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Gastrointestinal ParasitesThe Practice Guide to Accurate Diagnosis and Treatment

Supplement to Compendium: Continuing Education for VeterinariansTM

Volume 28 Number 8(A)August 2006

Gastrointestinal Parasites: The Practice Guide to Accurate Diagnosis and Treatment

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Gastrointestinal Parasites: The Practice Guide to Accurate Diagnosis and Treatment 3Michael W. Dryden, Patricia A. Payne, Robert K. Ridley, and Victorene E. Smith

Standard Centrifugation Fecal Examination: A Step-by-Step Guide 14Commentary: A Strategic Approach to Diagnosing and Treating Gastrointestinal Parasites 15Byron L. Blagburn, MS, PhD

Sponsored by educational grants fromBayer and IDEXX Laboratories

Copyright © 2006Veterinary Learning Systems

780 Township Line RoadYardley, PA 19067

This supplement is adapted from articles originally published inVeterinary Therapeutics: Research in Applied Veterinary Medicine®

T o ensure the health and well-being of petdogs and cats, coprologic examinationsfor parasite eggs, oocysts, and cysts are an

important part of the daily routine for mostveterinary practices. Although a fecal examina-tion is considered a routine procedure in manyclinics, it has been our experience that oftenlittle thought is given to performing the proce-dure correctly.

Many different procedures and techniquesare used, each with its own advantages andlimitations. For example, direct fecal smearsare useful for detecting motile protozoa,whereas sedimentation examinations are moresuitable for recovering heavy (e.g., Physalopteraspp) or operculated (e.g., fluke) eggs that donot float well because of the hypertonic effectsexerted by the flotation solution. However, themethods used most frequently to recover para-site eggs, oocysts, and cysts are flotation tech-niques, which rely on the differences in thespecific gravity (SG) of the egg(s), fecal debris,and flotation solution.

For parasite eggs to float, the SG of the flota-tion solution must be greater than that of theeggs. Flotation solutions are made by adding ameasured amount of salt or sugar to a specificamount of water to produce a solution with thedesired SG (see box, right); such solutions areeffective, easy to make or commercially avail-able, and relatively inexpensive. It is importantto ensure that the flotation solution used has theproper SG, which is best accomplished by usinga hydrometer calibrated to measure in thedesired range. Hydrometers used to measureurine SG do not cover the required SG rangeneeded for fecal examinations.

Flotation procedures vary from the simple tothe complex. The simplest procedure involves

mixing a small amount of feces with flotationsolution in a cylinder (shell vial or centrifugetube) and adding solution until the cylinder isnearly full. The preparation is then allowed to stand until the eggs float to the top, and asample from the top is removed to a micro-scope slide using a toolsuch as a wire loop, straw,needle hub, or glass rod. Arefinement of this methodinvolves filling the cylin-der until a slight positivemeniscus is formed andplacing a glass coverslipover it. Again, the cylinderis allowed to stand untilthe eggs have had time tofloat to the top, and thecoverslip is then removedto a microscope slide andexamined. A further re-finement of the flotationtechnique uses a cen-trifuge to spin down thedebris and accelerate themovement of eggs to thesurface of the solutionwhere they can be recov-ered. Veterinary hospitalsusually use one or moreof these methods basedon cost, ease of use, avail-ability of hardware, orsimply tradition.

Although coprologicexaminations should beperformed by veterinari-ans or trained veterinary technicians, the assign-ment is commonly given to the newest staff

Suppl Compend Contin Educ Vet • Vol. 28, No. 8(A), 2006

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Gastrointestinal ParasitesThe Practice Guide to Accurate Diagnosis and TreatmentMichael W. Dryden, DVM, PhDPatricia A. Payne, DVM, PhDRobert K. Ridley, DVM, PhD Victorene E. Smith, RVT

Department of Diagnostic Medicine/PathobiologyCollege of Veterinary MedicineKansas State UniversityManhattan, Kansas

Flotation Solutions for Helminth Ovaa

Magnesium Sulfate (MgSO4; SG 1.20)450 g MgSO4

1,000 ml tap water

Zinc Sulfate (ZnSO4; SG 1.18–1.20)331 g ZnSO4

1,000 ml warm tap water

Sodium Nitrate Solution (NaNO3; SG 1.18–1.20)338 g NaNO3

1,000 ml tap water

Saturated Salt (NaCl; SG 1.18–1.20)350 g NaCl1,000 ml tap water

Modified Sheather’s Solution (SG 1.27)454 g granulated sugar355 ml tap water6 ml formaldehyde

Dissolve sugar and water in the top of a double boiler or with gentle heat. Ifsolution is not clear, filter it through coarsefilter paper.aCheck specific gravity (SG) with a hydrometer that hasa range compatible with the solution being tested.Hydrometers with ranges of 1.000–1.400 are available.

member, often with very little instruction oremphasis on the importance of the task provided.Accurate evaluation of fecal samples is importantand must be taken seriously by all members of theclinical practice. Not only is pet health at stake,but several of the parasites that may be recoveredand identified are potentially zoonotic, such

as Toxocara canis, Toxocaracati, Ancylostoma caninum,Giardia spp, Cryptosporid-ium parvum, and Toxoplas-ma gondii.

