VETERINARY HELMINTHOLOGY

TAPEWORM/ CESTODESGeneral Characteristics:1. ribbon-like and dorsoventrally flattened2. most of the show indirect types of life cycle. The exceptional type of life cycle is found in Hymenolepis spp where direct and indirect types are found. 3. they are hermaphrodite4. cysts or bladderworms are intermediate or larval stage of the parasite5. the final host gets infection by ingestion of intermediate host or flesh of intermediate host containing the bladder worms6. the body can be divided into three broad parts

Head/ Scolex-very minute as compared to other parts-shape varies which may be roughly triangular,ball shaped or round-there is presence of sucker (armed or unarmed ) which is not used for taking food but used as apertures for attachment -anteriorly there is structure called rostellum

Neck-immediately behind the head and without any segment-segmentation starts here

Body -area is completely segmented Three types of segments are present:IMMATURE- the reproductive system and eggs are absentMATURE- completely developed reproductive system GRAVID- reproductive system is replaced by the eggs -either detached from the parasite or its disintegrated and the eggs are expelled out

Eggs:-have basic structure comprising oncosphere or hexacanth embryo, a striated shell or embryophore and a delicate membrane-the following are the events which occur during biological development: a. Eggs are expelled out from the gravid segment b. the eggs are ingested by the intermediate hosts and hatching occurs in the intermediate host or hatch in the environment ( Cotyloda) -metacestodes / bladderworms / cyst / larval stages are formed in the intermediate host-final host gets the infection by ingestion of the intermediate host or the muscles and flesh containing the cysts or bladderworms

Poultry TapewormGenus Raillietina-small to medium-sized tapeworm that inhabit the small intestine -cosmopolitan in distribution

Species: R. cesticillus R. echidnobothrida R. tetragona R. asiatica R. celebensis R. demerariensis

R. cesticillus Morphology: 1. smaller (4-15 cm) than R. tetragona, R. echidnobothrida 2. broad rostellum which is armed with 400- 500 hooks 3. circular sucker is unarmed 4. egg capsule contains single egg

R. echidnobothrida Morphology 1. size is 8.5-22 cm 2. suckers are circular and surrounded by several rows of hooks 3. rostellum is very small 4. egg capsule contains multiple eggs R. tetragona 1. 25 cm long and largest tapeworm in poultry 2. rostellum is small and possesses one or two rows of hooks 3. egg capsule contains multiple eggs 4. sucker is oval and surrounded by several rows of hooks

LIFE CYLCE: egg oncosphere cysticercoid ( infective stage ) adult

Ants and Musca domestica acts as IH of R. tetragona and R. echidnobothrida. The beetle acts as IH for R. cesticillus

Pathogenesis: 1. nodule formation in the intestine by R. echidnobothrida 2. enteritis by R. tetragona and R. cesticillus

Genus Davainea D. proglottina D. meleagridis

Morphology 1. very small only several mm that’s why it is advised to take mucosal scraping for its detection 2. has prominent rostellum armed with hammer- shaped hooks 3. presence of single set of reproductive organ which alternates regularly 4. has 4-9 segments 5. egg capsule contains single egg

Life cycle:EggOncosphereCysticercoid in IH (infective stage on ants or slugs)Adult The gravid segments crawl out of the host. The gravid segments are actively motile and crawl onto the grass blade due to its phototactic nature. The eggs are released during the act of crawling. The eggs hatch after ingested by IH and cysticercoid is formed within a month. The final host gets the infection when the infected snails are ingested by the birds.

Family Dipyliidae:Dipylidium caninum- double pored tapeworm of dogs

Morphology: 1. head or scolex is pyriform in shaped having hooks characteristically rose-thorn shaped 2. presence of two sets of reproductive system like Moniezia spp 3. mature segments are cucumber seed shape

LIFE CYCLE:eggonchospherecystercercoid in IH (flea C. canis, C. felis, T. canis, Pulex sp )adult

Gravid segments get detached from the adult tapeworm and crawl. During crawling the eggs are released from the gravid segment. The IH ingest the eggs and hatched in the gut and oncospheres are released and these migrate in the body cavity. A cysticercoid with tail appendage is formed within few weeks. Final host gets the infection by ingestion of the infected IH.

