zinc, which has a positive effect on weight gain of E. acervulina infected chickens (Bafundo et al., 1984b) and copper, that reduced E. tenella-induced mortality (Czarnecki & Baker, 1984; Zucker et al., 1967), most of the trace elements (like, cadmium, cobalt, copper, iron, lead, manganese) aggravate the effect of an E. acervulina infection by an increased absorption resulting in intoxications (Czarnecki & Baker, 1982; Southern & Baker, 1982, 1983; Bafundo et al., 1984a). Immunization of chickens against E. tenella coccidiosis is enhanced by selenium; moreover it reduces mortality and increases body weight in challenged birds (Colnago et al., 1984a). Jensen and co-workers (1978) previously observed similar positive effects of selenium on mortality after infection with six Eimeria spp. except E. necatrix. 4.3.3.2. Vitamins A vitamin is an organic molecule that is required in minute quantities for essential metabolic functions to preserve normal growth and health. Vitamins are bio-molecules, which are involved in chemical reactions as catalysts or as substrates. As catalysts they bind to enzymes as cofactor enabling specific chemical reactions. As coenzymes vitamins carry chemical groups between enzymes acting as substrates for these enzymes without forming permanent part of the enzyme structure. Based on their solubility, vitamins are classified in two groups: fat soluble and water soluble vitamins.


48

The fat soluble vitamins only dissolve in lipids and are found in association with fat in feed. Their intestinal absorption into the lymphatic system and blood circulation is promoted by the presence of fat. In chickens these vitamins can also be absorbed directly into the blood circulation due to the poor development of the lymphatic system. These vitamins can be stored in the liver and to a lesser extent in other tissues. The fat soluble vitamins are: vitamin A, D, E and K. The water soluble vitamins are readily dissolved in water and directly absorbed from the intestinal tract into the blood stream in order to reach the organs and tissues. They are available in every cell where they participate in metabolic functions by releasing energy from the nutrients. They are not stored in the organs or tissues and in excess they are easily excreted from the body. The water soluble vitamins are: vitamin B complex (B1, B2, B6, B12, niacin, pantothenic acid, folic acid, and biotin) and vitamin C. A number of vitamins like, biotin, thiamine, nicotinic acid, folium acid and riboflavin are known to be necessary for the complete development of the parasite within the host (Warren, 1968). Although the idea of using vitamin deficient diets to control coccidiosis seemed appealing, it proved unattainable as many vitamins are generated by the intestinal flora or the host (Banfield & Forbes, 1999). Vitamins as a strategy against coccidiosis infections were mainly studied in the period 1960-70. 4.3.3.2.1. Fat-soluble vitamins (A, D, E and K) Vitamin A has a positive effect on the growth performance, the reduction in mortality and oocyst excretion in E. acervulina or E. tenella infected chickens (Erasmus et al., 1960; Coles et al., 1970; Singh & Donovan, 1973). In agreement herewith, vitamin A deficiencies render chickens more susceptible to E. acervulina coccidiosis (Dalloul et al., 2002). This was explained by a reduction in gut immunity due to a decrease in intraepithelial lymphocyte (IEL) subpopulations, especially CD4+ cells, but also a reduction in the systemic immune response in vitamin A deficient birds (Dalloul, et al., 2002). Furthermore, although vitamin A is known to be essential for maintenance of the mucosal integrity as it plays an important role in the differentiations of epithelial cells (Chew & Park, 2004), a correlation between vitamin A levels in feed, intestinal epithelium changes and numbers of E. acervulina parasites, could not be found (Coles et al., 1970). High doses of vitamin D enhance E. tenella coccidiosis due to its immune suppressive properties (Sherkov & Denovski, 1964; Jiropongsananuruk et al., 2000; Becker et al., 2002). Vitamin E is the collective name of eight antioxidants, four tocopherols and four tocotrienols. α-Tocopherol is the most important one and is frequently found in nature. High doses of α-tocopherol (100 IU/kg instead of the 10 IU/kg recommended by the NRC, 1994) reduced the growth retardation of immunized birds and mortality in non-immunized chickens after a challenge with E. tenella (Colnago et al., 1984a). Mortality in non-immunized birds was also reduced in vitamin E supplemented animals after challenge with E. tenella (Jensen et al., 1978). An explanation for the obtained results is that vitamin E stimulates the innate and acquired immune response. In contrast to the previous results,

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49

diet supplementation with 25 or 225 mg/kg α-tocopherol did not affect the lesion scores and the amount of oocysts shed during an E. maxima infection (Allen & Fetterer, 2002a). These results are in accordance with earlier studies (Allen & Fetterer, 2002b) indicating that α-tocopherol supplemented in diets is not effective against an E. maxima infection. Adding γ-tocopherol to the diet at a concentration of 8 ppm and given to chickens infected with E. maxima improved the weight gain and reduced the amount of lesions, and oocyst excretion, but in case of an E. tenella infection no improvements were noticed (Allen et al., 1998) suggesting that α-tocopherol is more effective against E. tenella. The higher capability of γ-tocopherol to inactivate nitrogen dioxide in the intestine may provide an explanation for its superior activity against E. maxima (Cooney et al., 1993; Christen et al., 1997). Vitamin K is characterized by its coagulation promoting properties and has therefore been used to treat hemorrhages associated with coccidiosis and other diseases. Its supplementation reduced mortality induced by an E. necatrix and E. tenella infection, which are associated with blood loss, but no effect was found on growth, blood losses in faeces and hematocryt. Vitamin K had no effect on E. acervulina, E. brunetti or E. maxima infections (Baldwin et al., 1941; Ryley & Hardman, 1978). 4.3.3.2.2. Water-soluble vitamins (B and C) The B-vitamins are essential for the development of Eimeria parasites (Warren, 1968) and explains the coccidiosis enhancing effect of some of them. Hence, many anticoccidial drugs are antagonists of analogues of one or more representatives of the vitamin complex. Vitamin B1 increases E. tenella-induced mortality and oocyst shedding (Sherkov, 1976). In contrast, increasing the concentrations of PABA, a member of the vitamin B complex, had a coccidiosis impairing effect after a single (E. tenella) or a mixed species (E. tenella and E. maxima) infection (Warren, 1968; Waldenstedt et al., 2000b). Vitamin C is an antioxidant, which stabilizes membranes and could therefore be beneficial in coccidiosis. It has also been reported to stimulate cellular immunity (McKee & Harrison, 1995). Vitamin C is synthesized by chickens but under certain circumstances not in sufficient quantities. Animal model studies on the effect of vitamin C have yielded conflicting results. No effect on growth and mortality was found after E. maxima, E. necatrix, E. brunetti or E. tenella infection, however in a mixed infection model (E. acervulina, E. maxima, E. necatrix, E. brunetti and E. tenella) better growth was found after vitamin C supplementation, although mortality was enhanced (Little & Edgar, 1971). In layers, vitamin C supplementation reduced mortality and improved weight gain in E. tenella infected chickens (Attia et al., 1978). Using the same Eimeria spp. in broilers no effect was found on growth, although feed intake increased (McKee & Harrison, 1995).


50

4.3.4. Special additives Milk products Early treatment of coccidiosis was performed with milk products such as dry or liquid skim milk, buttermilk and condensed whey (Beach & Corl, 1925; Beach & Freeborn, 1927; Herrick & Holmes, 1936), which likely affect the intestinal flora. Although these products seemed to have an inhibitory effect against E. tenella (Beach & Corl, 1925), later on the effect of dried buttermilk could not be demonstrated unambiguously by Becker & Wilcke (1938). Egg albumen The value of egg albumen as a feed additive to control coccidiosis needs further research in view of the conflicting results obtained in a few experimental studies. The addition of egg albumen and thiamin (vitamin B1) to the feed of E. tenella infected chickens seems to have a coccidiosis promoting effect, most probably due to the presence of thiamin (Sherkov, 1976). However, in other studies, after adding egg albumin to the feed of E. acervulina, E. tenella and E. maxima infected chickens lower oocyst shedding was observed (Prasad, 1963; Warren & Ball, 1967) possibly due to the biotin (vitamin B7 essential for the coccidiosis parasite) binding properties of the protein avidin, which is available at high levels in egg albumin. Semipurified feed Considering the origin of basic feed ingredients three types of poultry feeds exist: natural, semisynthetic (semipurified) and synthetic. In the semisynthetic feed, a part of the natural basic ingredients has been substituted by purified ingredients and (chemically synthesized) nutrients, whereas in synthetic diets all basic ingredients are of purified origin and single nutrients are included. The greater the synthesized part of the feed is, the more constant its composition is, however its costs increase parallelly. Compared to a corn-soybean feed, a semipurified diet appeared to ameliorate an infection with E. tenella in chickens but not mixed infection with E. acervulina, E. maxima and E. brunetti) (Colnago et al., 1984c). In agreement with previous study, Koltveit (1969) obtained similar results for E. tenella earlier. Named scientist showed a spectacular reduction in E. tenella mortality in birds given a semipurified diet compared to a ration of natural feedstuffs, although clinical signs (onset and duration of bloody diarrhea, anorexia and depression) did not differ between both diets. It suggested that natural feedstuffs contain an unidentified ingredient(s) that enhances E. tenella lethality.

Table 11. Overview of the influence of feed components including, the active compound, dose and mode of action, on a coccidiosis infection in poultry Feed component Active compound & dose Mode of action Coccidiosis model Effect on clinical

parameters Global effect*

Reference

Eimeria spp. Infection dose (# oocysts)

Cereals Maize/corn 50, 100 and 200 g/kg Unknown E. tenella 2 x 105 Mort**

BWG** + Colnago et al., 1984b

Maize Vitamin A (x 1.8) Vitamin E (x 1.7)

Stimulating intestinal health & immunity

E. tenella 5 x 104 Mort - Williams, 1992a Warren, 1968

Wheat Niacin (x 2) Riboflavin (x 1.3)

Enhancing parasite development

E. tenella 5 x 104 Mort + Williams, 1992a Warren, 1968

Maize/wheat + soluble arabinoxynol (different levels enzymes)

Reduced viscosity Mixed infect. E. tenella E. acervulina

5 x 103 5 x 104

LS** BWG

Maize (-) Wheat (+)

Morgan & Catchpole, 1996

Wheat

Whole wheat (200-400 g/kg)

Increased viscosity E. acervulina 1.5 x 105 FCE** OPG** =

+/- Banfield et al., 2002

Wheat Whole wheat (400 g/kg) Increased digestive efficiency by modification of intestinal physiology (improved hydrolyses, absorption due to more beneficial microflora)

E. acervulina E. maxima E. tenella

2.5 x 105 5 x 103 2 x 104

BWG OPG

+ Gabriel et al., 2003 Gabriel et al., 2006

Macronutrients Carbohydrates Mono- and disaccharides

(≥ 500 g/kg) Changing intestinal flora E. tenella Severe BWG

OPG + Matsuzawa, 1979

NSP Fibres, 100 g/kg (crude fibre content)

Increased intestinal flora E. tenella ? Mort Haemorrhages

+ Mann, 1947

NSP Fibres 33, 66 and 99 g/kg (cellulose)

Increased intestinal flora E. tenella 2 x 105 No difference = Koltveit, 1969

NSP Fibres 90 g/kg Increased intestinal flora E. tenella E. acervulina

? OPG LS =

- Muir & Bryden, 1992

NSP Zymosan (β-glucans) Immune stimulation E. tenella ? OPG + Smith & Ovington, 1996 Proteins 130 g/kg (low) Decreased trypsin activity E. tenella ? LS - Mann, 1947 Proteins 0-50 g/kg (very low) Decreased trypsin activity E. tenella ? LS

Mort - Britton et al., 1964

Protein 160, 200 and 240 g/kg Increased trypsin activity E. acervulina E. tenella

105 104

Both species BWG and FCE

E. ac OPG E. ten Mort

+/- Sharma et al., 1973

Lipids (corn oil)

Unsaturated fatty acids Enhanced parasite development (reproduction) & influencing intestinal mucosa for the expression of pathology

E. mivati E. tenella

106 105

LS Mort

+ Charney et al., 1971

Lipids (coconuts oil)

Medium chain saturated fatty acids (saturated fatty acids)

Influencing intestinal mucosa for the expression of pathology

E. mivati E. tenella E. acervulina

106 105

6 x 105

LS Mort BWG

- -

Charney et al., 1971 Adams et al., 1996

Lipids (fish and flaxseed oil)

ω-3 fa (25, 50 and 100 g/kg)

Immune stimulation & reducing parasite development by oxidative stress

E. tenella E. maxima

5 x 104 5 x 104

LS BWG LS =

-

=

Allen et al., 1996 Allen et al., 1997a Korver et al., 1997 Allen et al., 1998

Macrominerals Calcium Ca (10, 15, 18, 20 or 27

g/kg) Increased trypsin activity E. acervulina

E. tenella Different doses

Mort BWG

+ Holmes et al., 1937 Zucker et al., 1967 Bafundo et al., 1984b

Buffers NaHCO3 (10 g/kg) Decreased coccidiosis-induced acidosis

E. acervulina

106, 5 x 105 BWG FCE

- Fox et al., 1987

Buffers NaHCO3 (2 to 4 g/kg) Potentiation ionophores & immune stimulation

E. acervulina E. maxima E. tenella

105 5 x 104 104

BWG FCE Mort LS

- Hooge et al., 1999

Microminerals Selenium Se (0.00025 to 0.001

g/kg) Immune stimulation by protection leucocytes during phagocytic activity

Six Eimeria spp. except E. necatrix

? BWG Mort

- Colnago et al., 1984a Jensen et al., 1978

Vitamins Vitamin A A (various from 4400 to

8000 IU/kg) Stimulation intestinal health & immunity

E. acervulina E. tenella

Various BWG Mort OPG

- Erasmus et al., 1960 Coles et al., 1970 Singh & Donovan, 1973 Dalloul et al., 2002

Vitamin D D (high) Immune suppression E. tenella ? ? + Sherkov & Denovski, 1964

Vitamin E E (100 IU/kg) Immune stimulation by reduction in synthesis of prostaglandins

E. tenella 1.5 x 105 BW

? M

? M + Sher

G Mort

- Colnago et al., 1984a

Vitamin E E (0.025 or 0.225 g/kg α-tocopherol)

Immune stimulation*** E. maxima Mild & severe BWG LS =

= Allen & Fetterer, 2002a Allen & Fetterer, 2002b

Vitamin E E (0.008 g/kg γ-tocopherol)

Inactivation of reactive nitrogen radicals

E. maxima E. tenella

? ?

BWG LS OPG No effect

-

=

Allen et al., 1998

Vitamin K K Enhanced coagulation intestinal mucosa

E. tenella E. necatrix

ort - Ryley & Hardman, 1978

Vitamin C C Stimulation immunity & healing intestinal mucosa

Eimeria spp. ? Conflicting results

+/- Little & Edgar, 1971 Attia et al., 1978 McKee & Harrison, 1995

1976 Vitamin B B (0.1 g/kg) Enhanced parasite development (schizogony (E. acervulina) & (gametogony (E. tenella)

E. tenella ort OPG

kov,

Special additives Milk products Dry or liquid skim and

buttermilk, condensed whey (as drinks or dry in the feed (100 and 400 g/kg)

Changed intestinal flora E. tenella E. tenella

? 105

Mort Mort

-

+

Beach & Corl, 1925 Becker & Wilcke, 1938

* - sign indicates that the component has an inhibiting effect on coccidiosis, + sign indicates that the component promotes coccidiosis and = indicates no effect on coccidiosis. ** BWG = body weight gain, FCE = feed conversion efficiency (g weight gain/g food intake), LS = lesion scores, Mort = mortality, OPG = oocysts per gram faeces. *** malabsorption (caused by the coccidiosis infection) prevented access of dietary vitamin E and thus immunity stimulation does not occur.


54

4.4. Toxins in feed Mycotoxins Mycotoxins are poisonous secondary metabolites produced by various species of moulds and yeasts developing in the feeds and bedding of animals. A great variety of mycotoxins (about 300 to 400) have been described and they may affect animal health and production differently. Due to their great resistance to decomposition, digestion and various treatments (high temperatures and cooking) mycotoxins can remain in the food chain. The major mycotoxins are: aflatoxins, citrinin, ergot alkaloids, fumonisins, ochratoxins, patulin and trichothecenes. Various feed components (e.g. corn, wheat, oats) are susceptible to moulds and should be tested regularly for the occurrence of mycotoxins. Even very low concentrations of mycotoxins in feed can result in a reduction of feed intake, but also in immune suppressed birds (Conway, 1996). Aflatoxins are produced by many species of Aspergillus. They are toxic and carcinogenic, and have been shown to enhance coccidiosis, especially E. tenella. Their influence on blood clothing explains the increased mortality associated with greater caecal bleedings found when aflatoxins are given to E. tenella infected birds (Edds et al., 1973; Wyatt et al., 1975; Witlock & Wyatt, 1978). In E. acervulina infection, aflatoxins provoked strong growth retardation, bad feed conversion and lesser pigmentation (Ruff, 1978; Southern et al., 1984). A negative influence of dietary aflatoxin on coccidiosis infected quails has also been described: aflatoxin supplemented and coccidiosis infected quails had higher mortality, coccidial lesion scores and oocyst shedding (Awadalla, 1998). Ochratoxins are produced by fungi of the genus Aspergillus and Penicillium and are mainly nephrotoxic. Most common is ochratoxin A, which has been shown to enhance an E. tenella or E. acervulina infection in chicks characterized by greater kidney function impairment, histopathological changes of organs and growth depression (Stoev et al., 2002; Koynarski et al., 2007). T-2 fusariotoxin, which belongs to the type A trichothecenes, is produced by various species of the genus Fusarium and may cause damage of cell membranes, structural lipids and inhibit protein (inhibition of peptidyl-transferase), DNA and RNA synthesis. T-2 fusariotoxin has been reported to negatively influence the efficacy of monensin in coccidiosis infected chickens (Ványi et al., 1989) and of lasalocid in E. tenella and E. mitis infected cockerels (Varga & Ványi, 1992). Mycotoxins have also been shown to impair the efficacy of some anticoccidial products. Aflatoxins reduced the effect of monensin on an E. tenella infection, although the efficacy of amprolium was not altered (Edds et al., 1973, Wyatt et al., 1975). In case of an E. acervulina infection the action of monensin was not influenced either (Southern et al., 1984).

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4.5. Feed management 4.5.1. Feed restriction Feed restriction is frequently applied to commercial poultry, especially reproduction broilers in order to control growth. During the past decades broilers have been genetically selected for increased growth rate and lower feed conversion. In order to allow reproduction broilers to survive until egg production and warrant longevity by avoiding health disorders associated with obesity (skeletal disorders, heart failure, thermal discomfort, reduced disease resistance, multiple ovulations, lower fertility of males, etc.), these birds need to be fed restricted. It is nevertheless believed to compromise seriously the welfare of chickens and ought to be discouraged. The use of slower-growing genotypes would render feed restriction unnecessary (SCAHAW, 2000). Feed restriction has been shown to have an inhibitory effect on E. tenella infections. It is thought to improve the immune response after the initial stress induced by restricted feeding has vanished. Indeed, White Plymouth Rock chickens that had been feed restricted three weeks before an infection with E. tenella showed less coccidiosis lesions compared to their ad libitum fed counterparts (Zulkifli et al., 1993). Another explanation for the greater resistance of feed restricted birds is the lower production of trypsin, which contributes to excystation of sporozoites in these chickens (Britton et al., 1964; Nir et al., 1987). In contrast to the results obtained with E. tenella during feed restriction, increased coccidiosis lesions were seen in feed restricted broilers infected with E. acervulina, E. maxima and E. tenella and supplemented with anticoccidial drugs (salinomycin or monensin) suggesting that higher levels of anticoccidial drugs are necessary during feed restriction (McNaughton et al., 1990). In model studies using E. maxima, Newcombe and others (1992) also found significantly higher coccidiosis lesion scores in male broilers subjected to feed restriction. More recently in another study, changing the protein concentration (15 or 19% CP) to restrict-fed broiler breeder pullets, did not influence mild coccidial infections induced via the administration of commercial anticoccidial vaccines (Yaissle et al., 1999).


56

inte

stin

al fl

ora

& m

ucos

a

immunity

Extra

inte

stin

al e

nviro

nmen

tIn

test

inal

lum

en

±±

±

viscosity

trypsine activity

proteinscalcium

±±

cornwheatwhole cereals

fibers (NSP)milk products

vitamin Kmedium chain FA

EFA

+

+

+

+

+

±

±

+

vitamin A, C

+

+

β-glucansvitamin Eγ-tocopherolselenium

+

vitamin D -

vitamin B

ionophores

ω-3 FA

+

+

+

-

aflatoxins

NaHCO3+

-

+-

feed restriction

+±

+

Figure 2. Vitamin B, essential fatty acids (EFA) and aflatoxins seem to influence the development of the Eimeria parasite positively. Moreover, aflatoxins also have a negative effect on the activity of ionophores. Therefore, the first two products should be avoided in excess and aflatoxins completely. Ionophores and ω-3 fatty acids (ω-3 FA) influence the development of the Eimeria spp. negatively. Sodium bicarbonate (NaHCO3) has a positive effect on the ionophores resulting in a negative effect on the development of the coccidiosis infection. Proteins and calcium may have, depending on their concentration in the feed, an indirect positive or negative effect on the development of the parasite. The viscosity, the intestinal flora & mucosa of the digestive tract may have a variable influence on the development of the parasite. The viscosity of the intestine content can be influenced by the presence of corn, wheat and whole cereals. These components can together with fibers (NSP) and milk products influence the intestinal flora. Additionally, the availability of whole cereals instead of ground cereals may influence the physiology of the digestive tract. The Eimeria parasite may induce lesions and hemorrhages in the intestinal mucosa. Components like vitamin K and medium chain fatty acids (FA) have a positive effect on the intestinal mucosa and coccidiosis-induced lesions by promoting coagulation and healing. Vitamin A and C have a positive influence on the intestinal mucosa and the immune system. Furthermore, β-glucans, vitamin E, γ-tocopherol, selenium and ω-3 FA also stimulate the immune system. Feed restriction showed conflicting results on the development of Eimeria.

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5. Other preventive strategies against coccidiosis 5.1. Introduction The prevention and control of coccidiosis in commercial poultry and mainly broilers is largely based on the administration of anticoccidial drugs in feed, although in some cases an anticoccidial drug administered shortly via drinking water is applied. Moreover, biosecurity measures aiming at preventing the introduction of the parasite to the farm can be of additional strategic value against clinical coccidiosis. During the last decade, live coccidiosis vaccination has become increasingly popular as an alternative strategy to control Eimeria. In feed products with supposed anticoccidial activity like herbs, essential oils, probiotics and prebiotics represent additional alternative strategies. Control of coccidiosis by means of feed composition and structure, which could also have been considered here, has been discussed previously (section 4).

The quest for alternative strategies for the control and prevention of coccidiosis has been propelled by increasing concerns of consumers on food safety. This has resulted in a loud call for residue-free poultry products, which in Europe has first been translated into a re-evaluation of all existing anticoccidial products and regulations safeguarding lower residues. It has also favoured politic debates on the use of in feed medication in general. Currently, the future status of anticoccidial drugs is uncertain: their status as feed additives may be maintained or new legislation and phasing-out of these drugs as feed additives could be proposed. Another contributing factor to the search for alternative control and prevention strategies has been the development of resistance against all in feed anticoccidial drugs used to date. 5.2. Management and biosecurity Good health and hence optimal immune response is essential in order to minimize the impact of infectious diseases. General management measures safeguarding the basic requirements of poultry should therefore always be implemented: birds should be provided with proper feed and drinking water intake, adequate bedding, temperature, humidity, lighting and ventilation. Management and biosecurity measures for the control of coccidiosis should focus on preventing the introduction of the parasite to the premises, which is almost impossible under practical circumstances, and control its multiplication and spread in case flocks have been infected. In the early days of coccidiosis research Johnson and Tyzzer (1920) already stressed that management and the environmental factors are very important in the incidence and epizootiology of coccidiosis (Chapman, 2003). This has become common knowledge and was more recently confirmed by Graat and others (1998) who quantified risk factors of coccidiosis in broilers using on-farm data based on a veterinary practice and statistical modeling following a case-control design. They found an enhanced risk of


58

coccidiosis due to environmental and management factors that increase the risk of introducing contamination or that are related to hygienic measures. 5.2.1. Avoiding the introduction of the parasite Eimeria parasites are ubiquitous and have enormous reproduction capabilities leading to high contamination levels of infected poultry houses and their surroundings. Moreover, the oocyst wall protects the parasite from desiccation and chemical disinfectants ensuring long-term survival in the environment from which it may be introduced to a farm through a variety of ways such as personnel, equipment, rodents, insects, etc. (Belli et al., 2006). Also contaminated water, feed and bedding can be a source of infection. On the other hand, oocysts may already be present in the farm house if cleaning and disinfection was not adequate. It is very difficult for infected premises to achieve freedom from coccidiosis as one oocyst, containing four sporocysts with each two sporozoites, is sufficient to start infection (see section 1.4 “Life cycle of avian Eimeria spp.”). Biosecurity measures aiming to prevent the introduction of Eimeria parasites to the farm are similar to those applied for the prevention of other infectious poultry diseases and should focus on:

1. Isolation. Birds should be separated from the environment by fencing and other animals including rodents and insects should be kept out.

2. Traffic control should not only be performed at the farm, but also traffic between farms should be restricted.

3. Sanitation includes disinfection of materials, people and equipment entering the farm and poultry house.

5.2.2. Control of coccidiosis on infected premises If performed adequately, cleaning and disinfection between flocks and maximizing the downtime period should reduce significantly the number of parasites in contaminated chicken houses, while biosecurity measures should prevent additional introductions. However, in practice it is almost impossible to keep poultry free of coccidiosis unless birds are housed under SPF-like housing conditions. 5.2.2.1. Environmental factors In case coccidiosis infections occur, their multiplication can not be restricted by influencing the climate environment of the chicken house as Eimeria thrives in atmospheric conditions that are beneficial to the birds also. In order for Eimeria to become infective, it must sporulate after excretion in the faeces. The degree and rate of sporulation of excreted oocysts determine the infection pressure in a chicken flock. Sporulation of the oocyst depends mainly on the following basic factors: temperature, humidity and aeration (access to oxygen) (Kheysin, 1972). The best sporulation temperature is approx. 24-28 ºC (Edgar, 1955), while a temperature above 35 ºC is lethal for oocysts (Schneider et al., 1979). Due to the fact that the ideal

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59

sporulation temperature is within the range of temperatures frequently encountered in the poultry environment and that high temperatures are detrimental to the birds, temperature is not a factor that can be used to control parasite multiplication. A general misconception, regarding humidity is the belief that the drier the climate, the less coccidiosis occurs. Research data have shown that in the field sporulation in wet litter is suboptimal possibly due to the occurrence of ammonia and bacteria (Williams, 1995); in fact, dry litter showed better sporulation rates (Graat et al., 1994; Waldenstedt et al., 2001). However, increasing the litter humidity as a control measure to reduce sporulation does not seem feasible as it might cause footpad lesions and skin burns in the birds. Adequate ventilation of the poultry house is essential for good performance and health of the birds although proper aeration will also favour sporulation. Theoretically, a higher bird density will result in greater oocyst accumulation in the litter and increase the chances of clinical coccidiosis (Williams et al., 2000). Thus, reducing bird density could help to control Eimeria infections. In order to prevent clinical coccidiosis it is essential that the birds have adequate access to the medicated feed. It is also vital that Eimeria spp. field strains concerned are sensitive to the anticoccidial drugs used, which underlines the necessity to perform AST on a regular basis. Moreover, rotation and shuttle programs eventually alternated with vaccination should be used to minimize the occurrence of resistance (see section 3). 5.2.2.2. Cleaning and disinfection Cleaning and disinfection between flocks and maximizing the downtime period is important in order to reduce significantly the number of parasites in contaminated chicken houses. However, there are mixed points of view regarding the use of cleaning and disinfection for the control of coccidiosis. Some consider that the presence of oocysts in the poultry environment enabling early establishment of immunity in order to avoid outbreaks at later age, beneficial. In case coccidiosis vaccines are used to repopulate the houses with drug sensitive strains, survival of vaccine parasites between vaccinated and non-vaccinated flocks is desired and therefore cleaning and disinfection should be skipped. Nevertheless, in case of severe clinical coccidiosis outbreaks especially due to anticoccidial drug resistant strains, it is customary in Europe, where birds are not housed on deep litter, to clean and disinfect the chicken houses in order to reduce infection pressure. The oocyst wall makes the parasite resistant to many disinfectants and environmental conditions. They are nevertheless sensitive for desiccation and high temperatures (Ryley, 1973). Despite the protecting capabilities of the oocyst wall, a limited number of chemical products is able to penetrate the oocyst through small pores, which are crucial for the access of oxygen. Lipid-soluble substances and small molecules, including ammonia, methyl bromide and carbon disulphide have been reported to penetrate the oocyst (Kheysin, 1935; Monné & Hönig, 1954; Ryley, 1973; Kuticic & Wikerhauser, 1996). Due to their toxicity, methyl bromide and carbon disulphide can not be used as disinfectants against Eimeria.


60

Ammonium hydroxide has been reported as a highly effective disinfectant against sporulated and non-sporulated oocysts. It has been shown to be effective at a concentration of ≥ 5% in both fluid and vapour form (Chroustova & Pinka, 1987). Also products that generate ammonia after mixing two components (ammonium salt and sodium hydroxide) have shown to be oocidal (Oocide®, Antec International Ltd, UK). More recently a cresol-based product (Neopredisan® 135-1, Menno Chemie, Norderstedt, Germany) has been marketed in Germany for the control of coccidiosis by chemical disinfection: a concentration of 4% and a contact time of 2 hours is advised. It has been shown to be efficient against E. tenella (Daugschies et al., 2002) and other Eimeria spp. (Houdek et al., 2002). In a recent study the efficacy of eight disinfectants against E. tenella unsporulated oocysts isolated from broilers was studied in vitro. The best disinfection efficacy was observed for the combination formol 37% and sodium dodecylbenzene sulfonate 12%; orthodichlorobenzene 60% and xylene 30%, and sodium hypochloride 2%, being 79.49%, 75.60%, 63.56%, respectively (Gumarães et al., 2007). There are no disinfectants specifically registered against coccidiosis in Netherlands. However, in practice, poultry houses are disinfected using calcium hydroxide in combination with ammonium sulphate (per 500 m2 40 kg calcium hydroxide is spread and subsequently moisturized with approximately 500 l water, after which 80 kg ammonium sulphate is added). Ammonium, which is lethal to the oocysts, is generated at combining the afore mentioned products. 5.3. Alternative coccidiosis control Various alternative methods like homeopathy, phytotherapy and aromatherapy have been used during the past decennia for the treatment of various poultry diseases. Homeopathy is a system for treating disease based on the administration of minute doses of a drug that in massive amounts produces clinical signs in healthy individuals similar to those of the disease itself. The treatment is thus based on law of similars, i.e. similia similibus curentur = the most similar remedy will cure (Saine, 2000). It is thought to enhance the body’s natural defenses. Homeopathy is often confused with herbalism also known as botanical medicine, medicinal botany, medical herbalism, herbal medicine, herbology and phytotherapy. It is based on the use of plant and plant extracts for the treatment and prevention of disease. Its scope is sometimes extended to include fungi, bee products, minerals, shells and certain animal parts. Aromatherapy, which is closely related to phytotherapy, is the treatment or prevention of disease by means of essential oils, and other scented compounds from plants. It involves the use of distilled plant volatiles, a twentieth century innovation. Essential oils differ in chemical composition from other herbal products because the distillation process only recovers lighter phytomolecules. Although many papers have been published on the efficacy of homeopathic treatment in humans, its effectiveness has remained a matter of debate to the scientific community. Studies assessing the methodological quality of a large number of human homeopathic experiments report a lack of evidence for efficacy of homeopathic treatments because of

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frequent low methodological quality and publication bias (Kleynen et al., 1991; Linde et al., 2001). According to Velkers and others (2005) ‘Efficacy of medicines should be beyond placebo effect and observation and interpretation should be without subjective elements. Therefore, all medicines, including homeopathic remedies, should be tested in a double blind randomized clinical trial’. Published studies on homeopathy in poultry are rare and similar to human studies are frequently affected by low methodological quality (Velkers et al., 2005). There are no scientific reports on the homeopathic treatment of coccidiosis. Some plant products or derived pharmaceutical drugs have been incorporated into mainstream medicine; nevertheless most herbal treatments have been developed without modern scientific assessment. Although later on many herbs have been found efficacious in in vitro, animal models and/or clinical studies (Srinivasan, 2005), there are also many studies showing negative results (Pittler et al., 2000). However, evaluation of the literature on complementary/alternative therapies is difficult due to the occurrence of location bias in the corresponding controlled clinical trials. More positive than negative trials are published, except in high-impact mainstream medical journals. Further, in complementary/alternative medicine journals positive studies are of poorer quality than corresponding negative studies. The latter was not the case in mainstream medical journals publishing on a wider range of therapies. Pre- and probiotics have also been included within alternative coccidiosis controls strategies although they are quite distinct from phyto- and aromatherapy. Probiotics consist of in feed administered live bacteria or yeasts, which are supposed to be beneficial for the individual’s health. In contrast, prebiotics are non digestible food ingredients, however, they also have a beneficial effect on the host health. 5.3.1. Plant (herb) extracts Many different herbal compounds have been investigated for their potential use as a dietary supplement to control coccidiosis and are reported next in alphabetical order. The main conclusions obtained in the research of alternative coccidiosis control have been summarized in Table 12 and Figure 3. 5.3.1.1. Artemisinin Artemisinin is a herbal extract, which can be obtained from Artemisia annua (annual wormwood) and A. sieberi. Its antimalarial activity in humans has been attributed to the ability to induce oxidative stress through the production of free radicals and to alkylate proteins (Klayman, 1985; Krungkrai & Yuthavong, 1987; Levander et al., 1989; Meshnick et al., 1989; Yang et al., 1994). To date only three manuscripts on the effect of artemisinin on coccidiosis in poultry have been published. The first study was reported by Oh and others (1995), who described improved weight gain and feed conversion as well as a reduction in lesion scores after an E. tenella infection in chickens supplemented with A. annua extracts. Later on, Allen and co-workers (1997b) showed that dried leaves of this plant at a dietary concentration of 5%


62

(equivalent to 17 ppm pure artemisinin) during three weeks provided a significant protection against lesions of E. tenella but not against lesions of E. acervulina and E. maxima. However, when pure artemisinin was fed for a period of 4 weeks at levels of 2, 8.5 and 17 ppm it significantly reduced oocyst output from single and dual species infection of E. tenella and E. acervulina. No reduction in oocyst excretion was notified in case of an E. maxima infection. Thus, artemisinin proved to be effective against at least two Eimeria spp. (Allen et al., 1997b). In another study it was shown that artemisinin isolated from A. sieberi was also active against E. tenella and E. acervulina but not against E. maxima (Arab et al., 2006), which is in agreement with the other studies mentioned above. 5.3.1.2. Betaine Betaine is a sweet crystalline alkaloid (trimethylglycine C5H11NO2), choline analogue and methyl donor occurring in sugar beets and other plants, which is used in the treatment of certain metabolic disorders (muscular weakness and degeneration). It has been shown to protect cells against osmotic stress by stabilizing cell membranes enabling the maintenance of osmotic pressure in the cells and ensuring normal metabolic activity (Rudolph et al., 1986). The osmoprotective effect of betaine is not restricted to the intestinal cells, but also affects developing stages of the coccidia. It protects different cell types against chemical and environmental stress (Kunin & Rudy, 1991), including the asexual stages (sporozoites) of E. acervulina against the destructive action of salinomycin (Augustine & Danforth, 1999). Nevertheless, feed efficacy and weight gain was significantly improved in birds infected with a mixture of E. acervulina, E. maxima and E. tenella if betaine (0.15%) and salinomycin (44 or 66 ppm) were supplemented separately, but much more if both components were given together suggesting a palliative effect of betaine on the coccidiosis infection. Betaine alone did not influence the severity of lesions scores and mortality (Augustine et al., 1997). Both products alone or in combination inhibited the invasion of E. acervulina and E. tenella (sporozoites) and the development of E. acervulina (second generation schizonts). The ionophore amplifying effect of betaine was only observed once and could not be found with other anticoccidial ionophores drugs like monensin and narasin in experiments performed by other scientists (Matthews et al., 1997; Waldenstedt et al., 1999). Waldenstedt and others proved that betaine, used as a single feed supplement also improved the weight gain of chickens infected with a mixture of Eimeria spp., but given in combination with narasin no positive effect could be achieved. Improvement of weight gain was also found in betaine supplemented birds infected with E. maxima, but not in E. acervulina or E. tenella infected birds (Fetterer et al., 2003), which seems in contradiction with the results obtained earlier. The weight gain and feed conversion promoting capabilities found in some studies may be explained by betaine’s osmoprotectant properties ensuring normal metabolism of intestinal cells. This may warrant normal development of the chicks despite the fact that the coccidiosis infection is not fully halted. Another contributing factor to the positive effect of betaine on coccidiosis infection may be the fact that it increases intraepithelial

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lymphocytes in the duodenum and the functional properties of phagocytes of Eimeria infected chickens (Klasing et al., 2002). 5.3.1.3. Citric Extracts A product based on citric extracts and organic acids amongst others supplemented to broilers showed a moderate efficacy against a challenge with various Eimeria spp. (E. acervulina, E. maxima, E. tenella, E. brunetti and E. mivati) considering coccidiosis lesion scores and oocyst production (Tamasaukas et al., 1997). In a previous study by the same group, extracts obtained from seeds of citric fruits also showed anticoccidial activity but not against E. tenella (Tamasaukas et al., 1996). 5.3.1.4. Echinacea purpurea The anticoccidial effect of Echinacea purpurea has been attributed to its immunomodulating properties, which have been widely documented (Stimple et al., 1984; Burger et al., 1997; See et al., 1997; Sun et al., 1999; Currier & Miller, 2001; Goel et al., 2002). In veterinary medicine Echinacea therapy has been reported in horses (O’Neill et al., 2002), swine (Stahl et al., 1990) and cattle (Schuberth et al., 2002), and more recently in chickens against coccidiosis. Ground root preparations of E. purpurea (0.1% - 0.5%) supplemented to broilers during two weeks reduced weight gain retardation and coccidial lesions after a mixed challenge infection at the age of 28 days with E. acervulina, E. maxima, E. tenella and E. necatrix (Allen, 2003). 5.3.1.5. Gentian violet Gentian violet also named crystal violet, methyl Violet and hexamethyl pararosaniline chloride is known for its antifungal and antibacterial properties, but also for its use in diagnostic bacteriology as part of the Gram stain test. It is not derived from gentians, but got its name since it is pink-violet like some gentians in the genera of Centaurium, Gentiana and Gentianella. Gentian violet is derived from coal tar. Gentian violet has been shown to reduce coccidiosis lesion scores in the duodenum and improve weight gain in Eimeria spp. challenged birds. In combination with anticoccidial drugs it improved feed conversion (Sharkey, 1978). 5.3.1.6. Mushrooms and their extracts Mushrooms and their extracts have gained interest in medicine and as dietary supplement due to their immune enhancing and antitumor properties. However, they should be used cautiously as mushrooms may harbour toxic levels of metals (arsenic, lead, cadmium and mercury) and radioactive contamination with 137Cs (Borchers et al., 2004). Polysaccharide extracts originating from Lentinus edodes and Tremella fuciformes as well as the herb Astragalus membranaceus showed a positive effect on the cellular and humoral immunity of E. tenella infected female broilers (Guo et al., 2004). In another study, the same extracts yielded better growth during immunization in comparison with the non-treated vaccinated birds. During challenge with E. tenella,


64

broilers supplemented with these mushroom extracts showed similar lesion scores as the vaccinated only birds, however they had lower oocyst countings (Guo et al., 2005). Extracted lectin from the mushroom Fomitella fraxinea injected in 18 day-old embryos, protected broilers inoculated with E. acervulina at one week post-hatch against weight loss and was associated with a significant reduction in oocyst shedding compared to untreated embryos. The mushroom lectins showed potent mitogenic activity on chicken splenic lymphocytes, they induced NO secretion in HD11 macrophages and suppressed tumor cell growth. This study suggested that the used lectines act as immunopotentiators of the innate immune response and could be used as an alternative anticoccidiosis strategy (Dalloul et al., 2006). 5.3.1.7. Oregano The essential oils of Origanum vulgare are known for their antibacterial activity (Hammer et al., 1999) and effect against some parasites (Milhau et al., 1997). Furthermore, some essential oils of oregano, mainly carvacrol and thymol, have an anticoccidial effect against E. tenella although lower than lasalocid (Giannenas et al., 2003). However, in subsequently performed studies with diets supplemented with a mixture of the essential oils, oregano thymol, eugenol, curcumin and piperin a beneficial effect of these oils on a coccidiosis vaccination was not found (Oviedo-Rondón et al., 2006). 5.3.1.8. Turmeric (Curcuma longa) Turmeric is a spice and colorant made from the rhizomes of the plant Curcuma longa, a leafy plant belonging to the ginger family. The rhizomes are boiled for several hours and then dried in ovens, after which they are ground into a deep orange yellow powder commonly used as a spice in curry. Turmeric is also known for having medical properties. Its medicinally active compound is the phenolic compound curcumin, which has been shown to have antioxidative, anti-inflammatory and antitumour properties (Mukhopadhyay et al., 1982; Conney et al., 1991; Ammon et al., 1993; Brouet & Ohshima, 1995). E. maxima infected chicks fed diets supplemented with 1% curcumin showed an improved weight gain and a reduction in the lesion scores and oocyst excretion. Nevertheless, the activity was only shown against E. maxima and not against E. tenella. A significant reduction of plasma NO2

¯ and NO3¯ was only found in E. maxima infected and curcumin

treated birds and provide a possible explanation for the difference in anticoccidial activity found for both Eimeria spp. (Allen et al., 1998). A similar effect on lesion scores, oocyst shedding, growth and plasma NO2

¯ and NO3¯ was found for γ-tocopherol. The

antioxidative properties of curcumin by inhibiting NOS induction by macrophages stimulated with lipopolysaccharide and interferon-γ, has been shown previously (Brouet & Ohshima, 1995). Although NO is an important defence mechanism against the invasion of different Apicomplexa parasites (Adams et al., 1990; Mellouk et al., 1991) it was suggested more recently that NO might promote the development of coccidial lesions (Allen, 1997a, b).

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5.3.1.9. Incidental reports on the anticoccidial activity of other herb(s) extracts A product prepared from Holarrhea pubescens, Berneris aristata, Embelia ribe and Acorus calamus was reported to be active against E. necatrix when supplemented to the diet at a concentration of 0.6% (Mandal et al., 1994). Preparations of Persian lilac (Melia azedarach) and the bitter melon (Momordica charantia) were shown to improve the weight gain retardation and reduce the oocyst excretion after an infection with different Eimeria spp. (Hayat et al., 1996). Fifteen different Asian plants were screened for their anticoccidial activity against E. tenella. A number of these extracts seemed to have a beneficial effect. The mortality, bloody diarrhea, clinical signs, lesion scores, body weight gains and oocyst excretions were mostly influenced positively by the extract of the rhizomes of Sophora flavescens, a small species of tree. Extracts of the seeds and barks of the elm (Ulmus macrocarpa) and the rhizomes of the Korean anemone (Pulsatilla koreana) reduced only the mortality and the coccidial lesions. The nuts of the Chinese honeysuckle (Quisqualis indica) improved the weight gain and extracts of the trunks and the roots of the deciduous climber plant Sinomenium acutum decreased the bloody diarrhoea. Both extracts of Quisqualis indica and Sinomenium acutum delayed the oocyst excretion period with one or two days (Youn & Noh, 2001). The anticoccidial activity of the fruits of the neem tree (Azadirachta indica) was investigated in comparison with salinomycin against an E. tenella infection. The results showed that neem fruits at a concentration of 150 g/50 kg feed had excellent performance in reducing the oocyst excretion and mortality as compared to the salinomycin treated group (Tipu et al., 2002). Using a herbal complex consisting of eight different herbs (Uncariae Ramulus cum Uncis, Agrimoniae Herba, Sanguisorbae Radix, Eclipta Prostrate Herba, Pulsatillae Radix, Sophorae Flavescentis Radix, Rehmanniae Radix and Glycyrrhizae Radix), the anticoccidial activity against an E. tenella infection was assessed. The complex significantly decreased the coccidiosis lesion scores and increased the bodyweight gain of the birds after infection. The herbs of the complex that mainly contributed to the anticoccidial effect remain to be identified (Du & Hu, 2004). In another study the dietary supplementation of Apacox, a commercial preparation of a mixture of four different herbal extracts, was investigated for its anticoccidial activity against E. tenella in comparison with lasalocid. Results showed that Apacox has an anticoccidial effect against E. tenella but this effect was significantly lower than the effect of lasalocid. Similar to the study of Du and Hu (2004), further research is required to identify the active components of Apacox (Christaki et al., 2004). More recently, in a study performed in Korea the anticoccidial effect against an E. maxima infection of green tea supplemented to diets was investigated. The parameters used to assess anticoccidial activity were oocyst excretion and body weight gain. The birds supplemented with green tea had significantly reduced oocyst excretion compared to E. maxima infected birds fed the standard diet. However, the body weight gain was not improved in the birds feed the green tea-based diet (Jang et al., 2007).