Giardiasis in particularis a diagnostic dilemma.We agree that Giardia isone of the most common-ly misdiagnosed, under-diagnosed, and overdiag-nosed parasites. Based onthe numerous phone callsand emails we receive, werealize that many veteri-nary practices find itdifficult to diagnose giar-diasis using fecal examina-tions. Many pseudopara-sites such as yeasts (Figure1), plant remnants, anddebris have been mistakenfor these tiny organisms.Identification of Giardiacysts is further compro-mised because microscopesused in private practice areoften not equipped withmicrometers that can allowmeasurement of cysts thatare as small as 8 to 12 × 7to 10 µm (Figure 2). Cystsare shed intermittently,and repeated fecal analysesmay be needed beforecysts are recovered in asample.1,2 Giardia cysts aredelicate and deterioraterapidly in fecal flotationsolutions; if a flotationsolution other than zincsulfate (ZnSO4) is used,the cysts may be distorted(Figure 3). In many clin-ics, the only techniqueused to detect Giardia isthe direct smear, but thetrophozoites are fragile and

are often found only in very fresh, diarrheic feces.Finally, because of the difficulty in detectingGiardia spp, veterinarians have told us that theyoften rely on a patient’s response to metronida-zole treatment as a presumptive diagnosis.

This article describes the findings of tworecent studies: (1) an evaluation of the efficacyof various fecal flotation methods and solu-tions in detecting common helminth eggsfrom canine feces3 and (2) a separate investiga-tion of methods to recover Giardia cysts,including the SNAP Giardia Test Kit (IdexxLaboratories) and a centrifugation fecal flota-tion technique using ZnSO4 and Sheather’ssugar solution.4 An illustrated step-by-stepguide provides detailed recommendations forperforming routine parasite diagnostic proce-dures in the clinical setting.

n LABORATORY EVALUATION OFCOMMON FECAL FLOTATIONTECHNIQUESTrials were conducted to evaluate and com-

pare the ability of different flotation tech-niques and solutions to recover commonhelminth eggs from canine feces. Unless statedotherwise, fecal samples used in these studieswere prepared by collecting feces from each ofthree dogs known to have mixed infections ofT. canis, A. caninum, and Trichuris vulpis; thesamples were thoroughly combined and repli-cate 2-g samples weighed out. Swing-head cen-trifugations were performed as illustrated inthe step-by-step guide on page 14, and all cen-trifugations were done at 280 ×g.

Role of Specific GravityThe first series of experiments compared the

ability of the 15-minute Ovassay (Synbiotics)and the 5-minute swing-head centrifugationtechnique to recover T. canis, A. caninum, andT. vulpis. The Ovassay was performed usingZnSO4 solutions with SGs of 1.1 and 1.2; thecentrifugation method used the same ZnSO4

solutions as well as a sugar solution with an SGof 1.2.

Hookworm (A. caninum) eggs (SG 1.05595)readily floated using the Ovassay method and1.1-SG ZnSO4 solution, but only one ascarid(T. canis) egg (SG 1.0900) and no whipworm(T. vulpis) eggs (SG 1.1453) were recovered.When the SG of the ZnSO4 solution was raisedto 1.2, T. vulpis and T. canis eggs were recoveredwith the Ovassay, albeit in fewer numbers thanwith the centrifugation method using either


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FIGURE 1. Yeasts (12–15 µm) recovered in afecal examination and incorrectly identified asGiardia cysts in a referring veterinary practice.

FIGURE 2. Giardia cysts stained with Lugol’siodine recovered using 1.18-SG ZnSO4 in aswing-head centrifuge.

FIGURE 3. Giardia cysts recovered using 1.27-SG Sheather’s sugar solution in a swing-headcentrifuge.

ZnSO4 or sugar. For all three parasites, the cen-trifugation method exhibited significantlyhigher fecal counts compared with the Ovassaymethod (Table 1). For A. caninum, no differ-ences were found between the 1.2-SG ZnSO4

and sugar solutions using the centrifugationmethod. Significantly higher T. vulpis eggcounts were obtained from the sugar solutionthan the zinc solution. In addition, both T.vulpis and T. canis fecal egg counts were signif-icantly higher when the SG of the solution was1.2 compared with 1.1.