Pathogenesis: 1. sloughing, denudation of mucosa

2. constant irritation of the anal sac resulting to anal pruritus 3. intoxication due to absorption of the metabolites released by the parasites which affects the nervous system

Diagnosis: 1. examination of fecal sample 2. dragging anus over the ground or any hard objects

Family Anoplocephalidae: common cestodes of equine

Morphology: 1. rostellum and hooks are present 2. segments are noticeably broad\ 3. presence of egg capsule or paruterine organ 4. eggs have 3 coverings; the outermost formed by the vitelline gland, middle albuminous and inner chitinous 5. eggs of many members bear a pear shaped structure called pyriform apparatus

Genera: Anoplocephala Moniezia Paranocephala Cittotaenia Pseudanocephala Other Species

Anoplocephala magna

Anoplocephalaperfoliata

Pseudoanoplocephala mamillana

1. Largest cestode found in the horse found in SI and stomach

Small intestine Si and stomach

2. 80 cm long 1-8 cm 0.6- 5 cm

3. Testes are arranged in rows. The number of testes are 400-500

250 100

4. Pyriform apparatus is not strong and large

Large and strong

Large and srong

Lappets are absent

present absent

LIFE CYCLE:EggOnchosphereCysticercoid in IH ( mite)Adult

Pathogenesis: A. perfoliata particularly affects the ileocecal orifices and they produce depressed ulcers which is dasrk in color and may cause perforation of SI A. magna causes hemorrhagic enteritis obstruction of the intestinal lumen P. mamillana less significant

Family Hymenolepididae

H. carioca H. diminuta H. nanadwarf

tapeworm1. 3-8 cm 2-6 cm 7-80 cm

2. 500 segments

500 segments Few segments

3. testes lie across the segment

Testes are ovoid

Testes lie in line and separated by the ovary

LIFE CYCLE:eggonchospherecysticercoid in IHadult

Family Taeniidae Morphology 1. large tapeworm 2. proglottids are rectangular 3. rostellum may or may not be present 4. segments are longer and broader 5. uterus has median stem and lateral branches 6. egg capsule is easily lost and the embryo pore is striated in appearnace

Intermediate Stage

Intermediate host

Taenia solium Cysticercus cellulosae

pig

Taenia saginata Cysticercus bovis

cattle

Taenia hydatigena

Cysticercus tenuicollis

Sheep, ruminants

Taenia pisiformis Cysticercus pisiformis

rabbits

Taenia taeniaformis

Cysticercus fasciolaris

rodents

Taenia multiceps Coenurus cerebralis

Sheep And goat

Taenia saginata Taenia solium

Host is man man

Rostellum is absent Present armed with hooks

1000-2000 segments 800- 1000 segments

Ovary is bilobed trilobed

Oval egg Spherical

Uterus has 14-32 branches

16 branches

Taenia solium

Life cycle:egg ( hatch after being ingested)Onchosphere ( migrates in different organs and tissues)Cysticercus ( infective stage in the pork )Adult ( ingestion of infected ham and pork )

Man gets infection by the ff: ways 1. ingestion of pork containing cysticercus 2. ingestion of eggs through the food and cysticercus develops in man 3. by autoinfection due to retrosperistaltic movement. The eggs return to the stomach and hatch

Predisposing factors: 1. eating habits of people 2. large scale implementation of insewcticide

Pathogenesis: Man 1. utilize the nutrition of the host 2. causes enteritis 3. neurocysticercosis Pig 1. measly pork- presence of cysticerci in different organs or tissue

Clinical signs: Man Neurocysticercosis 1. diarrhea 1. encephalitis and meningitis 2. abdominal pain 2. epileptic fit and excitement 3. vomiting 4. flatulence

Taenia multiceps

Life cycle:eggOnchosphereCoenurus ( infective stage in the brain of sheep and goat )Adult

Pathogenesis:Migratory onchospheres care dangerous in the sheep. This causes meningitis and encephalitis Gradually the cyst creates pressure in the brain as per the advancement of development of cyst. The brain muscles get atrophiedThe skull gets atrophied and ultimately maybe soft and easily felt when touchingAside from brain several nerves are also affected ( ocular, auditory )

Clinical signs: 1. the animal looses the condition and fails to respond to the environment 2. circling movement ( gid ) is an important sign 3. sometimes the animals move in straight and keep its head on the hard surface

Genus Echinicoccus E. granulosus E. vogeli E. multilocularis E. oligarthus

Morphology: 1. very small only few segments are present 2. terminal segment is the gravid segment 3. scolex has the rostellum which is armed with hooks 4. ovary is kidney shaped

Life cycle: egg onchosphere hydatid cyst in IH adult

Pathogenesis: 1. enteritis 2. pressure atrophy in the vital organs due to pressure of large- sized cyst 3. functional disturbance