66

5.3.2. Pre- and probiotics The term prebiotic was introduced by Gibson and Roberfroid (1995), who defined it as ‘a non digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health’. The positive influence of prebiotics on the intestinal flora has been confirmed by a number of studies (Van Loo et al., 1999). Recently, the definition of the prebiotics was narrowed with the introduction of a prebiotic index by Roberfroid (2005), who stated that a preparation might be called prebiotic if it is capable to produce at least 4 x 108 colony forming units of Bifidobacteria/gram faeces per daily dose (gram) ingested. Only three large groups meet this criterion: inulin and oligofructose, galactoseoligosaccharides and xylooligosaccharides. Probiotics consist of beneficial live bacteria or yeasts supplemented to the diet. According to the Food and Agriculture Organization (FAO) and World Health Organization (WHO) probiotics are ‘live microorganisms, which when administrated in adequate amounts confer a health benefit on the host’ (FAO/WHO, 2002). The most frequently used probiotics in humans are species of the genera Lactobacillus and Bifidobacteria whereas species of Bacillus, Enterococcus and Saccharomyces yeasts have been the most commonly used organisms in livestock. In poultry production, probiotics are known for their capacity to restore the intestinal microflora after being disrupted by antibiotic treatment or enteric infections (Rada & Rychly, 1995; Line et al., 1998; Pascual et al., 1999). They are also known for their ability to boost the immune system and used against allergies and other immune diseases (Zulkifli et al., 2000; Dalloul et al., 2003b; Kabir et al., 2004; Koenen et al., 2004). A treatment with prebiotics can be easily combined with a probiotic, in a so called ‘synbiotic’ approach (Gibson and Roberfroid, 1995). An advantage of this combination is the improved survival of probiotics when given in a medium of prebiotics. The use of pre- and probiotics in poultry has been recently reviewed by Patterson and Burkholder (2003). 5.3.2.1. Prebiotics Mannanoligosaccharides (MOS) are derived from the cell wall of the yeast Saccharomyces cerevisae and are widely used in animal feed to promote gastrointestinal health and performance. MOS have been described as a prebiotic but the mode of action may be different; they are thought to block the binding of pathogens to mannan receptors on the mucosal surface and stimulate the immune response (Spring et al., 2000). Some brand names are: BioMos®, SAF-Mannen®, Y-Mos® and Celmana®. In poultry MOS enhances the development of Bifidobacteria spp. and Lactobacillus spp. in the intestinal tract of young chickens and suppresses the number of enterobacteriacea (Fernandez et al., 2002). In an experiment performed with coccidia, dietary MOS (1 g/kg feed) was able to reduce the severity of a single E. tenella infection with 3500 or 5000 sporulated oocysts (Elmusharaf et al., 2006). In another experiment a dietary supplementation of MOS, at a concentration of 10 g/kg feed, reduced the oocyst excretion and diminished the severity of E. acervulina lesions of birds infected with a mixture of E.

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acervulina, E. maxima and E. tenella at subclinical doses of 900, 570 and 170 sporulated oocysts, respectively (Elmusharaf et al., 2007). In a study performed by McCann and others (2006) supplementation of MOS (0.5 g/kg feed) or tannin (0.5 g/kg feed) either individually or in combination did not reduce the severity of a mixed coccidiosis infection of E. acervulina, E. maxima and E. tenella given at clinical doses of 50,000, 15,000 and 15,000 sporulated oocysts, respectively. These contradictory results are possibly explained by differences in MOS concentrations in feed and the magnitude of Eimeria spp. inoculation doses. Further research is necessary to confirm whether MOS has anticoccidial activity when used at higher concentrations in feed in combination with higher challenge doses. 5.3.2.2. Probiotics Lower intestinal invasion and development of coccidia and lower oocyst production, explained by enhanced local cell-mediated immunity, was achieved with a Lactobacillus-based probiotic supplemented diet in E. acervulina infected broilers (Dalloul et al., 2003a; 2003b; 2005). More recently, in a study performed with a Pediococcus-based commercial probiotic (MitoGrow®) given to birds infected with an E. acervulina or E. tenella infection, increased resistance of birds against coccidiosis and a partial protection against growth retardation was demonstrated (Lee et al., 2007a). In another study performed with a Pediococcus- and Saccharomyces-based probiotic (MitoMax®) given to birds challenged with 5000 oocysts of either E. acervulina or E. tenella, less oocyst shedding and a better antibody response was found in probiotic fed birds compared to non-probiotic controls. These results suggest that MitoMax® may improve the resistance against coccidiosis by enhancing the humoral immune response when included in the diet (Lee et al., 2007b).

Table 12. Overview of the influence of alternative feed additives including, the active compound, dose and mode of action, on a coccidiosis infection in poultry Alternative feed additive

Active compound & dose

Mode of action Coccidiosis model Effect on clinical parameters

Global effect*

Reference

Eimeria spp. Infection dose (# oocysts)

Artemisia annua

Artemisinin extracts Induction oxidative stress (free radicals)

E. tenella ? BWG** FCE** LS**

- Oh et al., 1995

Artemisia annua

Dried leaves at 5, 10 & 50 g/kg 3 wks Pure artemisinin 0.002, 0.0085 & 0.017 g/kg 4 wks

Induction oxidative stress (free radicals)

E. acervulina E. tenella E. maxima

105 5 x 104 5 x 103

OPG** LS No effect

E. tenella - E. acervulina

-

E. maxima =

Allen et al., 1997b

Mushrooms extracts

Polysaccharide extracts (1 g/kg)

Immune stimulation E. tenella 6 x 104 9 x 104

BWG - Guo et al., 2004; 2005

Mushrooms extracts

Lectin (FFrL) injected into amniotic cavity (100 µg in 100 µL/egg)

Immune stimulation E. acervulina 104 BWG OPG

- Dalloul et al., 2006

Oregano Essential oil, carvacrol & thymol (0.3 g/kg)

Stimulation mucosal immunity (antimicrobial effect)

E. tenella 5 x 104 BWG

- Giannenas et al., 2003

Oregano Essential oil, thymol, eugenol, curcumin & piperin (0.1 g/kg)

Stimulation mucosal immunity (antimicrobial effect)

Advent® (day 1) Challenged (day 19) E. acervulina E. maxima E. tenella

2 x 102 102 5 x 103

No beneficial effect on vaccination

= Oviedo-Rondón et al., 2006

Herb(s) extracts

Various Indian herb extracts (6 g/kg)

Unknown E. necatrix ? LS - Mandal et al., 1994

Herb(s) extracts

Preparation of Persian lilac (Melia azedarach) 0.3 g/kg & bitter melon (Momordica charantia) 30 g/kg

Unknown Mixed infect. Eimeria spp.

5 x 104 BWG OPG

- Hayat et al., 1996

Herb(s) extracts Fifteen Asian herb(s) extracts (6-30 g/l drinkingwater)

Unknown E. tenella 105 Variable results different herbs

+/- Youn & Noh, 2001

Herb extract Neem fruit (Azadirachta indica) (1, 2 & 3 g/kg)

Unknown E. tenella 3 x 104 (3 g/kg) Mort OPG

- Tipu et al., 2002

Herb(s) extracts Complex of eight herbs (2 g/ml & 10 g/kg)

Unknown E. tenella 105 LS BWG

- Du & Hu, 2004

Herb(s) extracts Complex of four herbs (Apacox) (0.5 & 1.0 g/kg)

Unknown E. tenella 6 x 104 BWG FCE OPG

- Christaki et al., 2004

Herb extract Green tea (5 & 20 g/kg)) Unknown E. maxima 104 BWG = OPG

- Jang et al., 2007

Betaine (sugar beet solids)

Trymethylglycine (0.5, 0.75, 1, 1.5 & 5 g/kg)

Stabilization cell membranes and immune stimulation (osmoprotectant)

Mixed infect. E. acervulina E. tenella E. maxima

Various BWG OPG = LS =

- Augustine et al., 1997 Mathews et al., 1997 Waldenstedt et al., 1999 Klasing et al., 2002

Citric fruits Extracts & organic acids (2, 3, & 4 ml/10 l drinkingwater)

? Mixed infect. E. acervulina E. maxima E. tenella E. brunetti E. mivati

4.5 x 104 (E. tenella 5 x 103)

LS OPG Except for E. tenella

Mixed infect. -

E. tenella =

Tamasaukas et al., 1996 Tamasaukas et al., 1997

Echinacea purpurea

Dried ground root preparation including glycoproteins, chiroric acid & alkamides (1 to 5 g/kg first 2 wks)

Immune stimulation, enhancement macrophage activity

Immucox®C1 (day 1) Challenged (day 28)

115 (0.5 x dose) 2.3 x 105 (1000 x vaccine dose

BWG LS

- Allen, 2003

Turmeric (Curcuma longa)

Diferuleolymethane (phenolic compound, curcumin 10 g/kg)

Immune stimulation by inactivation of reactive nitrogen radicals (γ-tocopherol like)

E. maxima E. tenella

? ?

BWG LS OPG No effect

-

=

Allen et al., 1998

Prebiotics Mannanoligosaccharides 1, 0.5 & 10 g/kg (Bio-Mos®)

Immune stimulation and blocking binding to mucosal surface


Various Variable results +/- Elmusharaf et al., 2006 Elmusharaf et al., 2007 McCann et al., 2006

Probiotics Lactobacillus (Primalac®, 1 g/kg)

Stimulation local cell immunity

E. acervulina 104 OPG - Dalloul et al., 2003a Dalloul et al., 2003b Dalloul et al., 2005

Probiotics Pediococcus (Mito-Grow®, 1 & 2 g/kg)

Immune stimulation (enhanced humoral response)


5 x 103 or 104

5 x 103

BWG OPG BWG = OPG =

-

=

Lee et al., 2007a

Probiotics Pediococcus andSacchromyces (MitoMax® 0.1, 1 & 10 g/kg)

Immune stimulation (enhanced humoral response)


5 x 103 5 x 103

BWG = OPG

- Lee et al., 2007b

*- sign indicates that the substrate has an inhibiting effect on coccidiosis, + sign indicates that the substrate promotes coccidiosis and = indicates no effect on coccidiosis. ** BWG = body weight gain FCE = feed conversion efficiency (g weight gain/g food intake). LS = lesion scores. Mort = mortality. OPG = oocysts per gram faeces.

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71

inte

stin

al fl

ora

& m

ucos

a

immunity

Extra

inte

stin

alen

viro

nmen

tIn

test

inal

lum

en

artemisinin extractscitric fruits

different herb extracts

oregano extracts(carvacrol, thymol)

+

+betaineprebiotica

+

±±

±

Echinacea purpureamushroom extracts

turmericprobiotics

+

-

+

Figure 3. Artemisinin extracts, citric fruits, and different herb extracts seem to have an inhibitory effect on the development of Eimeria. Prebiotics and oregano have an indirect inhibitory effect on the development of Eimeria parasite. Betaine has an indirect effect on the development of the parasite through its osmoprotective properties on the intestinal mucosa and stimulation of the intraepithelial lymphocytes. Echinacea purpurea, mushrooms extracts, turmeric and probiotics have an indirect inhibitory effect on the development of Eimeria through stimulation of the immune system. 5.4. Vaccines Immunity to coccidiosis, which can be induced by passive or active immune responses, is generally defined as the occurrence of ‘resistance’ to a challenge infection with an Eimeria spp. and can be determined by a reduction of the pathogenic effects of coccidiosis: less macroscopically visible lesions and/or a decrease in oocyst production, and increased performance of birds. The first study showing that chickens infected with E. tenella were resistant to homologous challenge was reported by Beach and Corl (1925) and formed the basis of modern coccidiosis vaccinology. However, it would take another 27 years before the first commercial live coccidiosis vaccine CocciVac® was registered in the USA (Edgar & King, 1952).


72

During the last twenty years various reports describing coccidiosis vaccines and their use in poultry have been published (Shirley, 1988; Williams, 1992b, 1996, 1998, 1999, Chapman, 2000; Williams, 2002a, 2002b; Dalloul & Lillehoj, 2006; Shirley et al., 2007). In Table 13 an overview showing the available coccidiosis vaccines and their usage is given (Shirley et al., 2005; Williams, 2002a). Vaccination can be alternated with the anticoccidial drugs in feed within rotation programmes in combination with biosecurity. 5.4.1. Subunit vaccines Subunit vaccines are composed of a purified antigenic determinant that is separated from the virulent organism. Such vaccines can be obtained by different technologies and may consist of native antigens or of recombinant proteins expressed from DNA of various developmental stages (sporozoites, merozoites, gametes) of the Eimeria parasite. Despite an increasing number on manuscripts exploring the feasibility of subunit vaccines against coccidiosis, no commercial products, except CoxAbic®, have been marketed to date (Brother et al., 1988; Jenkins et al., 1989; Miller, et al., 1989; Jenkins et al., 1990; Crane, et al., 1991; Bhogal et al., 1992; Jenkins, 1998; Vermeulen, 1998; Jenkins, 2001; Vermeulen et al., 2001; Dalloul & Lillehoj, 2006). A major limiting factor has been the fact that until now none of the antigens responsible for potent protective immune response against Eimeria has been isolated. Systematic and detailed analysis of host-parasite interactions at the molecular and cellular levels including studies of basic immunology need to be completed before successful subunit vaccine products will be made available. In this regard, the E. tenella genome project may help to further understand how protective immune responses against Eimeria spp. are developed and help to identify antigens of vital importance in coccidial immunology (Shirley et al., 2007). 5.4.1.1. Maternal immunisation, transmission blocking immunity CoxAbic® is a vaccine against coccidiosis, which induces maternally derived antibodies to protect broiler chickens (Michael, 2003, 2007; Finger & Michael, 2005; Ziomko et al., 2005). It is an inactivated, subunit vaccine (oil emulsion) containing affinity purified proteins (230 kDa, 82 kDa and 56 kDa) from the oocyst wall-forming bodies of E. maxima gametocytes. Cross protection resulting in lower oocyst shedding of E. maxima, E. acervulina and E. tenella has been described after the administration of low dose challenge inocula (Wallach et al., 1995; Wallach, 1997). This is remarkable because after natural Eimeria infections cross immunity has not been described (Rose & Long, 1962). However, Crane and co-workers (1991) found cross protection against four Eimeria spp. (E. acervulina, E. maxima, E. necatrix and E. tenella) after administration of a single recombinant antigen. Offspring originating from vaccinated parent birds are fed an anticoccidial drug free diet in order to ensure natural exposure to the parasites and subsequent development active immunity after maternal antibodies have disappeared.

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5.4.2. Live vaccines Live Eimeria vaccines consist of sporulated oocysts and are either non-attenuated (wild type strains of Eimeria spp.) or attenuated. Further differentiation is based on the Eimeria spp. included, their anticoccidial drug sensitivity profile and application. Protective immunity can be achieved if chickens are infected with either a single high dose or multiple low doses (trickle infections) of Eimeria (vaccine) parasites (Joyner & Norton, 1973, 1976; Long et al., 1986). It is crucial that anticoccidial drugs are withdrawn from feed in case chicken flocks are vaccinated with drug sensitive live vaccine parasites in order to avoid vaccination failures. A beneficial side effect of the use of drug sensitive live coccidiosis vaccines is their association with increased sensitivity to anticoccidial drugs (Jeffers, 1976; Mathis & McDougald, 1989; Chapman, 1994, 1996; Newman & Danforth, 2000; Mathis & Broussard, 2006; Peek & Landman, 2006). See subject 3.3.2. “Management of resistance”. 5.4.2.1. Non-attenuated (or wild-type strains of Eimeria spp.) vaccines Non-attenuated vaccines consist of Eimeria parasites which have not been modified in any way to change their pathogenicity and originate from laboratory or field strains. Examples of such vaccines are: CocciVac®, Immucox®, VAC M®, Nobilis® COX ATM, Inovocox® and ADVENT®. Many of these vaccines are used worldwide covering the extensive coccidiosis market. Between the year 2001 and 2004 about 2500 million doses CocciVac® and Immucox® were sold (Shirley et al., 2005). CocciVac® is available as two different products CocciVac® B, containing E. acervulina, E. maxima, E. mivati and E. tenella, which is applied to broilers; CocciVac® D, containing E. acervulina, E. brunetti, E. hagani, E. maxima, E. mivati, E. necatrix, E. praecox and E. tenella, which is applied to breeders and layers. Likewise for Immucox® two different products exist. Immucox® C1 containing E. acervulina, E. maxima, E. necatrix, and E. tenella, is used in broilers; Immucox® C2 containing E. acervulina, E. brunetti, E. maxima, E. necatrix, and E. tenella, is used in breeders and layers. VAC M® was used in the USA for a defined period of time in areas where coccidiosis outbreaks with E. maxima strains resistant to ionophores occurred frequently. It consisted of a non-attenuated E. maxima strain. According to Williams (2002b) the E. maxima strain included in VAC M® was ionophore resistant and not sensitive as cited in the literature. Nobilis® COX ATM is composed of three Eimeria spp. E. acervulina, E. maxima (2 antigenic different strains) and E. tenella which are all ionophore tolerant. This enables the use of this vaccine in flocks exposed to anticoccidial drugs in feed. The advantage of this vaccine is that it allows the use of ionophores during the first 3-4 weeks when immunity is not complete and coccidiosis field strains could interfere (Schetters et al., 1999). ADVENT® is a non-attenuated coccidiosis vaccine harboring E. acervulina, E. maxima and E. tenella. It is used to immunize broilers against Eimeria parasites. ADVENT® enables in vitro assessment of parasite viability using ViacystSM (non-viable sporocysts


74

stain with ethidium bromide), an innovative aspect in coccidiosis vaccinology, allowing a better control of the viability of the vaccine dose administrated (Dibner et al., 2003). Inovocox® is a live coccidiosis vaccine consisting of four non-attenuated strains and three species (E. acervulina, E. maxima (2 antigenic different strains) and E. tenella). In contrast to all other vaccines it is applied to eggs using Inovoject® technology (Weber & Evans, 2003, Weber et al., 2004). During the usage of non-attenuated coccidiosis vaccines it is crucial that all birds are given the required dose and the occurrence of clinical coccidiosis is avoided. Therefore, application protocols should be followed strictly (Chapman et al., 2002). In order to diminish such risks attenuated vaccines have been developed. 5.4.2.2. Attenuated vaccines Attenuated vaccines consist of Eimeria spp. strains, which have been manipulated in the laboratory in order to decrease their virulence. Reduced virulence has been performed by serial passages of the parasite in chicken embryos; e.g. E. tenella in Livacox® vaccines. Selection for precocity is the second described method for attenuation; e.g. remaining Eimeria spp. in Livacox® and all lines in Paracox® vaccines (Shirley & Bedrnik, 1997; Shirley et al., 1995; McDonald & Shirley, 1984; Shirley & Miljard, 1986). Precocity is characterized by a shortened endogenous life cycle due to the fact that the number of generations of schizogony is decreased because last generations of schizogony disappear by selecting early oocysts. A consequence is that the number of oocysts produced during infection is reduced; however, the immunizing potential is maintained (Jeffers, 1975, 1986; McDonald et al., 1986; Shirley & Miljard, 1986). According to the poultry type targeted, Paracox® and Livacox® vaccine types are composed of different Eimeria spp. I.e. Paracox®-8 for breeder birds and layers has 8 Eimeria spp. (E. acervulina, E. brunetti, E. maxima (2 antigenic different strains), E. mitis, E. necatrix, E. praecox and E. tenella), while Paracox®-5, which was developed for broilers only has five Eimeria spp. (E. acervulina, E. maxima (2 antigenic different strains), E. mitis and E. tenella). Livacox® Q is composed of oocysts of E. acervulina, E. maxima, E. necatrix and E. tenella and is intended for the administration to breeder birds and layers. In contrast, Livacox® T, which only has E. acervulina, E. maxima and E. tenella, is applied to broilers. Eimeriavax® 4m is composed of attenuated lines of E. acervulina, E. maxima, E. necatrix and E. tenella and has been developed in Australia. It is used in breeders, layers and broilers by eye-drop application. Eimerivac® plus, which is composed of attenuated lines of E. acervulina, E. maxima and E. tenella has been developed in China, but registration of the vaccine has not been obtained yet. This vaccine is intended for use in breeders, layers and broilers through oral administration. Another Chinese coccidiosis vaccine is Supercox®, which is composed of wild strains of E. acervulina and E. maxima, and a precocious line of E. tenella (Suo et al., 2006). This vaccine is applied orally to broilers.

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A South American (Argentina) vaccine named Inmuner® Gel-Coc consists of four attenuated Eimeria spp.: E. acervulina, E. brunetti, E. maxima and E. tenella. This product is given orally to breeders, layers and broilers. Hipracox® Broilers is another coccidiosis vaccine that recently was introduced in Europe and is intended for use in broilers. It is composed of attenuated lines of E. acervulina, E. maxima, E. mitis, E. praecox and E. tenella and is applied in the drinking water. In the Netherlands up till now only both Paracox® vaccines (Paracox®-5 and Paracox®-8) have been registered and are currently used in the field.

A major drawback of live coccidiosis vaccines is their loss of infectivity with time affecting their expiry (Jeston et al., 2002). Other concerns are their high production costs and management shortcomings during their application such as dosage errors that may result in insufficient immune response or clinical coccidiosis in case non-attenuated vaccines are used, erroneously adding anticoccidial drugs to the feed frustrating effective vaccination of drug sensitive strains, vaccination of sick birds, etc. Further, reversal of virulence of live vaccines may be another point of concern. Subunit vaccines offer possibilities to circumvent mentioned drawbacks and could provide a sustainable solution for the coccidiosis problem in commercial poultry if with the help of new technologies their immunogenicity can be increased.

Table 13. Overview of anticoccidial vaccines that are being used or being registered for use in chickens (Shirley et al., 2005; Williams, 2002a; manufacturer’s technical information bulletins and websites) Vaccine (Manufacturer) Eimeria speciesa Attenuation Bird type Administration route First registration ADVENT® (Novus International)

Eac, Emax, Eten Non-attenuated Broilers Hatchery spray, water or feed spray

2002 (USA)

CocciVac®-B (Shering Plough Animal Health)

Eac, Emax, Emiv, Eten

Non-attenuated Broilers Ocular, hatchery spray, water or feed spray

1952 (USA)

CocciVac®-D (Shering Plough Animal Health)

Eac, Ebr, Eha, Emax, Emiv, Enec, Epra, Eten

Non-attenuated Breeders/layers Ocular, hatchery spray, water or feed spray

1951 (USA)

CoxAbic® (Abic Biological Laboratories)

Killed antigen of Emax gametocytes

Breeders (to protect hatchlings)

Killed antigen, one species, intramuscular

2002 (Israel)

Eimerivac® Plus (Guangdong academy of Agricultural Sciences)

Eac, Emax, Eten Attenuated Breeders/layers/broilers Oral expected (China)

Eimeriavax® 4m (Bioproperties Pty)

Eac, Emax, Enec, Eten

Attenuated (precocious) Breeders/layers/broilers Eye-drop application 2003 (Australia)

Hipracox® Broilers (Laboratorios Hipra, SA)

Eac, Emax, Emit, Epra, Eten

Attenuated Broilers Drinking water 2007 (Spain)

Immucox®C1 (Vetech Laboratories)


Non-attenuated Broilers Water or gel 1985 (Canada)

Immucox®C2 (Vetech Laboratories)

Eac, Ebr, Emax, Enec, Eten

Non-attenuated Breeders/layers Water or gel 1985 (Canada)

Inmuner® Gel-Coc (Vacunas Inmuner)

Eac, Ebr, Emax, Eten

Attenuated Breeders/layers/broilers Oral 2005 (Argentina)

Inovocox® (Embrex Inc. and Pfizer)

Eac, Emax x 2, Eten

Non-attenuated Broilers In ovo injection with the inovoject® system

2006 (USA)

Livacox® Q (Biopharm)


Attenuated (precocious, except Eten (embryo-adapted)

Breeders/layers Hatchery spray, water or feed spray

1992 (Czech Republic)

Livacox® T (Biopharm)

Eac, Emax, Eten Attenuated (precocious, except Eten (embryo-adapted)

Broilers Hatchery spray, water or feed spray

1992 (Czech Republic)

Nobilis® COX-ATM (Intervet international)

Eac, Emax x 2, Eten

Non-attenuated (all ionophore tolerant)

Broilers Water or feed spray 2001 (Netherlands)

Paracox®-8 (Schering Plough Animal Health)

Eac, Ebr, Emax x 2, Emit, Enec, Epra, Eten

Attenuated (precocious) Breeders/layers Water or feed spray 1989 (UK)

Paracox®-5 (Schering Plough Animal Health)

Eac, Emax x 2, Emit, Eten

Attenuated (precocious) Broilers Hatchery spray, water or feed spray

1989 (UK)

Supercox® (Qilu Animal Pharmaceutical Company)

Eac, Emax, Eten Attenuated (precocious: Eten) non-attenuated (Eac and Emax)

Broilers Oral hina)

Broilers Beak-o-Vac

2005 (C

VAC M® (Elanco)

Emax Non-attenuated (ionophore resistantb)

® machine 1989 (USA)

a Eac = E. acervulina, Ebr = E. brunetti, Eha = E. hagani, Emax = E. maxima, Emit = E. mitis, Emiv = E. mivati, Enec = E. necatrix, Epra = E. praecox, Eten = E. tenella and Emax x2 = two antigenically different lines of E. maxima. b According to personal communication of Dr. T.K. Jeffers (Williams, 2002a).


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6. Conclusions and perspectives Coccidiosis is a major parasitic disease of poultry with great economic impact, which mainly affects the intestinal tract of birds. The clinical and economic importance of coccidiosis is likely to remain unchanged during the coming decades as long as commercial poultry is reared in large numbers at high densities, which seems necessary to make the poultry industry profitable. Many studies concerning the effects of diet composition (ingredient and nutrient composition), feed structure and use of alternative feed additives (phyto- and aromatherapy) on Eimeria parasites have been published to date. The results of these studies are frequently ambivalent, while the number of papers describing clear direct anticoccidial activity against various Eimeria spp. is relatively scarce. More research is required on the mode of action and effects of nutrients, dietary constituents and additives in alleviating the negative effects of a coccidiosis infection. Comparing the mode of action of anticoccidial drugs with that of feed components and feed additives no similar mechanisms have been described in literature, except that of vitamin B (thiamine). From this literature review it can be concluded that future coccidiosis control is unlikely to be achieved solely through feed composition and management. However, some dietary compounds seem capable to reduce the effects of an Eimeria infection either by a direct effect on the parasite or indirectly by stimulating immune responses and recovery of the birds. In this regard, natural feed additives also seem promising. Considering the immune stimulating and intestinal health promoting effect of some feed constituents and a few natural feed additives, these products could also play a significant role in ameliorating the efficiency of anticoccidial vaccines, which at present seems the most solid anticoccidiosis strategy especially in case anticoccidial drugs are banned as feed additives. This is an area of research that also deserves future attention. To date coccidiosis control has relied mainly on chemoprophylaxis, however, the occurrence of resistance and the increasing regulations, and possible upcoming bans on the use of anticoccidial drugs as feed additives, have been the principal motivators in the quest for alternative control strategies, amongst which the application of live vaccines has proved most successful so far. Although there are a number of drawbacks associated with the production and use of live coccidiosis vaccines, their efficacy and the fact that they have been associated with increased sensitivity of Eimeria spp. isolates to anticoccidial drugs, have further stimulated their use. If the immunogenicity of subunit vaccines can be improved they could represent the next generation highly efficient and low cost anticoccidial strategy.

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Chapter 2

Anticoccidial drug resistance in the field

Resistance to anticoccidial drugs of Dutch avian Eimeria spp. field isolates originating from 1996, 1999 and 2001 H.W. Peek and W.J.M. Landman Animal Health Service (GD), Poultry Health Centre, P.O. Box 9, 7400 AA, Deventer, the Netherlands Avian Pathology (August 2003), 32(4), 391-/401 Summary Fifteen Eimeria spp. field isolates, sampled on Dutch broiler farms were subjected to an Anticoccidial Sensitivity Test (AST) in a battery cage study. Four isolates dated from 1996, another four from 1999 and the last seven isolates from 2001. The selected anticoccidial drugs were monensin, narasin, salinomycin, lasalocid, nicarbazin, diclazuril, halofuginone, maduramicin and meticlorpindol/methylbenzoquate. Maduramicin and halofuginone were not included in the AST of 1999 and 2001, while meticlorpindol/methylbenzoquate was not tested in 1996 and 1999. E. acervulina present in each of the four 1996 field isolates showed resistance for almost all products tested except maduramicin (1/4) and salinomycin (1/4) which appeared to be reduced sensitive. In 1999 the same species presented a similar resistance pattern for most products although reduced sensitivity occurred for salinomycin (1/4), and sensitivity was found for diclazuril (2/4), monensin (1/4) and narasin (1/4). In the year 2001 increased sensitivity to various products was found. Higher sensitivity was found for meticlorpindol/methylbenzoquate (7/7) and salinomycin and narasin (both 4/7), followed by nicarbazin (3/7) and monensin (2/7). Reduced sensitivity was found for monensin (3/7), lasalocid (2/7), salinomycin and narasin (1/7). E. maxima was only found in one field isolate per year. The E. maxima from 1996 was resistant to all products except narasin (sensitive) and halofuginone (reduced sensitive). In 1999 this species was reduced sensitive to narasin and lasalocid, showing resistance for the other products. The strain originating from the 2001 isolate was reduced sensitive to most products except monensin and narasin (resistant). Full sensitivity was found for meticlorpindol/methylbenzoquate. E. tenella was present in one isolate of 1996, two of 1999 and four of 2001. The AST of 1996 showed reduced sensitivity for nicarbazin, and sensitive to narasin, maduramicin and halofuginone. All other products showed resistance. In 1999 both strains show resistance to all products tested. For the year 2001 full sensitivity was found to meticlorpindol/methylbenzoquate. Sensitivity was also found for salinomycin (2/4), nicarbazin (2/4), diclazuril (2/4) and lasalocid (2/4), monensin (1/4) and narasin (1/4). Reduced sensitivity was found for nicarbazin (1/4), lasalocid (1/4) and narasin (1/4). The different resistance patterns of Dutch coccidiosis isolates and resistance of coccidia in general is discussed.

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Introduction A protozoan parasite belonging to the subclass Coccidia and family Eimeriidae causes coccidiosis in poultry. It is still a major health problem with great economic impact on poultry production. The economic costs are estimated at $ 1.5 billion world-wide (Weber, 1997).

Penetration of the intestinal villous and crypt epithelial cells by asexual (schizogony or merogony) and/or sexual (gametogony) stadia may result in clinical disease. The major pathologic manifestations of clinical coccidiosis are intestinal haemorrhage, malabsorption, diarrhoea and reduction of body weight gain (Lillehoj & Lillehoj, 2000).

Control of coccidiosis has focused on management, vaccines, natural feed additives and prophylaxis with anticoccidial drugs. Management practices may contribute to the control of parasitic disease and prove especially useful in cases that no other measures are effective or available. Mentioned practices should focus on good sanitation, cleaning out contaminated litter, the use of adequate ventilation and watering systems that safeguard good litter condition avoiding sporulation, not rising birds of different ages together, etc.

In view of the immunogenetic properties of the various Eimeria spp., vaccination represents another possible strategy to prevent coccidiosis. Live vaccines consisting of either attenuated or non-attenuated coccidial strains are becoming increasingly popular in the poultry industry. Attenuated vaccines which contain parasites of reduced virulence, can be obtained by passages through embryonated eggs or selection of precocious strains (Shirley, 1993). Although no recombinant vaccines are commercially available yet, considerable developmental work has been performed over the past ten years. The major impeding factors are the identification of protective antigens and the lack of cross-immunity between Eimeria spp. (Jenkins, 1998).

Natural feed additives have been investigated in search of alternative methods to control coccidiosis in view of increasing resistance development to anticoccidial drugs. Moreover, consumers are becoming more aware of the detrimental effects of residues in poultry products. A number of natural feed additives have shown anticoccidial activity. Amongst them fish oils, flaxseed oil, and whole flaxseed containing high concentrations of ω-3 fatty acids (docosahexaenoic acid, eicosapentaenoic acid and linolenic acid) (Allen et al., 1996), artemisinin isolated from the Chinese herb Artimisia annua (Allen et al., 1997), extracts from Sophora flavescens Aiton, Pulstilla koreana, Sinomenium acutum, Ulmus macrocarpa and Quisqualis indica (Young & Noh, 2001) and feed supplements such as γ-tocopherol, the spice tumeric and curcumin (Allen et al., 1996). However, large-scale application of these products has not been carried out yet.

Prophylactic medication with anticoccidial drugs in the feed has proven to be successful in the control of coccidiosis over the past half century and until now has been the most widely practised strategy to prevent outbreaks of clinical coccidiosis. To minimise the occurrence of drug resistance, rotation of various anticoccidial drugs, combining chemical and ionophore treatments or shuttle programs have been used. In spite of the use of such programmes resistance against in-feed medication against coccidiosis is becoming increasingly important. Development of resistance has been described for most

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anticoccidial drugs, chemical and ionophore compounds alike (Chapman, 1986, 1997). To optimise the use of prophylactic medication in the field, knowledge of the drug-sensitivity profile of the parasites concerned is vital. The only accurate method available to obtain such information is the in vivo anticoccidial sensitivity test (AST) (Chapman, 1998). In the present manuscript we present the results of the AST of Dutch avian Eimeria spp. field isolates dating from 1996, 1999 and 2001. Material and methods Experimental design Three AST were performed on Dutch Eimeria spp. field isolates. The first was carried out in 1996 on four isolates against eight anticoccidial products. The second test took place in 1999 analysing another four field isolates against six anticoccidial products, and the last in 2001 comprising seven isolates tested against seven anticoccidial drugs. As reference strain an E. acervulina Weybridge isolate was tested in 1999 against five products (Table 1). The drug concentrations per kg feed tested were: diclazuril (Clinacox®) 1 mg, halofuginone (Stenorol®) 3 mg, lasalocid (Avatec®) 90 mg, maduramicin (Cygro®) 5 mg, meticlorpindol/methylbenzoquate (Lerbek®) 100 mg, monensin (Elancoban®) 100 mg, narasin (Monteban®) 70 mg, nicarbazin (Nicarb®) 125 mg and salinomycin (Sacox®) 60 mg (Fowler, 1995). At the age of eight days (D 0) chicks fed with anticoccidial drugs were inoculated in the crop with a defined number of sporulated oocysts (see inocula). An Infected Untreated Control (IUC) group (positive control) was given the same inoculum, while the Uninfected Untreated Control (UUC) group was used as negative control. Access to the medicated feeds was enabled two days prior to inoculation of oocysts (D-2) until termination of the experiment. At six days post-inoculation a postmortem examination on five birds per experimental group was performed and coccidial lesions were determined. In 1996 and 1999 five birds were used per experimental group, while in 2001 nine chicks per group were used. The E. acervulina reference strain was tested in fivefold using three birds per group. Experimental animals, housing and (medicated) feed In each trial one-day-old male commercial broilers chicks were reared coccidiosis free on a large stain-less-steel wire cage (height x width x depth = 30 cm x 200 cm x 100 cm) in a separated room until the age of six days, during which period they received a feed without anticoccidial products. At the age of six days, two days prior to infection (D-2) the birds were, ad random, placed on battery stain-less-steel wire cages (height x width x depth = 30 cm x 40 cm x 50 cm) in the experimental room. The number of birds per experimental group, i.e. per anticoccidial drug and corresponding controls, has been mentioned in the experimental design.

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After transfer, the chicks were supplied with in-feed medication until termination of the experiment. Twenty five kg of a complete formulated broiler starter mash (Apparent Metabolizable Energy (AME) 12.0 MJ/kg)), free of anticoccidial products, was mixed with commercial anticoccidial drug premixes to produce the desired concentrations in the medicated rations. The required quantity of premix was first mixed with approximately 2.5 kg of mash to safeguard adequate mixing. Thereafter, it was further mixed in a blender (Naturamix, machine nr. m19091, Naturamix B.V., Haarlem, the Netherlands) with the remainder of the feed. Feed and water were offered ad libitum and the chicks were subjected to a lighting scheme of 22 hours of light. Table 1. Overview of the anticoccidial drugs analysed per Anticoccidial Sensitivity Test (AST)

1996 1999 2001 1999 E. acervulina

Diclazuril: Clinacox® (DIC) DIC DIC DIC Halofuginone: Stenorol® (HAL)

Lasalocid: Avatec® (LAS) LAS LAS Maduramicin: Cygro® (MAD) MAD

Meticlorpindol/methylbenzoquate: Lerbek® (METI/METH)

Monensin: Elancoban® (MON) MON MON MON Narasin: Monteban® (NAR) NAR NAR Nicarbazin: Nicarb® (NIC) NIC NIC NIC

Salinomycin: Sacox® (SAC) SAC SAC SAC Assessment of the mixing procedure of anticoccidial drugs in feed In order to asses the mixing procedure of anticoccidial drugs in feed, medicated feed samples were analysed prior to the start of two of the experiments (1999 and 2001). We also report the results of chemical analyses on anticoccidial drug concentrations in feed done in 1988, 1989 and 1990. For the chemical analysis of feed samples the following general procedure was performed: feed samples were grinded into particles of 1 mm3 and extracted in mixtures of organic solvents (e.g. methanol or acetonitrile depending on the product subjected to the analysis) and water. The extraction procedure lasted for one hour, during which time the mixture contained in an erlenmeyer of 300 ml was placed on a shaking device (Edmund Buhler SM25, Salm & Kipp B.V. Breukelen, the Netherlands). After filtration through paper (Schleicher & Schuell Faltenfilter, ref. no. 10311645, diameter 150 mm, Omnilabo, Breda, the Netherlands) the extracts were injected onto HPLC system, (autosampler Waters 717 plus, Etten-Leur, the Netherlands) equipped with a Reversed Phase C18 column (5 µm) and methanol/water or acetonitrile/water mixture were used as mobile phase. The elutes


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were analysed with a UV spectrophotometric detector (Photodiode Array Detector, Waters 966, Etten-Leur, the Netherlands) and computersystem (Waters millenium 32, Etten-Leur, the Netherlands). For some anticoccidial drugs (narasin, monensin and salinomycin) the elute was mixed with a solution of 4-methoxybenzaldehyde in a heated mixing coil before examination with the detector. Data on the proportions and concentrations of the extraction mixtures, which vary according to the product to be analysed, can be found in the corresponding references of lasalocid, monensin, salinomycin and narasin (Dusi & Gamba, 1999); clopidol (Dusi et al., 2000); halofuginone (Tiller et al., 1988); diclazuril (De Kock et al., 1992); maduramicin (Gliddon et al., 1988) and nicarbazin (Hurlbut et al., 1985). Origin of isolates The Eimeria spp. field isolates were obtained from samples of faeces/litter originating from Dutch broiler farms participating in the coccidiosis broiler monitoring program in the Netherlands (see below). The isolates from 1996 were selected from farms where clinical coccidiosis problems emerged, and those of 1999 and 2001 originated from farms with subclinical disease. The E. acervulina reference laboratory strain (Weybridge W119), was obtained from the Central Veterinary Laboratory (CVL), Weybridge, UK. This strain was kept at the Animal Health Service since 1990 and rejuvenated frequently. Parasitology and preparation of inocula Oocysts were purified from the faeces/litter samples by means of a saturated sodium salt flotation technique, and sporulated with modification of the method of Ryley et al. (1976). Briefly, approximately 450 g faeces were suspended in a saturated salt (NaCl) solution (3 l). The suspension was homogenised during 15 to 30 min in an erlenmeyer with a magnetic stirrer. Subsequently, the suspension passaged through a 1000-μm sieve to separate feathers and other coarse debris. The filtered fluid was transferred to 750 ml bottles and centrifuged (5 min at 250 x g) three times. After each centrifugation, the oocyst containing scum (approximately 20 ml) was removed with a pipette connected to a vacuum pump. The three crops of oocysts were diluted in water (700 ml) and centrifuged (15 min at 2750 x g). The supernatant was discarded and the sediment was resuspended in 2.5% (w/v) potassium dichromate (1 l). The suspension was aerated at 29 oC during three days for sporulation. Oocyst counting of the Eimeria inocula was performed with the aid of a Fuchs-Rosenthal haemocytometer counting chamber. The oocyst cultures were refrigerated at 2-8 °C until application. Each Eimeria spp. field isolate was passaged through male Specific Pathogen Free (SPF) broilers for multiplication and identification. The Eimeria species were identified by the location and appearance of the gross lesions in the intestine and by microscopical examination and measurement of the oocysts (Long et al., 1976; McDougald & Reid, 1997). From day 4 until day 7 post-infection, faeces samples were collected and subjected

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to oocysts purification as described above. The inoculation dose was adjusted to obtain a coccidial lesion score of 2 to 3 in the IUC group on the scale of Johnson & Reid (1970) and to avoid mortality. Adjustment was done based on data from literature (Conway et al., 1993), previously performed AST (non-published results) and, on the lesion scores and mortality recorded during the multiplication in SPF broilers. The inocula were prepared and the potassium dichromate was removed by means of centrifugation. The birds were inoculated individually in the crop with a calibrated syringe without needle in a volume of approximately 1 ml tap water. Further procedures, postmortem examination, coccidial lesion scores, Oocysts Per Gram faeces (OPG) and evaluation of resistance The birds were observed daily and deceased birds were subjected to postmortem examination. At six days post-inoculation (D+6) necropsy was performed on five birds per experimental group. The individual coccidial lesion scores were determined according to the method of Johnson & Reid (1970). Briefly, E. acervulina lesion score 1 features ladder-like white streaks in de duodenal loop (≤5/cm2); in lesion score 2 the lesion density is higher but not coalescent; in lesion score 3 the lesions are more numerous and coalesce, while thickening of the intestinal wall is visible, and finally in lesion score 4 the mucosal wall is greyish with lesions completely coalesced. Lesion score 1 of E. maxima is characterised by few small red petechiae in the mid-intestine, in score 2 more numerous petechiae are found and the intestinal content may be orange, in score 3 the intestinal wall might be ballooned and thickened with pinpoint blood clots and mucous filling the intestinal contents. Finally in lesion score 4 the intestinal wall is thickened and ballooned over most of its length, containing numerous blood clots and digested red blood cells. Lesion score 1 of E. tenella shows few scattered petechiae on the caecal wall, in score 2 noticeable blood can be found in the caecal contents, while the caecal wall is thickened. In lesion score 3 large amounts of blood or caecal cores are present, caecal walls are greatly thickened, and in lesion score 4 caecal walls are enormously distended with blood or large caseous cores. Thereafter, the mean lesion score per Eimeria spp. and experimental group was calculated. In fresh-collected faeces material (of 1996 and 1999 from D+4 till D+6 and of 2001 from D+4 till D+8) the OPG-countings were performed by means of a modification of the McMaster counting chamber technique of Hodgson (1970). Briefly, a 10% (w/v) faeces suspension in a salt solution (151 g/l) was made. After shaking vigorously, 1 ml of the suspension was pipetted into 9 ml of saturated sodium chloride (311 g/l). After mixing again, a proportion of the latter suspension was run into the McMaster counting chamber and the oocysts were count using 100 and 200 x magnification. The anticoccidial-sensitivity profile of each Eimeria spp. present in the field isolates and of the control isolate was based on the reduction of the mean lesion score of the medicated group compared to the IUC group using the formula: 100% - (mean lesion score of treated group/mean lesion score of the IUC group x 100%). A reduction percentage in the medicated birds compared with the IUC birds of 0-30% indicates coccidial resistance; 31-


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49% reduction indicates reduced sensitivity or partial resistance and 50% or more indicates full sensitivity to the tested anticoccidial drug (McDougald et al., 1986). Statistical analysis Statistical analyses were performed on the individual lesion scores of E. acervulina, E. maxima and E. tenella by means of the non-parametric Kruskal-Wallis test, testing differences in lesion score Rank sums between groups treated with different anticoccidial drugs and the IUC group (SAS, 1989). Differences were considered significant when P ≤ 0.05. Statistical analysis of the E. acervulina reference strain (1999) with respect to differences in lesion scores between treatments was performed by the Mantel-Haensel Chi-Square test which was corrected for differences in lesion scores between repetitions of the experiment. Differences were considered significant when P ≤ 0.05. Coccidiosis broiler monitoring program in the Netherlands In 1996 a coccidiosis broiler-monitoring program was started in the Netherlands. Broiler chickens from participating farms were sent to the Animal Health Service twice (between 22-25 days of age and between 30-32 days of age) during the fattening period. Each time five birds were sent in for postmortem analysis. The number of participating farms was 238 in 1996, 329 in 1997, 244 in 1998, 172 in 1999, 112 in 2000 and 99 in 2001. The number of broiler flocks analysed from 1996 until 2001 was 362, 510, 387, 267, 165 and 137 respectively. The participating farms belonged to 12 different integrators in 1996, 10 in 1997, five in 1998, four in 1999 and two in 2000 and 2001. The total Dutch broiler population varied from 44,142,000 in 1996 to 50,937,000 in 2000 (LEI & CBS, 2001). Results Inocula Half of the field isolates consisted of mixtures of two or three Eimeria species. All isolates contained E. acervulina. E. maxima was found in one isolate per year. This species occurred in combination with E. tenella in 1999 and 2001. Five other isolates also contained E. tenella (one in 1996, another in 1999 and three in 2001). The Eimeria isolates tested and the species involved as well as the inoculation doses are presented in Table 2.

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Table 2. Eimeria spp. present in the field isolates and inoculation dose (number of sporulated oocysts) per chick Eimeria spp. field isolates Eimeria spp. involveda Inoculation dose (x 103) A (1996) E. ac 75 B (1996) E. ac/E. max 150 C (1996) E. ac 100 D (1996) E. ac/E. ten 50 E (1999) E. ac 41 F (1999) E. ac/E. ten 20 G (1999) E. ac 25 H (1999) E. ac/E. max/E. ten 50 I (2001) E. ac/E. ten 20 J (2001) E. ac 50 K (2001) E. ac/E. ten 35 L (2001) E. ac 50 M (2001) E. ac/E. ten 50 N (2001) E. ac 50 O (2001) E. ac/E. max/E. ten 35 Reference isolate Weybridge (W119) E. ac 50 a E.ac = E. acervulina; E. max = E. maxima; E. ten = E. tenella. Assessment of the mixing procedure of anticoccidial drugs in feed The results of the chemical analyses show anticoccidial drug concentrations close to the desired dose for each compound. The average concentration (mg/kg ± standard deviation) found were 103.1 ± 3.7 for clopidol (n = 8), 0.94 ± 0.05 for diclazuril (n = 5), 2.53 ± 0.78 for halofuginone (n = 6), 101.8 ± 9.0 for lasalocid (n = 7), 106.0 ± 10.3 for monensin (n = 8), 70.5 ± 5.7 for narasin (n = 8), 127.2 ± 8.9 for nicarbazin (n = 9) and 70.0 ± 4.0 for salinomycin (n = 9 ). AST of 1996 E. acervulina from field isolates collected in 1996 showed resistance against all anticoccidial drugs tested except salinomycin and maduramicin which presented reduced sensitivity against two different isolates. The single E. maxima isolate was resistant for all products except narasin. Regarding E. tenella it was sensitive to narasin, maduramicin and halofuginone and reduced sensitive for nicarbazin. This strain was resistant for the remaining products. Three birds died during the AST in 1996. The birds were infected with isolate A receiving salinomycin, isolate B receiving diclazuril or isolate D receiving monensin. The latter bird succumbed due to the E. tenella infection. In the other cases the mortality was regarded as non-specific (Table 3).