Simple Flotation versus Swing-Head Centrifugation

The second set of experiments compared thenumber of eggs recovered using NaNO3 andsugar solutions in the simple flotation andswing-head centrifugation techniques. For thesimple flotation, a small amount of feces wasplaced in a centrifuge tube, flotation solutionwas added and mixed thoroughly, and thepreparation was allowed to stand for 5, 10, 15,or 20 minutes while the eggs rose to the surface.To ensure consistency, 15-ml polystyrene cen-trifuge tubes (product no. 889-205004, OxfordLabware, St. Louis) were used for both tech-niques. The SG of the NaNO3 solution was

adjusted to 1.2 and that of Sheather’s sugar solu-tion to 1.27; SGs were confirmed with ahydrometer. Forty-eight 2-g fecal samples wereevaluated.

For all three parasites, the centrifugationmethod using 1.27-SG Sheather’s sugar solu-tion resulted in significantly higher fecal eggcounts than the simple standing flotationmethod, regardless of the time interval (Table2). No significant differences in fecal eggcounts were shown between the time intervalswithin the simple flotation method.

For A. caninum, the centrifugationmethod using 1.2-SG NaNO3 solution result-ed in significantly higher fecal egg countsthan the simple flotation method with a 5- or10-minute stand time (Table 3); when thestand time was increased to 15 and 20 min-utes, the simple flotation method and cen-


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Accurate evaluation of fecal samples isimportant and must be taken seriously by all members of the clinical practice.

TABLE 1. Comparison of the Mean Counts of A. caninum, T. vulpis, and T. canis Eggs Recovered from Three 2-g FecalSamples Using the Ovassay and Centrifugation Methods in ZnSO4 (SG 1.1 and 1.2) or Sugar (SG 1.2)

Ovassay Centrifugation Ovassay Centrifugation CentrifugationParasite (ZnSO4; SG 1.1) (ZnSO4; SG 1.1) (ZnSO4; SG 1.2) (ZnSO4; SG 1.2) (Sugar; SG 1.2)

A. caninum 680a 1,365b 782a 1,475b 1,598b

T. vulpis 0a 0a 2.7b 7.3c 11.6d

T. canis 0.3a 1a 46.7b 147.7c 158.3c

a,b,c,dWithin each row, different letters indicate a statistically significant difference (P < .05).

TABLE 2. Comparison of 5-Minute Swing-Head Centrifugation and 5-, 10-, 15-, and 20-Minute Simple StandingFlotations for Recovering A. caninum, T. vulpis, and T. canis Eggs Using 1.27-SG Sheather’s Sugar Solution (Mean Egg Counts from Three 2-g Fecal Samples)

5-Min Swing-Head Simple Standing Flotation

Parasite Centrifugation 5-Min 10-Min 15-Min 20-Min

A. caninum 52.3a 1.7b 2.7b 5.3b 5.3b

T. vulpis 9a 0.7b,* 0.7b,* 1.7b 1.7b

T. canis 293.3a 22.3b 17.3b 20b 21b

a,bWithin each row, different letters indicate a statistically significant difference (P < .05).*Two of the three samples tested were negative for Trichuris sp.

trifugation method recovered significantlysimilar numbers of eggs. Relatively few T.vulpis eggs were retrieved using any of themethods, but the 5- and 10-minute simplefloats missed eggs in two of three samples.Centrifugation recovered significantly moreT. canis eggs than any of the flotation meth-ods (Table 3).

Evaluation of Time to Examination A third series of experiments evaluated

whether more parasite eggs could be recov-ered if tubes were allowed to sit undisturbedfor 10 minutes after samples were cen-trifuged. Fecal samples were mixed with 1.20-SG NaNO3 and centrifuged. Coverslips were

removed and examined either immediatelyafter the centrifuge stopped spinning or afterthe tubes sat undisturbed for an additional 10minutes.

A. caninum and T. canis fecal egg countswere significantly higher when samples wereallowed to sit for 10 minutes after being cen-trifuged (Table 4). The lack of a differencebetween the two methods in obtaining T.vulpis eggs is likely a reflection of the overalllow egg counts.

Comparison of Swing- and Fixed-Head Centrifugation Techniques

The fourth series of experiments comparedswing- and fixed-head centrifugation tech-niques. For the fixed-head centrifugation tech-nique, approximately 10 ml of flotation solution(sugar or NaNO3) was added to 2 g of feces, theslurry was mixed thoroughly, and more solutionwas added until the level in the tube was within1 cm from the top; the tube was then cen-trifuged at 280 ×g for 5 minutes. After beingcentrifuged, the tubes were placed vertically in atest tube rack, flotation solution was added untila slight positive meniscus formed, a coverslipwas placed, and the preparation was allowed tostand for 10 minutes before coverslips wereremoved to a glass slide and examined. Theswing-head method was performed as describedin the step-by-step guide.