Diagnosis: 1. examination of feces 2. detection of cysticercus in the tongue and other palpable areas 3. Casonis Test- hydatid fluid is inoculated in the suspected

individual and there would be hypersensitive reaction within 15 mins or less in positive cases

Family Mesocestoididae:Genus Mesocestoides M. lineatus M. jonesiM. variabilisM. tenuis

Morphology: 1. head or scolex is devoid of rostellum and hooks 2. presence of single set of reproductive system 3. genital pore is dorsally situated 4. bilobed ovary and vitelline glands 5. testes are situated on either side of the excretory canal

DH- dog, fox, catIH- 1st – mites 2nd - birds

Developmental stages:eggonchospherecysticercoid in IHtetrathyridium in birds, lizards, snakesadult

*M. corti can asexually multiply in the IH and DH

Pathogenesis: 1. enteritis 2. nervous disorder 3. anal priritus

Genus DiphyllobothriumSpecies: D. latum D. mansonoides

Morphology: 1. long and maybe reaching up to several meters 2. thousands of segments are presents 3. head is spatula shaped with a deep groove in the middle called bothria 4. no rostellum 5. genital organs are situated mid-ventrally 6. eggs are oval and operculated and have fair resemblance to trematodes 7. ovary is bilobed and uterus is rosette-shaped

Life cycle:EggCiliated coracidiumProcercoid (cyclops)Plerocercoid (fish)Adult

Pathogenesis 1. enteritis 2. anemia ( B12 def. or Pernicious anemia ) 3. anal pruritus 4. epileptic fit

NEMATODE

General morphology of nematode

1. are cylindrical in outline2. outer covering is the cuticle. The cuticle is formed by

a. hypodermisb. muscle layer

The cuticle not only acts as outer covering but also has significance in performing many roles in functional activity.3. The cuticle of the parasite may be expanded at the

anterior part of the parasite which is called as the cervical alae.

4. Cuticle may be expanded at the posterior part of the of the nematode which is called the caudal alae.

5. At the anterior part of the body, cuticle may form cervical papillae.

6. Cuticle may form the pre-cloacal and post cloacal papillae.

7. Cuticle from different types of thickenings which have got taxonomic importance. In Gongylonema there are many cuticular thickenings. In the Acuaria and Dispharynx there are presence of cordons which are recurring or non-recurring types. In some nematodes cuticles forms some ridges or in others, forms epaulletes ( Stephanurus ) or dentigerous structures. In some nematodes there may be formation of leaf crown ( Strongylus) or cutting plates or teeth (Ancylostoma). The cuticle also forms one important structure which is called bursa which is the posterior expansion of the cuticle (Haemonchus). Spicule is another structure formed by the cuticle. Some sensory organs are also formed by the cuticle, like phasmid (present in the posterior part of the nematode) and amphids (present in the anterior part of the nematode)

8. Moderately digestive system is found in the nematodes. The digestive system starts in the mouth. The mouth may be surrounded by lips. Structure and arrangements of lips varied.

9. Other structures found in the digestive system are pharynx, oesophagus, intestines, anus etc. Esophagus is very important in respect of taxonomic identification. The different types are:

Bulbus- presence of posterior bulb ( eg. Heterakis gallinarum). Some roundworms is double bulbed ( Oxyuroids) Rhabditiform- shows anterior pyriform and posterior bulbous appearance ( Strongyloides ) Ventriculus- anterior part of the esophagus is muscular and posterior part of the same is glandular (all spirurid worm ) Filariform- esophagus is tubular ( filarial worm) Trichuroid- esophagus is composed of cells arranged in a row ( Trichinella spp)10. Flame cells are absent. In most nematodes excretion is

performed by a ventral pore and a pair of lateral longitudinal vessels

11. The nervous system includes oesophageal nerve ring, nerve ganglia, nerve fibers connecting nerve ganglia, sense organs (phasmids, amphids, cervical papillae and genital papillae )

General biological development of nematodes 1. The eggs are expelled out. The eggs do not hatch in the

environment. Within the eggs the larvae develop. The larvae hatch after being ingested by the host. ( Ascarid worm)

2. The eggs are expelled out of the host and the eggs hatch in the presence of different environmental factors. The larvae develop to a certain limit to reach to the infective stage. Final host gets the infection by ingestion of infective larvae ( Strongyle )

3. The eggs are expelled out of the host and the eggs when these eggs are ingested by the intermediate hosts. In the Intermediate host the larvae reached to the infective stage. (Spiruroidea )

4. The eggs are hatched and the larvae developed to the infective stage after being ingested by the intermediate host. ( Metastrongyloidea)

5. The worms are viviparous and the larvae mix up in the blood or lymph of the host. These larvae reach to the infective stage in the IH (Filarid worms )

FAMILY ASCARIDIDAE Characteristics:

1. Three lips are present. One dorsal and two subventral. Each lips bears two papillae.

2. In between the lips there maybe small intermediate lips which are called interlabia.

3. Teeth or cutting plates are absent4. Pharynx and oesophageal bulb are absent.5. Usually two spicules are present. Bursa is absent.6. Eggs are typically round or subglobular and outer

wall is pitted.