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Table 3. Individual lesion scores (ILS), mortality (Mort) and oocysts per pram faeces (OPG) of the anticoccidial sensitivity test (AST) of 1996 Isolate nr/anticoccidial drug E. acervulina

ILS E. maxima

ILS E. tenella

ILS Mort

(n = 5) OPG

(x 103) Isolate A DIC 4 3 3 4 4a 0/5 790 HAL 4 4 3 4 4a 0/5 860 LAS 4 4 4 4 4a 0/5 970 MAD 3 4 4 4 3a 0/5 450 MON 3 4 4 3 4a 0/5 890 NAR 3 2 3 3 3a 0/5 1,400 NIC 3 3 4 4 4a 0/5 460 SAC 1 2 2 2 xb 1/5 580 IUC 3 3 3 4 3a 0/5 640 Isolate B DIC 3 3 3 1 xa 2 1 0 1 xa 1/5 410 HAL 3 4 3 3 3a 1 1 1 0 1a 0/5 310 LAS 3 4 2 3 3a 2 1 1 1 1a 0/5 700 MAD 1 1 2 2 1b 1 1 1 1 1a 0/5 260 MON 2 2 3 3 4a 1 1 1 1 1a 0/5 190 NAR 2 3 3 3 3a 1 0 0 0 1b 0/5 370 NIC 3 3 2 3 1a 1 1 1 1 1a 0/5 910 SAC 2 2 2 3 2a 1 1 1 1 1a 0/5 970 IUC 3 2 2 3 2a 2 1 1 1 1a 0/5 880 Isolate C DIC 4 4 4 3 3a 0/5 300 HAL 3 2 3 4 4a 0/5 520 LAS 3 3 3 4 4a 0/5 420 MAD 3 3 4 3 3a 0/5 1,200 MON 4 3 4 4 4a 0/5 49 NAR 3 2 1 3 3a 0/5 330 NIC 4 4 3 4 4a 0/5 490 SAC 2 3 2 3 3a 0/5 160 IUC 4 3 3 4 3a 0/5 320 Isolate D DIC 3 2 3 2 3a 1 1 2 2 1a 0/5 640 HAL 2 2 1 1 1a 0 0 0 0 0b 0/5 640 LAS 4 4 4 4 3a 3 1 1 2 3a 0/5 620 MAD 3 3 3 3 3a 0 1 0 0 0b 0/5 150 MON 3 3 3 4 xa 0 1 1 3 4a 1/5 310 NAR 4 3 2 2 3a 1 1 0 1 1b 0/5 310 NIC 3 3 4 4 4a 1 1 2 1 1a 0/5 650 SAC 1 1 1 1 3a 1 2 1 3 1a 0/5 440 IUC 1 2 2 1 3a 1 1 2 3 2a 0/5 610 UUC 0 0 0 0 0 0 0 0 0 0 0/5 0 a,b Treatment groups with no common superscript within columns differ significantly from the IUC group (P ≤ 0.05) with respect to lesion score Rank sums (non-parametric Kruskal-Wallis test).

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AST of 1999 E. acervulina in isolate H was sensitive for diclazuril, monensin, narasin and reduced sensitive to salinomycin. Another E. acervulina belonging to isolate F was sensitive to diclazuril. The remaining isolates were resistant. The only E. maxima isolate was reduced sensitive lasalocid and narasin. It was resistant to the other compounds. E. tenella present in two isolates was resistant to all drugs. No mortality was recorded (Table 4). Table 4. Individual lesion scores (ILS), mortality (Mort) and oocysts per gram faeces (OPG) of the anticoccidial sensitivity test (AST) of 1999 Isolate nr/anticoccidial drug E. acervulina

ILS E. maxima

ILS E. tenella

ILS Mort

(n = 5) OPG

(x 103) Isolate E DIC 2 3 3 3 3a 0/5 2,500 LAS 3 3 4 3 3a 0/5 4,600 MON 2 2 3 3 3a 0/5 1,500 NAR 4 3 3 2 2a 0/5 3,800 NIC 3 2 3 2 3a 0/5 9,100 SAC 3 3 2 3 3a 0/5 3,700 IUC 3 3 3 3 3a 0/5 4,400 Isolate F DIC 2 1 2 1 1b 2 2 2 3 3a 0/5 5,800 LAS 2 2 3 2 2a 2 2 2 2 2b 0/5 1,500 MON 3 3 3 3 3a 2 2 4 4 4a 0/5 1,400 NAR 2 2 3 2 2a 2 2 3 3 3a 0/5 1,900 NIC 2 3 2 3 2a 3 3 3 2 3a 0/5 1,400 SAC 3 2 2 3 2a 3 3 2 3 2a 0/5 1,100 IUC 3 3 3 3 3a 3 3 3 2 2a 0/5 7,900 Isolate G DIC 3 3 3 2 3a 0/5 3,700 LAS 3 2 3 3 3a 0/5 7,500 MON 2 3 2 3 2b 0/5 2,900 NAR 3 3 3 2 3a 0/5 13,000 NIC 3 2 2 3 3a 0/5 3,300 SAC 3 3 2 3 3a 0/5 4,400 IUC 3 3 3 3 3a 0/5 15,000 Isolate H DIC 2 1 2 1 1b 2 2 1 1 1a 2 2 2 4 1a 0/5 2,600 LAS 3 2 3 2 3a 1 1 1 1 1b 1 3 2 2 2a 0/5 1,100 MON 1 2 2 1 1b 3 2 1 1 1a 2 2 2 3 1a 0/5 1,100 NAR 1 2 1 2 1b 2 1 1 1 1a 2 2 3 2 2a 0/5 850 NIC 2 2 3 2 2a 1 2 2 1 1a 2 3 2 3 3a 0/5 1,600 SAC 2 2 1 2 1b 2 2 2 1 1a 2 3 2 2 2a 0/5 1,400 IUC 2 3 3 3 3a 2 3 2 1 1a 2 3 3 3 3a 0/5 2,200 UUC 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0/5 0 a,b Treatment groups with no common superscript within columns differ significantly from the IUC group (P ≤ 0.05) with respect to lesion score Rank sums (non-parametric Kruskal-Wallis test).


116

AST of 2001 Seven E. acervulina isolates were tested in 2001. All seven were resistant for diclazuril, five for lasalocid, four for nicarbazin, two for salinomycin, monensin and narasin. Reduced sensitivity was recorded for three isolates regarding monensin, two for lasalocid and one for salinomycin and narasin. Sensitivity was found for meticlorpindol/methylbenzoquate (seven isolates), salinomycin and narasin (four isolates), nicarbazin (three isolates) and monensin (two isolates). E. maxima was sensitive for meticlorpindol/methylbenzoquate, resistant to monensin and narasin, and reduced sensitive to the remaining drugs. Three out of the four E. tenella isolates were resistant to monensin, three for salinomycin, two for diclazuril and narasin, and one for nicarbazin and lasalocid. Reduced sensitivity was found in one isolate for nicarbazin, lasalocid and narasin. All isolates were sensitive for meticlorpindol/methylbenzoquate, two for nicarbazin, diclazuril and lasalocid, one isolate was sensitive for salinomycin, monensin and narasin. Some mortality was found in isolate I due to the severity of the E. tenella infection. In total seven out of 72 birds (eight groups of nine birds) died (Table 5). Table 5. Individual lesion scores (ILS), mortality (Mort) and oocyst per gram faeces (OPG) of the anticoccidial sensitivity test (AST) of 2001 Isolate nr/anticoccidial drug E. acervulina

ILS E. maxima

ILS E. tenella

ILS Mort

(n = 9) OPG

(x 103) Isolate I DIC 3 3 3 2 2a 2 3 3 3 3a 1/9 1,100 LAS 3 3 2 2 3a 3 3 3 3 3a 0/9 3,700 METI/METH 0 0 0 0 0b 0 0 0 0 0b 0/9 0.330 MON 1 2 2 3 1a 3 3 3 3 3a 2/9 1,800 NAR 1 1 2 1 2b 3 2 3 3 3a 1/9 2,200 NIC 2 3 2 3 2a 3 3 3 3 3a 0/9 1,400 SAC 1 1 1 2 1b 3 3 3 3 3a 1/9 500 IUC 3 2 3 3 3a 3 3 3 3 3a 2/9 3,800 Isolate J DIC 3 2 2 3 3b 0/9 750 LAS 3 3 3 3 3b 0/9 1,100 METI/METH 0 1 1 0 0b 0/9 0.330 MON 3 2 2 1 2b 0/9 250 NAR 1 1 2 2 1b 0/9 440 NIC 1 1 2 2 3b 0/9 650 SAC 1 1 1 1 1b 0/9 150 IUC 3 4 4 3 4a 0/9 920 Isolate K DIC 2 2 2 2 2a 0 0 0 0 0a 0/9 96 LAS 2 2 1 2 xa 0 0 0 0 xa 0/9 260 METI/METH 1 1 0 0 1b 0 0 0 0 0a 0/9 5.9 MON 1 1 1 0 1b 0 1 0 0 0a 0/9 380 NAR 2 2 1 1 2a 0 0 0 0 0a 0/9 310

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NIC 2 1 1 1 1b 0 0 0 0 0a 0/9 68 SAC 2 3 1 2 2a 0 1 0 0 1a 0/9 340 IUC 2 3 2 3 3a 0 0 0 0 1a 0/9 830 Isolate L DIC 2 3 3 3 3a 0/9 520 LAS 2 3 2 3 3a 0/9 940 METI/METH 0 0 0 0 0b 0/9 0.660 MON 1 1 1 1 1b 0/9 210 NAR 1 1 1 1 1b 0/9 540 NIC 2 2 3 2 2a 0/9 980 SAC 1 2 1 1 1b 0/9 710 IUC 3 3 2 3 3a 0/9 1,700 Isolate M DIC 2 2 2 3 2a 0 0 0 0 0b 0/9 1,500 LAS 2 1 3 2 1a 0 0 0 0 0b 0/9 420 METI/METH 0 0 0 1 0b 0 0 0 0 0b 0/9 36 MON 1 1 2 1 2b 0 1 0 2 0a 0/9 240 NAR 1 1 1 1 2b 0 1 0 1 2a 0/9 300 NIC 1 1 1 1 1b 0 0 0 0 0b 0/9 810 SAC 1 1 1 0 1b 1 1 0 0 0b 0/9 170 IUC 3 3 3 2 2a 2 1 1 1 1a 0/9 800 Isolate N DIC 3 3 3 3 3a 0/9 290 LAS 3 4 4 3 3a 0/9 3,100 METI/METH 1 1 1 0 1b 0/9 12 MON 3 3 3 3 3b 0/9 240 NAR 3 3 4 3 3a 0/9 950 NIC 3 4 4 3 4a 0/9 1,000 SAC 3 2 2 3 3b 0/9 1,100 IUC 3 4 4 4 3a 0/9 1,300 Isolate O DIC 2 3 3 3 2a 2 1 2 1 1b 2 2 3 2 2b 0/9 940 LAS 3 3 2 3 3a 1 1 2 2 2b 1 2 1 1 3b 0/9 700 METI/METH 0 0 0 0 0b 0 0 0 0 0b 0 0 0 0 0b 0/9 0.660 MON 3 2 2 3 2a 2 3 2 2 1a 3 3 2 3 3a 0/9 270 NAR 2 2 2 2 3a 2 2 2 2 3a 2 2 3 3 3a 0/9 1,000 NIC 3 3 2 1 2a 1 1 1 2 3a 2 2 2 2 2b 1/9 490 SAC 1 2 1 2 2a 1 1 2 2 1b 3 2 3 2 3a 0/9 1,300 IUC 2 2 3 2 3a 2 3 2 3 3a 3 3 3 3 3a 0/9 550 UUC 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0/9 0 a,b Treatment groups with no common superscript within columns differ significantly from the IUC group (P ≤ 0.05) with respect to lesion score Rank sums (non-parametric Kruskal-Wallis test). AST of the E. acervulina reference strain The E. acervulina reference strain was sensitive to all anticoccidial drugs tested. The individual lesion scores and OPG per anticoccidial product of the AST of the E. acervulina reference strain that was performed in fivefold in 1999 are outlined in Table 6.


118

Table 6. Individual lesion scores (ILS) (n = 3) and oocysts per gram faeces (OPG x 103) of the AST of the E. acervulina reference strain performed fivefold in 1999

Anticoccidial drug

Group 1 Group 2 Group 3 Group 4 Group 5

ILS OPG ILS OPG ILS OPG ILS OPG ILS OPG DIC 0 0 1b 0 1 0 1b 0 1 0 1b 0 1 0 1b 0 1 0 0b 0 MAD 0 0 0b 78 0 0 0b 34 0 0 0b 40 0 0 0b 16 0 0 0b 16 MON 0.0 1b 150 1 1 0b 32 1 1 1b 93 0 0 1b 25 1 1 0b 140 NIC 0 0.0b 4.3 0 0 0b 11 0 0 0b 1.0 0 0 0b 11 0 0 0b 3.3 SAC 0 1 1b 3.6 1 0 0b 19 1 1 0b 16 0 1 0b 4,3 1 1 0b 0.7 IUC 1 2 2a 720 1 2 2a 1,100 1 2 2a 1,700 1 2 2a 1,100 1 2 2a 1,000 a,b Treatment groups with no common superscript within columns differ significantly from the IUC group (P ≤ 0.05) with respect to lesion score Rank sums (non-parametric Kruskal-Wallis test). Evaluation of resistance In Table 7, the results of the interpretation of the calculated percent reduction of lesion score according to the criteria of McDougald et al. (1986) are presented. Table 7. Summarising classification of the AST per Eimeria spp. found in the field isolates* Anticoccidial drug E. acervulina E. maxima E. tenella R RS S R RS S R RS S DIC 4/2/7 0/0/0 0/2/0 1/1/0 0/0/1 0/0/0 1/2/2 0/0/0 0/0/2 HAL 4/-/- 0/-/- 0/-/- 0/-/- 1/-/- 0/-/- 0/-/- 0/-/- 1/-/- LAS 4/4/5 0/0/2 0/0/0 1/0/0 0/1/1 0/0/0 1/2/1 0/0/1 0/0/2 MAD 3/-/- 1/-/- 0/-/- 1/-/- 0/-/- 0/-/- 0/-/- 0/-/- 1/-/- METI/METH -/-/0 -/-/0 -/-/7 -/-/0 -/-/0 -/-/1 -/-/0 -/-/0 -/-/4 MON 4/3/2 0/0/3 0/1/2 1/1/1 0/0/0 0/0/0 1/2/3 0/0/0 0/0/1 NAR 4/3/2 0/0/1 0/1/4 0/0/1 0/1/0 1/0/0/ 0/2/2 0/0/1 1/0/1 NIC 4/4/4 0/0/0 0/0/3 1/1/0 0/0/1 0/0/0 0/2/1 1/0/1 0/0/2 SAC 3/3/2 1/1/1 0/0/4 1/1/0 0/0/1 0/0/0 1/2/3 0/0/0 0/0/1 * Data presented as 1996/1999/2001. - = not done. R = resistant; RS = reduced sensitive; S = sensitive.

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Coccidiosis broiler monitoring program in the Netherlands The results of the Dutch coccidiosis monitoring program in broiler shows an increase in the incidence of coccidiosis positive broiler flocks from approximately 70% in 1996 to 91% in 2000. In 2001 the percentage decreased being approximately 73%. The percentage of E. acervulina infected flocks ranged from 68 in 1996 to 84 in 2000. In 2001 67% of flocks showed E. acervulina coccidiosis. The percentage of E. maxima infected flocks ranged from 6 in 1996 to 33 in 2000. In 2001 25% of flocks showed E. maxima coccidiosis. Finally, the percentage of E. tenella infected flocks ranged from 21 in 1996 to 26 in 2000. In 2001 20% of flocks showed E. tenella coccidiosis. The percentages of coccidial infections mentioned above concern single species or mixed infections. The results of the Dutch broiler coccidiosis-monitoring program are presented in Figure 1.

0

10

20

30

40

50

60

70

80

90

100

1996

-I19

96-II

1996

-III

1996

-IV19

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1997

-II

1997

-III

1997

-IV19

98-I

1998

-II

1998

-III

1998

-IV19

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1999

-II19

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I19

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V20

00-I

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-II20

00-II

I20

00-I

V20

01-I

2001

-II20

01-II

I20

01-I

V

Time in quarter of year

% p

ositi

ve fl

ocks

Total coccidiosis E. acervulina

E. tenella E. maxima

Figure 1. Incidence of coccidiosis infections in Dutch broiler flocks participating in the coccidiosis monitoring program expressed as total percentage positive flocks and per Eimeria spp. per quarter of year.


120

Discussion Although the AST is the only accurate tool to detect resistance against anticoccidial drugs, it has some drawbacks. The test is slow and expensive. Moreover, the isolates tested frequently originate from farms with disease outbreaks, therefore the anticoccidial profile found may not be representative of what is occurring in the average broiler population in the field. Further, the resistance pattern and pathogenicity of field isolates may be influenced by the need to propagate them first in SPF broiler chickens for multiplication. During this procedure which can also affect the proportion of species in the isolate, non-relevant coccidia may be selected.

The field isolates analysed in the first AST originated from clinical cases of coccidiosis suggesting the occurrence of anticoccidial drug resistance. Indeed, the results of the first sensitivity study (1996) show a higher degree of anticoccidial drug resistance compared to subsequent studies (1999 and 2001) where the isolates originated from subclinical cases of coccidiosis. However, the fact that in the first study a higher inoculation dose was used, may have at least in part, further compromised the effectivity of the anticoccidial drugs tested. Conway et al. (1999) have shown a dose effect on the lesion score of unmedicated and salinomycin-medicated chickens; higher lesion scores occurred in both categories if a higher inoculation dose was used.

Resistance for all products tested has been reported previously i.e. for nicarbazin (McLoughlin & Gardiner, 1967), clopidol (McLoughlin & Chute, 1973), monensin (Jeffers, 1974), maduramicin (McDougald et al., 1987), salinomycin (Bedrnik et al., 1987), diclazuril (Chapman, 1989; Vertommen & Peek, 1993), narasin (Weppelman et al., 1977), halofuginone (Mathis & McDougald, 1982) and lasalocid (Weppelman et al., 1977).

The results of OPG are difficult to correlate with the outcome of the coccidiosis lesion scores in some cases. This might be due to the occurrence of a crowding effect (Williams, 2001), mixed infections and different sensitivity patterns of species in these mixed infections (Reid, 1975). Nevertheless, it is important to assess whether oocyst shedding takes place in view of its importance in the development of immunity. According to Tyzzer (1929) and Tyzzer et al. (1932) both E. maxima and E. praecox (and E. acervulina as well) develop in the upper/mid-small intestine but they differ in the sites of the intestinal villus where they invade. The zone of maximal invasion for E. maxima is the crypt region which has the youngest enterocytes ready to migrate to the apical region (Uni et al., 1998), while E. praecox and similarly E. acervulina target the mid and apical zone. In case of a mixed infection where E. maxima is controlled efficiently by an anticoccidial drug and E. acervulina is not, lesions due to the latter parasite may appear more severe as more target cells become available.

The E. acervulina reference strain (Weybridge 119) included in the AST of 1999 showed full sensitivity towards all anticoccidial drugs tested. However, clear differences were found in oocyst shedding between the various products analysed. The highest numbers of oocysts per gram faeces were found in the groups treated with the ionophores maduramicin and monensin. These drugs perform well due to their chemotherapeutic

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effect and the allowance of the development of an adequate immune response (Jeffers, 1989). Oocyst shedding in the presence of ionophores occurs even if parasites are not drug resistant (Chapman, 1976). This will nevertheless favour the development of immunity due to the occurrence of multiple small (trickle) infections. In the group treated with diclazuril oocysts shedding was absent, while at postmortem lesions containing oocysts were found. A similar effect of diclazuril on E. maxima and E. brunetti has been described previously (Verheyen et al., 1989). The normal pattern of oocyst wall establishment was completely disturbed, resulting in the formation of an abnormally thickened, incomplete oocyst wall and the necrosis of the zygote in all fertilised macrogamonts of both species. The different effects on oocyst shedding will have an impact on the development of immunity.

Despite the occurrence of resistance, other positive properties of anticoccidial products should be considered. Most anticoccidial drugs (mainly ionophores) have growth promoting properties, which may enhance the flock performance (Radu et al., 1987; Jeffers et al., 1988). Moreover, due to the occurrence of resistance, trickle infections that allow build up of immunity take place. This principle has formed the basis for the development of new vaccines consisting of Eimeria spp. resistant to ionophores. In fact a form of spontaneous vaccination might be occurring in the field as broiler flocks are being treated with anticoccidial drugs that show resistance against the prevailing Eimeria spp. This suggestion is evidenced by the occurrence of a high prevalence of coccidiosis infections in the field in the Netherlands during the past years (Figure 1), which did not result in an increase of clinical problems. Acknowledgements The authors thank A.R.W. Elbers for performing the statistical analysis and E. Kamps for his contribution to the Dutch broiler coccidiosis monitoring program. References Allen, P.C., Danforth H.D. & Levander, O.A. (1996). Diets high in n-3 fatty acids reduce cecal lesion

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Weppelman, R.M., Olson, G., Smith, D.A., Tamas, T. & Van Iderstine, A. (1977). Comparison of anticoccidial efficacy, resistance and tolerance of narasin, monensin and lasalocid in chicken battery trials. Poultry Science, 56, pp. 1550-1559.

Williams, R.B. (2001). Quantification of the crowding effect during infections with the seven Eimeria species of the domesticated fowl: its importance for experimental designs and the production of oocyst stocks. International Journal for Parasitology, 31, pp. 1056-1069.

Young, H.J. & Noh, J.W. (2001). Screening of the anticoccidial affects of herb extracts against Eimeria tenella. Veterinary Parasitology, 96, pp. 257-263.

Anticoccidial drug sensitivity profiles of German, Spanish and Dutch Eimeria spp. field isolates H.W. Peek and W.J.M. Landman Animal Health Service (GD), Poultry Health Centre, P.O. Box 9, 7400 AA, Deventer, the Netherlands Tijdschrift voor Diergeneeskunde (April 2004), 127(7), 210-214 Summary Anticoccidial drug sensitivity profiles of twenty-four Eimeria spp. field isolates originating from Dutch, German and Spanish broiler farms were determined. The tested anticoccidial products were diclazuril, halofuginone, lasalocid, meticlorpindol/methylbenzoquate, monensin, narasin, narasin/nicarbazin, nicarbazin, robenidine and salinomycin. The sensitivity tests were performed in cage trials. Almost all Eimeria spp. found in the field isolates showed resistance. Exceptions were some Eimeria acervulina strains, which were sensitive for meticlorpindol/methylbenzoquate (10/12), salinomycine (7/21), robenidine (3/6) and the combination narasin/nicarbazin (1/16). A number of E. tenella strains were sensitive for halofuginone (2/2), meticlorpindol/methylbenzoquate (3/3), diclazuril (2/4) and robenidine (1/1). E. maxima strains showed sensitivity to halofuginone (4/4), meticlorpindol/methylbenzoquate (5/8), the combination narasin/nicarbazine (5/8), nicarbazin (4/10) salinomycin (3/11) narasin (1/5) and robenidine (1/1).


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Introduction Coccidiosis is a disease caused by intracellular parasites belonging to the genera Eimeria and Isospora (phylum Apicomplexa). In the vertebrate (Chordata), 575 different species of which 362 species belong to mammals have been described. These are the Eimeria spp. of approximately 1.7% of the Chordata and 10% of the mammals. If the Chordata were thoroughly investigated, the number of Eimeria spp. could probably reach 35,000, of which 3,400 in mammals (Levine, 1973).

In chickens (Gallus gallus domesticus) nine different Eimeria spp. have been described: Eimeria acervulina, E. brunetti, E. maxima, E. mitis, E. mivati, E. necatrix, E. praecox, E. tenella and E. hagani (McDougald & Reid, 1997). All mentioned species parasitize the intestinal epithelial cells and can be differentiated from each other by their morphology, tissue tropism, pathogenicity and clinical signs (Johnson & Reid, 1970). In broilers, E. acervulina, E. maxima and E. tenella are most frequently diagnosed (Peek & Landman, 2003). E. mitis and E. praecox are diagnosed to a lesser extent and their pathogenicity has been subject of debate (Williams, 1998).

The lifecycle of the parasite (McDougald & Reid, 1997) starts with the ingestion of sporulated oocysts, which can be found in litter, water, feed, contaminated boots and/or equipment. During the life cycle intestinal epithelial cells and the mucosal surface may be destroyed by the intracellular replication of coccidia. In severe cases this may disrupt the uptake of nutrients and cause mortality.

The traditional control of coccidiosis is mainly based on the use of anticoccidial products in feed, while more recently vaccines are being used also. In broilers, these vaccines are not yet intensively used due to their relative high price and the unfounded fear for their negative influence on chicken performance and insufficient immunity build up with time (Williams, 2002).

A major drawback related to the use of anticoccidial products is the occurrence of resistance, which has been described for all products worldwide (Chapman, 1976; 1997; Braunius, 1980). The speed at which the onset of resistance occurs is directly related to the time the parasite is exposed to the anticoccidial product. Therefore, this period should be as short as possible. To realize this, ‘shuttle’ and ‘rotation programmes’ have been implemented. In case of a ‘shuttle programme’ at least two different anticoccidial products, with a likely different mode of action, within one grow-out period, are alternated. In case of a ‘rotation programme’ anticoccidial products are used during a pre-established period. Regularly a period of four months or two grow-outs are used before another product is applied. An alternative for a ‘rotation programme’ is a ‘continuous programme’ in which anticoccidial product(s) are used until a coccidiosis problem occurs or a new product is introduced on the market. ‘Shuttle programmes’ can be built-into ‘rotation programmes’. If full resistance occurs, exchange of anticoccidial products is often not enough to control the coccidiosis. In these cases vaccination of birds may represent a good and efficacious alternative. A welcome side effect of vaccination is its ability to increase the sensitivity of Eimeria spp. field isolates by seeding the vaccinated houses with drug sensitive vaccine

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Eimeria spp. and therefore restoring the efficiency of anticoccidial products (Vertommen, 1996; Chapman, 2000; Chapman et al., 2002).

Knowledge on the anticoccidial sensitivity patterns of the Eimeria spp. field isolates is crucial if the use of the steadily decreasing number of anticoccidial products is to be optimised. The only reliable method to obtain anticoccidial drug sensitivity profiles is by means of an in vivo anticoccidial sensitivity test (AST).

In the present study the anticoccidial sensitivity profiles of twenty-four Eimeria spp. field isolates recently obtained from German, Dutch and Spanish broiler farms have been assessed and the problem of resistance in general is discussed. Material and Method Experimental design In the period of 2000-2002 four ASTs were conducted. In Table 1, an overview of the investigated anticoccidial products per trial and participating country is given. At the age of eight days (D 0), chicks in groups fed medicated diets and in one group fed an unmedicated diet (infected unmedicated control (IUC)) were infected with the Eimeria spp. field isolates. At six days post-inoculation a postmortem examination was performed and coccidial lesion scores were determined. In fresh collected faeces the number of oocyst per gram was determined (see lesion scores and oocysts per gram faeces). In the ASTs with the German and Dutch field isolates, ten chicks per group were used whereas in the trial with the Spanish isolates 5. The birds were observed daily and deceased birds were collected for postmortem examination. Experimental animals and housing One-day-old Hybro male broiler chicks (Nutreco, Putten, the Netherlands) were reared coccidiosis free on a large stain-less-steel wire cage (height x width x depth = 30 cm x 200 cm x 100 cm) in a separated room until the age of 6 days. At the age of 6 days, two days prior to infection (D-2) the birds (n = 5) were, ad random, placed on battery stain-less-steel wire cages (height x width x depth = 30 cm x 40 cm x 50 cm) in the experimental room. After transfer, the chicks in the medicated groups were supplied with in-feed medication while the chicks in the unmedicated groups received a feed without medication. Feed and water were offered ad libitum and the chicks were subjected to a lighting scheme of 22 h light per twenty-four hours.


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Table 1. Overview of the anticoccidial products analysed per anticoccidial sensitivity test (AST) and country Country (year) Anticoccidial product Spain

(2000) Germany

(2001) Netherlands

(2001) Netherlands

(2002)

Diclazuril (Clinacox®)(DIC) X X X Halofuginone (Stenorol®)(HAL) X X Lasalocid (Avatec®)(LAS) X*

Meticlorpindol/methylbenzoquate (Lerbek®) (METI/METH)

X X X*

Monensin (Elancoban®)(MON) X Narasin (Monteban®)(NAR) X X Narasin/nicarbazin (Maxiban®)NAR/NIC X X X Nicarbazin (Nicarb®)NIC X X X Robenidine (Robenz®)(ROB) X Salinomycin (Sacox®)(SAL) X X X X * = with four field isolates, lasalocid was tested and with the remainder two isolates meticlorpindol/methylbenzoquate. Feed and anticoccidial products Twenty-five kilograms of a complete formulated broiler starter mash (Apparent Metabolizable Energy (AME) 12.0 MJ/kg), free of anticoccidial products, were mixed with commercial anticoccidial drug premixes. The concentrations of the anticoccidial products per kilogram feed were: diclazuril (Clinacox®) 1 mg, halofuginone (Stenorol®) 3 mg, lasalocid (Avatec®) 90 mg, meticlorpindol/methylbenzoquate (Lerbek®) 100 mg, monensin (Elancoban®) 100 mg, narasin (Monteban®) 70 mg, narasin/nicarbazin (Maxiban®) 40/40 mg, nicarbazin (Nicarb®) 125 mg, robenidine (Robenz®) 33 mg and salinomycin (Sacox®) 60 mg. To warrant a homogenous mixture, the required quantity was first mixed with approximately 2.5 kg mash. Thereafter, it was further mixed in a blender (Naturamix, machine nr. m19091, Naturamix B.V., Haarlem, the Netherlands) with the remainder feed. The concentrations of the anticoccidial products in the diets were controlled as described earlier by Peek & Landman (2003). Preparation of the inocula Oocysts of the Eimeria spp. field isolates were purified from the fresh faeces/litter samples and were passaged through Specified Pathogen Free (SPF) broilers for multiplication and identification (Ryley et al., 1976). The oocyst cultures were suspended in 2.5% (w/v) potassium dichromate and refrigerated at 2-8 ºC until application. The Eimeria spp. present in the field isolates were identified by the location and appearance of the gross lesions in the intestine and by microscopical examination and measurement of the oocysts

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(Long et al., 1976; McDougald & Reid, 1997). The inoculation dose was adjusted to obtain a coccidial lesion score of 2 to 3 in the IUC on the scale of Johnson & Reid (1970). The inocula were prepared and the potassium dichromate was removed by means of centrifugation and the oocysts were suspended in tap water. Oocyst counting of the inocula was performed with the aid of a Fuchs-Rosenthal haemocytometer counting chamber and the chicks were inoculated individually in the crop with a calibrated syringe without needle in a volume of 1 ml. Coccidial lesion scores and oocyst per gram faeces (OPG) At six days after infection (D+6) necropsy was performed on five birds per experimental group and the individual lesion scores were determined according to the method of Johnson & Reid (1970). In fresh collected faeces material from D+4 till D+8 (of the Spanish isolates from D+4 till D+6) the OPG-counting were performed by means of a modification of the McMaster counting chamber saturated salt flotation technique described by Peek & Landman (2003). Determination and evaluation of the sensitivity profiles The anticoccidial sensitivity profile of each Eimeria spp. present in the field isolates was based on the reduction of the mean lesion scores of the medicated group compared to the IUC group. The following formula was used: 100% - (mean lesion score of medicated group/mean lesion score of the IUC group x 100%). A reduction percentage of 0-30% indicates coccidial resistance, 31-49% reduction indicates reduced sensitivity or partial resistance and a reduction of 50% or more indicates full sensitivity to the tested anticoccidial product (McDougald et al., 1986; 1987). Results Inocula The twenty-four Eimeria spp. field isolates consisted of different Eimeria spp. E. acervulina was found in twenty-two isolates of which nine as single species, two in combination with E. tenella, nine in combination with E. maxima and two in a mixture with E. tenella and E. maxima. E. tenella and E. maxima were, beside the previous mentioned combinations, only once found as single species. E. acervulina was most frequently seen and was identified in 92% (22/24) of the field isolates. E. maxima was observed in 50% (12/24) field isolates and E. tenella 21% (5/24). The Eimeria spp. field isolates tested and the involved species as well as the inoculation dose (number of sporulated oocysts per chick) are given in Table 2.


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Lesion scores The mean lesion score ± standard deviation (SD) of E. acervulina (n = 105) in the infected unmedicated control was 2.1 ± 0.8, of E. tenella (n = 15) 2.3 ± 1.1 and of E. maxima (n = 55) 1.7 ± 0.9. The lesion scores of the Eimeria spp. present in the field isolates 2001-4 and 2001-11 are not included, as mortality occurred in these groups (see later on). Table 2. Eimeria spp. present in the field isolates and inoculation dose (number of sporulated oocysts) per chick Eimeria spp. field isolate Eimeria spp. involveda Inoculation dose (x 103) 2000-1 (ES) E. ac/E. max 50 2000-2 (ES) E. ac 35 2000-3 (ES) E. ac/E. max 10 2000-4 (ES) E. ac/E. max 50 2000-5 (ES) E. ac/E. ten 10 2001-1 (DEU) E. ac 50 2001-2 (DEU) E. ac 40 2001-3 (DEU) E. ac/E. max 50 2001-4 (DEU) E. ac/E. ten/E. max 15 2001-5 (DEU) E. ac/E. max 30 2001-6 (DEU) E. ac 50 2001-7 (DEU) E. ac/E. max 30 2001-8 (NL) E. max 36 2001-9 (NL) E. ac/E. max 41 2001-10 (NL) E. ac 53 2001-11 (NL) E. ten 10 2001-12 (NL) E. ac/E. max 40 2001-13 (NL) E. ac/E. ten/E. max 21 2002-1 (NL) E. ac 50 2002-2 (NL) E. ac 50 2002-3 (NL) E. ac 50 2002-4 (NL) E. ac/E. max 50 2002-5 (NL) E. ac 50 2002-6 (NL) E. ac/E. ten 10 a E. ac = E. acervulina; E. max = E. maxima; E. ten = E. tenella. (ES) = Spain; (DEU) = Germany; (NL) = the Netherlands. Anticoccidial sensitivity test (AST) An overview of the mean coccidial lesion scores and the OPG per anticoccidial product and Eimeria spp. field isolate is given in Table 3. The mortality of the chicks in the IUC group of field isolate 2001-4 was 80%. This mortality was caused by a pathogenic E. tenella strain present in this field isolate. Due to

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this high rate of mortality it was impossible to determine the sensitivity of E. acervulina and E. maxima also present in this field isolate. In the IUC group and the group medicated with narasin of isolate 2001-11, mortality which was caused by E. tenella was 40 and 60%, respectively. In Table 4 all anticoccidial drug sensitivity profiles per Eimeria spp. and field isolate according to the criteria of McDougald et al., 1986; 1987 are given.


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Table 3. Overview of the mean lesion scores and number of oocysts per gram faeces (x 106) per Eimeria spp. field isolate and anticoccidial product

DIC HAL LAS METI/METH MON ac te ma opg ac te ma opg ac te ma opg ac te ma opg ac te ma opg 2000-1 (ES) 2.4 --- 2.0 4.20 1.6 --- 1.0 0.48 2000-2 (ES) 2.8 --- --- 1.30 3.0 --- --- 1.20 2000-3 (ES) 1.4 --- 1.4 0.19 1.0 --- 1.0 0.18 2000-4 (ES) 3.0 --- 1.2 0.68 2.0 --- 1.0 0.70 2000-5 (ES) 0.8 0.0 --- 0.28 1.0 0.6 --- 0.36 2001-1 (DEU) 3.0 --- --- 1.30 0.4 --- --- 0.03 2001-2 (DEU) 2.0 --- --- 0.68 0.6 --- --- 0.15 2001-3 (DEU) 2.0 --- 0.0 0.11 0.0 --- 0.0 0.01 2001-4 (DEU) 0.4 0.8 0.4 0.26 0.0 0.0 1.2 0.03 2001-5 (DEU) 1.0 --- 0.6 0.25 0.2 --- 1.6 0.08 2001-6 (DEU) 2.2 --- --- 3.40 2.0 --- --- 0.28 2001-7 (DEU) 2.4 --- 0.2 1.40 1.6 --- 0.6 0.15 2001-8 (NL) --- --- 2.6 0.01 --- --- 2.6 0.08 2001-9 (NL) 1.2 --- 0.4 2.00 0.0 --- 0.0 0.00 2001-10 (NL) 1.4 --- --- 4.70 0.0 --- --- 0.00 2001-11 (NL) --- 0.0 --- 0.00 --- 0.0 --- 0.00 2001-12 (NL) 1.6 --- 1.0 4.00 0.4 --- 0.2 0.01 2001-13 (NL) 1.8 2.0 1.2 3.50 0.2 0.0 0.0 0.01 2002-1 (NL) 2.2 --- --- 2.10 1.4 --- --- 2.23 2.2 --- --- 3.80 2002-2 (NL) 2.4 --- --- 2.20 3.0 --- --- 3.10 2.4 --- --- 3.99 2002-3 (NL) 2.6 --- --- 3.37 1.8 --- --- 1.69 0.0 --- --- 0.00 2002-4 (NL) 3.0 --- 2.4 0.78 1.8 --- 0.0 0.68 0.0 --- 2.0 0.14 2002-5 (NL) 2.0 --- --- 4.50 2.4 --- --- 1.70 2.4 --- --- 6.19 2002-6 (NL) 0.8 2.6 --- 0.54 1.0 1.0 --- 0.07 1.0 2.0 --- 0.31

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DIC = diclazuril; HAL = halofuginone; LAS = lasalocid; METI/METH = meticlorpindol/methylbenzoquate; MON = monensin; NAR = narasin; NIC = nicarbazin; ROB = robenidine; SAL = salinomycin; IUC = infected unmedicated control. ac = Eimeria acervulina; te = E. tenella; ma = E. maxima. ES = Spain; DEU = Germany; NL = the Netherlands.

NAR NAR/NIC NIC ROB SAL IUC ac te ma opg ac te ma opg ac te ma opg ac te ma opg ac te ma opg ac te ma opg 2.4 --- 1.0 0.52 0.6 --- 1.4 0.19 2.2 --- 1.6 5.10 2.8 --- --- 2.00 1.0 --- --- 0.37 2.6 --- --- 1.20 1.8 --- 1.4 0.59 0.4 --- 0.8 0.10 1.8 --- 1.2 0.71 2.6 --- 0.0 0.32 1.4 --- 0.0 0.30 2.4 --- 1.2 0.07 1.0 0.8 --- 0.12 0.0 0,8. --- 0.18 1.0 0.8 --- 0.11 2,.2 --- --- 0.73 2.4 --- --- 1.50 2.2 --- --- 1.70 2.6 -- --- 2.40 2.2 --- --- 1.30 2.8 --- --- 1.50 2.4 --- --- 0.97 3.0 --- --- 2.40 2.4 --- 0.2 0.40 1.8 --- 1.0 0.20 1.2 --- 1.2 0.64 3.0 --- 1.2 1.40 0.8 3.0 1.0 0.26 0.8 3.2 0.8 0.10 1.0 2.6 1.2 0.29 0.0 4.0 0.0 0.44 1.0 --- 1.4 0.17 1.4 --- 1.8 0.17 1.0 --- 1.8 0.23 1.4 --- 2.2 0.35 2.6 --- --- 3.0 2.6 --- --- 2.60 2.6 --- --- 3.90 3.4 --- --- 3.80 1.6 --- 0.6 1.30 1.0 --- 1.0 1.00 1.6 --- 1.4 1.20 1.4 --- 2.2 1.10 --- --- 2.4 0.05 --- --- 1.2 0.02 --- --- 2.6 0.07 --- --- 1.6 0.05 --- --- 3.2 0.04 1.6 --- 0.2 2.20 1.4 --- 0.0 1.60 1.8 --- 0.0 2.30 1.2 --- 0.6 0.90 1.2 --- 1.0 2.20 1.4 --- --- 1.70 1.6 --- --- 2.50 1.6 --- --- 1.00 1.2 --- --- 1.40 2.2 --- --- 4.10 --- 3.6 --- 0.02 --- 3.0 --- 0.09 --- 3.2 --- 0.01 --- 3.2 --- 0.22 --- 3.6 --- 0.03 1.8 --- 0.8 2.10 2.2 --- 0.6 2.10 2.4 --- 0.4 3.00 1.0 --- 1.2 0.14 2.0 --- 0.8 3.40 1.8 2.4 1.4 3.30 1.0 2.6 0.8 1.80 1.2 2.8 1.4 2.60 1.0 2.8 0.8 1.40 1.6 3.0 1.6 4.00 1.4 --- --- 2.89 1.0 --- --- 2.00 1.6 --- --- 1.18 1.4 --- --- 1.05 2.2 --- --- 7.59 1.6 --- --- 2.90 2.0 --- --- 1.47 2.6 --- --- 2.59 2.6 --- --- 1.13 3.0 --- --- 6.79 2.8 --- --- 1.69 1.6 --- --- 2.29 1.0 --- --- 0.70 1.2 --- --- 1.44 2.6 --- --- 6.19 2.4 --- 1.6 0.96 1.8 --- 2.2 1.05 0.8 --- 0.0 0.20 2.2 --- 1.2 0.52 2.8 --- 2.1 2.70 2.2 --- --- 3.10 2.4 --- --- 3.80 0.2 --- --- 0.02 2.0 --- --- 2.90 1.6 --- --- 2.99 1.0 2.8 --- 0.74 1.0 2.8 --- 0.49 0.8 0.0 --- 0.11 1.0 3.0 --- 0.34 1.0 3.0 --- 0.84


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Table 4. Anticoccidial sensitivity profiles per Eimeria spp. found in the field isolates according to the criteria of McDougald et al. (1986; 1987) Anticoccidial product


R RS S R RS S R RS S DIC 5/-/3/6* 0/-/1/0 0/-/0/0 0/-/0/1 0/-/1/0 1/-/1/0 3/-/3/1 0/-/0/0 0/-/1/0 HAL -/3-/3 -/3/-/3 -/0/-/0 -/0/-/0 -/0/-/0 -/1/-/1 -/0/-/0 -/0/-/0 -/3/-/1 LAS -/-/-/4 -/-/-/0 -/-/-/0 -/-/-/0 -/-/-/1 -/-/-/0 -/-/-/- -/-/-/- -/-/-/- METI/METH -/1/0/0 -/1/0/0 -/4/4/2 -/0/0/- -/0/0/- -/1/2/- -/1/1/1 -/0/0/- -/2/3/0 MON 4/-/-/- 1/-/-/- 0/-/-/- 1/-/-/- 0/-/-/- 0/-/-/- 2/-/-/- 1/-/-/- 0/-/-/- NAR -/-/3/4 -/-/1/2 -/-0/0 -/-/2/1 -/-/0/0 -/-/0/0 -/-/3/1 -/-/0/0 -/-/1/0 NAR/NIC -/6/3/2 -/0/1/3 -/0/0/1 -/1/2/1 -/0/0/0 -/0/0/0 -/0/1/1 -/1/0/0 -/2/3/0 NIC 5/5/4/- 0/1/0/- 0/0/0/- 1/1/2/- 0/0/0/- 0/0/0/- 1/2/2/- 1/0/0/- 1/1/2/- ROB -/-/-/3 -/-/-/0 -/-/-/3 -/-/-/0 -/-/-/0 -/-/-/1 -/-/-/0 -/-/-/0 -/-/-/1 SAL 0/5/1/4 1/0/2/1 4/1/1/1 1/0/2/1 0/1/0/0 0/0/0/0 1/2/1/0 1/1/1/1 1/0/2/0 * Data represent successively the number of isolates per category of Spain (2000)/Germany (2001)/the Netherlands (2001)/the Netherlands (2002). DIC = diclazuril; HAL = halofuginone; LAS = lasalocid; METI/METH = meticlorpindol/methylbenzoquate; MON = monensin; NAR = narasin; NIC = nicarbazin; ROB = robenidine; SAL = salinomycin. R = resistant; RS = reduced sensitive; S = sensitive. - = not done. Discussion The infection doses of the inocula were chosen aiming at lesion scores of 2-3 on the scale of Johnson & Reid (1970) and no mortality in the IUC groups. The obtained mean lesion score of E. acervulina was 2.1, of E. tenella 2.3 and of E. maxima 1.7. Globally, the target lesion scores pursued, were obtained with the inoculations doses used. Exceptions were isolates 2001-4 and 2001-11, in which mortality was caused by a severe clinical E. tenella infection and E. maxima, with lesion scores below 2-3. The lower lesion score of E. maxima may have been the result of a small amount of E. maxima oocysts present in the inoculum. However, it is also possible that the infection of E. maxima was influenced by the E. acervulina infection, since this species has a shorter prepatent period in comparison with E. maxima. Moreover, a severe E. acervulina infection can affect large parts of the intestine beside the duodenum destroying intestinal epithelial cells used for the development of E. maxima (Williams, 2001).

All Eimeria spp. field isolates from this study were collected from broiler farms where no severe clinical coccidiosis problems had been diagnosed. However, the tested Eimeria spp. field isolates showed resistance against most anticoccidial products analysed.

Regarding the evaluation of sensitivity of E. maxima against diclazuril an important consideration should be made. Diclazuril is mainly active against the stages of the parasite found at the end of the lifecycle resulting in the formation of an abnormally thickened,

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incomplete oocyst wall and ending in necrosis of the produced zygote (Verheyen et al., 1989). Therefore, despite a fully sensitive anticoccidial profile of E. maxima against diclazuril, lesions can be observed in the intestine but then oocyst excretion is limited or even nullified. In contrast, if resistance occurs the oocyst excretion will not be limited or nullified.

The number of oocysts excreted after a coccidiosis infection with different Eimeria spp. field isolates varies greatly and may be difficult to interpret. This is explained by the fact that many field isolates consist of Eimeria spp. differing in their pathogenicity and oocyst production. Moreover, Eimeria spp. often have different anticoccidial sensitivity profiles (Reid, 1975), while the so called ‘crowding’ effect may additionally also influence oocyst production. This phenomenon occurs when many host cells are lost during the schizogony (asexual phase) and no cells to accomplish the gametogony (sexual phase) and hence the production of oocysts (Williams, 2001) remain. Another explanation can be the individual variation of the coccidiosis sensitivity (resistance) of the laboratory animals used, even if they are closely related. In this regard, as the trials were performed in different periods, dissimilarities between batches of laboratory animals may have played a role.

The OPG determined in groups inoculated with the same field isolate are often good interpretable. Especially, if the isolate is sensitive to the tested anticoccidial product. An example for this is the anticoccidial profile obtained for meticlorpindol/methylbenzoquate. The full sensitivity profile based on the reduction of coccidiosis lesion scores was confined by the OPG results.