In general, A. caninum fecal counts were notsignificantly different between the swing-headcentrifuge and the fixed-head method (Table 5).No significant differences were found betweencentrifuge types for T. canis fecal counts.

n STUDENT EVALUATION OF COMMONFECAL FLOTATION TECHNIQUESFor each of 5 years (2000–2004), second-

year veterinary students were given a short visu-al presentation on how to perform the directsmear, Ovassay, and swing-head centrifugationtechniques. For these procedures, students col-lected 5-g samples from cat and dog fecesknown to contain parasite eggs, and each sam-ple was tested using all three techniques.

For the direct smear, a small sample of feceswas placed on a glass slide and mixed with adrop or two of saline; the mixture was thenspread thinly over the slide (thin enough toread newsprint through it), and the slide wascovered with a glass coverslip. The Ovassay and


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Table 3. Comparison of 5-Minute Swing-Head Centrifugation and 5-, 10-, 15-, and 20-Minute Simple Standing Flotations forRecovering A. caninum, T. vulpis, and T. canis Eggs Using 1.20-SG NaNO3 (Mean Egg Counts from Three 2-g Fecal Samples)

5-Min Simple Standing FlotationSwing-Head

Parasite Centrifugation 5-Min 10-Min 15-Min 20-Min

A. caninum 23.7a 7.3c 13.7b,c 21.7a,b 19.3a,b

T. vulpis 2.3a 0.7a,* 0.7a,* 1.7a 2.0a

T. canis 262a 46.3b 53b 74.3b 76.7b

a,b,c Within each row, different letters indicate a statistically significant difference (P < .05).*Two of the three samples tested were negative for Trichuris sp.

Table 4. Comparison of Two Coverslip Examination Protocols:Immediate Removal and Examination versus Waiting 10 Minutes(Mean Egg Counts from Three 2-g Fecal Samples)*

ExaminationImmediate after Sample Sat

Parasite Examination for 10 Min

A. caninum 8.3a 24.0b

T. vulpis 3.7a 5.3a

T. canis 135.7a 262.7b

*Fecal samples were spun for 5 minutes in a swing-head centrifuge using 1.2-SG NaNo3 solution.a,bWithin each row, different letters indicate a statistically significant difference (P < .05).

centrifugation techniques were conductedusing 2-g fecal samples and Sheather’s sugarsolution with an SG of 1.23 to 1.27.

In total, students evaluated 206 fecal samplesknown to contain hookworm (A. caninum) eggs,171 samples known to contain ascarid (T. canisor T. cati) eggs, 203 samples known to containwhipworm (T. vulpis) eggs, 26 samples known tocontain tapeworm (Taenia spp) eggs, and 53samples known to contain coccidia (Isospora spp)oocysts. When all data were combined, the directsmear technique failed to detect hookworm eggs72.82% of the time, ascarid eggs 85.38% of thetime, whipworm eggs 92.61% of the time, tape-worm eggs 96.15% of the time, and coccidiaoocysts 94.34% of the time. The Ovassay andcentrifugation techniques yielded false-negativeresults 4.85% and 0.97% of the time, respective-ly, for hookworm eggs, 25.88% and 10.53% ofthe time for ascarid eggs, 32.02% and 4.93% ofthe time for whipworm eggs, 76.92% and11.54% for Taenia spp eggs, and 50.94% and5.66% of the time for Isospora oocysts (Table 6).

n VETERINARIAN AND VETERINARYTECHNICIAN EVALUATION OF COMMONFECAL FLOTATION TECHNIQUES Another demonstration of the superiority

of centrifugation as a flotation method to

detect parasites is provided by the results of astudy conducted during a “wet lab” at the 2005Central Veterinary Conference.4 Participants,which included veterinarians and registeredveterinary technicians, were given a fecal sam-ple from naturally parasitized dogs. The samplewas a pooled sample from several dogs andcontained eggs of A. caninum, Eucoleus boehmi,Taenia spp, T. canis, and T. vulpis; oocysts ofCystoisospora spp; and Giardia cysts.

Each participant collected two “quarter-sized” samples from the feces and evaluatedthem using the 15-minute Ovassay, the swing-head centrifugation technique, and the SnapGiardia Test Kit (Giardia findings are dis-cussed separately; see page 9). Participants weregiven a short lecture before the wet lab on howto conduct the various fecal examination tech-niques, provided written instructions, andshown color images of all parasite eggs,oocysts, and cysts that were in the fecal sample.