Genus Ascaris Ascaris suum Host- pig Site/location- small intestine Developmental stages: Eggs are expelled out. Larvae developed within the egg shell. Second larvae (L2) within the egg shell are the infective stage. The host gets the infection by ingestion of the infective eggs. Hatching occurs in the intestine and the larvae reach the liver either by active penetration by active penetration via peritoneal cavity or hepatoportal circulation. The larvae are transported to heart and then to lungs where these are found as 3rd larvae. Then the larvae follow the tracheal migration. The larvae are coughed up and develop to the fourth stage in the intestine and to adult stage subsequently.

Pathogenesis:1. Migration of larvae causes hemorrhagic lesions in

liver and creates a “milk spot” appearance.2. The migrating larvae also creates lesions in the

bronchiole and alveoli which results in pneumonia

Genus Toxocara Species: T. canis- dangerous to the puppies T. cati

T. vitolorum- causes calf-hood mortality in buffaloes in India

Toxocara canis ( also known as Arrow-headed worm or arrow worm) Life cycle: Egg> larva 1 in the egg shell> larva 2 in the egg shell (infective stage)> larva 3>larva 4 >adult

Routes of Infection a. oral infection or ingestion of infective stage of eggs i. tracheal route of migration -when the pups are below 3 months of age, the tracheal route of migration occurs. After ingestion of the eggs, hatching occurs due to the presence of different biochemical factors present in the host. The larvae come out and start migration. The larvae penetrate into the wall of the intestine and enter into the general circulation. By the hepatoportal circulation the larvae are transported to the liver and it penetrates the liver capsule. Then the larvae are transported to the lungs through the pulmonary circulation. The larvae are found first in the lower lung and then migrate to the upper part of the respiratory tract. They reach the bronchi, trachea etc. In the lung one moulting occurs and the second stage larvae are transformed into the third stage larvae. Then the larvae reached the GI tract when the cough containing the larvae is ingested and the larvae developed furthewr to become adult.

ii. somatic route of migration -occurs when the dog is pregnant. The larvae migrate to different organs and remain in dormant stage. The activity and mobility are seized. The reason of this dormancy is not clearly but it is supposed to be due to the alternation of hormonal status of the blood during pregnancy stage.After about 1.5 months of the infection the larvae mobilize from the dormant stage and reach the general circulation. Through the blood the larvae enter the different organs of the fetus. In the liver of the fetus the larvae perform one month moulting again. In this way the transuterine or congenital infection occurs.

b. transuterine infection (congenital infection)c. Transmammary infection ( lactogenic infection) -the offspring gets the infection when it sucks the colostrums from its mother. Through the colostrums the larvae enter the GI tract and they directly develop into the adult stage.

d. Paratenic host transmission - rodents acts as the paratenic host for transmission of the parasite.

Pathogenesis and clinical signs:1. hepatic damage due to migrating larvae2. alveolar destruction3. pneumonia ( ascarid pneumonia)4. vomiting5. pendulous pot bellied abdomen

Visceral Larva Mirgrans (VLM) This occurs in children due to migration of ascarid larvae in the different vital organs of the abnormal host ( means not the

definitive host which is the dog). The habit of dirt eating predispose to this condition. Mainly the liver is affected but some organs maybe affected too. Eosinophilia occurs in the organs affected. It is caused by Toxocara canis, T. cati, T. leonine , Capillaria hepatica and Lagochilascaris minor.

Family Oxyuridae: -whip like, non-bursate nematodes.

Genus Oxyuris Oxyuris equi ( pin worm or seat worm of horses) -causes rat tailed appearance due to the irritation caused by the crawling female worms in the anus

Life cycle: The female parasites crawl out of the anus and lay a number of eggs. Wirthin the eggs the larvae develop. The eggs fall on the ground and the host gets the infection by ingestion of the eggs along with the feed materials. After ingestion the eggs hatch and the larvae come out of the egg. The larvae develop to the adult stage in the intestine.( egg>larva1 in the egg shell>larva2 in the egg shell (infective stage)>larva3>larva4>adult)

Family Heterakidae Genus Ascaridia Ascaridia galli -non-bursate nematode of birds. The incidence or the manifestation of this parasitic infection does not apparently cause significant damage to the host

Life cycle: The eggs are expelled out of the host. In the environment the eggs develop to reach to the infective stage (L2). The birds get the infection when the eggs are ingested along with the food material. After ingestion the eggs hatch and the larvae come out and develop to adulthood. No migration occurs.