Resistance against all existing anticoccidial products is common and has been widely described (Chapman, 1986; 1990; 1997; McDougald et al., 1986; 1987; Vertommen & Peek, 1993). However, susceptibility to anticoccidial products may be regained after long periods of withdrawal from feed (Chapman, 1990). Evidence for this was also found in the ASTs performed with the product meticlorpindol/methylbenzoquate, which showed high anticoccidial activity likely due to its infrequent use (the product had almost not been used since 1999 according to the participating farms). Products with high anticoccidial activity could be used to effectively control coccidiosis at farms with resistance associated problems, while rotation with a live sensitive vaccine could increase the sensitivity of the existing Eimeria spp. field population to the anticoccidial products. The exact number of grow-outs that must be vaccinated successively in order to induce higher incidence of sensitive Eimeria spp. field isolates will depend upon the vaccine used and the pathogenicity of the resistant Eimeria spp. (Chapman, 2000; Chapman et al., 2002). By regularly performing ASTs, which currently is the only reliable method to measure the anticoccidial drug sensitivity, changes and evolution in anticoccidial drug profiles can be monitored.

Although, in recently performed ASTs anticoccidial drug resistance was extensively found in the Netherlands, the number of outbreaks of clinical coccidiosis was not increased (Peek & Landman, 2003). Possibly as a result of the (partial) inefficiency of the anticoccidial products due to resistance, immunisation of the birds caused by subclinical ‘trickle’ infections, as has been described during vaccination


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(Chapman, 1976; Jeffers, 1989), occurred. This may also explain the absence of severe clinical problems at the farms where the Eimeria spp. field isolates for this study were collected.

In general, ASTs are not performed on a regular basis, which is the cause for a paucity on actual and a continuous flow of data on anticoccidial drug resistance (Chapman, 1998). They are nevertheless of major significance for the optimal use of the anticoccidial products and the design of efficient coccidiosis prevention programs. The latter are crucial to prevent a further increase in the prevalence of multi drug resistant Eimeria spp. field isolates. References Braunius, W.W. (1980). Coccidiosis bij slachtkuikens, Tijdschrift voor Diergeneeskunde, 105, pp. 11-20. Chapman, H.D. (1976). Eimeria tenella in chickens: studies on resistance to the anticoccidial drugs

monensin and lasalocid. Veterinary Parasitology, 2, pp. 187-196. Chapman, H.D. (1986). Isolates of Eimeria tenella: studies on resistance to ionophorous anticoccidial

drugs. Research in Veterinary Science, 41, pp. 281-282. Chapman, H.D. (1990). Drug resistance in coccidia of the fowl. In Boray J.C., Martin, P.J. & Roush, R.T.

eds. Resistance of parasites to antiparasitic drugs. Rahway N.J: MSD Agvet, Merck & Co., Incorporate, pp. 33-41.



Chapman, H.D. (2000). Practical use of vaccines for the control of coccidiosis in the chicken. World Poultry Science, 56, pp. 7-20.

Chapman, H.D., Cherry, T.E., Danforth, H.D., Richards, G., Shirly, M.W. & Williams, R.B. (2002). Sustainable coccidiosis control in poultry production: the role of live vaccines. International Journal for Parasitology, 32, pp. 617-629.

Jeffers, T.K. (1989). Anticoccidial drug resistance: a review with emphasis on the polyether ionophores. In: Yvore, P. (Ed.). Proceedings of the Vth International Coccidiosis Conference, (pp. 295-308). Tours, France.


Levine, N.D. (1973). Introduction, history and taxonomy. In: The Coccidia 1. University Park Press, Baltimore.

Long, P.L., Millard, B.J., Joyner, L.P. & Norton, C.C. (1976). A guide to laboratory techniques used in the study and diagnosis of avian coccidiosis. Folia Veterinaria Latina, 6, pp. 201-217.


McDougald, L.R., DaSilva, J.M., Solis, J. & Braga, M. (1987). A survey of sensitivity to anticoccidial drugs in 60 isolates of coccidia from broiler chickens in Brazil and Argentina. Avian Diseases, 31, pp. 287-292.

McDougald, L.R. & Reid, W.M. (1997), Coccidiosis. In: Calnek, B.W., Barnes, H.J., Beard, C.W., McDougald, L.R. & Saif, Y.M. (eds.). Diseases of Poultry 10th edn,. (pp. 865-883). Ames: Iowa State University Press.

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Reid, W.M. (1975). Relative value of oocysts counts in evaluating activity. Avian Diseases, 19, pp. 802-811.


Verheyen, A., Maes, L., Coussement, W., Vanparijs, O., Lauwers, F., Vlaminckx, E. & Marsboom, R. (1989). Ultrastructural evaluation of the effects of diclazuril on the endogenous stages of Eimeria maxima and E. brunetti in experimentally inoculated chickens. Parasitology Research, 75, pp. 604-610.

Vertommen, M.H. & Peek, H.W. (1993). Anticoccidial efficacy of diclazuril (Clinacox®) in broilers: sensitivity tests; resistance development; cross resistance to Baycox®. In: Barta, J.R. & Fernando, M.A. (eds.). Proceedings of the VIth International Coccidiosis Conference (pp. 154-155). Guelph, Canada.

Vertommen, M. (1996). Coccidiosis control methods. In: Proceedings of the Paracox European Symposium (pp. 11-20). Annecy, France.

Williams, R.B. (1998). Epidemiological aspects of the use of live anticoccidial vaccines for chickens. International Journal for Parasitology, 28, pp. 1089-1098.

Williams, R.B. (2001). Quantification of the crowding effect during infections with the seven Eimeria species of the domesticated fowl: its importance for experimental design and the production of oocysts stocks. International Journal for Parasitology, 31, pp. 1056-1069.

Williams, R.B. (2002). Anticoccidial vaccines for broiler chickens: pathways to success. Avian Pathology, 31, pp. 317-353.

Chapter 3

Influence of ibuprofen, a mucolytic enzyme and a mannanoligosaccharide preparation (MOS) on a

coccidiosis infection in broilers

Effect of ibuprofen on coccidiosis in broiler chickens B. Vermeulena, H.W. Peekb, J.P. Remona and W.J.M. Landmanb aLaboratory of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Ghent University, Belgium bAnimal Health Service (GD), Poultry Health Centre, P.O. Box 9, 7400 AA Deventer, the Netherlands Avian Diseases (January 2004), 48(1), 68-76 Summary Ibuprofen (IBU), a non-steroidal anti-inflammatory drug (NSAID), inhibits the biosynthesis of prostaglandins (PG) with pro-inflammatory and immunosuppressive properties and is therefore proposed as a candidate molecule for the treatment of coccidiosis in broiler chickens. In all experiments, IBU was administered via drinking water. In a first experiment, chickens were infected at 10 or 21 days of age with oocysts of Eimeria acervulina (5 x 104), E. maxima (3 x 104) and E. tenella (7.5 x 103) and medicated with IBU at a dose of 15 mg/kg body weight (BW). In a second experiment, chickens were infected at six days of age with 104 oocysts of E. acervulina and medicated with IBU at a dose of 100 mg/kg BW. In the third experiment an inoculum consisting of 5 x 104 or 105 E. acervulina oocysts was administered at six days of age to chickens medicated with IBU at a dose of 100 mg/kg BW. In a fourth experiment, the effect of IBU on sporulation and infectivity of E. acervulina oocysts was studied. Coccidial lesion scores (CLSs), oocyst shedding and weight gain were used as evaluation parameters in all experiments, except the weight gain which was not taken into account in the fourth experiment. In addition, the sporulation percentage was determined in the last experiment. No influence of IBU on the indicated parameters was observed after providing the drug at a dose of 15 mg/kg BW, while CLSs and oocyst shedding were reduced when IBU was provided in a dose of 100 mg/kg BW. However, IBU did not significantly show any effect on the degree of sporulation and infectivity of E. acervulina oocysts at a dose of 100 mg/kg BW. Keywords: coccidiosis, prostaglandins, ibuprofen, drinking water, broiler chickens

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Introduction Coccidiosis is a widespread parasitic poultry disease with great economic relevance (Weber, 1997) and is caused by protozoa of the genus Eimeria (Phylum Apicomplexa). Of the seven Eimeria species described in chickens, E. acervulina, E. maxima and E. tenella are the most significant in broiler chickens. These different species can be distinguished by the morphology of the lesions and their location in the intestine, and the size of oocysts produced (McDougald & Reid, 1991).

Control of coccidiosis in broiler chickens is still problematic due to the large scale occurrence of resistance against most anticoccidial drugs (Chapman, 1997; Peek & Landman 2003) and the limited use of vaccines for economic reasons, non-founded supposed adverse effects on chick growth as well as fears for insufficiently developed immunity (Williams, 2002).

The previous mentioned shortcomings have prompted to a search for alternatives in the combat against this parasitic disease. A possible alternative such as non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen (IBU) was therefore investigated.

Host immune responses against coccidial infections are very complex. Similar to the immune responses to many other parasitic infections of the gastrointestinal tract, the role of humoral factors such as antibodies is not completely understood. In contrast, the role of T lymphocytes, which are involved in the development of cellular immunity, is well-documented (Lillehoj, 1998; Lillehoj & Lillehoj, 2000; Yun et al., 2000): T lymphocytes are involved in the production of different cytokines that participate in immune responses against coccidia. The five most important cytokines are interferon-γ (IFN-γ), tumour necrosis factor-α (TNF-α), interleukin-2 (IL-2), interleukin-15 (IL-15) and transforming growth factor-β (TGF-β) (Lillehoj & Lillehoj, 2000; Yun et al., 2000). IFN-γ and TNF-α are involved in the generation of nitric oxide (NO) from L-arginine (ARG) (Lillehoj & Lillehoj, 2000; Ovington et al., 1995) by activation of inducible nitric oxide synthase (iNOS). NO is an important defense mechanism against the invasion of different Apicomplexa parasites (Adams et al., 1990; Mellouk et al., 1991) however, Allen (1997a; 1997b) suggested that NO might promote the development of coccidial lesions and thereby contribute to the pathology of coccidiosis. Increased NO concentrations activate inducible cyclooxygenase (iCOX), which in turn is involved in the production of prostaglandins (PG) with pro-inflammatory and immunosuppressive properties (Vane et al., 1994). NSAID - known as inhibitors of COX - inhibit the biosynthesis of these PG.

Oral administration of another NSAID namely indomethacin had no effect on weight gain or coccidial lesions but reduced oocyst shedding in chickens infected with E. acervulina oocysts (Allen, 2000). Moreover, indomethacin also reduced oocyst shedding after infection of chickens with Cryptosporidium bailey (Hornok et al., 1999).

In the present manuscript, the effect of IBU on coccidiosis in broilers was assessed after administration of different doses of the drug via drinking water. In addition, the effect of IBU on the sporulation and infectivity of E. acervulina oocysts was studied.

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Material and methods Experimental design Three experiments were performed to study the effect of the drinking water administration of IBU on coccidiosis in broiler chickens. Another experiment (experiment 4) was carried out to study the effect of IBU on sporulation and infectivity of E. acervulina oocysts. Experiment 1 One medicated group (n = 20) treated with IBU at a dose of 15 mg/kg body weight (BW) was made. Medication was given from one day of age until seven days post-infection (p.i.) (17 or 28 days of age). Another group served as infected unmedicated control (n = 20). Ten chickens per group were infected at ten days of age with an inoculum consisting of 5 x 104 E. acervulina, 3 x 104 E. maxima and 7.5 x 103 E. tenella oocysts. Another ten chickens per group were infected with the same Eimeria species at 21 days of age, except the E. acervulina inoculum, which was administered at 23 days of age. In addition, a third group served as uninfected unmedicated control (n = 20). All birds were euthanased seven days p.i. to assess coccidial lesion scores (CLSs) according to the method of Johnson & Reid (1970). Oocyst shedding, expressed as the number of oocysts per gram faeces (OPG), was determined by collecting faeces 4-7 days p.i. in each cage. Oocyst shedding was performed on one sample of homogenized faeces material deposited in each cage. After homogenization of the faeces, oocysts were counted by means of a modification of the McMaster counting chamber technique of Hodgson (1970) as described by Peek & Landman (2003). Birds monitored for oocyst shedding were weighted before infection and three and six days p.i. to determine weight gain. Experiment 2 One medicated group consisting of 15 chickens was given IBU at a dose of 100 mg/kg BW from one day before infection (five days of age) until five days p.i. (eleven days of age). A second group served as infected unmedicated control (n = 15). At six days of age, the birds of both groups were infected with an inoculum of 104 E. acervulina oocysts. A third group served as uninfected unmedicated control (n = 15). Ten chickens per group were euthanased five days p.i. to determine CLSs as described in experiment 1. The remaining birds were used to determine oocyst shedding from 4-9 days p.i. The collected homogenized faeces were divided in two portions and two samples from each portion were prepared for oocyst counting. The number of oocysts per gram faeces and the weight gain were determined as described in experiment 1.

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Experiment 3 A group consisting of 20 chickens was medicated with IBU at a dose of 100 mg/kg BW and medication was provided from one day prior to infection (five days of age) until five days p.i. (eleven days of age). An uninfected unmedicated control and infected unmedicated control group each consisting of 20 birds also formed part of the experiment. An inoculum consisting of 5 x 104 E. acervulina oocysts was administered to ten birds of the medicated and unmedicated infected group at 6 days of age. The remaining birds of both groups (ten chickens per group) were infected with a dose of 105 E. acervulina oocysts at the same age. Intestinal lesions were assessed on five birds per group five days p.i., while oocyst shedding and weight gain were determined on the remaining birds as described in experiment 2. Experiment 4 One group of chickens (n = 15) was medicated with IBU at a dose of 100 mg/kg BW. The medication was provided one day prior to infection (five days of age) until five days p.i. (eleven days of age). Another group with the same number of birds served as infected unmedicated control. All birds were infected at six days of age with 5 x 104 E. acervulina oocysts. Eight birds per group were euthanased six days later (twelve days of age) to assess coccidial lesions as described before. From the remaining birds, oocyst shedding was determined on daily basis from 3-9 nine days p.i. (nine to fifteen days of age). After dividing the faeces as described in experiment 2, oocysts were counted as mentioned in experiment 1. Faeces excreted four days p.i. were collected to study the effect of IBU on sporulation and to prepare the inocula for the second part of the experiment in which the infectivity of oocysts originating from faeces of IBU medicated and unmedicated chickens was studied. Two groups of unmedicated chickens each of fifteen birds were infected at six days of age with E. acervulina oocysts either from unmedicated (A) or medicated chickens (B). Eight chickens per group were euthanased 6 days p.i. to determine CLSs as described above. Additionally, oocyst shedding was determined daily in droppings collected from 3-9 days p.i. Chickens and housing In experiment 1, commercial male Hybro (Nutreco, Putten, the Netherlands) chickens were obtained at one day of age and housed in three HEPA isolators (Beyer and Eggelaar, Utrecht, the Netherlands) with a volume of 1.3 m3 (140 cm length, 75 cm width, 125 cm height) each. After infection, chickens were transferred to stainless steel cages (200 cm length, 100 cm width and 30 cm height). A lighting scheme of 23 h light and 1 h dark was used in both, the isolators and the cages. In the other experiments, commercial male Ross (Belgabroed, Merksplas, Belgium) chicks were obtained at one day of age and housed in a large steel cage (150 cm length, 60 cm width and 40 cm height). One day prior to infection (five days of age), chickens were transferred to separate steel cages (75 cm


144

length, 60 cm width and 40 cm height) and provided with constant lighting. In all experiments, drinking water and a complete formulated broiler starter mash (Arkervaart-Twente, Nijkerk, the Netherlands) containing 12.0 megajoules/kg Apparent Metabolizable Energy (AME), were available ad libitum. Drinking water medication with ibuprofen IBU (Knoll Pharma Chemicals, Nottingham, England) was mixed with ARG (Orffa, Londerzeel, Belgium) to improve its solubility and enable drinking water medication. Equal weight amounts of IBU (24.5 g) and ARG were mixed and 2% (w/w) citric acid (Federa, Brussels, Belgium) was added to this mixture. The powders were moistened with 2 ml of an aqueous solution of 25% (w/w) Tween® 60 (Federa). Next the wet mass was passed through a 750 µm sieve and dried at room temperature (20 ± 2 °C) until constant weight. The drinking water medication was prepared daily and the required amount of the drug formulation was calculated based on daily average body weight and water consumption per group of chickens. Inocula Sporulated oocysts of E. acervulina (W119, Weybridge), E. maxima (Weybridge) and E. tenella (Houghton) laboratory strains were used to prepare the inocula. These strains were obtained from the Central Veterinary Laboratory (Weybridge, UK) and maintained alive by regular passage in chickens at the Animal Health Service - Poultry Health Centre (Deventer, the Netherlands). Sporulated oocysts were conserved in a 2.5% (w/v) K2Cr2O7 (Vel, Leuven, Belgium) solution to prevent bacterial and fungal contamination. The number of oocysts per ml suspension was counted with a haemocytometer (Fuchs-Rosenthal counting chamber). A volume containing the required number of sporulated oocysts was transferred into a scaled plastic tube and K2Cr2O7 was washed out by centrifugation. The chickens were individually inoculated in the crop with a scaled 1ml syringe containing the required number of sporulated oocysts in 0.5 ml tap water. Sporulation assessment In experiment 4, oocysts were purified from faeces collected four days p.i. (ten days of age) within 3 h after defecation by means of a saturated sodium salt flotation technique based on the method of Ryley et al. (1976) and modified by Peek & Landman (2003). Sporulation of oocysts occurred by aerating the oocyst suspensions at 29 °C during 72 h. Four samples of one ml of each suspension were removed 0, 3, 6, 9, 12, 18, 24, 30, 36, 48, 60 and 72 h after initiation of sporulation. The sporulation percentage was determined by means of an haemocytometer (Fuchs-Rosenthal counting chamber) and oocysts were counted as sporulated when four sporocysts could be seen at a 400 x magnification.

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Statistical analysis The results of CLSs were analyzed non-parametrically using the Kruskal-Wallis test and were considered significantly different at P ≤ 0.05. Data on weight gain and oocyst shedding were analyzed using a one-way ANOVA after verifying normality and homogeneity and were considered significantly different at P ≤ 0.05. Normality of data was verified using the Kolmogorov-Smirnov test and the Levene test was used to verify homogeneity of variances. For all statistical analyses, SPSS for Windows (version 10.0, 2001) was used. Results Drinking water medication with ibuprofen In experiment 1, a theoretical IBU dose of 15 mg/kg BW was attempted. The daily doses obtained varied from 9.8 to 18.2 mg/kg. The mean administered dose in the birds infected at ten days of age was 14.3 ± 2.9 mg/kg, while in chickens infected at 21 days of age a mean dose of 15.2 ± 2.3 mg/kg BW was found. In experiment 2 (IBU 100 mg/kg BW), the daily doses varied between 87 and 99 mg/kg BW, while a mean administered dose of 95 ± 5 mg/kg BW was found. Doses administered in experiment 3 (IBU 100 mg/kg BW) varied from 70 to 119 mg/kg BW while mean administered doses of 92 ± 19 and 96 ± 18 mg/kg BW were obtained after infection with 5 x 104 and 105 E. acervulina oocysts, respectively. In experiment 4 (IBU 100 mg/kg BW) the daily doses varied between 84 and 116 mg/kg BW. A mean administered dose of 102 ± 14 mg/kg BW was found. Experiment 1 The results of experiment 1 are shown in Table 1. CLSs due to E. acervulina were minimal after infection at ten days of age. In contrast, CLSs of 2.8 ± 0.4 and 2.4 ± 0.5 were obtained for the unmedicated and medicated group, respectively after infection at 23 days of age. E. maxima lesions were more severe after infection at 21 days of age (2.7 ± 0.7 and 2.5 ± 1.1 for the unmedicated and medicated group, respectively) compared with those after infection at ten days of age (1.7 ± 0.5 and 1.5 ± 0.5 for the unmedicated and medicated group, respectively). E. tenella lesion scores of 2.8 ± 0.4 (unmedicated group) and 2.8 ± 0.4 (medicated group) were obtained after infection at ten days of age, while scores of 3.1 ± 0.3 (unmedicated group) and 3.2 ± 0.4 (medicated group) were determined after infection at 21 days of age. CLSs of the medicated group did not differ significantly from the unmedicated group after infections at ten and 21 days of age. The number of oocysts counted per gram faeces, defined as oocyst shedding, was higher in the groups infected at ten days of age (2.32 x 106 and 2.44 x 106 for the unmedicated and medicated group, respectively) compared with chickens infected at 21 days of age (0.61 x 106 and 0.66 x 106 for the unmedicated and medicated group, respectively). Oocyst shedding was


146

not influenced by administration of IBU at any time. Compared with the uninfected unmedicated control chickens, the average weight gain was significantly (P ≤ 0.05) lower 3-6 days p.i. in the infected groups after infection at ten and 21 days of age. Experiment 2 The results of experiment 2 are outlined in Table 2. Significant (P ≤ 0.05) reduced CLSs were obtained in the medicated group (0.3 ± 0.5) compared with the unmedicated birds (0.9 ± 0.7). The number of oocysts per gram faeces was significantly (P ≤ 0.05) reduced in the medicated chickens (3.89 ± 0.09 x 104) compared with the unmedicated birds (6.28 ± 0.10 x 104). The average weight gain was not significantly reduced in the infected groups compared with the uninfected birds. Experiment 3 The results of experiment 3 are summarized in Table 3. CLSs were lower in the medicated group (2.0 ± 0.7) compared with the unmedicated group (2.8 ± 0.4) after infection with a dose of 5 x 104 E. acervulina oocysts. After infection with 105 E. acervulina oocysts, lesion scores were also lower in the medicated group (2.4 ± 0.5) compared with the unmedicated group (3.0 ± 0.7). Although lesion scores were less severe in medicated birds, this difference was not significant. In the medicated group, 1.00 ± 0.03 x 106 and 1.49 ± 0.04 x 106 oocysts per gram faeces were counted after infection with 5 x 104 and 105 E. acervulina oocysts, respectively. They were significantly (P ≤ 0.05) lower than in the unmedicated group. The numbers of oocysts counted per gram faeces in the unmedicated group were 1.99 ± 0.04 x 106 and 4.58 ± 0.09 x 106 after infection with 5 x 104 and 105 E. acervulina oocysts, respectively. A significant (P ≤ 0.05) lower weight gain was noted 3-6 days p.i. in the infected groups compared with the uninfected group after infection with 105 E. acervulina oocysts.

Table 1. Coccidial lesion scores (CLSs) (7 days p.i.), number of oocysts per gram faeces (OPG) (4-7 days p.i.) and weight gain (g) (0-3 (P1) and 3-6 days (P2 ) p.i ) of experiment 1 GroupC Medication Inoculum Age at CLSs ± SD (n = 10) OPGB Weight gain ± SD (g) E. ac E. max E. ten InfectionA E. ac E. max E. ten (x 106) P1 P2 UUC None 0 0 0 0 0 0 0 128 ± 7 152 ± 11a

IUC None 5 x 104 3 x 104 7.5 x 103 10 0.2 ± 0.4 1.7 ± 0.5 2.8 ± 0.4 2.32 129 ± 16 42 ± 21b

IM IBU 5 x 104 3 x 104 7.5 x 103 10 0.1 ± 0.3 1.5 ± 0.5 2.8 ± 0.4 2.44 128 ± 22 44 ± 23b

UUC None 0 0 0 0 0 146 ± 23 225 ± 34a

IUC None 5 x 104 3 x 104 7.5 x 103 21 & 23 2.8 ± 0.4 2.7 ± 0.7 3.1 ± 0.3 0.61 183 ± 18 69 ± 54b

IM IBU 5 x 104 3 x 104 7.5 x 103 21 & 23 2.4 ± 0.5 2.5 ± 1.1 3.2 ± 0.4 0.66 174 ± 27 83 ± 50b

A E. acervulina oocysts were administrated at 10 and 23 days of age, while other Eimeria spp. were administrated at 10 and 21 days of age. B Faeces collected from 10 chickens per experimental group were used for the determination of oocyst shedding. C UUC = uninfected unmedicated control; IUC = infected unmedicated control; IM = infected medicated with IBU 15 mg/kg body weight. a,b Values of groups with no common superscript within columns differ significantly (P ≤ 0.05). Table 2. Coccidial lesion scores (CLSs) (5 days p.i.), number of oocysts per gram faeces (OPG ± SD) (4-9 days p.i.) and weight gain (g) (0-3 (P1) and 3-6 days (P2) p.i.) of experiment 2 GroupA Medication Inoculum Age at infection CLSs ± SD OPGB ± SD Weight gain ± SD (E. acervulina) (Days) (n = 10) (x 104) P1 P2 UUC None 0 - 0 0 57 ± 14 86 ± 9 IUC None 104 6 0.9 ± 0.7a 6.28 ± 0.10a 70 ± 5 87 ± 6 IM IBU 104 6 0.3 ± 0.5b 3.89 ± 0.09b 56 ± 12 85 ± 7 A UUC = uninfected unmedicated control, IUC = infected unmedicated control, IM = infected medicated with IBU 100 mg/kg BW. B Faeces collected from 5 chickens per experimental group were used for determination of oocyst shedding. a, b Values of groups with no common superscript within columns differ significantly (P ≤ 0.05).

Table 3. Coccidial lesion scores (CLSs) (5 days p.i.), number of oocysts per gram faeces (OPG) (4-9 days p.i.) and weight gain (g) (0-3 (P1) and 3-6 days (P2) p.i.) of experiment 3 GroupA Medication Inoculum Age at CLSs ± SD OPGB Weight gain ± SD (g) (E. acervulina) Infection ) P (n = 5) (x 106

1 P2 UUC None 0 - 0 0 86 ± 13 106 ± 26 IUC None 5 x 104 6 2.8 ± 0.4 1.99 ± 0.04a 81 ± 15 79 ± 19 IM IBU 5 x 104 6 2.0 ± 0.7 1.00 ± 0.03b 92 ± 7 86 ± 16 UUC None 0 - 0 0 89 ± 6 74 ± 7a

IUC None 105 6 3.0 ± 0.7 4.58 ± 0.09a 96 ± 6 44 ± 15b

IM IBU 105 6 2.4 ± 0.5 1.49 ± 0.04b 79 ± 12 42 ± 16b

A UUC = uninfected unmedicated control; IUC = infected unmedicated control; IM = infected medicated with IBU 100 mg/kg BW. B Faeces collected from 5 chickens per experimental group were used for determination of oocyst shedding. a, b Values of groups with no common superscript within columns differ significantly (P ≤ 0.05).

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Experiment 4 Data on CLSs are outlined in Table 4. Lesions in IBU medicated chickens (1.8 ± 0.7) were significantly (P ≤ 0.05) lower compared with those in the unmedicated group (2.5 ± 0.5). CLSs of birds infected with E. acervulina oocysts originating from IBU medicated birds (Group B) (1.6 ± 1.1) were not significantly different from those of birds infected with unmedicated oocysts (Group A) (1.8 ± 0.7). The daily OPG for both groups are shown in Figure 1. In the first part of the experiment, the maximal oocyst shedding occurred 5-6 days p.i. and was reduced by 20% in the medicated group. Maximal oocyst shedding in the second part of the experiment was registered 3-4 and 4-5 days p.i. after infection with oocysts from unmedicated chickens and medicated birds, respectively. The percentage of sporulation is shown in Figure 2. It was 0% in both suspensions shortly after starting the sporulation process. After 12 h, 90% of oocysts isolated from the faeces of unmedicated birds were sporulated. The sporulation was decreased by 10% in the suspension containing oocysts from faeces of IBU medicated chickens. During the rest of the sporulation process these percentages remained unchanged. 5

0

1

2

3

4

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3-4 4-5 5-6 6-7 7-8 8-9

Days PI

# O

oc/g

faec

es (x

10

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unmedicated groupIBU medicated groupGroup AGroup B

Figure 1. Daily oocyst shedding (expressed as the number of oocysts per gram faeces) (x 105) in the first (μ unmedicated group, λ IBU medicated group) and second part (ο Group A, ν Group B) of experiment 4.


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0102030405060708090

100

0 3 6 9 12 18 24 30 36 48 60 72Time (h)

Spor

ulat

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unmedicated group IBU medicated group Figure 2. Sporulation percentage in function of time. Closed symbols represent sporulation percentages of oocysts originating from unmedicated broilers and open symbols those of oocysts collected from faeces of IBU medicated birds. Table 4. Coccidial lesion scores (CLSs) (6 days p.i.) of experiment 4

GroupA Medication Inoculum and origin CLSs ± SD (n = 8) Part 1 of experiment 4 5 x 104 (CVL)B 2.5 ± 0.5a

IUC None 5 x 104 (CVL 1.8 ± 0.7b

IM IBU Part 2 of experiment 4 Group A None 5 x 104 (IUC, part 1) 1.8 ± 0.7 Group B None 5 x 104 (IM, part 1) 1.6 ± 1.1

A IUC = infected unmedicated control; IM = infected medicated with IBU 100 mg/kg BW. B CVL = Central Veterinary Laboratory (Weybridge, UK). a, b Mean values ± SD. Per part of the experiment, values within columns having a different superscript are significantly (P ≤ 0,05) different. Columns without superscript are not significantly different.

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Discussion IBU, a NSAID, inhibits COX, which is involved in the biosynthesis of PG from arachidonic acid. COX exists in two isoforms: a constitutive enzyme (cCOX or COX-1) involved in different physiological functions and an inducible enzyme (iCOX or COX-2) activated in macrophages and other cells or tissues by inflammatory cytokines. Inducible COX is involved in the synthesis of PG with pro-inflammatory and immunosuppressive properties (Hornok et al., 1999). In coccidial infections, an increased PG biosynthesis might be expected after a NO mediated increased activity of iCOX (Vane et al., 1994).

When a COX inhibitor such as IBU is administered, the biosynthesis of pro-inflammatory PG is inhibited. Therefore, it was postulated that IBU could reduce lesions, oocyst shedding and weight gain suppression in case of coccidiosis. IBU was administered as a salt with a basic amino acid such as ARG to improve its solubility in water and enable drinking water medication. Although ARG is known as a substrate for the biosynthesis of NO, an increased ARG concentration could theoretically promote the formation of PG and subsequently aggravate the lesions caused by Eimeria oocysts. However, experimental data on supplemental administration of ARG to chickens did not shown such effect on the course of coccidiosis (Allen, 1999). IBU was administered via drinking water and doses close to the theoretical doses of 15 or 100 mg/kg BW were provided. Based on the registered water uptake, 15 to 20% deviations were found in experiments 1, 3 and 4. This was explained by a decrease in water consumption due to the infection. The decrease of water consumption was however difficult to predict. A smaller standard deviation was reached in experiment 2 due to a less pronounced decrease in water uptake as these birds were infected with a lower dose (104) of E. acervulina oocysts. Nevertheless, based on the obtained results it can be concluded that a reproducible dose of IBU can be provided when daily body weight and drinking water consumption are taken into account.

In experiment 1 (Table 1), E. acervulina lesions were not observed seven days p.i. in the groups infected at ten days of age. The absence of lesions can be explained by the shorter prepatent period (96 h) of this species compared with E. maxima (121 h) and E. tenella (115 h) (McDougald & Reid, 1991). Lesions caused by E. acervulina oocysts peak five to six days p.i. and epithelial cells occupied by this species are already partially or completely regenerated at seven days p.i. When chickens were infected with E. acervulina two days later than E. maxima and E. tenella as done in the second part of experiment 1, lesions were observed as expected. More severe E. maxima lesions were observed in chickens infected at 21 days of age compared with birds infected at ten days of age. Older chickens seem to be more sensitive for E. maxima infections. No influence of age of birds on E. tenella lesions was remarked.

The number of oocysts counted per gram faeces was lower in birds infected at 21 days of age compared with those infected at 10 days of age. This was explained by the fact that oocyst shedding is mainly determined by E. acervulina because, compared with E. maxima and E. tenella oocysts, this species has the best oocyst productive potential (Brackett & Bliznick, 1952). As birds infected at 21 days of age received the E.


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acervulina inoculum two days later, oocyst shedding to the full extent was missed compared with infection at 10 days of age. No significant differences in growth were obtained 0-3 days p.i., while weight gain was significantly (P ≤ 0.05) reduced in all infected groups compared with the uninfected group 3-6 six days p.i. From the results shown in Table 1, it can be concluded that the administration of IBU at a dose of 15 mg/kg BW has no influence on coccidial lesions, oocyst shedding and weight gain. Given the fact that IBU has a low oral bioavailability (Roder et al., 1996; Vermeulen & Remon, 2001), a dose of 15 mg/kg BW may be insufficient to affect the severity of coccidial lesions, the oocyst shedding and the weight loss. Therefore in subsequent studies IBU was administered in a dose of 100 mg/kg BW.

Indeed, medication with IBU at a dose of 100 mg/kg BW significantly (P ≤ 0.05) reduced CLSs after infection with 104 oocysts of E. acervulina (Table 2). Although after infection with 5 x 104 or 105 E. acervulina oocysts coccidial lesions were reduced in the medicated group, they were not significantly different from the unmedicated group (Table 3). A previous study published by Allen (2000) reported no effect of COX inhibitors such as indomethacin and nimesulide on coccidial lesions induced by 105, 5 x 105 and 106 E. acervulina oocysts. In the mentioned study the COX inhibitors were supplied via feed (solid form) or as a solution once or twice daily. Both ways of administration (solid form via feed and solution once or twice daily) are in contrast with the continuous supply of a dissolved formulation via drinking water as given in this study and this difference in drug administration might explain the discrepancy found. Moreover, oocyst shedding was significantly (P ≤ 0.05) reduced in the medicated group for each infection dose (104, 5 x 104 and 105 E. acervulina oocysts). The reduced intestinal lesions and oocyst shedding after medication with IBU at 100 mg/kg BW is most probably due to the inhibition of iCOX. No significant difference (P ≤ 0.05) in weight gain was reported in the infected groups compared with the uninfected group from 0-3 days p.i. for all infection doses. However, weight gain from 3-6 days p.i. was significantly reduced in the groups infected with 105 E. acervulina oocysts whether drinking water medication was provided or not (Experiment 3). From the observations obtained in experiments 2 and 3, it can be concluded that IBU administered at 100 mg/kg BW significantly (P ≤ 0.05) reduces oocyst shedding after infection with different doses (104, 5 x 104 and 105) of E. acervulina oocysts when compared with unmedicated chickens. Also, intestinal coccidial lesions are significantly (P ≤ 0.05) lower in medicated birds after infection with 104 E. acervulina oocysts compared with unmedicated chicks.

Because many anticoccidials have proved to reduce the sporulation rate of oocysts (Joyner & Norton, 1977; Ruff et al., 1978; Von Löwenstein & Kutzer, 1989 Arakawa et al., 1991) and to lower the infectivity of sporulated oocysts (Ruff et al., 1978), the effect of IBU on sporulation and infectivity of shedded oocysts was regarded. Oocysts obtained from both unmedicated and medicated chickens started sporulation at the same time (Figure 2). The maximum percentage of sporulation in oocyst suspensions of both groups was reached after 18 h. These results are in accordance with experimental data described elsewhere (Graat et al., 1994). E. acervulina oocysts sporulate within 17 hours with a maximum percentage oscillating between 85 and 95% if maintained under optimal

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conditions (29 ± 1°C, continuous aeration, 2.5% (w/v) K2Cr2O7. The maximum sporulation percentage was 80% and 90% in suspensions with oocysts obtained from medicated and unmedicated chickens, respectively. Unfortunately, this difference in sporulation will likely not be a significant contribution to the reduction of coccidiosis infection pressure in the poultry environment. Therefore, it can be concluded that IBU has no effect on the sporulation of excreted oocysts.

The CLSs obtained in the second part of experiment 4 were lower than those induced in the unmedicated group in the first part (Table 4). In the first part of the experiment, the oocysts derived from faeces sampled between four and seven days p.i., while in the second part of the experiment oocysts collected at four days p.i. were taken. Oocysts that are excreted earlier during a coccidiosis infection are less pathogenic than oocysts shedded later because they have completed their life cycle in the host faster (precocious lines) (Jeffers, 1975; Shirley, 1993). Inocula with the latter will induce less severe lesions. There were no significant differences in CLSs between birds infected with oocysts from unmedicated and medicated chickens. These results indicated that IBU medication does not decrease the infectivity of excreted oocysts.

It can be concluded that IBU administered via drinking water at a dose of 100 mg/kg BW significantly (P ≤ 0.05) decreased oocyst shedding after infection with doses of E. acervulina oocysts ranging between 104 and 105. However, CLSs were reduced for all those infection doses; they were significantly lower only after infection with 104 E. acervulina oocysts. In addition, IBU seems not to have effect on sporulation and infectivity of shedded oocysts. Acknowledgements The authors wish to thank D. Tensy, J. Welner and M. Esmann for their practical assistance during the experiments. References Adams, L.B., Hibbs, J.B., Taintor, R.R. & Krahenbuhl, J.L. (1990). Microbiostatic effect of murine-

activated macrophages for Toxoplasma gondii: role for synthesis of inorganic nitrogen oxides from L-arginine. Journal of Immunology, 14, pp. 2725-2729.

Allen, P.C. (1997a). Nitric oxide production during Eimeria tenella infections in chickens. Poultry Science, 76, pp. 810-813.

Allen, P.C. (1997b). Production of free radical species during Eimeria maxima infections in chickens. Poultry Science, 76, pp. 814-821.

Allen, P.C. (1999). Effects of daily oral doses of L-arginine on coccidiosis infections in chickens. Poultry Science, 78, pp. 1506-1509.

Allen, P.C. (2000). Effects of treatments with cyclooxygenase inhibitors on chickens infected with Eimeria acervulina. Poultry Science, 79, pp. 1251-1258.


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Arakawa, A., Tanaka, Y., Baba, E. & Fukata, T. (1991). Effects of clopidol on sporulation and infectivity of Eimeria tenella oocysts. Veterinary Parasitology, 38, pp. 55-60.

Brackett, S. & Bliznick, A. (1952). The reproductive potential of five species of coccidia of the chicken as demonstrated by oocyst production. Journal of Parasitology, 38, pp. 133-139.


Graat, E.A.M., Henken, A.M., Ploeger, H.W., Noordhuizen, J.P.T.M. & Vertommen, M.H. (1994). Rate and course of sporulation of oocysts of Eimeria acervulina under different environmental conditions. Parasitology, 108, pp. 497-502.

Hodgson, J.N. (1970). Coccidiosis: oocyst counting technique for coccidiostat evaluation. Experimental Parasitology, 28, pp. 99-102.

Hornok, S., Szell, Z., Shibalova, T.A. & Varga, L.(1999). Study on the course of Cryptosporidium baileyi infection in chickens treated with interleukin-1 or indomethacin. Acta Veterinaria Hungarica, 47, pp. 207-216.

Jeffers, T.K. (1975). Attenuation of Eimeria tenella through selection for precociousness. Journal of Parasitology, 61, pp. 1083-1090.

Johnson, J. & Reid, M.R. (1970). Anticoccidial drugs: lesion scoring techniques in battery and floor pen experiments with chickens. Experimental Parasitology, 28, pp. 30-36.

Joyner, L.P. & Norton, C.C. (1977). The anticoccidial effects of amprolium, dinitolmide and monensin against Eimeria maxima, E. brunetti and E. acervulina with particular reference to oocyst sporulation. Parasitology, 75, pp. 155-164.

Lillehoj, H.S. (1998). Role of T lymphocytes and cytokines in coccidiosis. International Journal for Parasitology, 28, pp. 1071-1081.

Lillehoj, H.S. & Lillehoj, E.P. (2000). Avian coccidiosis. A review of acquired intestinal immunity and vaccination strategies. Avian Diseases, 44, pp. 408-425.

McDougald, L.R. & Reid, W.M. (1991). Coccidiosis. In: Diseases of Poultry 9th ed. B.W. Calnek, H.J. Barnes, C.W. Beard, W.M. Reid, and H.W. Yoder Jr, Iowa. pp. 783. 1991.

Mellouk, S., Green, S.J., Nacy, C.A. & Hoffman, S.L. (1991). IFN-gamma inhibits development of Plasmodium Berghei exoerythrocytic stages in hepatocytes by an L-arginine-dependent effector mechanism. Journal of Immunology, 146, pp. 3971-3976.

Ovington, K.S., Alleva, L.M. &. Kerr, E.A. (1995). Cytokines and immunological control of Eimeria spp. International Journal for Parasitology, 25, pp. 1331-1351.


Roder, J.D., Chen, C.L., Chen, H. & Sangiah, S. (1996). Bioavailability and pharmacokinetics of ibuprofen in the broiler chicken. Journal of Veterinary Pharmacology and Therapeutics, 19, pp. 200-204.

Ruff, M.D., Anderson, W. L. & Reid, W.M. (1978). Effect of the anticoccidial aprinocid on production, sporulation, and infectivity of Eimeria oocysts. Journal of Parasitology, 64, pp. 306-311.


Shirley, M.W. (1993). Live vaccines for the control of coccidiosis. In: Proceedings of the 6th International Coccidiosis Conference. J.R. Barta, and M.A. Fernando, Guelph. pp. 61-73.

Vane, J.R., Mitchell, J.A., Appleton, I., Tomlinson, A., Bishop-Bailey, D., Croxtall, J. & Willoughby, D.A. (1994). Inducible isoforms of cyclooxygenase and nitric oxide synthase in inflammation. Proceedings of the National Academic of Sciences, USA 91. pp. 2046-2050.

Vermeulen, B. & Remon, J.P. (2001). The oral bioavailability of ibuprofen enantiomers in broiler chickens. Journal of Veterinary Pharmacology and Therapeutics, 24, pp. 105-109.

Von Löwenstein, M. & Kutzer, E. (1989). Zum Einfluß der Antikokzidia Diclazuril und Maduramicin auf die Sporulationsfähigkeit von Hühnerkokzidien. Wiener Tierärztliche Monatsschrift, 76, pp. 368-370.

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Weber, G.M. (1997). Optimum use of anticoccidial products for efficacious treatment of poultry coccidiosis. In: Proceedings of the 7th International Coccidiosis Conference. M.W. Shirley, F. M. Tomley, and B.W. Freeman, Oxford. pp 51-52.

Yun, C.H., Lillehoj, H.S. & Lillehoj, E.P. (2000). Intestinal immune responses to coccidiosis. Developmental and Comparative Immunology, 24, pp. 303-324.


Dietary protease can alleviate negative effects of a coccidiosis infection on production performance in broiler chickens H.W. Peeka, J.D. van der Klisb, B. Vermeulenc and W.J.M. Landmana

aAnimal Health Service (GD), Poultry Health Centre, P.O. Box 9, 7400 AA, Deventer, the Netherlands bDivision Nutrition and Food, Animal Sciences Group of Wageningen UR, Lelystad, the Netherlands Current address: Schothorst Feed Research, P.O. Box 533, 8200 AM, Lelystad, the Netherlands cOrotech N.V., Dijkstraat 30, 9140 Temse, Belgium Animal Feed Science and Technology (March 2009), 150(1-2), 151-159 Summary Two experiments were conducted to determine the effect of dietary protease on coccidiosis infection, production performance, the intestinal mucus layer thickness, and brush border enzyme activity using broilers challenged with Eimeria spp. laboratory isolates (Eimeria acervulina, E. maxima and E. tenella). In the first study the protease was supplied at a concentration of 2.5 x 104 amylase-DU per kg feed. Broiler chickens were housed in cages and were infected at ten days of age with 104.0 E. acervulina, 103.8 E. maxima or 103.3 E. tenella sporulated oocysts. Coccidial lesion scores, oocysts shedding, sporulation assessment and daily weight gain were used as parameters to quantify the effect of the protease. In the second study the effects of the protease (supplied at a concentration of 2.5 x 104 amylase-DU per kg feed) on the thickness of the mucus adherent layer and sucrase-isomaltase activity (SIA) of three regions (duodenum, jejunum and caecum) of the intestinal tract were determined. In experiment 1, no significant interaction between dietary enzyme supplementation and single Eimeria spp. challenge was observed on body weight gain. However, protease addition to the diet resulted in a significant (P = 0.046) higher weight gain after comparing all supplemented and non-supplemented groups. E. maxima infected chickens showed a significant lower body weight gain in comparison with the other Eimeria infected groups. Coccidial lesions were not significantly affected by the dietary protease supplementation, despite the slight tendency to a higher lesion score for E. acervulina on the enzyme supplemented diets. In Experiment 2, it was shown that the adherent mucus layer of the duodenum (P < 0.001), jejunum (P < 0.001) and caeca (P = 0.005) was significantly thicker in birds fed the enzyme supplemented diet. The sucrase-isomaltase activity (SIA) in mucosal scrapings of the jejunum was significantly lower (P = 0.005) in birds fed the enzyme supplemented diet, indicating a higher villus turnover rate. In conclusion, our data suggest that dietary supplementation with a protease reduced the negative impact of a coccidiosis infection on body weight gain of broilers, although the coccidial lesions and oocyst excretion remained unaffected.

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Introduction Coccidiosis in poultry is caused by a protozoan parasite belonging to the genus Eimeria of the family Eimeriidae (Phylum Apicomplexa). It is considered as the disease with greatest economic impact in the poultry industry. Worldwide the annual costs have been estimated at 2 billion € (Williams, 1999; Shirley et al., 2004; Dalloul & Lillehoj, 2006). Eimeria species are highly host specific (Levine, 1973; Joyner, 1982). Furthermore, it is well recognized that Eimeria parasites only infect particular cell types, tissues and organs. The underlying mechanisms are not yet fully understood and suggest distinct intraspecies and interspecies antigenic diversity among Eimeria parasites.

Infections with Eimeria spp. induce various pathological and immunological responses, which stimulate the host’s defense mechanisms and acquired immunity. However, prior to the development of an acquired immune response, non-specific immune pathways such as native microbial flora, mucus, lysozymes, increased gastric and bile salts secretions, and increased peristalsis are considered to be important defense routes (Lillehoj & Lillehoj, 2000; Yun et al., 2000). It has been suggested that these innate defense mechanisms may modulate the start of the Eimeria life cycle and hence determine the course of an acquired antigen specific immune response (Lillehoj and Trout, 1993).

The intestinal enterocytes are covered by a mucus layer, which is secreted by goblet cells throughout the gastrointestinal tract. Its thickness and fluidity affect nutrient digestion, absorption, intestinal barrier function and also the mucosa functionality (Smirnov et al., 2004).

It is well-known that nutrient digestibility will be adversely affected by coccidiosis. This might be due to: 1) the aforementioned non-specific defense mechanisms such as altered gastric and bile secretions, increased peristalsis, etc.; 2) decreased activity of important mucosal enzymes (Adams et al., 1996), which are anchored at the brush border membrane such as sucrase-isomaltase, peptidases and phosphatases (Semenza, 1986) and are involved in the final stages of hydrolysis; 3) increased thickness of the mucus layer due to the gastrointestinal defense mechanisms, which might reduce the transport rate of nutrients.