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We agree that Giardia is one of the mostcommonly misdiagnosed, underdiagnosed,and overdiagnosed parasites.

Table 5. Comparison of the Numbers of A. caninum and T. canis Eggs Recovered by Swing- and Fixed-Head CentrifugationMethods in 1.20-SG ZnSO4 or 1.27-SG Sheather’s Sugar Solution (Mean Egg Counts from Three 2-g Fecal Samples)

1.20-SG ZnSO4 1.27-SG Sheather’s Sugar Solution

Swing-Head Fixed-Head Swing-Head Fixed-HeadParasite Centrifuge Centrifuge Centrifuge Centrifuge

A. caninum 137.7a,b 111.7a 210.3b 176.3a,b

T. canis 35.3a 36.3a 49.3a 38.7a

a,bWithin each row, different letters indicate a statistically significant difference (P < .05).

Table 6. Combined Results of Student Evaluations

No. of Failure of Percentage of Samples

Known Direct Smear from Which >50 Eggs or

Positive to Detect False-Negative Results Oocysts/Slide Were Recovered

Parasite Samples Eggs/Oocysts Ovassay Centrifugation Ovassay Centrifugation

Hookworm (A. caninum) 206 72.82% 4.85% 0.97% 36.41% 74.76%Ascarid (T. canis or T. cati) 171 85.38% 25.88% 10.53% 1.18% 42.69%Whipworm (T. vulpis) 203 92.61% 32.02% 4.93% 2.96% 23.65%Tapeworm (Taenia spp) 26 96.15% 76.92% 11.54% 0.0% 15.38%Coccidia (Isospora sp) 53 94.34% 50.94% 5.66% 0.0% 33.96%

The participants were divided into two groups:

• Group 1 used 1.18-SG ZnSO4 for theflotation solution and added one drop ofLugol’s iodine to the slide before placingthe coverslip.

• Group 2 conducted fecal examinationsusing 1.27-SG Sheather’s sugar solution.

The data showed that centrifugation witheither 1.18-SG ZnSO4 or 1.27-SG Sheather’ssugar solution routinely recovered more eggs andoocysts than the passive Ovassay technique(Table 7). Not only did the centrifugation tech-nique recover more eggs and oocysts, but the par-ticipants recorded many more samples as positivewith this technique. Only once did the Ovassaytechnique recover all parasites in all samples; incontrast, only once did the centrifugation tech-nique fail to recover all parasites in all samples.Only two of 14 participants in Group 1 recoveredTaenia eggs using the centrifugation procedure,whereas all 13 participants in Group 2 recoveredTaenia eggs using the centrifugation technique.

Although ZnSO4 has been shown to be anefficient flotation solution and is often used inveterinary practices, findings from this studyhighlight a potential problem in using 1.18-SG ZnSO4, even in a centrifugation procedure.Whereas only two of 14 (14.29%) participantsusing the 1.18-SG ZnSO4 centrifugation pro-cedure correctly recorded that the sample waspositive for Taenia eggs, 100% of the partici-pants using the 1.27-SG Sheather’s sugar solu-tion recovered Taenia eggs from the same sam-ple. This result was not completely unexpectedbecause Taenia eggs have an average SG of1.2251.5 This indicates that veterinary prac-tices using 1.18-SG ZnSO4 as their flotationsolution are likely failing to identify some dogsinfected with Taenia tapeworms and possiblyother parasites that shed heavy eggs, such asPhysaloptera spp, which have eggs with an aver-age SG of 1.2376.5 Another investigation thatevaluated the SG of a fecal flotation solutionindicated that solutions with SGs of 1.22 to1.35 would be best for routine laboratory use.6


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Table 7. Veterinarian and Veterinary Technician Comparison of Ovassay and Centrifugation Techniques for Recovery ofParasite Eggs and Oocysts Using 1.18-SG ZnSO4 or 1.27-SG Sheather’s Sugar Solutiona

GROUP 1—ZnSO4 (n = 14)

Ovassay Centrifugation

PARASITES 0 1–10 11–50 >50 % Positive 0 1–10 11–50 >50 % Positive

T. canis 0 7 7 0 100.0 0 1 4 9 100.0

T. vulpis 2 9 3 0 85.71 0 2 8 4 100.0

A. caninum 1 12 1 0 92.86 0 4 7 4 100.0

Taenia spp 13 1 0 0 7.69 12 2 0 0 14.29

Eucoleus boehmi 10 4 0 0 28.57 0 9 5 0 100.0

Cystoisospora spp 10 4 0 0 28.57 0 6 8 0 100.0

GROUP 2—Sheather’s Sugar Solution (n = 13)