Genus Heterakis Heterakis gallinarum Life cycle: The eggs are expelled out the host .The eggs develop in the environment. Within the eggs, the second stage larvae are formed. The second stage larva within the shell is the infect5ive stage. The birds gert the infection when the eggs are ingested. After ingestion the eggs hatch and the larvae come out. The larvae develop very simply in the GI tract. No migration of the larvae occurs

Genus Subulura Subulura brumpti- pinmorm of fowl

Heterakis gallinarum Ascaridia galli1. occurs in the ceca of fowl

1. occurs in the small intestine

2. oesophagus has strong posterior bulb

2. oesophagus has no posterior bulb

3. earth worm may act as the transport host

3. there is no evidence of transport host

4. The eggs of Heterakis gallinarum transmit Histomonas melagridis

4. does not transmit any protozoan parasite

Family Strongyloididae Strongyloides spp discovered by Bavay in the year 1876Species: S.papillosus- Si of sheep, goat, cattle S. cati- cat S. westeri- pigs and horse S. ransomi- pigs S. stercoralis human being

Disease/pathological condition caused- Strongyloidosis, Foot rot, Larva migrans, Larva currens

Salient morphology:1. parasites show free living and parasitic life cycle2. oesophagus is rhabditiform in free living generation

and filariform in parasitic generation.3. the adult parasite has noticeably long esophagus4. the female worm is parthenogenetic

Life cycle: a. Homogonic

The eggs are expelled out of the host and hatch and larvae come out. The larvae reach the infective stage. The final host get the infection by skin penetration or orally. The larvae get entry into the blood circulation and transported to the lungs. They penetrate the lung alveoli and gradually ascend up the respiratory tract. Then they dome down to the esophagus and finally reach the intestine.

b. Heterogonic The eggs are expelled out of the host and hatch in the environment and larvae cone out. The larvae directly develop to adult male and female. This free living male and female parasite copulate and the gravid female lay the eggs. The eggs hatch in the environment and the larvae come out. The larvae directly develop to become infective stage parasite. The final host gets the infection by skin penetration performed by the infective larvae or by ingestion. Further development occurs as that mentioned in homogenic life cycle.

Pathogenesis: The larvae cause formation of lesion when they penetrate the skin. Foot rot condition is commonly found in the sheep and goat. The cutaneous lesion is called larva migrans. The lesions are circular or straight in appearance as linear urticarial lesion called as larva currens

Control: Biological control is applied by nematode-trapping fungi, Arthrobotrys oligospora

Family Trichuridae: Salient morphology:

1. appearance is like a whip2. parasite is slender anteriorly and thick posteriorly3. the anterior part contains the GI tract and the

posterior part contains the reproductive system4. The posterior end of the male parasite is slightly

spiral and one spicule is protruded out of the hind end. The spicule remains within a spicule sheath.

*guys kindly check your manual regarding this, sorry coz I consulted a picture regarding the parts of trichuris and it showed that the posterior part bears the whip.. *Life cycle: The host gets the infection by ingestion of infective stage of eggs. After hatching the larva comes out and then the parasite reaches the adult stage after several moultings.

Capillaridae: -known as hair worms -egg barrel shaped and with sides nearly parallel and with polar plugs.

Family Trichinellidae: Morphology

1. spicules are absent2. the parasite is posteriorly thicker than the anterior

part. 3. the male parasite has two lateral flaps on either

side at the posterior end.

Life cycle: The seat of predilection site of the parasite is small intestine. After copulation the male parasite dies and the female parasite burrows the wall of the intestine. During this activity the larvae get entrance in the blood circulation via lymphatic vessel and the larvae enter the different musculatures like subcostal muscles, tongue and diaphragm. The affected muscle is called nurse cell. The larvae get maturity in the striated muscle fiber and the larvae remain there forming a coil. The whole coil remains encapsulated. The final host gets infection by ingestion of the muscles containing the larva. ( egg>L1 the infective stage>L2>L3>L4 >adult)

PICTURES1. Trichuris trichura a. female, b. male

ova of Toxocara canis

Ova of Toxocara cati

Ova of capillaria

ova of trichuris

Trichinella spiralis larva

Trichuris trichiura male and female