Proteases might counteract the negative effects of a coccidiosis infection on the nutrient digestion and absorption via partial degradation of the mucus layer and hence the attachment of Eimeria parasites (sporozoites-merozoites) to the mucus. Subsequently, coccidia may be excreted as passants instead of binding to and invading epithelial cells. In addition, the protease could have direct effect on the dietary protein by digesting it and subsequently mitigating the detrimental consequences of the coccidiosis infection.

In the present study the effect of a protease supplied via feed on E. acervulina, E. maxima or E. tenella challenged broilers was studied.

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Material and methods Experimental design In experiment 1, eight experimental groups consisting of ten birds each were used (Table 2). Four groups received a diet supplemented with the protease1 while the other four groups were fed the control diet without the protease. Within the groups fed the protease supplemented diet, three groups were infected at day ten with E. acervulina, E. maxima or E. tenella, while the fourth group acted as non-inoculated uninfected control group. The four groups fed the control feed received exactly the same treatments. Birds were orally inoculated and six days post-inoculation (p.i.) five birds per group were sacrificed for postmortem examination and assessment of coccidial lesion scores. The number of oocysts per gram faeces (OPG) was determined in droppings collected from day four till day eight p.i. Bodyweight gain was calculated between ten and sixteen days of age for each group. In experiment 2, the effect of the protease on the thickness of the adherent mucus layer and the sucrase-isomaltase activity (SIA) of three intestinal regions (duodenum, jejunum and caeca) of sixteen day-old uninfected broilers was analyzed. Chickens and housing In experiment 1, eighty day-old male Hybro broilers (Nutreco, Putten the Netherlands) were reared coccidiosis free in a large stainless-steel cages with a wired floor (height x width x depth = 30 cm x 200 cm x 100 cm) and received a diet without anticoccidial products. At six days of age eight groups of ten randomly chosen birds were placed in stainless steel battery cages (height x width x depth = 30 x 40 x 50 cm). Each bird was tagged in the neck with a unique number (Swiftack®). After transfer, four experimental groups were provided a diet supplemented with protease, while the other four received a control diet without the protease. Birds were fed per group. In experiment 2, fifteen day-old Hybro broilers were reared coccidiosis free and at the age of six days transferred to the stainless steel battery cages. Directly after transfer, one group of ten birds received the diet supplemented with protease while the other group, consisting of five birds, was given the diet without the protease. During both trials a lighting scheme of 23 h of light was used. The birds were observed daily and deceased birds were collected for postmortem examination. The study was performed with approval of the Animal Experimental Committee in accordance with the Dutch law on experimental animals.

1 Supplied by DSM Food Specialities – Agri Ingredients, Delft, the Netherlands


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Table 1. Ingredients and composition of the feed

Ingredient g/kg Maize 291.0 Wheat 299.9 Soybean meal 275.0 Peas 50.0 Soybean oil 15.2 Animal fat 20.2 Chalk stones 11.2 Monocalcium phosphate 10.4 Sodium bicarbonate 2.3 Ronozyme wx (CT)A 0.3 PremixB 10.0 SporavitC 5.0 Natuphos (phytase) 2.0 Avilamycin 2.0 Lysine 5.0 Threonine 0.5 Total 1000 Calculated chemical composition

AME (MJ/kg) 12.0 Crude protein 207.7 Calcium 9.4 Phophorus 6.4 Sodium 1.6 Chloride 2.1

A Coated non-dusty light brown granulate with a minimum xylanase acitivity of 1000 FXU/g. B The premix consists per kg of: Vitamin A (1,000,000 IU), Vitamin D3 (200,000 IU), Vitamin E (2,500 IU), Vitamin B1 (50 mg), Vitamin B2 (500 mg), pantothenic acid (800 mg), nicotinic acid (4,000 mg), Vitamin B6 (300 mg), folic acid (100 mg), Vitamin B12 (1.5 mg), biotin (10 mg), Vitamin K3 (125 mg), choline (20,000 mg), methionine (200 g), CuSO4·5H2O (1,200 mg), FeSO4·H2O (4,500 mg), MnO (7,000 mg), ZnSO4·H2O (3,700), Ca(IO3)2 (100 mg) and Na2SeO3·5H2O (15 mg). C Sporavit consists per kg of: Vitamin A (1,000,000 IU), Vitamin D3 (100,000 IU), Vitamin E (5,000 IU), Vitamin B1 (400 mg), Vitamin B2 (800 mg), pantothenic acid (2,000 mg), nicotinic acid (4,000 mg), Vitamin B6 (400 mg), folic acid (200 mg), Vitamin B12 (3 mg), Vitamin C (10,000 mg), biotin (10 mg), Vitamin K3 (200 mg), choline (40,000 mg), Fe (12,000 mg), Mn (10,000 mg), Co (40 mg) and I (40 mg). Protease and feed A protease produced by DSM Food Specialties, Agri Ingredients, Delft, the Netherlands, was used in this experiment. The protease was obtained from Bacillus licheniformis and

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contained 558,700 DU2/ml. In both experiments the enzyme was mixed in a concentration of 25,000 DU/kg feed in a broiler starter mash (Arkervaart-Twente, Nijkerk, the Netherlands) free of anticoccidial products (Table 1). Feed and water were provided ad libitum. Origin of Eimeria spp. laboratory isolates and inocula Three Eimeria spp. laboratory strains provided by the Central Veterinary Laboratory (CVL, Weybridge, UK) were used. All strains have been rejuvenated approximately every half year and were conserved as a suspension of sporulated oocysts at 2-8 °C in a 2.5% (w/v) potassium dichromate (K2Cr2O7, Vel, Leuven, Belgium) solution until application. The number of oocysts per ml suspension was counted with a haemocytometer (Fuchs-Rosenthal counting chamber). The inoculation doses were adjusted to induce lesion scores of 2-3 for each Eimeria spp. on the scale of Johnson & Reid (1970). The amount of volume containing the required number of sporulated oocysts was taken from the suspensions and K2Cr2O7 was washed out by centrifugation. Inocula containing 104.0, 103.8 and 103.3 sporulated oocysts were obtained for E. acervulina, E. maxima and E. tenella, respectively. The birds were inoculated individually in the crop with a calibrated syringe without needle using a volume of 1 ml tap water. Bodyweight gain, coccidial lesion scores and oocyst shedding Individual bodyweight (BW) was measured daily between six and sixteen days of age. The mean BW gain (± SEM) per experimental group was calculated from ten until sixteen days of age (zero to six days p.i.). At sixteen days of age five birds per group were sacrificed for postmortem examination. Parasitological examination of the entire gut was carried out and the coccidial lesion scores (CLS) were determined according to the method of Johnson and Reid (1970). Briefly, E. acervulina lesion score 1 features ladder-like white streaks in the duodenal loop (≤ 5/cm2); in lesion score 2 the lesion density is higher but not coalescent; in lesion score 3 they are more numerous and coalesce, while thickening of the intestinal wall is visible; and finally in lesion score 4 the mucosal wall is greyish with lesions completely coalesced. Lesion score of 1 of E. maxima is characterized by few small red petechiae in the mid-intestine, in score 2 more numerous petechiae are found and the intestinal content may be orange, and in score 3 the intestinal wall might be ballooned and thickened with pinpoint blood clots and mucous filling the intestinal contents. Finally, in lesion score 4 the intestinal wall is thickened and ballooned over most of its length, containing numerous blood cloths and digested red blood cells. Lesion score 1 of E. tenella shows a few scattered petechiae on the caecal wall, and in score 2 noticeable blood can be found in the caecal contents, while the caecal wall is thickened. In lesion score 3 large amounts of blood or caecal cores are present and in the caecal walls are greatly

2 One DU is defined as the quantity of enzyme that liberates 7 micromoles of paranitroaniline from casein per minute.


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thickened, and in lesion score 4 the caecal walls are enormly distended with blood or large caseous cores. The mean coccidial lesion score for each experimental group was subsequently calculated. Oocyst shedding – expressed as the number of oocysts per gram faeces (OPG) – was determined in one homogenized sample of collected faeces droppings (4-8 days p.i.) per cage. Countings were performed by means of a modification of the McMaster counting chamber technique as described by Peek & Landman (2003, 2004). Assessment of sporulation Faeces collected within 4 hr after defecation at sixteen days of age (six days p.i.) were suspended (6%, w/v) in a solution of 2.5% (w/v) K2Cr2O7. Sporulation was induced by aeration of the suspensions at 29 °C during 36 hr. Samples of each suspension were removed 0, 12, 24, and 36 hr after initiating sporulation and the sporulation percentage was determined by using a light microscope (400 x magnification). Oocysts were counted as sporulated when four sporocysts were observed (Tyzzer, 1929; Wagenbach & Burns, 1969). Histopathology and sucrase-isomaltase activity In experiment 2, the influence of the protease on the thickness of the mucous adherent layer of three regions of the intestine tissue (duodenum, jejunum and caeca) of sixteen days-old uninfected broilers was measured by the modified method of Jordan et al. (1998). Briefly, a 1 cm fragment of the duodenum, jejunum and caeca was longitudinally cut inside out, snap frozen in liquid nitrogen and stored at –70 °C. Cryostat cross-sections of 15-20 µm of the whole frozen tissue were made and stained according to the modified procedure of the Periodic Acid Schiff/Alcian Blue (PAS/AB) technique described by Jordan. The mucus thickness was measured using a light microscope (400 x magnification) fitted with an ocular eyepiece graticule with divisions of 10 µm. Approximately seven measurements were made on each slide of the mucus layer from the duodenum, jejunum and caeca. Sucrase-isomaltase activity of mucosal scrapings, isolated from the intestinal sections (duodenum, jejunum and caeca) was determined according to the method of Messer & Dahlqvist (1966). Briefly, the mucosal scrapings were snap frozen and stored in liquid nitrogen. For analysis the scrapings were transferred to plastic tubes and milliQ water was added to a final concentration of 5% (w/v) and homogenised with the Ultra-Turrax at full speed (2 x 104 rpm) twice during 30 s separated by an interval of 30 s. Then, the homogenate was diluted 5 times and sonicated twice for 15 s separated by a 15 s interval at an amplitude of 30 µm with a MSE Soniprep 150. The protein content of the samples was determined by the Pierce BCA assay kit (Smith et al., 1985) in microtitreplates. Subsequently, the specific enzyme activity (SEA) of sucrase (EC 3.2.1.48) -isomaltase (EC 3.2.1.10) was measured by adding saccharose as substrate, incubating for 60 min at 37 °C and measuring the extinction at 405 nm spectrophotometrically. The SEA activity is

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expressed in units/g protein (U/g). One unit is the amount of enzyme that produces 1 µmol disaccharide per minute. Statistical analyses The individual bird was used as experimental unit for comparing the effects of diets (+ protease vs. – protease) on weight gains and coccidiosis infections. The influence of the protease on weight gain after coccidial infection was analyzed by a two-way ANOVA. Tests of homogeneity of variances were performed by the Levine test. Residuals were checked on normality by inspecting their normality plots. Pairwise comparison were done using the Bonferroni test (SPSS®, 2008). The influence of the enzyme on the coccidial lesion scores was analyzed with the non-parametric Wilcoxon Rank Sum Test (Statistix®, 2003). The influence of the protease on the thickness of the mucus layer in the duodenum, jejunum and caeca was assessed using GEE model (Stata®, 2008), which corrects for correlation within animals. The influence of protease on the mucosal SIA was analyzed by means of the Kruskal-Wallis test (Stata, 2008). Differences were considered significant if P < 0.05. Results Bodyweight gain, coccidial lesion scores and oocyst shedding Mean CLS as determined six days p.i., the OPG per experimental group and the mean BW gain between 10 and 16 days of age are presented in Table 2 and Table 3. There was no significant interaction on BW gain (P ≥ 0.05) between the protease supplementation and single species coccidiosis infections, therefore the main effects were further investigated and showed a significantly (P = 0.046) higher average growth in all groups receiving the protease supplemented diet. The weight gain of birds infected with E. maxima was significantly lower in comparison with the remaining groups (Table 3). No significant influence of dietary protease supplementation on the severeness of CLS was found after statistical analysis. Only E. acervulina showed a tendency towards higher lesion scores in birds receiving the diet supplemented with the protease (Table 2). The obtained oocyst shedding was in agreement with the achieved lesions scores in all groups.


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Table 2. Experimental groups, mean coccidial lesion scores (CLS)(n = 5) and number of oocysts per gram faeces (OPG)

Experimental groups Experimental results Group nr. Infection Eimeria spp.

(# oocysts/bird) Protease Mean CLS

± SEM OPG

1 E. acervulina (104.0) Yes 2.6± 0.25a 106.5 2 E. acervulina (104.0) No 2.0 ± 0.00a 106.3 3 E. maxima (103.8) Yes 2.2 ± 0.37b 104.9 4 E. maxima (103.8) No 2.8 ± 0.20b 104.8 5 E. tenella (103.3) Yes 0.0 ± 0.00c 105.0 6 E. tenella (103.3) No 0.2 ± 0.20c 105.4 7 Uninfected Yes 0 0 8 Uninfected No 0 0 a-c Groups with different superscript per Eimeria spp. infection (E. acervulina, E. maxima or E. tenella) are significantly different from each other (P < 0.05). Table 3. Mean body weight gain ± SEM (g) (n = 10) measured between 10 and 16 days of age and statistical analyses with the Bonferroni test Diet type Uninfected E. acervulina E. maxima E. tenella Main effect

protease - Protease 273 ± 8.6 272 ± 7.0 191 ± 9.7 254 ± 14.0 247 ± 7.3a

+ Protease 277 ± 14.2 284 ± 9.0 224 ± 8.0 264 ± 11.9 262 ± 6.4b

Main effect coccidiosis

275 ± 8.1a 278 ± 5.7a 208 ± 7.2b 259 ± 9.0a

Difference between (Bonferroni test)

Mean difference

P Lower bound

Upper bound

E. maxima Uninfected 67.5 ≤0.001 37.3 97.7 E. maxima E. acervulina 70.2 ≤0.001 40.0 100.4 E. maxima E. tenella 51.2 ≤0.001 21.0 81.4 - protease + protease 15.1 0.046 0.2 30.0 a, b Groups with different superscript within the row main effect coccidiosis or the column mean effect protease are significantly different from each other (P < 0.05, Bonferroni test). Assessment of sporulation There was no sporulation shortly after initiating the sporulation process (0 h) while after 12 h sporulation started for all Eimeria spp. At this time the sporulation percentages of oocysts isolated from the faeces of E. acervulina was 80 and 86%, of E. maxima 42 and

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50% and of E. tenella 75 and 70% in the groups receiving diets supplemented with or without the protease, respectively. After 24 hr, 90 and 96% of E. acervulina and 90% (both groups) of E. tenella oocysts were sporulated as for E. maxima oocysts these high percentages (both groups 90%) were reached after 36 hr. These percentages remained unchanged for the rest of the sporulation process. Histopathology and sucrase-isomaltase activity (SIA) The mean (± SEM) thickness and results of statistical analyses of the adherent mucus layer of the duodenum, jejunum and caeca are shown in Table 4. A significant thicker mucus layer was measured in the duodenum (P < 0.001), jejunum (P < 0.001) and caeca (P = 0.005) of birds with dietary protease enzyme supplementation. The SIA (± SEM) of the mucosal scrapings per gram of intestinal protein (U/g protein) is presented in Table 4. The SIA was significantly lower (P = 0.005) in mucosal scrapings from the jejunum of chickens receiving the diet supplemented with the protease. No significant influence of the supplementation of the protease on the SIA of the scrapings obtained from the duodenum and caeca samples was noted. Table 4. Mean thickness of adherent mucus layer (AML) (µm) and mean sucrase-isomaltase activity (SIA) (U/g protein) in mucus of duodenum, jejunum and caeca Intestinal region Protease AML ± SEM (n) SIA ± SEM (n) Duodenum Yes 8.8 ± 0.29a (61) 29 ± 3.2a (10) Duodenum No 6.3 ± 0.39b (35) 35 ± 2.9a (5) Jejunum Yes 8.6 ± 0.36a (64) 78 ± 6.9a (10) Jejunum No 5.4 ± 0.20b (35) 124 ± 5.7b (5) Caeca Yes 6.4 ± 0.36a (45) -2 ± 3.6a (10) Caeca No 4.9 ± 0.31b (23) 7 ± 3.5a (5) a, b Groups with different superscript per intestinal region (duodenum, jejunum and caeca) are significantly different from each other (P < 0.05). Discussion The mean CLS (± SEM) of birds given the non-supplemented diets and infected with E. acervulina, E. maxima or E. tenella were 2.0 ± 0.0, 2.8 ± 0.2 and 0.2 ± 0.2, respectively, while for the supplemented birds the mean CLS were 2.6 ± 0.25, 2.2 ± 0.37 and 0.0 ± 0.0, respectively. The results of both treatment categories were not significantly different from each other. Therefore, it seems reasonable to conclude that dietary supplementation of protease did not influence the severity of coccidial lesions. This was also the case for the oocyst shedding. The fact that the OPG levels for E. maxima and E. tenella were almost


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similar while their lesion scores varied greatly can be explained by differences in oocyst yield between these species (Williams, 2001). The low mean CLS obtained with E. tenella was explained by the low inoculation dose administrated as the isolate was known to be very pathogenic in previously performed experiments (data not shown).

Only sporulated oocysts are infectious and it is known from literature that some anticoccidial drugs diminish the infective potential of the excreted oocysts by reducing the sporulation rate (Joyner & Norton, 1977; Ruff et al., 1978; Von Löwenstein & Kutzer, 1989; Arakawa et al., 1991). Nevertheless, it was shown that dietary protease supplementation had no influence on the rate and onset of sporulation of all Eimeria species studied, suggesting that in feed administration of protease will not reduce the coccidiosis infection pressure in the poultry environment.

Significantly increased thickness of the mucus layer was measured in the duodenum, jejunum and caeca regions compared to the same regions of non-protease supplemented birds (Table 4). A possible explanation for this increase in mucus thickness is a higher mucus production due to the activity of the protease. This can lead to a partial immature layer of different composition and increased thickness. The variations in mucus composition may result in local pH differences and subsequent differences in Alcian blue staining as confirmed by the variation in coloration observed during the thickness measurements.

The SIA measured in the jejunum of protease supplemented and non-supplemented birds was greater than that of duodenum, which in turn was greater than that of caeca, being in agreement with the work of Major & Ruff (1978) and Adams et al. (1996). The SIA was lower in all mucosal scrapings of birds fed the protease supplemented diet. A significant decrease was found in mucosal scrapings of the jejunum, whereas it was not affected in the duodenum and caeca (Table 4). These measurements suggest a higher mucosal turnover rate in the jejunum, which might represent a lower mucosal protection against an Eimeria infection.

The effect of the protease treatment on BW gain was least in the uninfected group (4 g), while a higher BW gain of 12 (4%), 33 (15%) and 10 g (4%) was observed in E. acervulina, E. maxima and E. tenella infected birds, respectively. Compared to the uninfected chickens, E. acervulina or E. tenella infected broilers with or without protease did not show significant growth retardation, whereas the reduced body weight gain in chickens infected with E. maxima with or without protease was shown to be statistically significant. These observations agree earlier studies (Conway et al., 1993) showing that impairment of body weight development is dependent on the numbers of oocysts in the inoculum, which will also determine the severeness of the clinical coccidiosis. In the present study, only the oocysts doses used for E. maxima were close to the growth retardation-inducing doses described by Conway et al. (1993). There was no significant interaction on BW gain (P ≥ 0.05) between the protease supplementation and single species coccidiosis infections, therefore the main effects were further investigated and showed a significantly (P = 0.046) higher average growth in all groups receiving the supplemented diet.

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During a coccidiosis infection, BW gain suppression is generally caused by a reduced feed intake, a disturbed digestibility and decreased nutrient utilization due to a diminished digestive absorptive surface caused by damaged, shortened or flattened villi of the intestinal cells (Fernando & McCraw, 1970). The protease can possibly have influenced this process by initiating a higher rate of mucus production and jejunal mucosal turnover resulting in an increased mucus layer thickness, which may have had a protective effect against the parasite although in the present study it could not be measured using CLS. The protease could also have stimulated feed intake resulting in better BW development. Another explanation is that it may have prevented/reduced the leakage of plasma proteins caused by parasite stages damaging the intestinal mucosa through increased mucus thickness (Rose & Long, 1969; Schalm et al., 1975; Shane et al., 1985). Also changes in the mucus layer induced by protease treatment may have favored digestibility of nutrients. Alternatively a combination of these factors may have occurred.

In conclusion, the results of this study suggest that dietary protease supplementation stimulates BW gain, which seems more prominent in coccidiosis infected broilers. This experiment did not support the suggestion that an increased thickness of the mucus layer reduced the absorbability of nutrients as the protease did stimulate mucus production as well as BW gain. Differences in feed intake between treatments might have been a confounding factor and need further research. Acknowledgements We acknowledge Peter C.J. Tooten for his assistance in the sucrase-isomaltase detection assay, Dr. R.M. Dwars for performing the histopathology and Prof. Dr. J.A. Stegeman for critically reading the manuscript. References Adams, C., Vahl, H.A. & Veldman, A. (1996). Interaction between nutrition and Eimeria acervulina

infection in broiler chickens: development of an experimental infection model. British Journal of Nutrition, 75, pp. 867-873.

Arakawa, A., Tanaka, Y., Baba, E. & Fuktata, T. (1991). Effects of clopidol on sporulation and infectivity of Eimeria tenella oocysts. Veterinary Parasitology, 38, pp. 55-60.

Conway, D.P., Sasai, K., Gaafar, S.M. & Smothers, C.D. (1993). Effects of different levels of oocyst inocula of different Eimeria acervulina, E. tenella and E. maxima on plasma constituents, packed cell volume, lesion scores, and performance in chickens. Avian Diseases, 37, pp. 118-123.

Dalloul, R.A. & Lillehoj, H.S. (2006). Poultry coccidiosis: recent advancements in control measures and vaccine development. Expert Reviews of Vaccines, 5, pp. 143-163.

Fernando, M.A. & McCraw, B.M. (1970). Mucosal morphology and cellular renewal of chickens following a single infection of Eimeria acervulina. Journal of Parasitology, 59, pp. 493-501.



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Joyner, L.P. & Norton, C.C. (1977). The anticoccidial effects of amprolium, dinitolmide and monensin against Eimeria maxima, E. brunetti and E. acervulina with particular reference to oocyst sporulation. Parasitology, 75, pp. 155-164.

Joyner, L.P. (1982). Host and site specificity. In: Long, P.L. (ed.). The biology of the Coccidia. Baltimore, University Park Press, pp. 35-62.

Jordan, N., Newton, J., Pearson, J. & Allen, A. (1988). A novel method for the visualization of the in situ mucus layer in rat and man. Clinical Science, 95, pp. 97-106.

Levine, N.D. (1973). Protozoan Parasites of domestic animals and of man. Burgess, Minneapolis. Lillehoj, H.S. & Trout, J.M. (1993). Coccidia: a review of recent advances on immunity and vaccine

development. Avian Pathology, 22, pp. 21-31. Lillehoj, H.S. & Lillehoj, E.P. (2000). Avian coccidiosis. A review of acquired intestinal immunity and

vaccination strategies. Avian Diseases, 44, pp. 408-425. Major, J.R.Jr. & Ruff, M.D. (1978). Disaccharidase activity in the intestinal tissue of broilers infected

with coccidia. Journal of Parasitology, 64, pp. 706-711. Messer, M., & Dahlqvist, A. (1966). A one Step ultramicro method for the assay of intestinal

disaccharidases. Analytical Biochemistry, 14, pp. 376-392. Peek, H.W. & Landman, W.J.M. (2003). Resistance to anticoccidial drugs of Dutch avian Eimeria spp.

field isolates originating from 1996, 1999 and 2001. Avian Pathology, 32, pp. 391-401. Peek, H.W. & Landman, W.J.M. (2004). Gevoeligheidsonderzoeken van Spaanse, Duitse en Nederlandse

Eimeria spp. veldisolaten voor anticoccidiosemiddelen. Tijdschrift voor Diergeneeskunde, 129, pp. 210-214.

Rose, M.E. & Long, P.L. (1969). Immunity to coccidiosis: gut permeability changes in response to sporozoite invasion. Experientia, 25, pp. 183-184.

Ruff, M.D., Anderson, W.I. & Reid, W.M. (1978). Effect of the anticoccidial aprinocid on production, sporulation, and infectivity of Eimeria oocysts. Journal of Parasitology, 64, pp. 306-311.

Schalm, O.W., Jain, N.C. & Caroll, E.J. (1975). Veterinary Hematology, 3rd edition, Lea and Febriger, Philadelphia, PA.

Semenza, G. (1986). Anchoring and biosynthesis of stalked brush border membrane proteins: Glycosidases and peptidases of enterocytes and renal tubuli. Annual Review of Cell Biology, 2, pp. 255-313.

Shane, S.M., Gyimah, J.E., Harrington, K.S. & Snider, T.G. (1985). Etiology and pathogenesis of necrotic enteritis. Veterinary Research Communications, 9, pp. 269-287.

Shirley, M.W., Ivens, A., Gruber, A., Madeira, A.M.B.N., Wan, K.L., Dear, P.H. & Tomley, F.M. (2004). The Eimeria genome projects: a sequence of events. Trends in Parasitology, 20, pp. 199-201.

Smirnov, A., Sklan, D. & Uni, Z. (2004). Mucin dynamics in the chick small intestine are altered by starvation. Journal of Nutrition, 134, pp. 736-742.

Smith, P.K., Krohn, R.I., Hermanson, G.T., Mallia, A.K., Gartner, F.H., Provenzano, M.D., Fujimoto, E.K., Goeke, N.M., Olson, B.J. & Klenk, D.C. (1985). Measurement of protein using bicinchoninic acid. Analytical Biochemistry, 150, pp. 76-85.

SPSS® (2008) SPSS 16.0 for Windows®. SPSS Inc., Chicago, Illinois, USA. STATA® (2008) Stata 10.0 for Windows®. StataCorp LP, College Station, Texas, USA. STATISTIX® (2003) Statistix 8.0 for Windows®. User’s manual analytical software version 8.0.

Tallahassee, USA. Tyzzer, E.E. (1929). Coccidiosis in gallinaceous birds. American Journal of Hygiene, 10, pp. 269-383. Von Löwenstein, M. & Kutzer, E. (1989). Zum Einfluβ der Antikokzidia Diclazuril und Maduramicin auf

die Sporulationsfähigkeit von Hühnerkokzidien. Wiener Tierärztliche Monatsschrift, 76, pp. 368-370. Wagenbach, G.E. & Burns, W.C. (1969). Structure and respiration of sporulating Eimeria stiedae and E.

tenella oocysts. Journal of Protozoology, 16, pp. 257-263. Williams, R.B. (1999). A compartmentalised model for the estimation of the costs of coccidiosis to the

world’s chicken production industry. International Journal for Parasitology, 29, pp. 1209-1229.

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Williams, R.B. (2001). Quantification of the crowding effect during infections with the seven Eimeria species of the domesticated fowl: its importance for experimental design and the production of oocyst stocks. International Journal for Parasitology, 31, pp. 1056-1069.

Yun, C.H., Lillehoj, H.S. & Lillehoj, E.P. (2000). Intestinal immune responses to coccidiosis. Developmental and Comparative Immunology, 24, pp. 303-324.

The effect of an in-feed mannanoligosaccharide preparation (MOS) on a coccidiosis infection in broilers M.A. Elmusharafa, H.W. Peekb, L. Nolletc and A.C. Beynena aDepartment of Nutrition, Faculty of Veterinary Medicine, Utrecht University, the Netherlands bAnimal Health Service (GD), Poultry Health Centre, Deventer, the Netherlands cAlltech Biotechnology Centre, Dunboyne, Ireland Animal Feed Science and Technology (April 2007), 134(3-4), 347-354 Summary In the current study with broiler chickens, the objective was to assess whether a mannanoligosaccharide (MOS) preparation would have anticoccidial activity. One-day-old birds were given a single, mild coccidiosis infection with a mixture of three Eimeria species: Eimeria acervulina, Eimeria maxima and Eimeria tenella. Infected and non-infected birds were fed a diet without or with 10 g MOS/kg. Growth performance, feed intake and feed conversion were not different (P > 0.05) among the treatment groups. The feeding of the MOS preparation reduced oocyst excretion and diminished the severity of coccidiosis lesions induced by E. acervulina (P < 0.05) but did not affect the lesions mediated by E. maxima and E. tenella (P = 0.69 and 0.84, respectively). Further research is necessary to explain the observed effects in terms of mechanisms and to assess their practical relevance. Keywords: broilers; coccidia; mannanoligosaccharide

EFFECT OF MANNANOLIGOSACCHARIDE (MOS) ON COCCIDIOSIS IN BROILERS

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Introduction The protozoan parasite of the genus Eimeria may cause coccidiosis in poultry, an infectious disease causing major economic losses through increased mortality and reduced growth (McDougald, 2003). In order to control coccidiosis in poultry, coccidial vaccination, in drinking water and in-feed supplementation of anticoccidial products, are commonly used. However, it is expected that within 5 years from now (2012), the anticoccidial products currently used will be banned (van den Ban et al., 2005). Thus, there is an urgent need for alternative agents to control coccidiosis in poultry. In this context, mannanoligosaccharide (MOS) preparations, which are derived from the cell wall of the yeast Saccharomyces cerevisiae, can be useful. In broiler chickens infected with Eimeria tenella, the feeding of a MOS preparation was shown to reduce the number of the asexual stage schizonts in the lamina propria of the caecum (Elmusharaf et al., 2006). The outcome of that study was interpreted as evidence for a protective effect of MOS against coccidiosis infection and enhanced immunity in broilers. Jeurissen et al. (1996) found in immune chickens that significantly fewer sporozoites reached the crypt epithelium and that the formation of schizonts was inhibited.

In a previous study (Elmusharaf et al., 2006), the chickens were infected with only one species of Eimeria. In the present study, the possible anticoccidial activity of MOS was further investigated in broiler chickens infected mildly with a mixture of three Eimeria species: Eimeria acervulina, E. maxima and E. tenella. Infected and non-infected birds were fed a diet without or with MOS. Growth performance, intestinal lesions and oocyst excretion were measured. Materials and methods Animals and diets The experiment was of a factorial design, with/without MOS and with/without Eimeria mixture. Two hundred and fifty-six one-day-old male broiler chickens (Ross 308) were purchased from a local hatchery. On the day of arrival (day one), the birds were wing banded, weighed and randomly allocated to four treatment groups of 64 birds each. Each group was further divided into eight replicates of eight birds each. All replicates were housed in 32 separate wire-suspended cages equipped with plastic sides and bottoms covered with clean wood shavings. Continuous lighting was provided. The temperature in the cages was 32 °C on arrival of the chickens and from day 8 of the experiment the temperature was decreased gradually by 2 °C every day until it reached 20 °C by day fourteen. Two groups received the control diet and the other two groups were fed the basal diet supplemented with MOS. The diets did not contain growth promoters or anticoccidial products (Table 1). The experimental diet was prepared by adding a MOS preparation (Bio-Mos™, Alltech) at a level of 10 g/kg diet at the expense of an identical amount of

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cornstarch. The diets were in a pelleted form (2.5 mm in diameter). Throughout the experiment, the birds had free access to their diet and tap water. Body weights were measured on days 1, 7, 14 and 19. Amounts of feed provided and leftovers were weighed per cage. Feed intakes were determined per week per cage and expressed as g/bird/day. Feed conversion ratio is calculated as feed intake per cage divided by weight gain of birds in the cage. Table 1. Ingredients and the composition of the basal diet Ingredient g/kg Wheat (+ xylanase) 250 Maize 321 Peas 50 Soybean meal (467 g CP/kg) 225 Sunflower (320 g CP/kg) 40 Fish meal (720 g CP/kg) 25 Potato protein 15 Soybean oil 40 PremixA 5 Salt 1.7 Limestone 13.5 Sodium chloride 5 Calcium carbonate 1.7 Monocalcium phosphate 4 L-Lysine HCL 0.8 DL-Methionine 1.7 L-Threonine 0.5 Natuphos 5000G (phytase) 0.1 Total 1000 Calculated chemical composition

AMEn (MJ/kg) 11.7 Crude protein (g/kg) 215.6

A 10 g premix consists of 24.0 mg Vitamin A (500,000 IU/g), 6.0 mg Vitamin D3 (100,000 IU/g), 60.0 mg Vitamin E (500 IU/g), 6.6 mg Vitamin K3 (purity, 22.7%), 100.0 mg Vitamin B12 (purity, 0.1%), 2000.0 mg biotin (purity, 0.01%), 1100.0 mg choline chloride (purity, 50%), 1.1 mg folic acid (purity, 90%), 65.2 mg nicotinic acid (purity, 100%), 16.3 mg d-pantothenate (purity, 92%), 4.5 mg Vitamin B6 (purity, 100%), 12.5 mg riboflavin (purity, 80%), 2.5 mg Vitamin B1 (purity, 100%), 32.00 mg CuSO4·5H2O, 333.20 mg FeSO4·H2O, 166.80 mg MnO, 1.00 mg Na2SeO3·5H2O, 220.00 mg ZnSO4·H2O, 4.80 mg CoSO4·7H2O, 0.56 mg KI, 100.00 mg ethoxyquin and 5742.94 mg corn meal as carrier.


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Coccidiosis infection On day one, one group fed the control diet and one group fed the experimental diet were challenged with a mixture of Eimeria containing 900 sporulated oocysts of E. acervulina (Weybridge strain), 570 sporulated oocysts of E. maxima (Weybridge strain) and 170 sporulated oocysts of E. tenella (Houghton strain). The oocysts were obtained from the Animal Health Service Ltd., Deventer, the Netherlands. The oocysts were laboratory strains and the dose and the species used simulated commercially available live vaccines (Williams, 2002). The sporulated oocysts were administered with 1ml of tap water directly into the crop via a scaled 1-ml syringe without needle. The non-infected groups were given 1 ml of oocyst-free water into the crop. In order to avoid cross-contamination, the cages were equipped with plastic sides, and the non-infected groups were always taken care of first. On day fourteen, one bird per cage per treatment was randomly selected and killed by cervical dislocation and used for lesion scoring. On day nineteen, three birds per cage and treatment were killed by cervical dislocation, dissected and the different coccidial lesions were scored. Oocyst counting Fresh excreta samples were collected from the four corners and the middle of each cage on days 5, 7, 9, 12, 14, 16 and 19 of the experiment for oocyst counting. Excreta collection was done in the evening and the samples were stored overnight in a refrigerator. The amount of oocysts per gram faeces of each cage (eight samples/treatment) were counted the next day and expressed as the number of oocysts per gram of faeces. For oocyst counting, a modified McMaster counting chamber technique of Hodgson (1970) was used. A 10% (w/v) faeces suspension in a salt solution (151 g NaCl mixed into 1 l of water) was prepared. After shaking thoroughly, 1 ml of the suspension was mixed with 9 ml of a salt solution (311 g of NaCl mixed into 1 l of water). Then, the suspension was put into the McMaster chamber using a micropipette and the number of oocysts was counted (Peek & Landman, 2003). Lesion scoring On days fourteen and nineteen of the experiment, eight and twenty-four birds per treatment, respectively, were randomly selected and coccidial intestinal lesion scored. The 0–4 lesion scoring system of Johnson & Reid (1970) was used. The areas scored were the upper, middle and the caecal regions of the intestine which are the natural infected sites for E. acervulina, E. maxima and E. tenella, respectively. Based upon severity of the lesions, a score of 0 (no lesions), 1 (mild lesions), 2 (moderate lesions), 3 (severe lesions) or 4 (extremely severe lesions) is recorded for each chicken. The severity of coccidial lesions was scored while the investigator was blinded to treatment modality.

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Statistical analysis All data for each variable were subjected to univariate analysis of variance using SPSS® (2006) (SPSS® Inc., Chicago, USA). The oocyst values were logarithmically transformed (log10 (X + 1)) to create a normal distribution before being analyzed, and lesion scores were transformed using multinomial transformation. When significant treatment effects were disclosed, differences between the four treatments were evaluated by the post hoc multiple comparison least significant difference (LSD) test. Lesion scores were compared using the non-parametric Mann–Whitney test. The level of statistical significance was pre-set at P ≤ 0.05. Results Chick performance in the various intervals of the experiment showed no significant differences between all groups (P > 0.05) (Table 2). Oocysts were not detected in the excreta obtained from non-infected groups. The pattern of oocyst shedding shows peaking on days 5, 12 and 16. The two earlier peaks were most pronounced in the infected controls. The feeding of MOS significantly lowered (P < 0.05) the number of oocysts per gram of faeces on days five and twelve of the experiment (Figure 1). In the non-infected birds, no lesions were found for either day fourteen or nineteen. Lesion scores for day fourteen of the experiment showed no significant difference (P > 0.05) between the infected birds fed either the diet without or with MOS (data not presented). For day nineteen, there were twenty-four dissected birds per treatment and the results showed a significant reduction (P ≤ 0.05) in E. acervulina lesions in the infected group fed the diet with MOS (Table 3). The lesions induced by E. maxima and E. tenella showed no difference (P > 0.05) between the two infected groups. Table 2. Body weight gain (g), feed conversion (feed/gain) of uninfected and infected broiler chickens fed diets without (Control) or with a mannanoligosaccharide preparation (MOS) Variable Control MOS Pooled

SEM P-value

Uninfected Infected Uninfected Infected Body weight gain Days 1-7 86 97 85 93 4.9 0.293 Days 7-14 241 247 253 229 9.2 0.319 Days 14-19 264 264 265 262 11.9 0.999 Feed conversion Days 1-7 1.26 1.20 1.22 1.22 0.04 0.73 Days 7-14 1.28 1.46 1.37 1.48 0.06 0.48 Days 14-19 1.54 1.45 1.44 1.43 0.09 0.81


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Infected MOSInfected Control

Figure 1. Oocyst excretion pattern (number of oocysts per gram of faeces) of infected birds fed diets without (control) or with a mannanoligosaccharide preparation (MOS). * Statistically different P < 0.05, n = 8 samples/treatment. Table 3. Mean lesion scores ± SEM and frequencies of lesions scores at day 19 in infected birds fed diets without (control) or with a mannanoligosaccharide preparation (MOS) Variable Infected control Infected MOS P-value Mean lesion scores E. acervulina 0.46a ± 0.1 0.13b ± 0.09 < 0.05 E. maxima 0.71 ± 0.14 0.63 ± 0.13 0.690 E. tenella 0.42 ± 0.13 0.33 ± 0.1 0.841 Frequencies of lesion scoresA Score 0 1 2 3 0 1 2 3 E. acervulina 13 11 0 0 22 1 1 0 E. maxima 10 11 3 0 11 11 2 0 E. tenella 16 6 2 0 16 8 0 0 a, b Mean ± SEM values within the same row with different superscript letters are significantly different (P < 0.05). A Number of birds dissected 24/treatment.

*

0.00 1.00 2.00 3.00 4.00 5.00 6.00

OPG *(x 105)

19 0 5 7 9 12 14 16

Day

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Discussion In the current experiment, the infection of broiler chickens with coccidiosis was successful based on the intestinal lesions and oocyst shedding. No effect of the infection on performance was seen. The lack of effect of infection on growth performance may relate to the mildness of the infection. Under conditions of more severe infection with Eimeria, weight gain is generally reduced (Johnson & Reid, 1970; Conway et al., 1993; McDougald, 2003; Chapman et al., 2004).

The pattern of oocyst excretion as found in this experiment was fairly predictable (Figure 1). This was because the initial infection dose was low and more or less equal to the dose of a non-attenuated vaccine. Williams (2002) reported that in vaccinated birds the oocyst stage of Eimeria that follow excystation initiate the vaccinal infection, hence stimulating immunity, and during subsequent recycling of infection maintains this immunity. The phenomenon establishes ‘trickle’ infections that have been shown to be very effective in stimulating protective immunity (Joyner & Norton, 1973; 1976). On days five and twelve, the infected birds fed the diet with MOS showed significant lower peak excretions of oocysts compared to the infected control (Figure 1). The MOS-induced reduction in oocysts production indicates that it might have anticoccidial activities. Thus, it can be concluded that the MOS preparation has the potential to lower the severity and the pressure of the infection and at the same time maintain the oocysts production, which is crucial for the re-infection and the maintenance of the immunity stimulated by the initial infection. It has been shown that the feeding of a MOS preparation reduced the number of the asexual stage schizonts in the lamina propria of the caecum broiler chickens infected with E. tenella (Elmusharaf et al., 2006). The protective effect of MOS may be due to the increase in the villi length and improved integrity and uniformity of the gut as observed in chickens fed a diet supplemented with MOS (Loddi et al., 2002). Moreover, Ferket et al. (2002) observed modulation of the systemic immunity in birds fed a diet fortified with MOS. Williams (1995) has reported that there is reciprocity between the immune status of chickens and their excretion of oocysts.

Intestinal lesion scores on day nineteen of the experiment showed that E. acervulina lesions in the infected birds fed MOS were significantly reduced (P < 0.05), whereas the severity of lesions produced by the two other species of Eimeria were reduced but not significantly. The absence of the lesions due to E. maxima and E. tenella on day fourteen is probably due to the very low initial dose and the low oocyst productive potential of both species compared to E. acervulina (Brackett & Bliznick, 1952). The lesions seen on days fourteen and nineteen should be considered as secondary and third lesions (Williams & Andrews, 2001). Thus, it appears that the MOS preparation had anticoccidial activity which counteracted the secondary and third (due to the recycling of the infection after the initial infective dose) attack by E. acervulina and not the secondary and third attack by E. maxima and E. tenella.

In conclusion, the results of the current experiment show that supplementation of the diet with MOS preparation reduced oocyst excretion on days five and twelve of the


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experiment and diminished the severity of E. acervulina lesions but not those due to E. maxima and E. tenella infection. References Brackett, S. & Bliznick, A. (1952). The reproductive potential of five species of coccidia of the chicken

as demonstrated by oocyst production. Journal of Parasitology, 38, pp. 133–139. Chapman, H.D., Marsler, P. & LaVorgna, M.W. (2004). The effects of salinomycin and roxarsone on the

performance of broilers when included in the feed for four, five, or six weeks and infected with Eimeria species during the starter or grower phase of production. Poultry Science, 83, pp. 761–764.

Conway, D.P., Sasai, K., Gaafar, S.M. & Smothers, C.D. (1993). Effects of different levels of oocyst inocula of Eimeria acervulina, E. tenella, and E. maxima on plasma constituents, packed cell volume, lesion scores, and performance in chickens. Avian Diseases, 37, pp. 118–123.

Elmusharaf, M.A., Bautista, V. & Beynen, A.C. (2006). Effect of a mannanoligosaccharide preparation on Eimeria tenella infection in broiler chickens. International Journal of Poultry Science, 5, pp. 583–588.

Ferket, P.R., Parks, C.W. & Grims, J.L. (2002). Benefits of dietary antibiotic and mannanoligosaccharide supplementation for poultry. In: Proceedings of the Multi-State Poultry Feeding and Nutrition Conference, Indianapolis, Ind., May 14–16.

Hodgson, J.N. (1970). Coccidiosis: oocyst counting technique for coccidiostat evaluation. Experimental Parasitology, 28, pp. 99–102.

Jeurissen, S.H.M., Janse, E.M., Vermeulen, A.N. & Vervelde, L. (1996). Eimeria tenella infections in chickens: aspects of host–parasite interaction. Veterinary Immunology and Immunopathology, 54, pp. 231–238.

Johnson, J. & Reid, W.M. (1970). Anticoccidial drugs: lesion scoring techniques in battery and floor-pen experiments with chickens. Experimental Parasitology, 28, pp. 30–36.

Joyner, L.P. & Norton, C.C. (1973). The immunity arising from continuous low-level infection with Eimeria tenella. Parasitology, 67, pp. 333–340.

Joyner, L.P. & Norton, C.C. (1976). The immunity arising from continuous low-level infection with Eimeria maxima and Eimeria acervulina. Parasitology, 72, pp. 115–125.

Loddi, M.M., Nakaghi, L.S.O., Edens, F., Tucci, F.M., Hannas, M.I., Moraes, V.M.B. & Ariki, J. (2002). Mannanoligosaccharide and organic acids on intestinal morphology of broilers evaluated by scanning electrons microscopy. In: Proceedings of the 11th European Poultry Science Conference, Bremen, Germany, September 6–10, pp. 121.

McDougald, L.R. (2003). Coccidiosis. In: Saif, Y.M., Barnes, H.J., Fadly, A.M., Glisson, J.R., McDouglad, L.R., Swayne, D.E. (Eds.), Poultry Diseases. Iowa State Press, Iowa, pp. 974–991.

Peek, H.W. & Landman, W.J.M. (2003). Resistance to anticoccidial drugs of Dutch avian Eimeria spp. field isolates originating from 1996, 1999 and 2001. Avian Pathology, 32, pp. 391–401.

SPSS® (2006) SPSS 15.0 Command Syntax reference 2006. SPSS Inc., Chicago Illinois, USA. van den Ban, E.C.D., Aarts H.J.M., Bokma-Bakker, M.H., Bouwmeester, H. & Jansman, A.J.M. (2005).

AMGB’s en coccidiostatica in pluimveevoeders: Zijn er goede en veilige alternatieve toevoegingsmiddelen? Rapport 05/I00648 Animal Sciences Group van Wageningen UR, Lelystad.

Williams, R.B. (1995). Epidemiological studies of coccidiosis in the domestic fowl (Gallus gallus): IV. Reciprocity between the immune status of floor-reared chickens and their excretion of oocysts. Applied Parasitology, 36, pp. 290–298.

Williams, R.B. & Andrews, S.J. (2001). The origin and biological significance of the coccidial lesions that occurs in chickens vaccinated with live attenuated anticoccidial vaccine. Avian Pathology, 30, pp. 215–220.

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Williams, R.B. (2002). Anticoccidial vaccines for broilers chickens: pathway to success. Avian Pathology, 31, pp. 317–353.