Ovassay Centrifugation

PARASITES 0 1–10 11–50 >50 % Positive 0 1–10 11–50 >50 % Positive

T. canis 3 5 5 0 76.92 0 0 4 9 100

T. vulpis 2 7 4 0 84.62 0 0 6 7 100

A. caninum 7 4 2 0 46.15 0 0 7 6 100

Taenia spp 5 8 0 0 61.54 0 3 10 0 100

Eucoleus boehmi 10 3 0 0 23.08 0 4 9 0 100

Cystoisospora spp 7 6 0 0 46.15 0 3 10 0 100aParticipants recorded the number of eggs recovered as 0, 1–10, 11–50, or >50 eggs/slide.

n DETECTING Giardia sppAs discussed, Giardia cysts are particularly

difficult to recover and identify. The cysts aresmall and fragile, and infected animals shed thecysts intermittently. Several studies have demon-strated that recovery of Giardia cysts can best beaccomplished using a 1.18-SG ZnSO4 centrifu-gation technique,1,2,7,8 but a single negative flota-tion using ZnSO4 and a swing-head centrifugedoes not necessarily rule out Giardia infection.In addition, even though this technique recoversand maintains the integrity of Giardia cystsmore consistently than passive flotation tech-niques, it does not alleviate the problem ofproper cyst identification. In our experience,many practices using the 1.18-SG ZnSO4 cen-trifugation technique still struggle with theaccurate identification of Giardia spp. Severalfecal antigen tests have been developed thatappear to have high sensitivity in detectingGiardia antigen in human feces; however, theydo not have the same level of sensitivity indetecting giardiasis in dogs and cats when com-pared with centrifugation using ZnSO4.2,7,9

Thus, we recently conducted several studiescomparing the Snap Giardia Test Kit (Figure 4)with the swing-head centrifugation techniqueusing 1.18-SG ZnSO4.

Veterinary Student EvaluationsDuring the fall of 2005, 107 second-year

veterinary students participated in an exerciseon recovering and identifying Giardia cysts.They had recently attended a lecture on giar-diasis, been given a short visual presentation onidentification of Giardia cysts, and had previ-ously conducted direct smears and fecal exam-inations using the swing-head centrifugationtechnique. The students were also given writ-ten instructions on how to use the SNAPGiardia Test Kit.

Fecal samples from 116 puppies were pro-vided by a local broker. Each fecal sample wasanalyzed via direct smear, centrifugation, andthe SNAP Giardia Test Kit. Samples and tech-niques were recorded as either positive or neg-ative. The direct smear was performed asdescribed previously, except that a drop ofLugol’s iodine was added to the slide before thecoverslip was placed.

Almost half (56 of 116) of the puppy fecalsamples were recorded as positive for Giardia.Only four direct-smear samples were identifiedas Giardia positive, although the data may beartificially low because the fecal samples were

collected several hoursbefore being tested andtrophozoites may havebeen dead at time ofexamination. Eleven sam-ples that were negative forGiardia using the ZnSO4

centrifugation techniquetested Giardia positiveusing the SNAP GiardiaTest Kit (Table 8). It is un-known how many of theseresults were true false-negatives on the ZnSO4

centrifugation techniqueor false-positives on theSNAP Giardia Test Kit.

Findings from theCentral VeterinaryConference Wet Lab

In addition to the wetlab evaluations discussedearlier, this study alsocompared the SNAPGiardia Test Kit with theOvassay and swing-headcentrifugation techniqueusing 1.18-SG ZnSO4

and 1.27-SG Sheather’s sugar solution. Eventhough the participants in the wet lab weretold the samples were positive for Giardiacysts, recovery and identification of Giardiacysts was problematic for the participantsregardless of flotation technique used. Onlysix of 27 participants were able to recover andidentify Giardia cysts from a known positivesample (Table 9): one participant each usingthe centrifugation technique with ZnSO4, theOvassay with ZnSO4, and the Ovassay with

Sheather’s sugar solution and three using thecentrifugation technique with Sheather’s sugarsolution. However, all 27 participantsobtained a positive result using the SNAPGiardia Test Kit.


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Figure 4. (A) SNAP Giardia Test Kit. (B) A positive result is shown on the leftand a negative result on the right.

B

A

Eleven samples that were negative forGiardia using the ZnSO4 centrifugationtechnique tested Giardia positive usingthe SNAP Giardia Test Kit.

n CLINICAL IMPLICATIONS In today’s litigious society, failure to detect a

light parasitic infection in a pet, regardless ofwhether treatment was initiated, could be signif-icant from a legal standpoint. Although lawsuitsresulting from ocular larva migrans have usuallyrevolved around failure to initiate appropriatedeworming procedures, inappropriate diagnos-tic methodology could be an issue.