Chapter 4

Influence of live coccidiosis vaccination on the occurrence of anticoccidial drug resistance

Higher incidence of Eimeria spp. field isolates sensitive for diclazuril and monensin associated with the use of live coccidiosis vaccination with Paracox™-5 in broiler farms H.W. Peek and W.J.M. Landman Animal Health Service (GD), Poultry Health Centre, P.O. Box 9, 7400 AA, Deventer, the Netherlands Avian Diseases (September 2006), 50(3), 434-439 Summary Twenty European Eimeria spp. field isolates were subjected to AST. The anticoccidial drugs tested were diclazuril (Clinacox®) and monensin (Elancoban®). The assay was performed in a battery cage trial. Infected medicated birds were compared with an unmedicated control group. Coccidial lesion scores and oocyst shedding were used as parameters. The results of the AST show that resistance is common amongst coccidiosis field isolates especially E. acervulina (68 and 53% resistance for diclazuril and monensin, respectively). Resistance is less frequent amongst E. maxima (38 and 50% resistance for diclazuril and monensin, respectively) and E. tenella isolates (23 and 38% resistance for diclazuril and monensin, respectively). A highly significant influence of the coccidiosis prevention program (live coccidiosis vaccination with Paracox™-5 versus anticoccidial drugs in feed) on the sensitivity patterns of Eimeria spp. field isolates for both diclazuril (P = 0.000) and monensin (P = 0.001) was found. Further, when looking at the single species and each anticoccidial drug level significantly more sensitivity of E. acervulina for monensin (P = 0.018), E. maxima for diclazuril (P = 0.009) and E. tenella for diclazuril (P = 0.007) was found in isolates originating from vaccinated flocks. Moreover, for E. acervulina and diclazuril, E. maxima and monensin, and E. tenella and monensin a trend towards higher sensitivity of isolates for these products was found when live coccidiosis vaccination was applied. The present study shows that sensitivity for the anticoccidial drugs diclazuril and monensin is more frequent in Eimeria spp. field isolates originating from broiler farms where a coccidiosis vaccination policy is followed. Keywords: coccidiosis, broiler chickens, vaccination, anticoccidial drugs, sensitivity test, Eimeria acervulina, E. maxima, E. tenella

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Introduction Coccidiosis in poultry is caused by a protozoan parasite belonging to the phylum Apicomplexa (Levine, 1988) and is of great economic importance to the poultry industry. Despite large financial investments involved in the prevention and treatment of coccidiosis its absolute control is still out of reach.

At present a number of strategies are used for the prevention and control of coccidiosis in broilers. Until recently anticoccidial drugs in feed has been by far the most popular approach, while in some cases an anticoccidial drug administered shortly via drinking water is applied. Also, management measures focusing on good sanitation, cleaning out contaminated litter and good litter condition in broiler houses are considered of strategic value in controlling this parasitic disease. Lately, live coccidiosis vaccination has added to this list and is becoming increasingly popular to control the coccidiosis problem.

A major drawback of the use of anticoccidial drugs is the development of resistance, which has been described for all anticoccidial drugs introduced so far (Chapman, 1986a, 1997; Peek & Landman, 2003, 2004). To minimize the occurrence of anticoccidial drug resistance rotation of various anticoccidial drugs or shuttle programs (ideally based on knowledge of the anticoccidial sensitivity profiles of field isolates) are used. The rationale behind it is the reported loss of resistance following propagation of resistant parasites in unmedicated birds (Chapman, 1986a) and chickens given unrelated anticoccidial drugs (Ryley, 1980; Chapman, 1982). However, most studies indicate that resistance is stable even in the absence of drug selection pressure (Gardiner & McLoughlin, 1963; Ball, 1968; McLoughlin & Chute, 1968; Williams, 1969; Chapman, 1986b) which explains why these measures have not completely solved the coccidiosis resistance problem in the field.

In case of resistance the use of live coccidiosis vaccines can be considered as an alternative prophylactic measure against coccidiosis. Furthermore, a few studies have reported an improved sensitivity of coccidiosis field isolates for anticoccidial drugs as a welcome side-effect of coccidiosis vaccination due to seeding of the houses with drug sensitive vaccine oocysts (Mathis & McDougald, 1989; Chapman, 1994; Chapman, 1996; Newman & Danforth, 2000). However, large scale field studies reporting on the occurrence of a higher incidence of anticoccidial drug sensitivity of coccidiosis isolates associated with the use of live coccidiosis vaccination programs are lacking. Therefore, the aim of the present work was to perform a study on the association between the coccidiosis prevention program (vaccination with a live attenuated coccidiosis vaccine or anticoccidial drugs in feed) and the occurrence of sensitivity for diclazuril and monensin of Eimeria spp. field isolates.

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Material and methods Experimental design Three experimental groups of nine chicks were used for each Eimeria spp. field isolate. Group 1 was medicated with diclazuril (Clinacox® product code 01-080.0) at a dose of 1 mg/kg feed, group 2 received monensin (Elancoban® product code 01-126.0) at a dose of 100 mg/kg feed and the third group acted as an infected unmedicated control (IUC). For all field isolates (n = 20) one uninfected unmedicated control (UUC) group of nine birds was used as negative control. Both, the IUC and UUC groups were given feed free of anticoccidial products. Animals, housing and medicated feed One-day-old male commercial broilers (Hybro) were reared coccidiosis free. At the age of six days, two days prior to the inoculation (D -2) the birds were transferred ad random to battery stain-less-steel cages (height x width x depth = 30 cm x 40 cm x 50 cm) and given access to the medicated feed. The birds were subjected to 22 hours light per day. Feed and water were supplied ad libitum. The feed, a broiler starter (Apparent Metabolizable Energy (AME) 12.0 MJ/kg), was mixed with commercial anticoccidial premixes and concentrations of in feed medication was assessed by chemical analyses (Peek & Landman, 2003). The birds were observed daily and deceased birds were subjected to postmortem examination. Eimeria spp. field isolates, identification, assessment of pathogenicity and preparation of inocula Twenty Eimeria spp. field isolates from six European countries were analyzed: Germany (seven isolates), Italy (seven isolates), Greece (two isolates), Portugal (two isolates), Romania (one isolate) and Denmark (one isolate). Oocysts were purified and sporulated as described (Peek & Landman, 2003), followed propagation in SPF broilers. The inoculum for propagation ranged from approximately 104 to 5 x 104 sporulated oocysts per chicken. Birds were inoculated at eight days of age followed by postmortem analysis seven days later at which time identification and assessment of the pathogenicity of the species present in the field isolate were performed. The Eimeria spp. were identified by the location and appearance of the gross lesions in the intestine and by microscopic examination and measurement of the oocysts (Johnson & Reid, 1970; Long et al., 1976). Faeces samples were gathered from day four (D +4) to 8 (D +8) post-inoculation, oocysts were purified and sporulated for the AST. At an age of eight days (D 0) chicks were inoculated in the crop with a defined number of sporulated oocysts. The inoculation dose for the AST was adjusted to induce a lesion score of 2 to 3 on the scale of Johnson and Reid (1970) and avoid mortality in the IUC (Conway

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et al., 1993; Peek & Landman, 2003). The oocyst countings of the inocula were performed using a Fuchs-Rosenthal haemocytometer counting chamber. The inoculation doses are outlined in Table 1. Coccidial lesion scores, OPGs and evaluation of sensitivity Six days post-infection (fourteen days of age) five birds per experimental group were sacrificed for postmortem examination to determine the individual coccidial lesion scores (ILSs). The ILSs were determined according to the method of Johnson and Reid (1970). The mean lesion scores (MLS) per Eimeria spp. and experimental group (n = 5) was subsequently calculated. In fresh collected faeces material the OPG per experimental group were performed (Peek & Landman, 2003). The anticoccidial sensitivity profile of each isolate was based on the percentage reduction of the MLS per Eimeria spp. compared to the IUC group {McDougald formula: 100% - (MLS of treated group / MLS of the IUC group x 100%)}. A reduction percentage of 0-30% indicates coccidial resistance, 31-49% indicates reduced sensitivity or partial resistance and 50% or more indicates full sensitivity to the tested anticoccidial product (McDougald et al., 1986). Statistical analysis Differences in coccidial lesion scores between medicated and non-medicated infected groups were assessed statistically using the non-parametric Kruskal-Wallis test (StataCorp, 2004). Agreement analysis (Fleiss et al., 1969; Fleiss, 1981) was performed for all field isolates per Eimeria spp. and anticoccidial drug between the results obtained with the Kruskal-Wallis test and the sensitivity profiles obtained with the formula of McDougald et al. (1986). If the Kruskal-Wallis test detected a significant difference in lesion scores between medicated and non-medicated infected birds the isolate was rated as sensitive for that particular drug, if the contrary happened, the isolate was rated as resistant. All profiles of field isolates obtained with both methods were summed up per Eimeria spp. and anticoccidial drug and subsequently ordered in 2 x 2 tables for agreement analysis. Reduced sensitive isolates were considered resistant for the agreement analysis. Then, the overall effect of treatments (anticoccidial drug or preventive vaccination) on the occurrence of sensitive, reduced sensitive and resistant Eimeria spp. isolates for either diclazuril or monensin was assessed with the Chi-Square test. For this purpose the total number of isolates sensitive, reduced sensitive or resistant per anticoccidial drug were counted and analyzed. Then, follow-up Chi-Square tests were performed counting the isolates per profile category, species and anticoccidial drug to assess in which cases the association of vaccination with sensitivity profiles were significant. Pearson Chi-Square was used if cell frequencies were ≥ 5 in 80% of cells, otherwise Fisher’s exact test was used (SPSS®, 2001). For all tests differences were considered significant if P < 0.05.


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Results Chemical analysis of the anticoccidial products in the feed The results of the chemical analysis show that the anticoccidial product concentrations in feed were close to the desired dose. For diclazuril the concentration found was 1.1 mg/kg and for monensin 103 mg/kg. Eimeria spp. field isolates and inocula During multiplication it became apparent that most field isolates consisted of mixtures of two or three Eimeria spp. Only three isolates comprised a single species, namely E. acervulina, which was found in all isolates except isolate 14 (Germany). E. maxima was detected in sixteen field isolates and always occurred in combination with other species. E. tenella was present in thirteen isolates in combination with one or two other species. The mixture of three Eimeria spp. was prevailing and occurred eleven times. Field isolate number, countries of origin, sampling date, coccidiosis prevention program in use, previously used anticoccidial programs, Eimeria spp. identified in the field isolates and inoculation dose (number of sporulated oocysts) per bird are given in Table 1. Coccidial lesion scores, OPGs and evaluation of sensitivity In Table 2 the MLS, OPGs and anticoccidial sensitivity profile of each Eimeria spp. field isolate are outlined. In the IUC groups, the overall average lesion score for E. acervulina was 1.58, for E. tenella it was 1.55 and for E. maxima 1.40. Mortality due to the coccidiosis infection was only recorded in the IUC group of the Greek field isolate (number 6). In this group 4/9 birds died due to the E. tenella infection, which seemed to be quite pathogenic. Moreover, a summary of the sensitivity profiles per Eimeria spp. in relation to the coccidiosis prevention program is given in Table 3. Resistance was common amongst the tested field isolates especially E. acervulina; 68.4% (13/19) isolates were resistant to diclazuril, while 52.6% (10/19) showed resistance against monensin. Resistance was less frequent amongst E. maxima and E. tenella field isolates. The former species showed resistance in 37.5% (6/16) cases for diclazuril and 50% (8/16) for monensin. E. tenella isolates showed resistance for diclazuril in 23.0% (3/13) cases and 38.5% (5/13) for monensin. The Kruskal-Wallis test showed significant differences between medicated and non-medicated infected groups in a number of cases (Table 2). The strength of agreement between the significances obtained with the Kruskal-Wallis test and the sensitivity profiles ranged from good (Kappa (κ) = > 0.6 ≤ 0.8) to very good (κ = > 0.8 ≤ 1) for the sensitivity profiles of E. tenella for monensin (κ = 0.649 ± 0.22), of E. acervulina for diclazuril (κ = 0.759 ± 0.16), of E. maxima for monensin (κ = 0.871 ± 0.12) and of E. tenella for diclazuril (κ = 0.831 ± 0.16). The agreement was moderate (κ = > 0.4 ≤ 0.6) only for the

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profiles of E. acervulina for monensin ((κ = 0.565 ± 0.22). Kappa-values were not calculated for the sensitivity profiles of E. maxima and diclazuril, because here lesion scores were not used to calculate statistical differences between medicated and non-medicated infected groups or establishing the anticoccidial sensitivity profiles to McDougald’s formula. For the agreement analysis, ten reduced sensitive isolates were considered resistant, of these seven did not show a significant difference between medicated and non-medicated infected birds in the Kruskal-Wallis test.

Table 1. Field isolate number, countries, age (days) at collection of samples, coccidiosis prevention program in use, previous anticoccidial (Ac.) programs, Eimeria spp. identified in the field isolates and inoculation dose (number of sporulated oocysts) per bird used in the anticoccidial sensitivity test Isolate Country* Age of

collection Coccidiosis prevention program in use

Previous anticoccidial programs Eimeria spp. Inoculation dose (x 103)

1 DEU 31 Monensin Five flocks or more with monensin E. acervulina/E. tenella 21 2 GRC Ac. not specified Ac. not specified E. acervulina 53 3 ITA 27 Paracox™-5

(2nd vaccination) Three flocks maduramicin & monensin and three flocks narasin/nicarbazin & monensin

E. acervulina/E. maxima/E. tenella

27

4 DNK 39 salinomycin One flock narasin and 4 flocks salinomycin

E. acervulina/E. maxima 39

5 ITA 34 monensin Four flocks salinomycin and two flocks monensin

E. acervulina/E. maxima 85

6 GRC 26 Paracox™-5 Three or more flocks Paracox™-5 E. acervulina/E. maxima/E. tenella

39

7 ROM 34 Ac. not specified Ac. not specified E. acervulina/E. maxima/E. tenella

35

8 ITA 27 Paracox™-5 Six or more flocks Paracox™-5 E. acervulina/E. maxima 63 9 ITA 21 Paracox™-5 Six or more flocks Paracox™-5 E. acervulina/E. maxima/E.

tenella 27

10 PRT 21-28 narasin/nicarbazin & robenidine

Six flocks narasin/nicarbazin & salinomycin


49

11 PRT 28-35 narasin/nicarbazin & maduramicin

Six flocks narasin/nicarbazin & salinomycin


15

12 DEU 29 Paracox™-5** (1st vaccination)

Ac. not specified E. acervulina/E. maxima 51

13 DEU 33 Ac. not specified Ac. not specified E. acervulina/E. maxima/E. tenella

32

14 DEU 19 Paracox™-5 Six or more flocks Paracox™-5 E. maxima/E. tenella 26

15 DEU 26 Paracox™-5 Six or more flocks Paracox™-5 E. acervulina/E. maxima/E. tenella 63 16 DEU 24 narasin/nicarbazin

monensin &

&

One flock narasin/nicarbazin & monensin and six flocks monensin

E. acervulina 62

17 DEU 30 narasin/nicarbazin monensin

One flock narasin/nicarbazin & monensin and six flocks monensin

E. acervulina 45

18 ITA 31 Paracox™-5 Six or more flocks Paracox™-5 E. acervulina/E. maxima/E. tenella 3519 ITA 27 Paracox™-5 Six or more flocks Paracox™-5 E. acervulina/E. maxima/E. tenella 63 20 ITA 27 Paracox™-5 Three or more flocks Paracox™-5 E. acervulina/E. maxima/E. tenella 48

* = country abbreviations (ISO 3166). ** = considered as non-vaccinated.


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Chi-Square test: association with live vaccination The results of the overall Chi-Square test showed a highly significant influence of the treatment (vaccination versus other preventive coccidiosis program) on the sensitivity profiles of the field isolates for both diclazuril (P = 0.000) and monensin (P = 0.001). In Table 3 the results of the follow up Chi-Square tests of sensitivity profiles per Eimeria spp. and anticoccidial drug versus treatment are given. When looking at the species level we find significant results for the association of vaccination and the sensitivity of E. acervulina for monensin (P = 0.018), of E. maxima for diclazuril (P = 0.009) and of E. tenella for diclazuril (P = 0.007). These cases are responsible for the significance found with the overall Chi-Square. For all remaining isolates a trend towards higher sensitivity for the anticoccidial drugs tested was found if preventive vaccination had taken place on the farms of origin. Table 2. Mean lesion score (D +6), sensitivity profile (according to the criteria of McDougald et al., 1986 and OPG (D +4 till D +8) per treatment and Eimeria spp. field isolate Field isolate Treatment Mean lesion scores (Sensitivity profile)**

(n = 5) OPG (x 103)

E. acervulina E. maxima E. tenella 1. (DEU) DIC 1.0a (R) 0.6a (R) 2390 MON 1.0a (R) 0.6a (R) 1470 IUC 1.2a 0.8a 3690 2. (GRC) DIC 1.6a (R) 4890 MON 1.4a (R) 939 IUC 1.8a 1890 3. (ITA) DIC 1.6a (R) 1.6a (R) (*S) 0.0b (S) 539* MON 0.8a (RS) 0.2b (S) 0.6a (S) 1170 IUC 1.4a 1.2a 1.2a 979 4. (DNK) DIC 1.2a (R) 1.2a (RS) (*S) 1290* MON 0.8a (RS) 0.4b (S) 839 IUC 1.4a 1.8a 3590 5. (ITA) DIC 0.4b (S) 1.0b (RS) 839 MON 1.8a (R) 1.4a (R) 1180 IUC 2.0a 1.6a 1690 6. (GRC) DIC 0.2b (S) 1.0a (R) 0.0b (S) 679 MON 0.8a (R) 1.0a (R) 1.2b (S) 969 IUC 1.0a 1.3a 3.2a 1120 7. (ROM) DIC 1.2a (R) 1.2a (R) 2.6a (R) 1420 MON 1.6a (R) 2.0a (R) 2.6a (R) 1280 IUC 1.4a 1.2a 3.0a 2790 8. (ITA) DIC 1.0b (S) 1.0a (R) (*S) 569* MON 0.6b (S) 0.0b (S) 889 IUC 2.8a 1.0a 2090 9. (ITA) DIC 1.0a (R) 1.0a (R) (*S) 0.0b (S) 2290*

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MON 0.6a (S) 0.0b (S) 0.0b (S) 719 IUC 1.2a 1.2a 0.6a 2790 10. (PRT) DIC 2.0a (R) 1.6a (R) 1.2a (RS) 5690 MON 1.4b (RS) 1.4a (R) 2.8a (R) 719 IUC 2.2a 1.6a 2.0a 4090 11. (PRT) DIC 0.8a (R) 1.2a (R) 2.0a (R) 2590 MON 1.0a (R) 1.2a (R) 1.0a (RS) 1120 IUC 1.0a 1.6a 1.6a 1990 12. (DEU) DIC 1.2a (R) 1.0a (R) 3990 MON 1.4a (R) 1.6a (R) 5790 IUC 1.0a 1.4a 5590 13. (DEU) DIC 1.0b (RS) 1.6a (R) 0.6a (S) 2690 MON 1.0b (RS) 1.2a (R) 0.4b (S) 1370 IUC 1.6a 1.4a 1.2a 2630 14. (DEU) DIC 1.0a (R) (*S) 0.0b (S) 0* MON 1.4a (R) 1.0a (RS) 365 IUC 1.4a 1.6a 313 15. (DEU) DIC 0.0b (S) 1.2a (RS)(*S) 0.0b (S) 0,390* MON 1.2a (RS) 1.2a (RS) 0.6a (RS) 1650 IUC 1.8a 1.8a 1.0a 2790 16. (DEU) DIC 1.8a (R) 4890 MON 2.0a (R) 6890 IUC 2.4a 3590 17. (DEU) DIC 1.4b (R) 2990 MON 1.8a (R) 4720 IUC 2.0a 2990 18. (ITA) DIC 0.0b (S) 1.4a (R) (*S) 0.4b (S) 69* MON 0.0b (S) 1.0b (RS) 1.4a (R) 1360 IUC 1.0a 1.6a 1.8a 1490 19. (ITA) DIC 1.4a (R) 1.4a (R) (*S) 0.2b (S) 699* MON 0.0b (S) 0.4b (S) 1.2a (R) 1000 IUC 1.4a 1.2a 1.2a 1290 20. (ITA) DIC 1.4a (R) 1.4a (R) (*S) 0.0b (S) 1740* MON 1.0a (R) 0.0b (S) 0.4a (S) 930* IUC 1.2a 1.0a 0.8a 1180 None UUC 0 0 0 0 * = No E. maxima oocysts were found in faeces. ** R = resistant; RS = reduced sensitive; S = sensitive. DIC = diclazuril; IUC = infected unmedicated control; MON = monensin; OPG = oocyst per gram faeces; UUC = uninfected unmedicated control. a, b Treatment groups with no common superscript within columns differ significantly from IUC group (P < 0.05) (Kruskal-Wallis test).


192

Table 3. Summary of the anticoccidial sensitivity profiles per Eimeria spp. and anticoccidial drug (diclazuril or monensin) in relation to the coccidiosis prevention program. The significance of the association between the coccidiosis prevention program and the sensitivity profiles found was assessed using the Chi-Square test (P-values are found in the left column; P < 0.05 = significant) Prevention program Vaccination Anticoccidial drugs Eimeria species Classification Sensitivity profile diclazuril E. acervulina Sensitive 4 1 (n = 19) Reduced sensitive 0 1 Resistant 4 9 P = 0.111 Sensitive/total 4/8 (50%) 1/11 (9%) E. maxima Sensitive 8 1 (n = 16) Reduced sensitive 0 1 Resistant 1 5 P = 0.009 Sensitive/total 8/9 (89%) 1/7 (14%) E. tenella Sensitive 8 1 (n = 13) Reduced sensitive 0 1 Resistant 0 3 P = 0.007 Sensitive/total 8/8 (100%) 1/5 (20%) Eimeria species Classification Sensitivity profile monensin E. acervulina Sensitive 4 0 (n = 19) Reduced sensitive 2 3 Resistant 2 8 P = 0.018 Sensitive/total 4/8 (50%) 0/11 (0%) E. maxima Sensitive 5 1 (n = 16) Reduced sensitive 2 0 Resistant 2 6 P = 0.060 Sensitive/total 5/9 (55%) 1/7 (14%) E. tenella Sensitive 4 1 (n = 13) Reduced sensitive 2 1 Resistant 2 3 P = 0.767 Sensitive/total 4/8 (50%) 1/5 (20%) Discussion The rate at which E. acervulina was found, was similar to previous studies (Peek & Landman, 2003, 2004). However, E. maxima and E. tenella were detected more often. Other authors also have found a higher number of Eimeria spp. in vaccinated flocks compared to anticoccidial drug treated ones (Jenkins et al., 2005).

Ideally a lesion score ranging between 2 and 3 should be obtained. Adjustment of the inoculum dose to obtain such lesions proved to be difficult in the present study because most isolates consisted of two or three Eimeria spp. In these cases the most pathogenic species determines the inoculation dose, which can result in lower lesion scores for other

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species lowering the average. Despite the fact that the obtained lesion scores were lower than aimed, it was still possible to adequately calculate the reduction in lesion scores.

The results of the AST show that resistance is still common amongst European coccidiosis field isolates especially E. acervulina (68 and 53% resistance for diclazuril and monensin, respectively), although it was lower than in previous studies (Peek & Landman, 2003, 2004). Resistance was less frequent amongst E. maxima (38 and 50% resistance for diclazuril and monensin, respectively) and E. tenella isolates (23 and 38% resistance for diclazuril and monensin, respectively), also when compared to previously reported AST (Peek & Landman, 2003, 2004). The higher incidence of sensitivity found was attributed to the use of live coccidiosis vaccination on a number of farms from which the field isolates originated, although a cause-effect remains to be demonstrated. Regarding the higher incidence of sensitivity of E. maxima for diclazuril found in this study it was in part explained by the fact that sensitivity here was assessed based on the absence of oocyst shedding. In some field isolates exposed to diclazuril E. maxima oocyst shedding was absent, while at postmortem lesions containing oocysts were found. If so, these isolates were considered to be sensitive to diclazuril. According to Verheyen et al. (1989) and Maes et al. (1989), the absence of oocysts during E. maxima and E. brunetti infections is explained by the fact that the normal pattern of oocyst wall establishment is completely disturbed after treatment with diclazuril. It results in the formation of an abnormally thickened, incomplete oocyst wall and the necrosis of the zygote in all fertilized macrogamonts of both species. This explains the occurrence of E. maxima coccidial lesions without oocyst shedding, in which case the field isolate is considered sensitive for diclazuril.

A number of manuscripts suggesting the restoration of anticoccidial drug sensitivity in Eimeria spp. isolates have been published in the past. The first paper portraying this phenomenon was by Ball (1966), who found that when a small number of oocysts of a glycarbylamide-resistant E. tenella strain were mixed with a larger number of sensitive oocysts and the combination was serially passaged in unmedicated chickens, the percentage of recovered resistant oocysts diminished progressively at each passage. Later studies (McLoughlin, 1970; Jeffers, 1976; McLoughlin & Chute, 1979) all pointed out that an infusion of drug-sensitive oocysts into a drug-resistant population causes a decrease of resistance within the mixed population, confirming Ball’s results (1966). This loss of detectable resistance was attributed to dilution and not to a natural loss of resistance, while Long et al. (1985) also suggested that drug-sensitive parasites are likely to dominate in the absence of medication outgrowing their resistant counterparts possibly due to a reproductive advantage.

Restoration of anticoccidial drug sensitivity (for monensin and salinomycin) under field circumstances has been described after the use of the non-attenuated coccidiosis vaccine Coccivac®-B (Chapman, 1994; Chapman, 1996; Newman & Danforth, 2000), drug sensitive parasites supposedly replacing the resistant isolates after one to five vaccinated flocks. A similar effect has been reported briefly without further details on anticoccidial sensitivity profiles for the vaccine Paracox™-8 (Vertommen, 1996), in spite of its precocious nature, and the attenuated vaccine Livacox® (Oliveira, 2001).


194

How the resistance of Eimeria spp. parasites is reverted under experimental and field circumstances is currently unknown. As mentioned previously, outgrowing of resistant parasites by reproductive more advantageous sensitive strains and thereby replacing the resident population might be a possibility. However, interbreeding between vaccine and field parasites leading to improved anticoccidial sensitivity should also be considered. Additionally, in case precocious vaccines are used not only could the resistance be ameliorated, but the virulence of the field isolates could be reduced as well (Williams, 2002). It has been shown that the precocious nature of some Eimeria strains is a genetically stable trait (McDonald et al., 1986; Shirley, 1988), which will recombine with that of drug resistance described by Shimura & Isobe (1994), resulting in a less virulent interbreed.

In the present study a significant association between preventive coccidiosis vaccination with live attenuated vaccines and the occurrence of sensitivity for diclazuril and monensin of Eimeria spp. field isolates was found. Although a shift in the sensitivity profiles was not demonstrated (for that matter anticoccidial sensitivity testing should have been performed before and after the application of live coccidiosis vaccines), it might well have occurred as demonstrated by others for other non-attenuated vaccines (Mathis & McDougald, 1989; Chapman, 1994; Newman & Danforth, 2000). References Ball, S.J. (1966). The development of resistance to glycarbylamide and 2-chloro-4- nitrobenzamide in

Eimeria tenella in chicks. Parasitology, 56, pp. 25-37. Ball, S.J. (1968). The stability of resistance to glycarbylamide and 2-chloro-4-nitrobenzamide in Eimeria

tenella in chicks. Research in Veterinary Medicine, 9, pp. 149-151. Chapman, H.D. (1982). Anticoccidial drug resistance. In: The biology of the coccidia. P.L. Long, ed.

Baltimore, University Park Press. pp. 429-452. Chapman, H.D. (1986a). Drug resistance in coccidia: recent research. In: Proceedings of the Georgia

Coccidiosis Conference. L.R. McDougald, L.P. Joyner & P.L. Long, eds. Georgia, USA. pp. 330-341. Chapman, H.D. (1986b). Eimeria tenella: stability of resistance to halofuginone, decoquinate and

aprinocid in the chicken. Research Veterinary Science, 40, pp. 139-140. Chapman, H.D. (1994). Sensitivity of field isolates of Eimeria to monensin following the use of a

coccidiosis vaccine in broiler chickens. Poultry Science, 73, pp. 476-478. Chapman, H.D. (1996). Restoration of drug sensitivity following the use of live coccidiosis vaccines.

World Poultry special Supplement Coccidiosis, 2, pp. 20-21. Chapman, H.D. (1997). Biochemical, genetic and applied aspects of drugs resistance in Eimeria parasites

of the fowl. Avian Pathology, 26, pp. 221-244. Conway, D.P., Sasai, K., Gaafar, S.N. & Smothers, C.D. (1993). Effects of different levels of oocyst

inocula of Eimeria acervulina, E. tenella, and E. maxima on plasma constituents, packed cell volume, lesion score, and performance in chickens. Avian Diseases, 37, pp. 118-123.

Fleiss, J.L. (1981). Statistical methods for rates and proportions. 2nd Edition, John Wiley & Sons, New York, pp. 221.

Fleiss, J.L., Cohen, J. & Everitt, B.S. (1969). Large sample standard errors of Kappa and weighted Kappa. Psychological Bulletin, 72, pp. 323-327.

Gardiner, J.L. & McLoughlin, D.K. (1963). Drug resistance in Eimeria tenella. III. Stability of resistance to glycarbylamide. Journal of Parasitology, 49, pp. 657-659.

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Jeffers, T.K. (1976). Reduction of anticoccidial drug resistance by massive introduction of drug-sensitive coccidia. Avian Diseases, 20, pp. 649-653.

Jenkins, M.C., Klopp, S., Wilkins, G. & Miska, K. (2005). Comparison of drug-sensitivity and species composition of Eimeria isolated from poultry farms utilizing either anti-coccidial drugs or a live oocyst vaccine to control avian coccidiosis. In Proceedings of the IXth International Coccidiosis Conference, Foz de Ignuassu, Parana, Brazil. pp. 157.


Levine, N.D. (1988). The protozoan phylum Apicomplexa, 2 vols. CRC Press, Inc., Boca Raton, FL. Long, P.L., Joyner, L.P., Miljard, B.J. & Norton, C.C.(1976). A guide to laboratory techniques in the

study and diagnosis of avian coccidiosis. Folia Veterinary Lat, 6, pp. 201-217. Long, P.L., Johnson, J. & Baxter, S. (1985). Eimeria tenella: relative survival of drug resistant and drug-

sensitive populations in floor pen chickens. Poultry Science, 64, pp. 2403-2405. Maes, L., Coussement, W., Vanparijs, O. & Verheyen, F. (1989). Species- specificity action of diclazuril

(Clinacox®) against different Eimeria species in the chicken. In: Proceedings of the Coccidia and intestinal Coccidiomorphs, Vth International Coccidiosis Conference, Tours, France. pp. 259-264.

Mathis, G.F. & McDougald, L.R. (1989). Restoration of drug sensitivity on turkey farms after introduction of sensitive coccidia during controlled-exposure immunization. In: Proceedings of Coccidia and intestinal Coccidiomorphs, Vth International Coccidiosis Conference, Tours, France. pp. 17-20.

McDonald, V., Shirley, M.W. & Bellatti, M.A. (1986). Eimeria maxima: characteristics of attenuated lines obtained by selection for precocious development in the chicken. Experimental Parasitology, 61, pp. 192-200.


McLoughlin, D.K. & Chute. M.B. (1968). Drug resistance in Eimeria tenella. VII. Acriflavine-medicated loss of resistance to amprolium. Journal of Parasitology, 54, pp. 696-698.

McLoughlin, D.K. (1970). Coccidiosis: experimental analysis of drug resistance. Experimental Parasitology, 28, 129-136.

McLoughlin, D.K. & Chute, M.B. (1979). Loss of amprolium resistance in Eimeria tenella by admixture of sensitive and resistant strains. Proceedings of the helminthological society of Washington, 14, pp. 138-141.

Newman, L.J. & Danforth, H.D. (2000). Improved sensitivity of field oocyst populations to coccidiostat following vaccination with live oocyst vaccine. Poultry Science, 79 (supplement 1), pp. 4.

Oliveira, C. de. (2001). Latest thinking on avian coccidiosis. In: Vaccination at Work in Commercial Broilers. Driffield UK: Positive Action Publications Ltd. pp. 9.


Peek, H.W. & Landman, W.J.M. (2004). Gevoeligheidsprofielen van Spaanse, Duitse en Nederlandse Eimeria spp. veldisolaten voor anticoccidiose middelen. Tijdschrift voor Diergeneeskunde, 129, pp. 210-214.

Ryley, J.F. (1980). Drug resistance in coccidia. Advances in veterinary Science and Comparative Medicine, 24, pp. 99-120.

Shimura, K. & Isobe, T. (1994). Pathogenicity and drug resistance of a recombinant line between a precocious line and a drug resistant field isolate of Eimeria tenella. Proceedings Second Asian Conference Coccidiosis, Guangzhou: China. pp. 119-123.

Shirley, M.W. (1988). Control of coccidiosis with vaccines, In: Proceedings Second Asian/Pacific Poultry Health Conference, Surfers Paradise, Australia. pp. 129-157.

SPSS® (2001). SPSS 11.0 for Windows®. SPSS Inc., Chicago, Illinois, USA. StataCorp. (2004). Stata/SE 8.2 for Windows®. StataCorp, College Station, Texas, USA.


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Verheyen, A., Maes, L., Coussement, W., Vanparijs, O., Lauwers, F. & Marsboom, R. (1989). Ultrastructural evaluation of the effects of diclazuril on the endogenous stages of Eimeria maxima and E. brunetti in experimentally inoculated chickens. Parasitology Research, 75, pp. 604-610.

Vertommen, M.H. (1996). Coccidiosis control methods. In: Proceedings of the Paracox European Symposium, Annecy. France. pp. 11-20.

Williams, R.B. (1969). The persistence of drug resistance in strains of Eimeria species in broiler chickens following a change in coccidiostat. Research Veterinary Science, 10, pp. 490-492.


Chapter 5

Improvement of live anticoccidial vaccines

Cross protection studies between Eimeria acervulina and E. maxima, and E. tenella H.W. Peeka, M.H. Vertommenb and W.J.M. Landmana,c aAnimal Health Service (GD), Arnsbergstraat 7, 7418 EZ Deventer, the Netherlands bZeelandia 4, 3901 GZ Veenendaal, the Netherlands cDepartment of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, the Netherlands Submitted Summary Three successive animal passages with extraintestinal blood stages of an Eimeria acervulina strain were performed in commercial broiler chickens to select an E. acervulina vaccine line. Subsequently, commercial broilers were vaccinated at one day of age by coarse spray with graded doses of the obtained E. acervulina vaccine line to determine the vaccination dose and to establish the protection against challenge with virulent strains of E. acervulina, E. tenella and E. maxima with time. Vaccinated birds showed complete protection against challenge with E. acervulina, partial cross protection against E. tenella and no cross protection against E. maxima. Keywords: Eimeria, chickens, extraintestinal stages, vaccine, cross protection

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1. Introduction Coccidiosis, an intestinal disease of chickens, is caused by a protozoan parasite belonging to the genus Eimeria within the family Eimeriidae and the Phylum Apicomplexa. In poultry, this disease has a great economic impact and the worldwide costs for production losses and prophylaxis against coccidiosis have been estimated at US$ 2400 million per annum (Shirley et al., 2005).

During the past 50 years, control of avian coccidiosis has mainly relied on prophylactic chemotherapy. In the broiler industry – the largest sector of the poultry industry – chickens are given anticoccidial drugs from hatch until a few days before slaughter. The intensive prophylactic use of anticoccidial products has resulted in the development of resistance to all of them despite the strategic use of rotation and shuttle programs (Chapman, 1997; Peek & Landman, 2003; 2004).

The increasing occurrence of resistance and the possible ban of anticoccidial drugs as feed additives at least in Europe has further stimulated the use of vaccination, which was first described in 1925 (Beach & Corl), as an efficient alternative control measure against coccidiosis. Different types of anticoccidial vaccines have been developed during the past decades and live vaccines are most frequently used. Although research exploring the feasibility of subunit vaccines against coccidiosis has been substantial, no commercial products except CoxAbic® have been marketed yet. Identification of vital antigens in coccidial immunology seems to be the major limiting factor (Shirley et al., 2007).

Live anticoccidial vaccines consist of sporulated oocysts of either non-attenuated (wild type) or attenuated Eimeria spp. lines. To date two approaches have been used for the attenuation of Eimeria spp. from chickens. The first approach is the use of a vaccine composed of parasites obtained after serial passages in embryonated eggs and the second approach is based on selection for precocity, which is characterized by a shortened endogenous life cycle due to a decreased number of schizogony cycles. During the last two decades numerous reports describing anticoccidial vaccines have been published and a recent overview of available vaccines has been given by Williams (2002a) and Shirley et al. (2005).

Major disadvantages of live anticoccidial vaccines are: 1/ propagation has to be performed in the natural host, 2/ yield of oocysts is lowered for attenuated precocious vaccines due to precocity characteristics and 3/ all relevant Eimeria spp. must be included in the vaccine further increasing production costs. Coccidiosis vaccines could be produced more efficiently if cross protection between Eimeria spp. would be relevant enough to reduce the number of species included in the vaccine and/or reduce the vaccination doses. Therefore, cross protection studies between an E. acervulina vaccine line obtained through three successive animal passages with early extraintestinal blood stages of the parasite and E. tenella, and E. maxima were performed.

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2. Material and methods 2.1. Eimeria spp. laboratory strains/lines 2.1.1. Challenge strains The E. acervulina (Weybridge), E. maxima (Weybridge) and E. tenella (Houghton) strains were obtained from the Veterinary Laboratory Agency (VLA), Weybridge, UK. The E. acervulina (Weybridge) strain was provided in 1990 while the E. maxima (Weybridge) and the E tenella (Houghton) strains were obtained in 2000. All Eimeria spp. strains were rejuvenated approximately every half year. The terminology for populations of Eimeria spp. used in this manuscript i.e. isolate, strain and vaccine line are in agreement with the definitions given previously by Chapman et al. (2005). 2.1.2. Vaccines lines The E. acervulina (Weybridge) strain was used to obtain an E. acervulina vaccine line by means of animal passages with extraintestinal blood stages. All strains/lines were stored as oocyst suspensions at 2-8 °C in a 2.5% potassium dichromate (w/v) solution. During preparation of the inocula the potassium dichromate was removed by means of centrifugation and assessment of the oocyst concentrations was performed by a Fuchs-Rosenthal haemocytometer counting chamber. Inoculations were given individually in the crop with a calibrated syringe without needle using a volume of 1-ml tap water. 2.2. Selection of the E. acervulina vaccine line through animal passages with early extraintestinal blood stages of the parasite Three passages of early extraintestinal blood stages of E. acervulina were performed by subsequently infecting donor birds orally with approximately 107 sporulated oocysts per bird and debleeding them within 3 hours post infection in order to inoculate recipient birds with 3 ml heparinized blood as described by Fernando et al. (1987). E. acervulina oocysts obtained from faeces of recipient birds after the animal passages with the early extraintestinal blood stages were multiplied in SPF broilers in order to obtain sufficient oocysts to proceed with further research. 2.3. Purity of Eimeria spp. strains/lines The E. acervulina vaccine line used in vaccination Experiment 1 was multiplied once after this trial to rule out contaminations with other coccidiosis species. During this multiplication a high dose inoculum of 106 sporulated oocysts/bird was used and at 6 days post inoculation (PI) of ten birds the intestines were thoroughly examined for coccidiosis lesions of E. acervulina and other species according to the method of Johnson & Reid (1970).

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In Experiment 2, at 13 and 20 days post vaccination (PV), five birds from the vaccinated group were autopsied to determine the coccidial lesion scores and also rule out contaminations with other species. At 25 days of age, just prior to the challenge infection, three birds of the vaccinated group and three of the negative control group (non-vaccinated group in the isolator) were autopsied and investigated for coccidial lesions according to the method of Johnson & Reid (1970). Moreover, the E. acervulina vaccine line was subjected to Polymerase Chain Reaction (PCR) analysis performed as described by Haug et al., 2007 in order to assess its purity also. Briefly, optimized single PCR arrays targeting the ITS-1 of seven valid Eimeria species (E. acervulina, E. brunetti, E. maxima, E. mitis, E. necatrix, E. praecox and E. tenella) were performed. Additionally, the detection level of contamination of E. acervulina vaccine line with E. tenella was studied by spiking the E. acervulina line with decreasing concentrations of E. tenella oocysts (1%, 0.1%, 0.01% and 0.001%). PCR procedure. The Eimeria spp. stock suspensions were washed to remove the potassium dichromate by repeated centrifugation and resuspension in water. Subsequently, 1 ml of the stock suspension of each Eimeria spp. containing 106 sporulated oocysts per ml was centrifuged at 14,000 x g for 3 min. The pellet was resuspended in 500 μl molecular biological quality water and mechanically disrupted using a Magalyser (Roche) and green beads (Roche, ref. 03358941) for 1 min at 6,500 x g. Thereafter, 20 μl of a lysing reagent (Lyse-N-Go. Pierce, ref 7882) was added to 20 μl supernatant, mixed and incubated in a heating block at 99 ºC for 2 min. Then the suspension was centrifuged for 3 min at 14,000 x g after which the supernatant was collected for PCR. Amplification of the species specific ITS-1 sequences of the rDNA coding region was based on a protocol described by Haug et al., 2007. Briefly, the PCR was carried out in a reaction volume of 20 μl, containing 200 μM of each deoxynucleotide triphosphate, 8 pmol of species-specific forward and reverse primers, 2.75 mM MgCl2, 1x PCR buffer (Applied Biosystems), 0.4 U DNA polymerase (AmpliTaq Gold, Applied Biosystems), and 2 μl of DNA template (sample). The amplification was performed in a thermocycler (Variti, Applied Biosystems). The initial activation step was 5 min at 95 ºC and was followed by 35 cycles of denaturation during 30 s at 95 ºC, annealing during 30 s at 65 ºC and elongation during 1 min at 72 ºC. Final extension was done during 5 min at 72 ºC. Of each PCR product 10 μl was added to 10 μl loading buffer and size fractioned by electrophoresis at 80V during 1 h in 2% agarose gels containing 0.5 μg/ml ethidium bromide. The PCR products were visualized with UV light and identified by size using a 50 bp DNA ladder (Boehringer). 2.4. Experimental animals and housing Multiplication and rejuvenation of the obtained E. acervulina vaccine lines was performed in SPF (Specified Pathogen Free) broiler chickens (Animal Health Service (GD), Deventer, the Netherlands). In the cross protection studies male broiler chickens (Arbor Acres) purchased from a commercial hatchery (Putten, the Netherlands) were used.


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Chicks were housed in stainless steel battery cages (height x width x depth = 30 x 40 x 50 cm) for the selection of E. acervulina lines through animal passages with extraintestinal blood stages, the determination of the vaccination doses and the challenge experiments. Birds were housed in isolated floor pens with a density of 20 chicks/m2 with wood shavings as bedding during further vaccination studies. A complete formulated broiler starter mash (Arkervaart-Twente, Nijkerk, the Netherlands) (2868 kcal/kg, 203.9 CP/kg) free of anticoccidial products was used in all experiments. Feed and water were provided ad libitum and during all trials a lighting scheme of 23 h of light per day was used. The birds were observed daily and deceased birds were collected for postmortem examination. 2.5. Oocyst counts (oocyst per gram faeces (OPG)), purification and multiplication In the experiments regarding the selection of E. acervulina vaccine lines through animal passages with extraintestinal blood stages, faeces from recipient birds were collected per battery cage from day 3 or 4 until day 6 PI and assessed for the presence of oocysts. Briefly: about 25 fresh droppings per cage were weighed and suspended in a 10% (w/v) solution of sodium chloride (density = 1.1) and mixed until a homogeneous suspension was obtained. In triplicate, 1 ml of this faeces suspension was mixed with 9 ml saturated salt solution (density = 1.2) and this dilution was used to fill a McMaster counting chamber for the examination of the presence of oocysts. If oocysts were present in the counting chamber purification of oocysts from faeces was performed using a modification of the salt flotation technique as described earlier by Peek & Landman (2003). After purification, the oocysts were suspended in a 2.5% (w/v) potassium dichromate solution and sporulated under aeration during 48-72 hours at a temperature of 29 ± 1 °C (Ryley et al., 1976). Subsequently, the oocyst suspensions of the Eimeria spp. lines were multiplied in SPF broilers for rejuvenation and identification as described by Peek & Landman (2003) and refrigerated (2-8 °C) in a solution of 2.5% potassium dichromate (w/v) until further use. 2.6. Vaccination and challenge studies 2.6.1. Assessment of vaccination dose Commercial male broilers were vaccinated with graded doses sporulated oocysts of the E. acervulina vaccine line. Hereto, six groups of ten broiler chicks were vaccinated with doses of 9 x 101, 4 x 102 or 6 x 102 sporulated oocysts per chick performed in duplicate. The vaccination was applied by a coarse spray to day old chicks at a rate of 0.5 ml/chick. Examination of individual cloacal faeces sampled on day 5 and 6 PV was done to determine the percentage of coccidiosis positive chickens per vaccination dose. Therefore, individual cloacal faeces samples (± 0.5 g) were homogenized with 4 ml of a saturated salt solution using a Vortex mixer. This faeces suspension was then used to fill one compartment of a McMaster counting chamber. Subsequently, the counting chamber was examined for the presence of oocysts by light microscopy.

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2.6.2. Experiment 1: vaccination of birds with the E. acervulina vaccine line and challenge with a mixture of E. acervulina, E. maxima and E. tenella at day 7, 14, 21, 28 or 35 of age Two groups of birds were used. Group 1, consisting of 50 birds, was housed in an isolator (Beyer & Eggelaar, Utrecht, the Netherlands) and served as a non-vaccinated group. Group 2, consisting of 149 birds, was housed in a floor pen and served as a vaccinated (V) group. Birds of Group 2 were vaccinated at one day of age using a coarse spray. A dose of 6 x 102 sporulated oocysts of the E. acervulina vaccine line was applied using a volume of 0.5 ml per chick. The vaccine uptake was monitored by examining individual cloacal faeces taken from ninety-six birds of Group 2 at six days PV (as described on the assessment of the vaccination dose). After vaccination, oocyst shedding per gram faeces (OPG) of the floor pen group was monitored. The oocyst shedding was assessed in fresh faeces samples collected at 4, 5, 6, 8, 10, 13, 15, 17, 20, 22, 27, 31, 34, 36, 38 and 41 days of age by means of the oocyst counting as described earlier. Birds were challenged at day 7, 14, 21, 28 or 35 of age. At each challenge moment ten randomly selected birds per group were transferred to the stainless cages. The challenge inoculum consisted of a mixture of 105 E. acervulina (Weybridge), 3 x 104 E. maxima (Weybridge) and 5 x 103 E. tenella (Houghton) sporulated oocysts. The inoculation dose used, was adjusted to obtain a coccidial lesion score of 2 to 3 in the non-vaccinated birds on the scale of Johnson & Reid (1970) and avoid mortality. Six days after challenge, five birds (50%) per group were euthanized in order to determine the coccidiosis lesion scores. Faeces samples were collected of the remaining five birds per group from day 5 until day 9 post challenge for assessment of the OPG. 2.6.3. Experiment 2: vaccination of birds with the E. acervulina vaccine line and challenge with E. acervulina, E. tenella or with a mixture of both species at 25 days of age Eighty commercial day-old broiler chicks were divided in two groups. Group 1 (n = 20) was housed in an isolator while Group 2 (n = 60) was housed in an isolated floor pen. Chicks in the floor pen group were vaccinated by coarse spray (0.5 ml/bird) with the E. acervulina vaccine line using a dose of 5 x 102 sporulated oocysts/bird. Birds in the isolator were used as negative control and were not vaccinated. The vaccine uptake was monitored by examination of individual cloacal faeces samples taken from forty birds of Group 2 at six days PV. During the growing phase the oocyst excretion pattern of birds in the floor pen group was monitored by determining the number of oocysts per gram of fresh collected faeces at 4, 5, 6, 9, 13, 15, 18, 20, 22 and 25 days of age. In the non-vaccinated group, three mixed faeces sample were examined for the presence of oocysts just prior to the challenge infection. At 13 and 20 days PV, five birds from the vaccinated group were autopsied to determine the coccidial lesion scores. At 25 days of age, just prior to the challenge infection, three birds of the vaccinated group and the negative control group (non-vaccinated group in the isolator) were autopsied and investigated for coccidial lesions.