Our results show that centrifugation consis-tently recovered more eggs than the other tech-niques, even when comparing a 5-minute cen-trifugation with a 20-minute simple flotation.Failure to ensure that a flotation solution hasthe proper SG could result in the practitionermissing a diagnosis of T. vulpis or T. canis, bothof which are pathogenic parasites in dogs.Solutions should be properly prepared follow-ing standard formulas (when using bulk sugaror salts) or specific label directions (whenhydrating commercial salt solutions). After the

solution has been prepared, it is recommendedthat the SG be checked with a hydrometercapable of measuring SGs in the desired range.Veterinarians might be well advised to reevalu-ate their fecal examination protocols or, at thevery least, to ensure their flotation solutions areformulated to attain an SG heavy enough toallow T. vulpis eggs to float. Spirurid (e.g.,Physaloptera spp; SG 1.23765) and tapeworm(e.g., Taenia spp; SG 1.2251) eggs are evenheavier and require an SG of 1.224 or greaterto effectively recover eggs from fecal samples.

Fecal flotation using a swing-head centrifugeand a 1.18-SG ZnSO4 flotation solution shouldbe adequate for the diagnosis of Giardia spp bytrained personnel,1,2,7 but because many clinicsdo not use centrifugation techniques and cystshedding is intermittent, it is often necessary toexamine several sequential daily samples toensure accuracy of diagnosis. In fact, it maytake three consecutive ZnSO4 fecal flotationsover a 7- to 10-day period to obtain an accuratediagnosis of Giardia spp using the centrifuga-tion flotation technique. Of course, this is oftenimpractical in private practice.

Furthermore, even though the ZnSO4 cen-trifugation procedure conducted by a well-trained technician has been considered the goldstandard for the diagnosis of Giardia spp indogs,1,2,7,8 participants in the Central VeterinaryConference wet lab using ZnSO4 as their flota-tion solution recorded 13 of 14 samples as cystnegative that were positive on the SNAPGiardia Test Kit and were unable to identifycysts even when told that the samples were def-initely positive for Giardia. Inability to recog-


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Table 8. Evaluation by Second-Year Veterinary Students of 1.18-SG ZnSO4 Centrifugation Fecal Flotations and SNAPGiardia Tests to Identify Giardia spp in Puppies

Giardia+ bySNAP+/ ZnSO4+/ SNAP+/ SNAP–/ Combined

Category SNAP+ ZnSO4+ ZnSO4 – SNAP– ZnSO4+ ZnSO4 – Methods

No. of samples in each 55 45 11 1 44 60 56category (total no. of samplestested = 116)

Percentage of samples 47.41 38.79 9.48 0.86 37.93 51.72 48.28in each category

Percentage of 56 samples 98.21 80.36 19.64 1.79 78.57recorded as Giardia positive identified as positive byeach specific procedure

Table 9. Number of Samples Identified as Giardia Positive byAttendees of the Central Veterinary Conference Wet Lab UsingOvassay and Centrifugation with 1.18-SG Zn SO4 or 1.27-SGSheather’s Sugar Solution or Using the SNAP Giardia Test Kit

No. of SamplesMethod Testing Positive

Centrifugation with ZnSo4 1Ovassay with ZnSo4 1Centrifugation with Sheather’s Sugar Solution 3Ovassay with Sheather’s Sugar Solution 1SNAP Giardia Test Kit 27

nize a few Giardia cysts is likely one of the prob-lems encountered by the veterinarians and vet-erinary technicians who participated in the wetlab. The sample did not contain numerousGiardia cysts, and the cysts are smaller thanother parasite eggs and oocysts in the sample. Aswe walked around the room to assist the partic-ipants, we observed cysts in almost every sampleprepared using either ZnSO4 or Sheather’s sugarsolution; many of the participants, however,were unable to recognize the small cysts.

Because cyst shedding is notoriously inter-mittent, the number of Giardia cysts recoveredon any given day is likely not a good indicatorof the level of infection. In a previous investi-gation, it was noted that dogs could havealmost a 10-fold change in the number of cystsrecovered on quantitative fecal examinationsconducted 3 days apart.2 In that study, thecysts/g of one control dog went from less than10 to 3,190 within 3 days. In another dog, thecyst/g count increased from 150 to 44,610within 3 days. The clinical implication of find-ing only a few Giardia cysts on fecal analysismay be no different from finding hundreds.Therefore, fecal examination from dogs or cats

suspected of having giardiasis requires carefulmicroscopic examination in case they are shed-ding low numbers of cysts.