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At the age of 25 days, birds from both groups were transferred to the stainless battery cages and infected with the challenge inocula. The inocula consisted of 9 x 104 sporulated E. acervulina (Weybridge) oocysts, 8 x 103 sporulated E. tenella (Houghton) oocysts or of a mixture of both species. For each challenge inoculum, five birds of Group 1 and ten birds of Group 2 (floor pen) were used. Six days after the challenge, all birds per group were euthanized in order to determine the coccidial lesion scores and oocyst counts were performed in faeces collected from day 4 until day 6 PI. 2.7. Statistics Differences in coccidial lesion score per Eimeria spp. between experimental groups in both experiments were analyzed using the non-parametric Kruskal-Wallis test (Statistix®, 2003). Differences were considered significant if P ≤ 0.05. 3. Results 3.1. Selection of the E. acervulina vaccine line through animal passages with early extraintestinal blood stages of the parasite During the animal passage with extraintestinal blood stages, recipient birds showed oocyst positive faeces samples when inoculated with donor blood obtained 3 h PI with the E. acervulina parent strain. E. acervulina vaccine lines obtained from faeces samples from recipient birds at day 5 to 6 PI were randomly chosen for subsequent animal passages and further investigations. 3.2. Vaccination studies 3.2.1. Assessment of vaccination dose Clinical signs of coccidiosis were not observed in any of the vaccinated birds. At least 50% of the cloacal faeces samples contained oocysts after vaccination with the low dose (90 sporulated oocysts) on both sampling days (five and six days post spraying). An increasing number of oocyst positive cloacal faeces samples was found parallel with an increased vaccination dose (Table 1). Therefore the highest vaccination dose was chosen for further vaccination studies.

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Table 1. Proportion of broilers (%) with oocyst positive cloacal faeces sample following spray vaccination with an E. acervulina line at one day of age, related to vaccination dose. Vaccination doses were studied in duplicate (A, B) Experimental group (vaccination dose; # sporulated oocysts)

Duplicate (n = 10)

5 DPV*

6 DPV

1 (9 x 101) A 5/10** (50) 3/6 (50) B 4/5 (80) 5/8 (62) 2 (4 x 102) A 5/8 (62.5) 4/8 (50) B 8/8 (100) 6/8 (75) 3 (6 x 102) A 8/8 (100) 6/6 (100) B 5/7 (71) 7/8 (87.5) *DPV = days post vaccination. **No. of positive broilers/no. examined. 3.2.2. Experiment 1: vaccination with the E. acervulina vaccine line and challenge with a mixture of E. acervulina, E. maxima and E. tenella with time No clinical signs of coccidiosis were observed in the vaccinated and control group. The proportion of individual positive cloacal faeces samples from birds in the vaccinated group assessed at six days PV was 75/96 (87.1%) which indicates that the vaccination was performed successfully. The OPG of pooled faeces samples collected from the vaccinated birds in Group 2 showed an oocyst shedding pattern that started at 5 days PV and ceased after 8 days PV. Thereafter, oocyst excretion was evoked again at 10, 13 and 17 days of age. The results of the challenge experiment showed that vaccination with the E. acervulina line protected the birds almost completely against the homologous challenge from day 7 of age onwards. There was no cross protection between E. acervulina and E. maxima. E. maxima lesion scores did not differ significantly between the control and vaccinated group at any point in time. In contrast partial cross protection was observed between E. acervulina and E. tenella based on a reduction in the severity of the coccidial lesions. The partial cross protection started at 14 days PV with an optimum on day 21 and 28 PV and declining again at day 35. E. tenella coccidiosis lesions of vaccinated birds were significantly lower than those of controls at 21 days PV (Table 2).


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Table 2. Mean lesion score (MLS ± SEM) per Eimeria spp. and number of oocysts per gram of faeces (OPG) per experimental group (i.e. vaccinated with an E. acervulina line at one day of age and non-vaccinated) following a mixed challenge infection at different ages with E. acervulina, E. maxima and E. tenella. MLS and OPG were assessed at six days after challenge Age challenge (days) MLS ± SEM 7 n E. acervulina E. maxima E. tenella OPG (x103) Vaccinated 5 0.4b ± 0.3 0.8a ± 0.2 3.0a ± 0.0 180 Non-vaccinated 5 1.2a ± 0.2 0.8a ± 0.2 3.0a ± 0.0 260 14 Vaccinated 5 0.0b ± 0.0 1.2a ± 0.2 1.6a ± 0.7 580 Non-vaccinated 5 2.2a ± 0.2 1.0a ± 0.0 2.4a ± 0.3 370 21 Vaccinated 5 0.0b ± 0.0 1.2a ± 0.2 0.4b ± 0.3 110 Non-vaccinated 5 2.4a ± 0.3 1.0a ± 0.0 1.8a ± 0.4 1100 28 Vaccinated 5 0.0b ± 0.0 1.8a ± 0.2 0.6a ± 0.4 35 Non-vaccinated 5 2.8a ± 0.2 1.8a ± 0.2 1.4a ± 0.3 93 35 Vaccinated 5 0.0b ± 0.0 1.8a ± 0.2 1.4a ± 0.4 150 Non-vaccinated 5 2.0a ± 0.3 1.8a ± 0.2 2.2a ± 0.2 610 a,b Groups with different superscript per time point within column differ significantly. Lesion scores differ significantly between groups if P ≤ 0.05. 3.2.3. Experiment 2: vaccination with the E. acervulina vaccine line and challenge with E. acervulina, E. tenella or with a mixture of both species at 25 days of age No clinical signs of coccidiosis were seen in the vaccinated and control group. The proportion of individual positive cloacal faeces samples from birds in the vaccinated group assessed at six days PV was 29/40 (72.5%). The OPG of pooled fresh faeces samples collected from the vaccinated birds showed a similar oocyst shedding pattern as Experiment 1. Oocyst excretion started at day 5 through day 18 PV and oocysts were also found at day 22 and 25 PV but at lower numbers. No oocysts were found in pooled faeces samples from control birds housed in the isolator. The results of the challenge experiment showed that birds in the control group were fully susceptible to both E. acervulina and E. tenella. No coccidial lesions of E. acervulina were observed in vaccinated birds after homologous challenge. After heterologous challenge of vaccinated birds a significant reduction of lesion scores was seen in comparison to control birds. The same results were obtained after a mixed challenge with E. acervulina and E. tenella (Table 3).

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3.3. Purity of Eimeria spp. strains/lines During the multiplication of the E. acervulina vaccine line, used in Experiment 1, no intestinal lesions of any other Eimeria spp. than E. acervulina (with a mean score of 2.9) were found. Similarly in Experiment 2, also only E. acervulina coccidiosis lesions (with a mean score of 1.6) were observed. Coccidiosis lesions were not found at other time points in any of the examined birds. The PCR generated strong signals for the positive control sample tested included (Paracox™-8). PCR products of the expected size were found for all known Eimeria spp. (Figure 1). The results of the PCR of the E. acervulina vaccine line and the E. acervulina (Weybridge) strain only generated products corresponding to these species (Figure 2). The E. tenella strain used at decreasing concentrations to spike the E. acervulina vaccine line could be detected up to a concentration of 0.01% (i.e. 102 oocysts E. tenella per 106 oocysts E. acervulina) (Figure 3).

Figure 1. Agarose gel electrophoresis of PCR products of the ITS-1 gene from different Eimeria spp.: lanes 1-7 correspond to E. brunetti, E. mitis, E. necatrix, E. praecox, E. acervulina, E. tenella and E. maxima respectively. Lane M is molecular weight marker (50 bp ladder).

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F LIVE ANTICOCCIDIAL VACCINES

Figure 2. Agarose gel electrophoresis of PCR products of the ITS-1 gene from different E. acervulina strain/line: lanes 1-3 correspond to the negative control, the E. acervulina vaccine line and the E. acervulina (Weybridge) strain, respectively. M lane is molecular weight marker (50 bp ladder).

Figure 3. Agarose gel electrophoresis of PCR products of the ITS-1 gene from different Eimeria species: lanes 1-7 correspond to E. tenella (Houghton) strain, E. acervulina vaccine contaminated with 1% E. tenella, 0.1% ibid, 0.01% ibid, 0.001% ibid, the E. acervulina vaccine line and the negative control respectively. M lane is molecular weight marker (50 bp ladder). The lowest contamination level visible as a faint line is 0.01% E. tenella (lane 4).

Table 3. Mean lesion score (MLS ± SEM) per Eimeria spp. and number of oocysts per gram of faeces (OPG) per experimental group (i.e. vaccinated with an E. acervulina line at one day of age and non-vaccinated) following challenge at 25 days of age with E. acervulina, E. tenella or a mixed inoculum of both species. MLS and OPG were assessed at six days after challenge Challenge

E. acervulina E. tenella E. acervulina/E. tenella

MLS ± SEM MLS ± SEM MLS ± SEM

n E. ac E. ten OPG OPG n E. ac E. ten n E. ac E. ten OPG

Vaccinated 10 100.0a ± 0.0 - 0 10 - 1.4a ± 0.2 104,00 10 0.0a ± 0.0 1.4 ± 0.3a 2.78

Non-vaccinated 5 2.8b ± 0.2 - 106.43 5 - 103.0b ± 0.0 103.70 5 3.0b ± 0.0 3.0 ± 0.3b 6.40

E. ac = E. acervulina, E. ten = E. tenella. a,b Groups with different superscript within columns differ significantly (P ≤ 0.05).


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4. Discussion The occurrence of extraintestinal stages of Eimeria spp. in poultry blood was first described by Kogut & Long (1984), who were able to transfer coccidiosis to chickens by the administration of blood and other tissues from turkeys and chickens previously inoculated with Eimeria spp. The transfer of coccidiosis to recipient birds was possible up to 4 days after inoculation of donor birds. Infective stages of E. acervulina, E. brunetti, E maxima and E. praecox in blood, liver and spleen were later described by Fernando et al. (1987). They found that the transfer of blood and tissue stages of the parasite was more successful if done within a short time after inoculation of donors as confirmed by oocyst shedding of recipient birds. Although no specific time was mentioned as optimal for the transfer of stages of the parasite in blood, our results indicate that the highest rate of successful transfer is achieved at three hours post inoculation of donor birds.

Vaccination of the birds by means of coarse spray using the medium and higher vaccination dose (4 x 102 and 6 x 102 sporulated oocyst/bird) induced an average percentage of coccidiosis positive chickens (oocyst positive cloacal faeces samples) of 81.3 and 62.5% for the medium dose at day 5 and 6 PV, respectively. The percentage positive birds for the higher dose was 85.7 and 93.8% at day 5 and day 6 PV, respectively. The higher dose was therefore used in the floor pen studies and induced percentages of coccidiosis positive birds of 87.1% and 72.5% in Experiment 1 and 2 at day 6 PV, respectively. These percentages are in agreement with results obtained after hatchery spray vaccinations performed by Cherry T.E. in Chapman et al. (2002) and by Schetters et al. (1999). The method used to determine oocyst shedding was relatively insensitive as the yield of cloacal faeces was often below expectation and only one compartment of the McMaster counting chamber was examined. Therefore, the actual number of chicks shedding oocysts after vaccination may have been higher.

The OPG counts performed after vaccination of the birds in Experiment 1 and 2 showed oocyst shedding patterns, which have been described for trickle infections, as recycling of coccidiosis infections is a well-known pattern occurring after spray vaccination with live coccidiosis vaccine consisting of several Eimeria spp. (Williams, 2002b). In the present study, the trickle infection pattern was dominated by a prominent peak in the oocyst shedding pattern at day 13, probably because the vaccination was performed with a single Eimeria spp. line (E. acervulina) with a relative short prepatent period of 97 h.

The results of Experiment 1 and 2 showed that vaccination of birds with the E. acervulina vaccine line obtained through animal passages of extraintestinal blood stages conferred excellent protection against homologous challenge provided as a mixed infection including also E. maxima and E. tenella. The protection was already noticeable at 7 days PV, showing maximal effect from 14 days PV onwards. The homologous protection found is in agreement with described literature for other E. acervulina lines (Shirley & Millard, 1986; Rose, 1987; Williams, 1992).

The E. tenella lesion scores found in the vaccinated chickens of Experiment 1 decreased with time starting to be noticeable at 14 days PV reaching a maximum at 21

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days PV (being significantly different, P = 0.0214) indicating the occurrence of partial cross protection between the E. acervulina vaccine line tested and E. tenella. The decrease in E. tenella lesion scores at day 28 PV was lower but still in the same range as that of day 21 PV. However, the partial cross protective effect became less at day 35 PV suggesting that it probably only lasts a few weeks. Nevertheless in order to get a definitive answer on this matter longer follow up studies should be performed. The significant differences in coccidiosis lesion scores between E. acervulina vaccinated and non-vaccinated coccidiose challenged birds at different time points as shown in Table 2 were calculated using the non-parametric Kruskal-Wallis test. If corrections for multiple comparisons were made then 2 out of 6 significant differences (E. acervulina challenged at day 7 and E. tenella challenged at day 21) became non significant. However, this would not affect the significance of the reduction in lesion scores found (E. acervulina challenged at day 7 with a mean lesion score of 0.4 versus 1.2 and of E. tenella challenged at day 21 with a mean lesion score of 0.4 versus 1.8). This is demonstrated by the fact that a reduction in mean lesion score of 50% or more would change the classification of an Eimeria spp. field isolate subjected to an anticoccidial sensitivity test from resistant to sensitive (McDougald et al., 1986). Therefore, results were presented without the latter corrections. Moreover, the clinical and statistical significance of our findings was confirmed in Experiment 2 where similar results were obtained. No signs of reduction in lesion scores were found after challenging birds with E. maxima.

As interaction between Eimeria spp. in a mixed challenge model can not be ruled out, the challenge in Experiment 2 was performed using both, single species inocula and inocula consisting of a mixture of E. acervulina and E. tenella. A number of interactions between species in a mixed infection model have been reported. E. acervulina decreased the oocyst output of other Eimeria spp. in simultaneous mixed infection (Williams, 1973; Hein, 1975, while Tyzzer (1929) observed a late onset of immunity of Eimeria spp. during mixed infections.

In Experiment 2, no coccidiosis lesions (for single and mixed species infection) and oocyst shedding (for single species infection) were found after homologous challenge at 25 days PV indicating an excellent protection. Partial cross protection as described in the first experiment was confirmed in Experiment 2, although the reduction in E. tenella lesions, which were significantly different from those of challenged control birds, was less pronounced.

Cross protection could have been induced by contamination of the E. acervulina vaccine line with E. tenella, however, the purity of isolates was assessed by both, the occurrence and distribution of coccidiosis lesions scores, and by means of PCR analysis. In neither case, indications for a contamination of the E. acervulina vaccine line with E. tenella were found. The PCR analysis was able to detect contamination levels of 100 oocysts of E. tenella per million oocysts of the E. acervulina vaccine line (Figure 3)

Protection against Eimeria spp. was for long believed to be species specific (Tyzzer et al., 1932; Johnson, 1938). However, Rose was the first to report cross protection between E. tenella and E. necatrix (Rose, 1967a). She also reported on the occurrence of cross immunisation between E. brunetti and E. maxima (Rose, 1967b), which could not be


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confirmed by Hein (1971). More recently, Augustine (1999) suggested that E. acervulina elicits a small degree of protection against infection with E. tenella that is expressed primarily in increased weight gain. In contrast, reverse immunisation, (i.e. with E. tenella) had little effect on the response of chickens to E. acervulina infection.

The disadvantages of the conventional coccidiosis vaccines (Lillehoj and Trout, 1993; Jeston et al., 2002) have propelled the quest for the alternative products using a.o. epitope mapping, hybridoma and recombinant DNA technology. Species cross immunity to Eimeria is very important for the development of such vaccines and has been focus of research during recent years. Partial resistance to E. tenella and also to E. acervulina, E. maxima and E. necatrix was obtained using the recombinant antigen CheY-So7 of E. tenella (Crane et al., 1991). Thereafter, cross protection against challenge with E. acervulina but not E. maxima was found after in ovo vaccination with the E. tenella EtMIC2 gene (Ding et al., 2005). Recently, partial cross protection of an E. tenella DNA vaccine against challenge with E. necatrix and E. acervulina, but not E. maxima was shown (Song et al., 2009). However, the new approach has failed to yield a successful commercial anticoccidial vaccine so far, live attenuated anticoccidial vaccine being most commonly used to date. Therefore, we pursued to further investigate cross protection between E. acervulina and E. tenella using live parasites.

In the present study, further research into the cross protection between E. acervulina and E. tenella was performed. In contrast with Augustine’s work (1999), in which two-week-old birds were immunized with five inoculations of 3 x 105 sporulated oocysts of E. acervulina during a two week period, our chickens were vaccinated once by coarse spray at day-old and allowed to be auto exposed to a trickle infection by housing them in floor pens mimicking more closely the situation in the field. Another difference was that challenge was performed at different time intervals instead of 11 days after the last immunisation, i.e. at thirty eight days of age, which is too late for the immunisation of broiler chickens in the field. A third difference was that the birds were housed in cages, while in this study they were placed in floor pens making repeated immunizations redundant. A fourth difference was that challenge experiments were performed using a mixture of E. acervulina, E. maxima and E. tenella (Experiment 1) or single species consisting of E. acervulina or E. tenella, or a mixture of those (Experiment 2) instead of E. tenella only. A fifth difference was that the degree of cross protection in our experiments based on lesion scores was much higher and a last difference is that we used broilers instead of white leghorn chickens.

Although the lower degree of cross protection found by Augustine (1999) could by explained by differences in immunisation protocol, housing and breed of chickens, the selection method to obtain an E. acervulina line trough animal passages of extraintestinal blood stages may have resulted in a line with enhanced cross protective capabilities. Further research comparing E. acervulina lines from different sources could unravel whether differences in cross protective properties exist. E. acervulina lines showing enhanced cross protection against E. tenella could then be used to improve current live anticoccidial vaccines.

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References Augustine, P.C. (1999). Prior or concurrent exposure to different species of avian Eimeria: effect on

sporozoite invasion and chick growth performance. Avian Diseases, 43, pp. 461-468. Beach, J.R. & Corl, J.C. (1925). Studies in the control of avian coccidiosis. Poultry Science, IV, pp. 83-

93. Chapman, H.D. (1997). Biochemical, genetic and applied aspects of drug resistance in Eimeria parasites

of the fowl. Avian Pathology, 26, pp. 221-244. Chapman, H.D., Cherry, T.E., Danforth, H.D., Richards, G., Shirley M.W. & Williams, R.B. (2002).

Sustainable coccidiosis control in poultry production: the role of live vaccines. International Journal for Parasitology, 32, pp. 617-629.

Chapman, H.D., Roberts, B., Shirley, M.W. & Williams, R.B. (2005). Guidelines for evaluating the efficacy and savety of live anticoccidial vaccines, and obtaining approval for their use in chickens and turkeys. Avian Pathology, 34, pp. 279-290.

Crane, M.S.J. Goggin, B., Pellegrino, R.M., Ravino, O.J., Lange, C., Karkhanis, Y.D., Kirk, K.E. & Chakraborty, P.R. (1991). Cross-protection against four species of chicken coccidia with a single recombinant antigen. Infection and Immunity, 59, pp. 1271-1277.

Ding, X., Lillehoj, H.S., Dalloul, R.A., Min, W., Sato, T., Yasudo, A. & Lillehoj, E.P., (2005). In ovo vaccination with the Eimeria tenella EtMIC2 gene induces protective immunity against coccidiosis. Vaccine, 23, pp. 3733-3740.

Fernando, M.A., Rose, M.E. & Millard, B.J. (1987). Eimeria spp. of domestic fowl: the migration of sporozoites intra- and extra-enterically. Journal of Parasitology, 73, pp. 561-567.

Haug, A., Thebo, P.& Mattson, J.G. (2007). A simplified protocol for molecular identification of Eimeria species in field samples. Veterinary Parasitology, 146, pp. 34-45.

Hein, H.E. (1971). Eimeria brunetti: Cross infections in chickens immunized to E. maxima. Experimental Parasitology, 29, pp. 367-374.

Hein, H.E. (1975). Eimeria acervulina, E. brunetti and E. maxima: Immunity in chickens with low multiple doses of mixed oocysts. Experimental Parasitology, 38, pp. 271-278.

Jeston, P.J., Blight, G.W., Anderson, G.R., Molloy, J.B. & Jorgensen, W.K. (2002). Comparison of infectivity of Eimeria tenella oocysts maintained 4, 12 or 28 ºC up to 10 months. Australian Veterinary Journal, 80, pp. 91-92.

Johnson, W.T. (1938). Coccidiosis of the chicken with special reference to species. Standard Bulletin Oregon Agriculture Experiment station, 358, pp. 3-33.

Johnson, J. & Reid, W.M. (1970). Anticoccidial drugs: lesion scoring techniques in battery and floor pen experiments with chickens. Experimental Parasitology, 28, pp. 30-36.

Kogut, M.H. & Long, P.L. (1984). Extraintestinal sporozoites of chicken Eimeria in chickens and turkeys. Zeitschrift für Parasitenkunde, 70, pp. 287-295.

Lillehoj, H.S. & Trout, J.M. (1993). Coccidia: a review of recent advances on immunity and vaccine development. Avian Pathology, 22, pp. 3-31.


Peek, H. W. & Landman, W.J.M. (2003). Resistance to anticoccidial drugs of Dutch avian Eimeria spp. field isolates originating from 1996, 1999 and 2001. Avian Pathology, 32, pp. 391-401.

Peek, H. W. & Landman, W.J.M. (2004). Gevoeligheidsprofielen van Spaanse, Duitse en Nederlandse Eimeria spp. veldisolaten van anticoccidiose middelen. Tijdschrift voor Diergeneeskunde, 129, pp. 210-214.

Rose, M.E. (1967a). Immunity to Eimeria tenella and Eimeria necatrix infection in the fowl. I Influence of the site of infection and the stage of the parasite. II Cross-protection. Parasitology, 57, pp. 567-583.

Rose, M.E. (1967b). Immunity to Eimeria brunetti and Eimeria maxima infections in the fowl. Parasitology, 57, pp. 363-370.


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Rose, M.E. (1987). Eimeria, Isospora and Cryptosporidium. In E.J.L Soulsby (ed.), Immune responses in parasitic infections: immunology, immunopathology and immunoprophylaxis. CRC Press, Inc., Boca Raton, Fla, pp. 275-312.

Ryley, J.F., Meade, R., Hazelhorst, J. & Robinson, T.E. (1976). Methods in coccidiosis research: separation of oocysts from faeces. Parasitology, 73, pp. 311-326.

Schetters, T.P.M., Janssen, H.A.J.M. & Vermeulen, A.N. (1999). A new vaccination concept against coccidiosis in poultry. World Poultry, Special Supplement Coccidiosis, 3, pp. 26-27.

Shirley, M.W. & Millard, B.J. (1986). Studies on the immunogenicity of seven attenuated lines of Eimeria given as a mixture to chickens. Avian Pathology, 15, pp. 629-638.

Shirley, M.W., Smith, A.L. & Tomley, F.M. (2005). The biology of avian Eimeria with an emphasis on their control by vaccination. Advances in Parasitology, 60, pp. 285-330.

Shirley, M.W., Smith, A.L. & Blake, D.P. (2007). Challenges in the successful control of the avian coccidia. Vaccine, 25, pp. 5540-5547.

Song, K.D., Lillehoj, H.S., Choi, K.D., Yun, C.H., Parcells, M.S., Huynh, J.T. & Han, J.Y. (2009). A DNA vaccine encoding a conserved Eimeria protein induces protective immunity against live Eimeria acervulina. Vaccine, 19, pp. 243-252.

Statistix®. ( 2003). Statistix 8.0 for Windows®. User’s manual analytical software version 8.0. Tallhassee, USA.

Tyzzer, E.E. (1929). Coccidiosis in gallinaceous birds. American Journal of Hygiene, 10, pp. 269-383. Tyzzer, E.E., Theiler, H. & Jones, E.E. (1932). Coccidiosis in gallinaceous birds. II. A comparative study

of species of Eimeria of the chicken. American Journal of Hygiene, 15, pp. 319-393. Williams, R.B. (1973). The effect of Eimeria acervulina on the reproductive potentials of four other

species of chicken coccidia during concurrent infections. British Veterinary Journal, 129, pp. 29-31. Williams, R.B. (1992). The development, efficacy and epidemiological aspects of Paracox, a new

coccidiosis vaccine for chickens. Mallinckrodt Veterinary Ltd. Breakspear Road South, Harefield, Uxbridge UB9 6LS, U.K.

Williams, R.B. (2002a). Fifty years of anticoccidial vaccines for Poultry (1952-2002). Avian Diseases, 46, pp. 775-802.

Williams, R.B. (2002b). Anticoccidial vaccines for broiler chickens: pathway to success. Avian Pathology, 31, pp. 317-353.

Chapter 6

Summarizing discussion

SUMMARIZING DISCUSSION

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Summarizing discussion The aim of the thesis was to investigate the occurrence of Dutch and other European Eimeria spp. field isolates resistant against anticoccidial drugs (Chapter 2). This was preceded by an extensive literature review on anticoccidial products and alternative prevention strategies (Chapter 1). Other aims of the thesis were to assess the anticoccidial potency of ibuprofen, a mucolytic enzyme and mannanoligosaccharide as alternative coccidiosis control strategies (Chapter 3) and to investigate the influence of vaccination on the anticoccidial drug sensitivity profiles of Eimeria spp. field isolates (Chapter 4). Finally, cross protection between an E. acervulina vaccine line and E. tenella, and E. maxima, which may in future help to improve coccidiosis vaccines, was studied (Chapter 5).

In Chapter 1, coccidial infections with Eimeria spp. in poultry are described. After an introduction, the history and classification of the genus Eimeria is given, followed by a description of the occurrence of Eimeria spp. in farm and game birds and their clinical significance. Further attention is paid to the life cycle of avian Eimeria spp., species determination and diagnosis. In chickens, seven Eimeria spp. are considered of which E. acervulina, E. maxima and E. tenella are the most relevant as they most frequently affect broilers and these birds form the major part of the poultry industry. The diagnosis of coccidiosis is generally performed at postmortem by identifying the localization and morphology of the lesions in the intestines and is complemented by analyzing native intestinal scrapings with light microscopy in order to morphologically identify schizonts and oocysts. Due to the shortcomings in the traditional diagnosis system (visual identification of species is not accurate), new coccidiosis identification technologies are being developed. Recently, identification of Eimeria oocysts was greatly improved by classification through computational analysis of microscopic analysis. Also, molecular biology techniques have been the focus of research and development by many groups involved in coccidiology. Various PCR-coupled and other molecular techniques for the identification of coccidia have been studied during the past decade. Particular attention has been given to the usefulness of ITS-1 and -2 markers for the diagnosis and the analysis of genetic variation of Eimeria. It is a dynamic, constantly evolving area of research.

In the second heading of the review, the host and site specifity of Eimeria spp. is presented. Host specificity of coccidia was thought to be very strict; however, research showed that this is only true as far as completion of their life cycle is concerned. Eimeria spp. are able to infect other species of hosts, restrictions being less pronounced the closer host species are genetically related. Mechanisms responsible for host specificity are parasite biochemistry and nutrition, the host genome and host immune system. Regarding site specificity, coccidia invade narrowly defined cell types within a tissue or organ. In chickens, Eimeria spp. parasitize and develop only in specific defined regions of the intestine, which not only is the case in the natural host but also in foreign hosts.

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In the third part of the review a historical overview is given of the mode of action, the occurrence of resistance and efficacious use of anticoccidial products. Most anticoccidial drugs have more than one biochemical effect on a specific developmental stage of coccidia. Despite the lack of detailed knowledge on the selective action of anticoccidials, a broad categorization of their mode of action has been performed. Products affecting cofactor synthesis are ethopabate, sulphonamides, pyrimethamines and thiamine analogues like amprolium; products affecting mitochondrial functions are quinolones (buquinolate, decoquinate and nequinate), pyridinols (meticlorpindol), nicarbizin, robenidine and toltrazuril; products that affect cell membrane function are polyether antibiotics or ionophores (monensin, semduramycin, narasin, salinomycin, lasalocid and maduramicin) and products with unknown mode of action are diclazuril and halofuginone. The worldwide use of anticoccidial drugs has inevitably led to the development of resistance to all anticoccidial products used to date as long term exposure to any drug will result in loss of sensitivity. Resistance against anticoccidial drugs has been reported in scientific literature in the United States, South America, Europe and China. In order to minimize the occurrence of resistance, rotation (an anticoccidial product is used during a maximum of two months or two fattening periods) of various anticoccidial drugs or shuttle programmes (two or more anticoccidial drugs are used within a growing period) are used. The rationale behind this is the fact that loss of sensitivity is related to the duration of drug exposure, which should be kept as short as possible. Due to the occurrence of cross resistance between anticoccidial drugs, anticoccidial drugs with distinct mode of action should be used within rotation and shuttle programmes. Ideally, rotation and shuttle programmes should be designed based on knowledge of anticoccidial sensitivity profiles of relevant Eimeria spp. field isolates. A relative new approach in the management of anticoccidial drug resistance is the incorporation of live coccidiosis vaccines into rotation programmes. Seeding of poultry houses with drug sensitive lines of vaccine coccidia has shown to increase the incidence of anticoccidial drug sensitive Eimeria spp. field isolates.

In the fourth heading, the influence of feed structure, composition (macro and micro ingredients, special additives), toxins and feed management on the course of coccidiosis is reported. Various feed components seem to affect Eimeria parasites, either directly by affecting the development and multiplication of coccidia or indirectly by stimulating the immune system, influencing the intestinal flora and mucosa, changing the physiology of the digestive tract, etc. Some feed components show activity during the acute phase of the disease, while others favour recovery of infected birds. Feed components that have been shown to favour recovery from coccidiosis infections are: proteins, vitamin A, C and K. Feed components which negatively affect Eimeria parasites directly are ω-3 fatty acids, while variable effects have been described for protein concentration and feed restriction. Development of coccidia is negatively influenced in an indirect way by β-glucans, vitamin E, selenium, feed restriction, ω-3 fatty acids, vitamin A and C and NaHCO3, which boost the immune system. The development of coccidia is also negatively influenced indirectly by vitamin K, medium chain fatty acids and, vitamins A and C. These components promote mucosal health and therefore are of help against coccidiosis. Variable indirect effects on the parasite have been described for wheat affecting viscosity and intestinal


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flora, the latter is also influenced by fibres and milk products. Whole cereals indirectly affect Eimeria by their influence on the physiology of the digestive tract. Finally, feed components known to stimulate directly Eimeria development are: calcium, aflatoxins, vitamin B, essential fatty acids and chemotrypsine. These products should be avoided or if necessary not given at Eimeria promoting concentrations.

In heading five, other preventive strategies against coccidiosis including management and biosecurity, alternative methods of control like homeopathy, phytotherapy and vaccines, have been discussed. Management and biosecurity measures should aim at avoiding the introduction of the parasite to the poultry premises through isolation, traffic control and sanitation; although in practice it is nearly impossible to raise chickens free of coccidiosis, unless SPF-like housing conditions are used. Under field circumstances infected poultry houses are best sanitated by using a lot of cleansing water and disinfection with a 5-10% solution of ammonia. Phyto- and aromatherapy have become increasingly popular during the last decade due to a renewed interest in natural medicine. A number of plant extracts have been studied for their potential use as dietary supplement against coccidiosis. Products showing a direct inhibitory effect on the development of Eimeria parasites are artemisinin and citric extracts. Oregano also showed a direct effect on coccidia, however, it had also some conflicting results about the inhibitory effect on the development of the Eimeria parasite. Herbal products showing an indirect effect on the development of coccidia have also been described. Echinacea, mushrooms (lectin) and turmeric seem to boost the immune response and therefore soothen the severity of coccidiosis infection, while betain acts indirectly by stimulating the immune response but also due to its osmoprotective properties in the intestinal environment. The prebiotic (MOS) has been reported to act directly on coccidia and either inhibit the development of the parasite or show no effect. Probiotica have an indirect hindering effect on Eimeria parasites by stimulating the humoral immune response. Live vaccines, both attenuated and non-attenuated are becoming increasingly popular as an alternative control strategy against coccidiosis. Nevertheless, a number of drawbacks such as high production costs, loss of infectivity with time affecting their expiry and management shortcomings during application (dosage errors, presence of anticoccidial drugs in feed frustrating vaccination with drug sensitive vaccine strains, etc.) have limited their use in practice. Additionally, reversal of virulence of live vaccines may also be a point of concern. An important beneficial side effect of live coccidiosis vaccines is their association with increased sensitivity of Eimeria spp. to anticoccidial drugs by seeding of poultry houses with drug sensitive vaccine parasites. This has promoted their use in alternation with anticoccidial drugs in rotation programs. Subunit vaccines may circumvent most shortcomings of live vaccines; however, at present these products underperform due to lack of immunogenicity. Identification of antigens eliciting protective immune responses through the E. tenella genome project may hold promise for a more prominent role of subunit vaccines in the control of coccidiosis.

It can be concluded that the occurrence of anticoccidial drug resistant Eimeria spp. field isolates will at best remain unchanged, but most likely will further increase if

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commercial poultry farming keep using anticoccidial products in a non-rational fashion (i.e. not guided by anticoccidial drug sensitivity tests and timely shift in anticoccidial drugs). Although some dietary compounds, phytochemicals, pre- and probiotica and even non-steroidal anti-inflammatory drugs seem capable to reduce the effects of an Eimeria infection either by a direct effect on the parasite or indirectly by stimulating immune responses and recovery of the birds, this seems to be insufficient to control the disease. Therefore, named strategies do not represent an effective alternative to solve the problem of anticoccidial drug resistance. At present, vaccination seems to be the most solid anticoccidiosis strategy, despite some drawbacks. In case immunogenicity of subunit vaccines can be improved substantially, these vaccines might form the core of future anticoccidial strategy.

In Chapter 2 the anticoccidial sensitivity profiles of a variety of Eimeria spp. field isolates gathered from broiler farms are outlined.

In two studies fifteen Eimeria spp. field isolates sampled on Dutch broiler farms, four from 1996, four from 1999 and seven from 2001 and twenty-four Eimeria spp. field isolates originating from Dutch, German and Spanish broiler farms collected in the period 2000-2002 were subjected to an Anticoccidial Sensitivity Test (AST) in a battery cage study. The selected anticoccidial drugs were diclazuril, halofuginone, lasalocid, maduramicin, meticlorpindol/methylbenzoquate, monensin, narasin, narasin/nicarbazin, nicarbazin, robenidine and salinomycin. The results showed a high degree of resistance against most tested anticoccidial products. However, despite the high prevalence of coccidiosis infections in the field in the Netherlands, an increase of severe clinical coccidiosis was not observed. Possible “spontaneous vaccination” occurs in the field as despite anticoccidial drug resistance a residual effect of anticoccidial drugs (especially ionophores) would mitigate the severeness of coccidiosis without inhibiting immunisation.

Taking together, during the period 1996-2002 a total of thirty nine Eimeria spp. field isolates, of which the majority contained more than one species, were investigated for their sensitivity against most commonly used anticoccidial products. The tested field isolates consisted of thirty six E. acervulina isolates, fourteen E. maxima isolates and twelve E. tenella isolates (Table 1). The anticoccidial sensitivity-profiles were based on the criteria of McDougald et al. (1986).

Resistance of E. acervulina isolates to anticoccidial drugs is very common as 145 of the 221 (66%) assays showed resistance against at least one anticoccidial products. The number of E. maxima assays showing resistance to one or more products was 39 out of 79 (49%). E. tenella isolates showed resistance to at least one anticoccidial drug in 45 assays out of 76 (59%).

The coccidial lesion score system according to Johnson & Reid (1970) gives a good impression of the severity of the pathology induced by a coccidiosis infection and is likely the most commonly used method to investigate the efficacy of anticoccidial products (Chapman, 1998). In both anticoccidial sensitivity studies, mentioned coccidiosis lesion scoring system was used to determine the severity of the coccidiosis infection of sensitivity against the anticoccidial products. The criteria of McDougald et al. (1986) were


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used to calculate the extent of resistance/sensitivity to the anticoccidial products tested using the formula: 100% - (mean lesion score of treated group/mean lesion score of the infected unmedicated control group x 100%). A reduction in the medicated birds compared with the infected unmedicated control birds of 0 to 30% indicates coccidial resistance; 31 to 49% reduction indicates reduced sensitivity or partial resistance and 50% or more indicates full sensitivity to the tested anticoccidial drug. Table 1. Anticoccidial sensitivity-profiles expressed in number of resistant (R), reduced sensitive (RS) and sensitive (S) Eimeria spp. isolates per anticoccidial product. Eimeria spp. field isolates were obtained from broiler flocks in the Netherlands, Germany and Spain during 1996-2002 Anticoccidial drug E. acervulina E. maxima E. tenella n R RS S n R RS S n R RS S Diclazuril (Clinacox®) 30 27 1 2 11 9 1 1 11 6 1 4 Halofuginone (Stenorol®) 16 10 6 0 5 0 1 4 3 0 0 3 Lasalocid (Avatec®) 19 17 2 0 3 1 2 0 8 4 2 2 Maduramicin (Cygro®) 4 3 1 0 1 1 0 0 1 0 0 1 Meticlorpindol/methylbenzoquate (Lerbek®)

19 1 1 17 9 3 0 6 7 0 0 7

Monensin (Elancoban®) 20 13 4 3 6 5 1 0 8 7 0 1 Narasin (Monteban®) 25 16 4 5 8 5 1 2 10 7 1 2 Narasin/nicarbazin (Maxiban®) 16 11 4 1 8 2 1 5 4 4 0 0 Nicarbazin (Nicarb®) 30 26 1 3 13 7 2 4 11 7 2 2 Robenidine (Robenz®) 6 3 0 3 1 0 0 1 1 0 0 1 Salinomycine (Sacox®) 36 18 7 11 14 6 5 3 12 10 1 1 Total 221 145 31 45 79 39 14 26 76 45 7 24 However, unanimity on the parameters required for anticoccidial sensitivity testing is lacking. Moreover, there are concerns about the infection model used in the sensitivity test (i.e. infection dose versus spontaneous (trickle) infections), rising doubts regarding the extrapolation of laboratory tests results to the field (Bafundo et al., 2008). Differences between artificial and natural infection doses may explain conflicting results between experimental settings and practice (Watkins, 1997), Despite the drawbacks of the anticoccidial sensitivity test, at present, it is the only tool available to study anticoccidial drug sensitivity profiles of Eimeria spp. field isolates. Although, as said previously, the results of sensitivity testing should not be translated directly to the field one on one, they can be a valuable tool as a predictor that will help to implement timely strategic changes of the anticoccidial drugs (Ruff et al., 1997).

In Chapter 3 the anticoccidial potential of three alternative compounds is outlined. In the first section the anticoccidial effect of ibuprofen (IBU), a non-steroidal anti-

inflammatory drug that inhibits the biosynthesis of prostaglandins with pro-inflammatory

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and immunosuppressive properties is presented. IBU was administered via the drinking water in all experiments. IBU at a dose of 15 mg/kg body weight (BW) had no effect on infections with oocysts of Eimeria acervulina (104.7), E. maxima (104.5) and E. tenella (103.9). IBU given at a dose of 100 mg/kg BW significantly (P ≤ 0.05) decreased oocyst shedding after infection with doses of sporulated E. acervulina oocysts between 104 and 105 per bird. Coccidial lesion scores were reduced for all infection doses; but significant reduction only occurred in birds infected with a dose of 104 sporulated E. acervulina oocysts. A significant effect on body weight gain was not observed and treatment with IBU did not affect the sporulation and infectivity of excreted oocysts.

In the second section of Chapter 3 two experiments are presented. In the first experiment the effect of dietary protease on a coccidiosis infection in broilers and their performance after challenge with E. acervulina (104.0), E. maxima (103.8) or E. tenella (103.3) was investigated. In the second experiment the influence of dietary protease on the intestinal mucus layer thickness and brush border enzyme activity was established. In both studies the protease was supplied at a concentration of 2.5 x 104 DU per kg feed. No significant interaction was observed on body weight gain between dietary enzyme supplementation and single Eimeria spp. infection. However, protease addition to the diet resulted in a significant (P = 0.046) higher weight gain after comparing all supplemented with non-supplemented groups. Coccidial lesions were not significantly affected by the dietary protease supplementation, despite the slight tendency to a higher lesion score for E. acervulina on the enzyme supplemented diets. Dietary protease significantly thickened the adherent mucus layer of the duodenum, jejunum and caeca. The sucrase-isomaltase activity in mucosal scrapings of the jejunum was significantly lower in birds fed the enzyme supplemented diet, indicating a higher villus turnover rate. In conclusion, our data suggest that dietary supplementation with the protease reduced the negative impact of a coccidiosis infection on body weight gain of broilers, although the coccidial lesions and oocyst excretion remained unaffected.

In the third section of Chapter 3 a study to examine the anticoccidial activity of a mannanoligosaccharide (MOS) preparation is shown. One-day-old broilers were given a single, mild coccidiosis infection with a mixture of three Eimeria species: E. acervulina (102.95), E. maxima (102.75) and E. tenella (102.23). Infected and non-infected birds were fed a diet with or without 10 g MOS/kg. Growth performance, feed intake and feed conversion were not significantly different (P > 0.05) among the treatment groups. Feeding of the MOS preparation reduced oocyst excretion and diminished the severity of coccidiosis lesions induced by E. acervulina (P ≤ 0.05), but did not affect the lesions mediated by E. maxima and E. tenella. All three tested alternative compounds (IBU, protease and MOS) only showed a slight anticoccidial effect but could not be considered as anticoccidial drugs. The growth promoting effect of the protease deserves further research.


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In Chapter 4 the influence of anticoccidial programs (anticoccidial product in feed or vaccination with an attenuated anticoccidial sensitive vaccine) on the sensitivity profiles of Eimeria spp. field isolates is described.

Twenty European Eimeria spp. field isolates were subjected to an AST. The anticoccidial drugs tested were diclazuril and monensin. The results showed again that resistance is common amongst coccidiosis field isolates, 68% and 53% of the E. acervulina isolates were resistant against diclazuril and monensin, respectively, while resistance was less frequent amongst E. maxima isolates, 38% and 50% were resistant to diclazuril and monensin, respectively. Resistance of E. tenella isolates occurred in 23% and 38% of cases against diclazuril and monensin, respectively. A comparison of the total results obtained in 2004 with anticoccidial sensitivity studies performed in the period 1996-2002 (Chapter 2) showed a decrease in the number of Eimeria spp. isolates resistant to diclazuril and monensin. Further analysis of the sensitivity study of 2004 with the overall Chi-square test showed a highly significant influence of the coccidiosis prevention program (live coccidiosis vaccination with Paracox™-5 versus anticoccidial drugs in feed) on the sensitivity pattern of Eimeria spp. field isolates for both diclazuril (P = 0.000) and monensin (P = 0.001) (Table 2). Table 2. Number of diclazuril and monensin resistant Eimeria spp. field isolates obtained from European broiler flocks in 2004 (related to anticoccidial program) and in 1996-2002 Eimeria spp. Year/period Anticoccidial program Diclazuril (%) Monensin (%) E. acervulina 2004 13/19 (68) 10/19 (53) Vaccination (Paracox™-5) 4/8 (50) 2/8 (25) Anticoccidial drug 9/11 (82) 8/11 (73) 1996-2002 27/30 (90) 13/20 (65) E. maxima 2004 6/16 (38) 8/16 (50) Vaccination (Paracox™-5) 1/9 (11) 2/9 (22) Anticoccidial drug 5/7 (71) 6/7 (86) 1996-2002 9/11 (81) 5/6 (83) E. tenella 2004 3/13 (23) 5/13 (38) Vaccination (Paracox™-5) 0/8 (0) 2/8 (25) Anticoccidial drug 3/5 (60) 3/5 (60) 1996-2002 6/11 (54) 7/8 (88) Additional analysis (Chi-square test) at the single species level and each anticoccidial drug showed significantly more sensitivity of E. acervulina for monensin (P = 0.018), of E. maxima for diclazuril (P = 0.009) and of E. tenella for diclazuril (P = 0.007) in field isolates originating from vaccinated flocks (Table 3).

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Table 3. Number of diclazuril and monensin sensitive Eimeria spp. isolates obtained from European broiler flocks in 2004 in relation to the anticoccidial program Eimeria spp. Paracox™-5 Anticoccidial drug Chi-square (P)* Diclazuril E. acervulina 4/8 1/11 0.111 E. maxima 8/9 1/7 0.009 E. tenella 8/8 1/5 0.007 Monensin E. acervulina 4/8 0/11 0.018 E. maxima 5/9 1/7 0.060 E. tenella 4/8 1/5 0.767 *The significance of the association between the coccidiosis prevention program and the anticoccidial sensitivity profiles was assessed using the Chi-square test (P ≤ 0.05 is considered significant).

In Chapter 5 studies on cross protection between an E. acervulina vaccine line obtained by animal passages of extraintestinal blood stages of the parasite and E. maxima, and E. tenella are presented. Three successive bird passages with early extraintestinal blood stages of an E. acervulina strain were performed in commercial broiler chickens in order to obtain an E. acervulina vaccine line. Subsequently, commercial broilers were vaccinated at one day of age with graded doses of the obtained E. acervulina vaccine line by coarse spray to determine a vaccination dose and to establish the protection against a challenge infection with virulent strains of E. acervulina, E. maxima and E. tenella with time. Vaccinated birds showed complete protection against challenge with E. acervulina, partial cross protection against E. tenella but no cross protection against E. maxima. Further research comparing E. acervulina lines from different sources could unravel whether differences in cross protective properties exist. E. acervulina lines showing enhanced cross protection against E. tenella could then be used to improve current live anticoccidial vaccines. Conclusions and perspectives To date coccidiosis control in broilers has relied mainly on chemoprophylaxis, however, the high degree of resistance against anticoccidial drugs, as shown in Chapter 2, strengthening regulations, and possible upcoming bans on the use of anticoccidial drugs as feed additives, have been the principal motivators in the quest for alternative control strategies.

A wealth of papers concerning the effect of diet composition (ingredient and nutrient composition), feed structure and the use of alternative feed additives (phyto- and aromatherapy) on Eimeria parasites have been published to date. However, the results of these studies are frequently ambivalent, while the number of manuscripts describing a clear anticoccidial activity against various Eimeria spp. is relatively scarce. It is therefore


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concluded that future coccidiosis control is unlikely to be achieved solely through feed composition, structure and the use of alternative feed additives. In agreement herewith are the results obtained in Chapter 3 of this thesis, in which the anticoccidial potency of alternative preventive treatments for coccidiosis (a non-steroidal anti-inflammatory drug (ibuprofen), a mucolytic enzyme (protease) and a prebiotic (MOS)) was investigated. All three tested alternative compounds only showed a slight anticoccidial effect and could not be considered as promising anticoccidial drugs.

Despite the high costs and a number of drawbacks associated with the production and use of live anticoccidial vaccines, their use has increased considerably during the last decade due to their efficacy and their association with increased sensitivity of Eimeria spp. field isolates to anticoccidial drugs. To date, they represent the best alternative to anticoccidial products considering resistance and residues. However, if the immunogenicity of subunit vaccines can be improved substantially they might form the core of future anticoccidial strategy.

Based on this thesis the following recommendations relevant to the broiler industry can be made:

1. In view of the anticoccidial drug resistance problem as shown in Chapter 2 monitoring of the sensitivity of Eimeria spp. isolates to anticoccidial products is needed to optimize the use of these drugs in rotation and shuttle programs.

2. Data obtained from the literature review (Chapter 1) and studies performed with mannanoligosaccharide, ibuprofen and a mucolytic enzyme (Chapter 3) indicate that alternative coccidiosis control strategies excluding vaccination seem insufficient to prevent clinical coccidiosis.

3. Vaccination with live attenuated anticoccidial drug sensitive Eimeria lines has shown to be associated with a higher incidence of anticoccidial drug sensitive coccidiosis field isolates (Chapter 4). Vaccination could therefore be used in rotation programmes in order to efficiently control clinical disease and at the same time reduce the anticoccidial drug resistance problem. Anticoccidial programs should be guided by ASTs in order to use anticoccidial drugs as well as vaccines, in the (economically) most efficient manner.

4. In view of the results obtained in Chapter 5, vaccines could be produced more efficiently if cross protection can be further exploited. In this context, research into the mechanisms ruling cross protection and screening of Eimeria strains for enhanced expression of this property are of crucial relevance.

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References Bafundo, K.W., Cervantes, H.M. & Mathis, G.F. (2008). Sensitivity of Eimeria field isolates in the

United States: responses of nicarbazin-containing anticoccidials. Poultry Sciences, 87, pp. 1760-1767. Chapman, H.D. (1998). Evaluation of the efficacy of anticoccidial drugs against Eimeria species in the

fowl. International Journal for Parasitology, 28, pp. 1141-1144. Johnson, J. & Reid, W.M. (1970). Anticoccidial drugs: lesion scoring techniques in battery and floor-pen

experiments with chickens. Experimental Parasitology, 28, pp. 30-36. McDougald, L.R., Fuller, L. & Solis, J. (1986). Drug sensitivity of 99 isolates of coccidia from broiler

farms. Avian Diseases, 30, pp. 690-694. Ruff, M.D., Danforth, H.D. & Wilkens, G.C. (1997). Interpreting results of anticoccidial testing. In:

Proceedings of the VIIth International Coccidiosis Conference, Control of coccidiosis into the next Millennium. Oxford, UK, pp. 52.

Watkins, K.l. (1997). Are sensitivity test results good predictors of anticoccidial field efficacy? In: Proceedings of the VIIth International Coccidiosis Conference, Control of coccidiosis into the next Millennium. Oxford, UK, pp. 53.

Samenvatting Doel van het proefschrift was om de resistentie van Nederlandse en Europese Eimeria spp. veldisolaten tegen de in gebruik zijnde anticoccidiosemiddelen te onderzoeken (Hoofdstuk 2). Dit onderzoek werd voorafgegaan door een uitgebreide literatuurstudie betreffende coccidiose, anticoccidiosemiddelen en alternatieve preventieve behandelingen en strategieën (Hoofdstuk 1). Tevens beoogde het proefschrift de anticoccidiose werkzaamheid van ibuprofen, een mucolytisch enzym en mannanoligosaccharide als alternatieve coccidiose controle strategie vast te stellen (Hoofdstuk 3). Bovendien werd de invloed van vaccinatie op de gevoeligheidprofielen van Eimeria spp. veldisolaten ten opzichte van anticoccidiosemiddelen onderzocht (Hoofdstuk 4). Tenslotte, werd de kruisbescherming van een E. acervulina vaccinlijn tegen E. tenella en E. maxima bestudeerd, aangezien kruisbescherming verbetering van de effectiviteit van coccidiosevaccins zou betekenen (Hoofdstuk 5).

In Hoofdstuk 1 wordt aan de hand van een uitgebreid literatuuroverzicht de ziekte “coccidiose” beschreven. De geschiedenis van de ziekte en de classificatie en de levenscyclus van de parasiet worden gedetailleerd toegelicht alsmede de mogelijkheden tot identificatie van de species en het stellen van de diagnose. In enkele overzichtstabellen worden de verschillende Eimeria spp. van het commercieel gehouden pluimvee beschreven en getoond. Bij de kip zijn zeven Eimeria spp. beschreven waarvan E. acervulina, E. maxima en E. tenella de belangrijkste zijn aangezien deze species bij vleeskuikens frequent voorkomen en deze dieren het overgrote deel van de pluimveehouderij vormen. De diagnose “coccidiose” wordt doorgaans bij postmortem onderzoek gesteld door de locatie en morfologie van de letsels in de darm. Dit onderzoek wordt aangevuld door lichtmicroscopisch onderzoek van natieve darmschraapsels voor morfologische identificatie van schizonten en oöcysten. Aangezien deze traditionele manier van diagnostiek zijn beperkingen kent, zijn nieuwe identificatiemethoden ontwikkeld. Zo is recentelijk de identificatie van Eimeria-oöcysten sterk verbeterd door analyse en classificatie van microscopische opnamen met behulp van een computerprogramma. Daarnaast zijn moleculairbiologische technieken het speerpunt van veel lopend onderzoek. Op dit moment is het mogelijk om middels PCR techniek, gebruik makend van de ITS-1 en ITS-2 markers, de bij pluimvee voorkomende Eimeria spp. te identificeren. Dit onderzoeksgebied is volop in beweging.

In het tweede gedeelte van het overzichtsartikel worden de gastheer- en plaatsspecificiteit van de parasiet beschreven. Eimeria spp. kunnen genetisch nauw verwante gastheren infecteren maar voor de complete ontwikkeling van de levenscyclus blijkt de gastheerspecificiteit zeer strikt te zijn. Het mechanisme dat hiervoor verantwoordelijk is, wordt toegeschreven aan de biochemie en voeding van de parasiet enerzijds en het genoom en het immuunsysteem van de gastheer anderzijds. Ten aanzien van de plaatsspecificiteit is vastgesteld dat sporozoieten van Eimeria spp. zeer specifieke weefsels of orgaancellen infecteren van niet alleen de natuurlijke gastheer maar ook die

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van andere gastheren. De karakteristieken van deze weefsels of organen die door een groot aantal gastheren gedeeld worden, blijken hiervoor verantwoordelijk te zijn.

In het derde deel wordt een historisch overzicht gegeven van alle anticoccidiosemiddelen en worden deze middelen ingedeeld op basis van hun chemische samenstelling en werkingsmechanisme. Ondanks het feit dat de meeste anticoccidiosemiddelen meer dan één biochemisch effect op de ontwikkeling van een specifiek stadium van de parasiet hebben en ondanks een gebrek aan gedetailleerde kennis over een selectieve werking van deze producten is toch een grove indeling gemaakt. Middelen die de cofactor-synthese beïnvloeden zijn ethopabaat, sulfonamides, pyrimethamines en thiamine-analogen zoals amprolium. Middelen met invloed op mitochondriale functies zijn de quinolonen (buquinolaat, decoquinaat en nequinaat), de pyridinolen (meticlorpindol), nicarbazine, robenidine en toltrazuril. Middelen die de celmembraamfuncties beïnvloeden zijn de polyether-antibiotica (ook wel ionoforen genoemd) (monensin, semduramicin, narasin, salinomycin, lasalocid en maduramicin). Daarnaast is van enkele middelen het werkingsmechanisme onbekend (diclazuril en halofuginone). Het wereldwijde intensieve gebruik van anticoccidiosemiddelen heeft uiteindelijk geleid tot de ontwikkeling van resistentie tegen al deze middelen. Resistentie tegen anticoccidiosemiddelen is in de wetenschappelijke literatuur in de Verenigde Staten, Zuid Amerika, Europa en China gerapporteerd. Om resistentie zoveel mogelijk te beperken worden de middelen geroteerd (een bepaald middel gedurende maximaal twee maanden of twee groeirondes gebruiken) of worden shuttleprogramma’s (twee of meer middelen in één groeiperiode gebruiken) toegepast. De gedachte hierachter is dat verlies van gevoeligheid gerelateerd is aan de gebruiksduur van het middel. Door het optreden van kruisresistentie tussen anticoccidiosemiddelen met hetzelfde werkingsmechanisme zouden producten met verschillende werkingsmechanismen afwisselend gebruikt moeten worden in de rotatie en shuttleprogramma’s. In het ideale geval zouden rotatie en shuttleprogramma’s gebaseerd moeten zijn op kennis van de gevoeligheidsprofielen van de Eimeria spp. veldisolaten. Een relatief nieuwe benadering in het terugdringen en beperken van resistentie tegen anticoccidiosemiddelen is het gebruik van levende coccidiosevaccins in rotatieprogramma’s. Verspreiding van gevoelige Eimeria spp. vaccinlijnen in de pluimveestallen heeft een toename van de incidentie van gevoelige Eimeria spp. veldisolaten te weeg gebracht.

In het vierde deel van het literatuuroverzicht wordt stilgestaan bij de mogelijkheid om door middel van voerstructuur, voersamenstelling (micro- en macro-ingrediënten, speciale additieven), toxinen in het voer en voermanagement, coccidiose-infecties te beïnvloeden. Verschillende voercomponenten blijken de parasiet direct (invloed op de vermeerdering van de parasiet) of indirect (stimulatie immuunsysteem, invloed op darmflora en slijmlaag in de darm, verandering van de fysiologie van de darm, enz.) te beïnvloeden. Sommige voercomponenten zijn actief tijdens de acute fase van de ziekte terwijl andere het herstel bevorderen. Voercomponenten die het herstel bevorderen zijn eiwitten en de vitaminen A, C en K. Voercomponenten die de ontwikkeling van de parasiet direct negatief beïnvloeden zijn ω-3 vetzuren. Voor eiwitconcentratie en

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voerrestrictie zijn wisselende effecten beschreven. De ontwikkeling van de parasiet wordt op een indirecte manier negatief beïnvloed via stimulatie van het immuunsysteem door β-glucanen, vitamine E, selenium, voederbeperking, ω-3 vetzuren, vitaminen A en C en natriumbicarbonaat (NaHCO3). De ontwikkeling van de parasiet wordt ook indirect negatief beïnvloed door middellange keten vetzuren en de vitaminen A, C en K. Deze componenten bevorderen de “gezondheid” van de slijmlaag in de darm en beschermen zo tegen coccidiose-infecties. Wisselende indirecte effecten op de ontwikkeling van de parasiet zijn beschreven voor tarwe dat de viscositeit en darmflora beïnvloedt. De darmflora wordt ook beïnvloed door vezels en melkproducten. Hele granen hebben een indirect effect op de Eimeria-parasiet via hun invloed op de fysiologie van de darm. Tot slot, voercomponenten die de ontwikkeling van de parasiet direct bevorderen zijn calcium, aflatoxinen, vitamine B, essentiële vetzuren en trypsine. Deze componenten moeten dan ook indien maar enigszins mogelijk niet gebruikt te worden in concentraties die de ontwikkeling van de parasiet bevorderen.

In deel vijf worden andere alternatieve preventieve methoden zoals management en bioveiligheid, homeopathie, phytotherapie en vaccinatie beschreven. Management- en bioveiligheidsmaatregelen zijn ervoor bedoeld om zoveel mogelijk insleep van de parasiet in pluimveestallen te voorkomen door isolatie, controle van voertuigen (verkeer) en hygiënemaatregelen. In de praktijk is het echter vrijwel onmogelijk om kuikens coccidiose vrij te houden tenzij gebruik gemaakt wordt van SPF-achtige huisvestingscondities. Besmette pluimveestallen kunnen het beste met veel water gereinigd worden waarna ontsmetting met een ammoniak oplossing (5-10%) dient plaats te vinden. Phytotherapie en aromatherapie kennen gedurende het laatste decennium een groeiende belangstelling door vernieuwde interesse in natuurgeneeskunde. Een groot aantal plantenextracten (kruiden) is onderzocht op werkzaamheid tegen coccidiose. Middelen die een negatief effect op de ontwikkeling van de parasiet vertonen zijn artemisinin, extracten van citrusvruchten en mengsels van kruidenextracten. Oregano vertoonde een wisselend effect op de ontwikkeling van de Eimeriaparasiet. Betaine, Echinacea, paddestoelen (lectines) en turmeric (curcumine) stimuleren het immuunsysteem waardoor de ernst van de coccidiose-infectie afneemt. Betaine heeft bovendien osmoprotectieve eigenschappen in de darmtractus. Het effect van het prebioticum MOS op coccidiose is niet eenduidig. Soms werd een directe werking aangetoond door de ontwikkeling van de parasiet te verhinderen en soms vertoonde het geen effect. Probiotica hebben een indirect belemmerend effect op de parasiet door stimulatie van de humorale immuunrespons. Vaccinatie met levende afgezwakte of niet afgezwakte Eimeria spp. lijnen wordt steeds meer beschouwd als een betrouwbare alternatieve maatregel tegen coccidiose. Levende coccidiosevaccins hebben echter ook enkele nadelen zoals hoge productiekosten, beperkte houdbaarheid en fouten bij toediening (doseringsfouten, aanwezigheid van anticoccidioseproducten in het voer die de vaccinatie met voor deze middelen gevoelige vaccinlijnen frustreren). Bovendien kan ook herstel/toename van de virulentie van de levende afgezwakte vaccinlijnen een punt van zorg zijn. Een gunstige nevenwerking van vaccinatie met levende voor anticoccidiosemiddelen gevoelige vaccinlijnen is dat er verschuiving plaatsvindt van resistente naar gevoelige veldisolaten. Dit fenomeen heeft het

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gebruik van deze vaccins in rotatieprogramma’s sterk bevorderd. Subunit-vaccins missen veel van de onvolkomenheden van de levende vaccins, maar thans presteren deze producten teleurstellend door gebrek aan immunogeniteit. Het E. tenella genoom project kan ontdekking van essentiële immunogene antigenen die wel voldoende bescherming induceren dichterbij brengen. En dan kunnen de subunit-vaccins de hooggespannen verwachtingen mogelijk waarmaken.

Geconcludeerd kan worden dat het vóórkomen van tegen anticoccidiosemiddelen resistente Eimeria spp. veldisolaten op zijn minst onveranderd zal blijven. Aannemelijker is dat resistentie verder zal toenemen vooral als de commerciële pluimveehouderij vasthoudt aan het gebruik van anticoccidiosemiddelen op een niet-rationele manier dat wil zeggen niet begeleid door gevoeligheidstesten en zonder tijdige afwisseling van anticoccidiosemiddelen. Hoewel sommige voercomponenten, fytochemicaliën, prebiotica/probiotica en een niet-steroïd anti-inflammatoir geneesmiddel in staat bleken te zijn om de nadelen van een coccidiose-infectie te verminderen, hetzij door een direct effect op de parasiet hetzij indirect door immuunstimulatie en door bevordering van het herstel, blijken deze effecten onvoldoende om de ziekte te kunnen controleren. Genoemde middelen bleken dan ook geen oplossing voor het probleem van de anticoccidiosemiddelen resistentie. Op dit moment is vaccinatie dan ook de meest voor de hand liggende en betrouwbare anticoccidiose strategie ondanks zijn onvolkomenheden. Indien het immuniserend vermogen van de subunit vaccins sterk verbeterd zou kunnen worden, zouden deze vaccins het belangrijkste onderdeel van de toekomstige anticoccidiose strategie kunnen zijn.

In Hoofdstuk 2 worden de anticoccidiosemiddelen gevoeligheidprofielen van een aantal Eimeria spp. veldisolaten afkomstig van vleeskuikenkoppels, gepresenteerd en bediscussieerd.

In twee onderzoeken werden vijftien Eimeria spp. veldisolaten van Nederlandse bedrijven, vier uit 1996, vier uit 1999 en zeven uit 2001 en vierentwintig veldisolaten afkomstig van Nederlandse, Duitse en Spaanse vleeskuikenbedrijven in de periode 2000-2002 onderzocht op gevoeligheid voor anticoccidiosemiddelen. De onderzochte anticoccidiosemiddelen waren: diclazuril, halofuginone, lasalocid, maduramicin, meticlorpindol/methylbenzoquate, monensin, narasin, narasin/nicarbazine, nicarbazine, robenidine en salinomycin. De resultaten vertoonden een hoge mate van resistentie tegen de meeste anticoccidiosemiddelen. Desondanks bleven ernstige coccidiose problemen in het veld uit, terwijl de coccidiose prevalentie in Nederland hoog was. Een mogelijke verklaring hiervoor is dat de resistentie tegen de anticoccidiosemiddelen niet volledig is en in het veld “natuurlijke vaccinatie” en immuniteitsopbouw plaatsvindt onder de partiële protectie van het anticoccidiosemiddel.

In de periode van 1996 tot 2002 werden in totaal negenendertig verschillende Eimeria spp. veldisolaten, waarvan het merendeel uit meer dan één species bestond, onderzocht op gevoeligheid voor de meest gebruikte anticoccidiosemiddelen. De onderzochte veldisolaten bestonden uit zesendertig E. acervulina isolaten, veertien E. maxima isolaten

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en twaalf E. tenella isolaten (Tabel 1). Voor het vaststellen van de anticoccidiosemiddelen gevoeligheidprofielen werden de criteria (zie later) van McDougald et al. (1986) gehanteerd. Tabel 1. Anticoccidiosemiddelen gevoeligheidprofielen uitgedrukt in aantal resistente (R), verminderd gevoelige (VG) en gevoelige (G) Eimeria spp. isolaten per anticoccidiosemiddel. Eimeria spp. isolaten waren afkomstig van vleeskuikenbedrijven in Nederland, Duitsland en Spanje in de periode 1996-2002 Anticoccidiosemiddel E. acervulina E. maxima E. tenella n R VG G n R VG G n R VG G Diclazuril (Clinacox®) 30 27 1 2 11 9 1 1 11 6 1 4 Halofuginone (Stenorol®) 16 10 6 0 5 0 1 4 3 0 0 3 Lasalocid (Avatec®) 19 17 2 0 3 1 2 0 8 4 2 2 Maduramicin (Cygro®) 4 3 1 0 1 1 0 0 1 0 0 1 Meticlorpindol/methylbenzoquate (Lerbek®)

19 1 1 17 9 3 0 6 7 0 0 7

Monensin (Elancoban®) 20 13 4 3 6 5 1 0 8 7 0 1 Narasin (Monteban®) 25 16 4 5 8 5 1 2 10 7 1 2 Narasin/nicarbazin (Maxiban®) 16 11 4 1 8 2 1 5 4 4 0 0 Nicarbazin (Nicarb®) 30 26 1 3 13 7 2 4 11 7 2 2 Robenidine (Robenz®) 6 3 0 3 1 0 0 1 1 0 0 1 Salinomycin (Sacox®) 36 18 7 11 14 6 5 3 12 10 1 1 Totalen 221 145 31 45 79 39 14 26 76 45 7 24 Resistentie van E. acervulina isolaten tegen de anticoccidiosemiddelen komt veel voor: in 145 van de 221 (66%) bepalingen werd resistentie tegen tenminste één anticoccidiosemiddel vastgesteld. Het aantal E. maxima isolaten dat resistentie vertoonde tegen één of meer anticoccidiosemiddelen bedroeg 39 uit 79 (49%). De E. tenella isolaten vertoonden in 45 van de 76 (59%) bepalingen tegen één of meerdere anticoccidiosemiddelen resistentie.

Het coccidiose laesie score systeem volgens Johnson and Reid (1970) geeft een goede indruk van de pathologie van een coccidiose-infectie en is één van de meest gebruikte methoden voor vaststelling van het effect van anticoccidioseproducten op coccidiose-infecties (Chapman, 1998). In beide gevoeligheidsonderzoeken is van dit systeem gebruik gemaakt. Vervolgens werden de criteria van McDougald et al. (1986) toegepast om het gevoeligheidsprofiel vast te stellen van de afzonderlijke Eimeria spp. aanwezig in de veldisolaten met betrekking tot de anticoccidiosemiddelen. Hierbij werd gebruik gemaakt van de formule: laesie reductie = 100% - (gemiddelde laesie score van de behandelde groep/gemiddelde laesie score van de niet behandelde geïnfecteerde controle groep x 100%). Een reductie van 0-30% duidt op resistentie, 31-49% reductie staat voor verminderde gevoeligheid of gedeeltelijke resistentie en een reductie van 50% of meer betekent volledige gevoeligheid voor het geteste anticoccidiosemiddel. De vertaling van

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de laboratoriumresultaten naar praktijkomstandigheden is discutabel (Bafundo et al., 2008). Extrapolatie van de resultaten van de laboratorium gevoeligheidstest naar praktijkomstandigheden is ingewikkeld aangezien in de laboratoriumtest een eenmalige hoge infectiedosis gebruikt wordt, die in de praktijk waarschijnlijk nauwelijks voorkomt. Het is mogelijk dat het anticoccidiosemiddel onder proefomstandigheden minder effectief is dan in de praktijk. Dit kan aanleiding geven tot fouten bij de interpretatie van de testresultaten (Watkins, 1997). Desondanks is de test tot op dit moment de enig beschikbare methode om de anticoccidiosemiddelen gevoeligheidsprofielen van Eimeria spp. veldisolaten vast te stellen. Overigens kan de test wel degelijk belangrijke informatie geven over verslechtering van het anticoccidiosemiddelen gevoeligheidspatroon van een Eimeria spp. veldpopulatie, nog voordat er problemen optreden en dat kan dan reden zijn om een effectief anticoccidioseprogramma toch te veranderen (Ruff et al., 1997).

In Hoofdstuk 3 wordt de anticoccidiose activiteit van drie alternatieve middelen gepresenteerd.

In het eerste deel wordt het onderzoek met ibuprofen - een niet-steroïd anti-inflammatoir geneesmiddel – beschreven. Ibuprofen werd via het drinkwater verstrekt. Toediening van 15 mg/kg lichaamsgewicht vanaf een leeftijd van dag één tot zeven dagen na de infectie bleek geen effect te hebben op een coccidiose-infectie met een samengesteld inoculum van 5 x 104 E. acervulina, 3 x 104 E. maxima en 7,5 x 103 E. tenella gesporuleerde oöcysten per kuiken. Ibuprofen, verstrekt in een dosis van 100 mg/kg lichaamsgewicht vanaf één dag voor de infectie tot vijf dagen na de infectie, verminderde de oöcystenuitscheiding significant (P ≤ 0,05) bij infectiedoses tussen de 104 tot 105 gesporuleerde E. acervulina oöcysten per kuiken. Hoewel de coccidiose-laesiescores voor alle genoemde infectiedoses lager waren dan die van de controle groepen, werd alleen bij de infectie met 104 E. acervulina oöcysten per kuiken een significant lagere score vastgesteld. Een effect op de groei van de kuikens werd niet waargenomen en de behandeling met ibuprofen had geen invloed op de sporulatie en infectiviteit van de uitgescheiden E. acervulina oöcysten.

In het tweede gedeelte van dit hoofdstuk worden de resultaten van twee experimenten gepresenteerd. In het eerste experiment werd het effect onderzocht van de toediening van een mucolytisch enzym (protease) via het voeder op een coccidiose-infectie met 104 E. acervulina, 6,3 x 103 E. maxima of 1,9 x 103 E. tenella gesporuleerde oöcysten per dier. In een tweede experiment werd de invloed van het enzym op de dikte van de darmslijmlaag en de borstelzoom enzym activiteit bestudeerd. In beide experimenten werd de protease in een dosering van 2,5 x 104 DU per kg voer verstrekt. In het eerste experiment werd vastgesteld dat het enzym geen invloed had op de groei noch op laesie en oöcystenuitscheiding bij enkelvoudige Eimeria spp. infecties. Wel werd een significant verschil (P = 0,046) gevonden tussen de gemiddelde groei van alle dieren ten gunste van de dieren die voeder met protease kregen. In het tweede experiment werd vastgesteld dat de slijmlaag van de dunne darm, jejunum en blinde darm significant dikker was en de sucrase-isomaltase enzym activiteit in de borstelzoom van het jejunum significant lager was bij de dieren die voeder met protease kregen. Deze resultaten duiden

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op een hogere ‘villus turnover rate’ en suggereren dat het mucolytisch enzym de negatieve invloed van een coccidiose-infectie op de groei vermindert hoewel de coccidiose laesies en oöcystenuitscheiding onveranderd bleven.

In het derde gedeelte van dit hoofdstuk wordt het effect van een mannanoligosaccharide (MOS) preparaat op een milde coccidiose-infectie, beschreven. Eén dag oude vleeskuikens werden geïnoculeerd met een milde gemengde coccidiose-infectie van 900 E. acervulina, 570 E. maxima en 170 E. tenella gesporuleerde oöcysten per kuiken. Geïnfecteerde en niet-geïnfecteerde dieren kregen voer met 10 g MOS/kg of zonder MOS. Geen significante invloed van MOS werd vastgesteld op groei, voeropname en voederconversie. Wel bleek MOS de ernst van de E. acervulina laesies evenals de oöcystenuitscheiding significant (P ≤ 0,05) te verminderen. Het preparaat had echter geen invloed op de laesies van E. maxima en E. tenella. De drie onderzochte alternatieve producten (ibuprofen, protease en MOS) vertoonden slechts een geringe mate van anticoccidiose-activiteit en kunnen derhalve niet als een anticoccidiosemiddel beschouwd worden. Het groeibevorderende effect van het mucolytisch enzym verdient nader onderzoek.

In Hoofdstuk 4 wordt de invloed van anticoccidioseprogramma’s (anticoccidioseproduct in het voer of vaccinatie met een afgezwakt coccidiose vaccin dat gevoelig is voor anticoccidiosemiddelen) op de resistentie van Eimeria spp. veldisolaten voor anticoccidiosemiddelen beschreven.

Twintig Europese Eimeria spp. veldisolaten werden onderzocht op hun gevoeligheid voor diclazuril en monensin. Opnieuw bleek dat resistentie veel voorkomt bij coccidiose veldisolaten. Van de E. acervulina isolaten bleek 68 respectievelijk 53 procent resistent te zijn tegen diclazuril en monensin. Bij E. maxima isolaten bedroegen deze percentages 38 en 50 en bij E. tenella isolaten 23 en 38. Uit vergelijking van deze resultaten met die van eerder uitgevoerde studies (Hoofdstuk 2, periode 1996-2002) blijkt de resistentie tegen diclazuril en monensin minder te zijn. Statistische analyse met de Chi-square test toonde een significante relatie aan tussen de toegepaste anticoccidioseprogramma’s (levende anticoccidiose vaccinatie met Paracox™-5 versus anticoccidiosemiddelen in het voer) en het gevoeligheidsprofiel van de Eimeria spp. veldisolaten voor diclazuril (P = 0,009) en monensin (P = 0,001) (Tabel 2).

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Tabel 2. Aantal diclazuril en monensin resistente Eimeria spp. veldisolaten afkomstig van Europese vleeskuiken koppels in 2004 (in relatie met anticoccidioseprogramma) en in 1996-2002 Eimeria spp. Jaar/periode Anticoccidioseprogramma Diclazuril (%) Monensin (%) E. acervulina 2004 13/19 (68) 10/19 (53) Vaccinatie (Paracox™-5) 4/8 (50) 2/8 (25) Anticoccidiosemiddel 9/11 (82) 8/11 (73) 1996-2002 27/30 (90) 13/20 (65) E. maxima 2004 6/16 (38) 8/16 (50) Vaccinatie (Paracox™-5) 1/9 (11) 2/9 (22) Anticoccidiosemiddel 5/7 (71) 6/7 (86) 1996-2002 9/11 (81) 5/6 (83) E. tenella 2004 3/13 (23) 5/13 (38) Vaccinatie (Paracox™-5) 0/8 (0) 2/8 (25) Anticoccidiosemiddel 3/5 (60) 3/5 (60) 1996-2002 6/11 (54) 7/8 (88) Nadere statische analyse (Chi-square test) op enkelvoudig species niveau en per anticoccidiosemiddel toonde significant meer gevoeligheid aan bij E. acervulina voor monensin (P = 0,018), bij E. maxima (P = 0,009) voor diclazuril en bij E. tenella (P = 0,007) voor diclazuril in Eimeria spp. veldisolaten afkomstig van gevaccineerde koppels (Tabel 3). Tabel 3. Aantal diclazuril en monensin gevoelige Eimeria spp. veldisolaten afkomstig van Europese vleeskuiken koppels in 2004 in relatie tot het anticoccidioseprogramma Eimeria spp. Paracox™-5 Anticoccidiosemiddel Chi-square (P)* Diclazuril E. acervulina 4/8 1/11 0,111 E. maxima 8/9 1/7 0,009 E. tenella 8/8 1/5 0,007 Monensin E. acervulina 4/8 0/11 0,018 E. maxima 5/9 1/7 0,060 E. tenella 4/8 1/5 0,767 *De significantie van de associatie tussen het coccidiose preventieprogramma en de anticoccidiose gevoeligheidsprofielen is vastgesteld door statistische analyse met de Chi-square test, P ≤ 0,05 is significant.

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In Hoofdstuk 5 wordt onderzoek naar kruisbescherming tussen een E. acervulina

vaccinlijn, verkregen door dierpassages met vroege extra-intestinale parasitaire bloedstadia, en E. maxima, en E. tenella beschreven.

Drie achtereenvolgende dierpassages met extra-intestinale bloedstadia van een E. acervulina stam werden uitgevoerd in commerciële vleeskuikens ter verkrijging van een E. acervulina vaccinlijn. Vervolgens zijn één dag oude commerciële vleeskuikens met deze E. acervulina vaccinlijn per spray geënt en is de mate van bescherming tegen een gecombineerde herinfectie van E. acervulina, E. tenella en E. maxima in de tijd vastgesteld. Gevaccineerde dieren vertoonden complete bescherming tegen de herinfectie met E. acervulina, een gedeeltelijke bescherming tegen E. tenella maar geen bescherming tegen E. maxima. Vervolgonderzoek met andere E. acervulina lijnen zal moeten uitwijzen of verschillen in kruisbeschermende eigenschappen voorkomen. E. acervulina lijnen die een kruisbescherming tegen E. tenella vertonen zouden dan gebuikt kunnen worden om de huidige levende coccidiosevaccins te verbeteren. Conclusies en perspectief Tot op heden berust de controle van coccidiose bij vleeskuikens voornamelijk op chemoprofylaxis. De in hoofdstuk 2 aangetoonde hoge mate van resistentie tegen anticoccidiosemiddelen, de toenemende wetgeving en het mogelijke verbod op het gebruik van anticoccidiosemiddelen als voederadditief, vormen echter belangrijke redenen om naar alternatieve controlemaatregelen te zoeken.

Talrijk zijn de studies betreffende de invloed van voersamenstelling (ingrediënten en samenstelling) voerstructuur en het gebruik van alternatieve voeder additieven (phyto- en aromatherapie) op Eimeria parasieten. De resultaten van deze studies zijn echter veelal ambivalent terwijl het aantal dat een duidelijke directe anticoccidiose werking tegen verschillende Eimeria spp. beschrijft, relatief gering is. Geconcludeerd kan worden dat het onwaarschijnlijk is dat toekomstige controle van coccidiose op basis van alleen voersamenstelling, voerstructuur en het gebruik van alternatieven voeradditieven gerealiseerd zal worden. In analogie hiermee zijn de in hoofdstuk 3 van dit proefschrift behaalde resultaten met alternatieve preventieve behandelingen tegen coccidiose. De drie onderzochte alternatieve producten ((een niet-steroïd anti-inflammatoir geneesmiddel (ibuprofen), een mucolytisch enzym (protease) en een prebioticum (MOS)) vertoonden slechts een geringe mate van anticoccidiose werking en kunnen derhalve niet als alternatief voor de huidige chemoprofylaxe worden beschouwd.

Ondanks hoge kosten en een aantal nadelen met betrekking tot de productie en toepassing van levende coccidiosevaccins, is het gebruik van deze vaccins gedurende het laatste decennium aanzienlijk toegenomen vanwege hun effectiviteit en het feit dat zij geassocieerd worden met een terugkerende gevoeligheid van Eimeria spp. veldisolaten voor anticoccidiosemiddelen. Tot nu toe zijn vaccins op basis van gesporuleerde oöcysten het beste alternatief voor anticoccidiosemiddelen. Wanneer, echter de immunogeniteit van

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subunit-vaccins verbeterd zou kunnen worden dan zouden deze vaccins een belangrijk onderdeel kunnen vormen van de toekomstige anticoccidiose strategie.

Gebaseerd op dit proefschrift kunnen de volgende aanbevelingen, relevant voor de

vleeskuikenhouderij gedaan worden:

1. Gegeven het resistentie probleem, zoals aangetoond in hoofdstuk 2, is monitoren van de gevoeligheid van de Eimeria spp. veldisolaten voor anticoccidiosemiddelen noodzakelijk om het gebruik van deze middelen in rotatie en shuttleprogramma’s te optimaliseren.

2. Uit de literatuurstudie (Hoofdstuk 1) en het onderzoek met ibuprofen, een

mucolytisch enzym en mannanoligosaccharide (Hoofdstuk 3) blijkt dat alternatieve coccidiose-controle strategieën, met uitzondering van vaccinatie, niet in staat blijken klinische coccidiose te voorkomen.

3. Vaccinatie met levende, afgezwakte en voor anticoccidiosemiddelen gevoelige

Eimeria spp. lijnen leidt tot een hogere incidentie van anticoccidiosemiddelen gevoelige veldisolaten (Hoofdstuk 4). Vaccinatie kan derhalve in rotatieprogramma’s gebruikt worden om enerzijds de ziekte zo efficiënt mogelijk te controleren en anderzijds gelijktijdig de resistentieproblematiek te verminderen. Anticoccidioseprogramma’s zouden door gevoeligheidstesten begeleid moeten worden teneinde anticoccidiosemiddelen en vaccins zo efficiënt mogelijk te gebruiken.

4. Vaccins die kruisbescherming bieden zijn in principe mogelijk (Hoofdstuk 5).

Screening van Eimeria lijnen op kruisbescherming en onderzoek naar het mechanisme van deze eigenschap zijn van belang.

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Literatuur Bafundo, K.W., Cervantes, H.M. & Mathis, G.F. (2008). Sensitivity of Eimeria field isolates in the

United States: responses of nicarbazin-containing anticoccidials. Poultry Sciences, 87, pp. 1760-1767. Chapman, H.D. (1998). Evaluation of the efficacy of anticoccidial drugs against Eimeria species in the

fowl. International Journal for Parasitology, 28, pp. 1141-1144. Johnson, J. & Reid, W.M. (1970). Anticoccidial drugs: lesion scoring techniques in battery and floor-pen

experiments with chickens. Experimental Parasitology, 28, pp. 30-36. McDougald, L.R., Fuller, L. & Solis, J. (1986). Drug sensitivity of 99 isolates of coccidia from broiler

farms. Avian Diseases, 30, pp. 690-694. Ruff, M.D., Danforth, H.D. & Wilkens, G.C. (1997). Interpreting results of anticoccidial testing. In:

Proceedings of the VIIth International Coccidiosis Conference, Control of coccidiosis into the next Millennium. Oxford, UK, pp. 52.

Watkins, K.l. (1997). Are sensitivity test results good predictors of anticoccidial field efficacy? In: Proceedings of the VIIth International Coccidiosis Conference, Control of coccidiosis into the next Millennium. Oxford, UK, pp. 53.

Dankwoord Het doet me een groot genoegen om allen te bedanken die een belangrijke bijdrage geleverd hebben bij de onderzoeken die beschreven zijn in mijn proefschrift.

Allereerst gaat mijn dank gaat uit naar mijn promotor Arjan Stegeman, die de

mogelijkheid van de promotie faciliteerde en de voortgang van mijn proefschrift op de voet volgde. Arjan, onze regelmatige bijeenkomsten lieten mij door jouw ogen zien hoe mijn proefschrift langzaam maar zeker in de tijd groeide. Speciale dank voor de totstandkoming van mijn proefschrift gaat uit naar mijn co-promotor Wil Landman. Wil, bedankt voor de zeer vele tekstuele correcties in mijn manuscripten, het vertrouwen in mijn ervaring op het gebied van coccidiose, je niet-aflatende stimulans bij het schrijven en je oprechte belangstelling in het onderzoek. In mijn persoonlijke en wetenschappelijke ontwikkeling heeft Mattie Vertommen een zeer belangrijke rol gespeeld. Mattie, door jouw toedoen ben ik indertijd bij de Gezondheidsdienst voor Pluimvee (GVP) in dienst getreden. Bedankt voor het vertrouwen dat je in mij had en voor de fijne samenwerking gedurende de tijd bij de GVP. Het was voor mij een zeer actieve en creatieve periode waarbij wij ontzettend veel werk verzet hebben. Eigenlijk is destijds al, ondermeer door de uitvoering van de vele anticoccidiose gevoeligheidstesten, de basis van mijn proefschrift gelegd. Ik wil de GD hartelijk danken voor de mogelijkheid dat ik gedurende een langere aaneengesloten periode aan één en hetzelfde onderwerp heb kunnen werken. Teun, bedankt voor het vertrouwen in de goede afloop en de tijd die ik mocht gebruiken voor de afronding van mijn proefschrift. Verder dank ik alle collega’s bij de GD die een bijdrage hebben geleverd aan de, in mijn proefschrift beschreven, onderzoeken. Een bijzonder woord voor dank heb ik voor ‘de jongens’ (Machiel, Johan en Ad) van Lab 2 die altijd bereid waren om een helpende hand te bieden bij de uitvoering van de dierproeven. Jongens bedankt voor de inspanningen en vele gedachtenwisselingen die we over allerhande aangelegen (ook aangaande de GD) gevoerd hebben. Graag wil ik Brenda Vermeulen bedanken voor haar initiatief in het onderzoek naar de invloed van ibuprofen op coccidiose. Brenda, bedankt voor je bijdrage bij de aanloop en afronding van mijn proefschrift en voor de lange en indringende gesprekken over het werk en de zeer fijne samenwerking. Ik heb altijd veel waardering gehad voor je zichtbaar onuitputtelijke energie en je grote vertrouwen in mijn kennis van coccidiose. Dank aan Mohammed Ali Elmusharaf en Anton Beynen bij het onderzoek naar de werkzaamheid van een prebioticum tegen coccidiose. Ook dank aan Jan Dirk van der Klis die het onderzoek naar de invloed van een mucolytische enzym op een coccidiose-infectie mogelijk maakte. Jan Dirk, je snelheid van denken en het (in)zien van oplossingen heeft me aangenaam verrast. Ik ervoer dat vaak als stimulerend en verfrissend. Op de valreep wil ik Jo van Eck bedanken voor de allerlaatste correcties in mijn proefschrift en de door de jaren heen lopende licht filosofische relativerende discussies en gesprekken. Die

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levenshouding van jou heb ik altijd in je bewonderd en enorm op prijs gesteld en dikwijls als een verademing (verlichting) van de alledaagse zorgen ervaren. Tenslotte gaat mijn dank uit naar mijn ouders. Beste Ma, het is jammer dat Pa niet meer bij ons is, hij zou ongetwijfeld zeer trots geweest zijn en heeft onmiskenbaar zijn aandeel hierin bijgedragen. Daarnaast wil ik mijn broers en zussen bedanken die ieder op zijn/haar manier er toe hebben bijgedragen dat ik me ontwikkeld heb tot wie ik nu ben. Gerard, Ria, Wim, Gerda, Ruud en Corien, Thankx!!!

Curriculum vitae Herman W. Peek werd op 2 december 1952 te Harmelen geboren. Nadat hij in 1972 zijn HAVO-diploma behaald heeft en daarna in militaire dienst is geweest, heeft hij de zoölogische HBO-A opleiding richting histologie van 1975-1978 bij het dr. ir. W.L. Ghijsen instituut te Utrecht gevolgd. Daarna is hij bij het RIVM (Rijksinstituut voor Volksgezondheid en Milieu) in dienst getreden en heeft tot 1980 op de afdeling toxicologie aan onderzoek op het gebied van embryotoxiciteit bij vissen gewerkt. Vervolgens is hij tot 1983 als analist bij de Faculteit voor Diergeneeskunde Vakgroep Tropische Diergeneeskunde bij het onderzoek van Toxoplasmose werkzaam geweest. In augustus 1984 is hij bij de GVP (Gezondheidsdienst voor Pluimvee) in Doorn in dienst getreden en heeft tot op heden als onderzoeksanalist aan diverse coccidiose projecten bij pluimvee gewerkt. Uiteindelijk hebben de werkzaamheden op het gebied van coccidiose bij de GD (Gezondheidsdienst voor Dieren) tot dit proefschrift geleid.

List of publications Manuscripts Peek, H.W., Vertommen, M.H., & Landman, W.J.M. (2009). Cross protection studies between Eimeria

acervulina and E. maxima, and E. tenella. Submitted. Peek, H.W., van der Klis, J.D., Vermeulen, B. & Landman, W.J.M. (2009). Dietary protease can alleviate

negative effects of a coccidiosis infection on production performance in broiler chickens. Animal Feed Science and Technology, 150, pp. 151-159.

Elmusharaf, M.A., Peek, H.W., Nollet, L. & Beynen, A.C. (2007). Effect of an in-feed mannanoligosaccharide preparation (MOS) on a coccidiosis infection in broilers. Animal Feed Science and Technology, 134, pp. 347-354.

Peek, H.W. & Landman, W.J.M. (2006). Higher incidence of Eimeria spp. field isolates sensitive for diclazuril and monensin associated with the use of live coccidiosis vaccination with Paracox™-5 in broiler farms. Avian Diseases, 50, pp. 434-439.

Peek, H.W. & Landman, W.J.M. (2004). Gevoeligheidsprofielen van Spaanse, Duitse en Nederlandse Eimeria spp. veldisolaten voor anticoccidiosemiddelen. Tijdschrift voor Diergeneeskunde, 129, pp. 210-214.

Vermeulen, B., Peek, H.W., Remon, J.P. & Landman, W.J.M. (2004). Effect of ibuprofen on coccidiosis in boiler chickens. Avian Diseases, 48, pp. 68-76.


Hornok, S., Heijmans, J.F., Bekesi, L., Peek, H.W., Dobos-Kovacs, M., Dren, Cs.N. & Varga, I. (1998). Interaction of chicken anaemia virus and Cryptosporidium bailey in experimentally infected chickens. Veterinary Parasitology, 76, pp. 43-55.

Vertommen, M.H., Peek, H.W. & van der Laan, A. (1990). Efficacy of toltrazuril in broilers and development of a laboratory model for sensitivity testing of Eimeria field isolates. The Veterinary Quarterly, 12, pp. 183-92.

Cornelissen, A.W.C.A., Overdulve, J.P. & Peek, H.W. (1982). The role of the stomach and the small intestine on the development of Isospora (Toxoplasma) gondii in cats infected directly into the small intestine by laparotomy. In thesis of A.W.C.A. Cornelissen. (Ploidy, meiosis and Sex Differentiation in Isospora (Toxoplasma) gondii with some considerations on other coccidian parasites. A study combining the results of monoclonal infection and cytophotometry).

Cornelissen, A.W.C.A., Overedulve, J.P. & Peek, H.W. (1982). Sex determination and sex differentiation in coccidia: gametogony and oocyst production after monoclonal infection of cats with intermediate host stagess of Isospora (Toxoplasma) gondii. In thesis of A.W.C.A. Cornelissen. (Ploidy, meiosis and Sex Differentiation in Isospora (Toxoplasma) gondii with some considerations on other coccidian parasites. A study combining the results of monoclonal infection and cytophotometry).

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Conference proceedings/abstracts/posters Landman, W.J.M. & Peek, H.W. (2005). Anticoccidial sensitivity profiles of recently obtained Dutch,

German and Spanish Eimeria spp. isolates. In the Proceedings of the IV International Poultry Symposium, pp. 133-152. Istanbul, Turkey.

Peek, H.W. & Landman, W.J.M. (2005). Anticoccidial sensitivity profiles of recently obtained Dutch, German and Spanish Eimeria spp. isolates. In the Proceedings of the IXth International Coccidiosis Conference, pp. 170, Iguaçu Falls, Brazil.

Landman, W.J.M. & Peek, H.W. (2005). Higher incidence of Eimeria spp. field isolates sensitive for diclazuril and monensin after live coccidiosis vaccination with Paracox™-5. In the Proceedings of the IXth International Coccidiosis Conference, pp. 157, Iguaçu Falls, Brazil.

Mohammed Ali Elmusharaf, Herman Peek, Anton Beynen, Lode Nollet and Lucy Tucker. (2005). Development of a coccidiostat challenge model for screening of gut health promoting additives in broilers. Alltech symposium.

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resistance to anticoccidial drugs: alternative strategies ... · performed in the natural host, 2/...

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