If giardiasis is on the differential list of a dogor cat with diarrhea, the data indicate that con-ducting both ZnSO4 centrifugation fecalexamination and a SNAP Giardia Test Kit mayincrease the chances of recording a positivefinding. However, it must also be rememberedthat a single negative examination, even if bothtests are conducted simultaneously, does notnecessarily rule out giardiasis. Although usingthe proper Giardia cyst recovery technique isimportant, identification of recovered cysts iscritical. In the Central Veterinary Conferencewet lab, veterinarians and veterinary techni-cians had great difficulty identifying cysts evenwhen informed the samples were positive.Proper training of veterinarians and clinicalstaff to identify Giardia cysts is important andwould greatly improve diagnostic accuracy. Animportant point when using the SNAPGiardia Test Kit is that even a very slight colorchange indicates a positive test result.

The major question is, “What procedure orprocedures should be conducted for routine


11

Summary—What Every Practitioner Should Know about Diagnosing and Treating Gastrointestinal Parasites

Fecal examinations are important in diagnosing internal parasites in dogs and cats. As has been shown in the studies reportedhere, technique is critical:

• For most parasites, the swing-head centrifugation technique—including centrifuging the tube for 5 minutes and thenallowing it to stand for 10 minutes before removing the coverslip—is better able to recover eggs and oocysts than is a direct smear or simple flotation technique.

• Sheather’s sugar solution, with a specific gravity of 1.27, is the preferred flotation solution because it will float the heavierparasite eggs, such as Taenia spp.

• Some of the salt flotation solutions may be used as a practical alternative, but the specific gravity of any flotation solutionshould be confirmed with a hydrometer.

• In areas where Giardia is a concern, fecal examinations should also include the SNAP Giardia fecal antigen Test Kit.

• Once a diagnosis is confirmed, treatment with an appropriate dewormer is indicated. Several anthelmintics are effective forthe treatment of T. vulpis in dogs, such as febantel, milbemycin oxime, and fenbendazole, whereas Taenia spp infections canbe treated with praziquantel, epsiprantel, or fenbendazole. With three active ingredients with different modes of action andspectra of activity after a single dose, Drontal Plus (Bayer Animal Health) is an excellent broad-spectrum dewormer. DrontalPlus contains praziquantel to eliminate cestodes (tapeworms), pyrantel pamoate to eliminate hookworms and ascarids, andfebantel to eliminate nematode parasites, including whipworms.

• Metronidazole, fenbendazole, and the combination of praziquantel, pyrantel pamoate, and febantel are commonly used for thetreatment of giardiasis. We have found the combination of praziquantel, pyrantel pamoate, and febantel (5, 5, and 25 mg/kg,respectively; administered for 3 to 5 days) in Drontal Plus to be very effective for the treatment of giardiasis in dogs.

Because of the zoonotic potential of many internal parasites infecting cats and dogs, the importance of fecal examinationscannot be ignored. All personnel performing fecal examinations should be properly trained, and the attitude that “it’s just afecal” must be eradicated.

fecal examinations?” Data from the studies dis-cussed here3,4 suggest that the swing-head cen-trifugation technique using 1.27-SG Sheather’ssugar solution is an efficient method of recov-ering many commonly encountered parasiteeggs and oocysts. However, although the sugarsolution is effective for many eggs and oocysts,it distorts and/or destroys most Giardia cysts,often rendering them unrecognizable to mostveterinarians and technicians (Figure 3). Inaddition, currently used sugar solutions mustbe mixed on-site and some chemical (e.g., phe-nol, formalin) must be added to prevent bacte-rial growth; furthermore, sugar solutions aresticky and can attract flies and ants. Manypractices, therefore, use commercially availablesalt solutions for routine fecal examinations;however, as demonstrated in this investigation,a 1.18-SG ZnSO4 flotation solution may notbe able to float parasite eggs with a higher SG.

n TREATMENTOnce these updated diagnostic procedures

are implemented, it is anticipated that manypractices will see a marked increase in thenumber of positive fecal examinations. Certainparasites such as whipworms in dogs andTaenia spp tapeworms in dogs and cats willcertainly be diagnosed with much greater fre-quency, which will necessitate an increase inantiparasitic treatments and follow-up exami-nations. Several anthelmintics are currentlyapproved for treatment of T. vulpis in dogs,including Drontal Plus (Bayer Animal Health;praziquantel, pyrantel pamoate, and febantel),Interceptor (Novartis Animal Health; milbe-mycin oxime), Sentinel (Novartis Animal

Health; milbemycin oxime and lufenuron),and Panacur (Intervet; 3-day course of fenben-dazole). Because of the long prepatent period(70 to 90 days) of T. vulpis and tolerance ofimmature stages to anthelmintics, treatmentsshould be administered on days 0 and 3 andthen again at 4 weeks and 3 months.10 In ourexperience, clinical Trichuris infections are besttreated initially with either Drontal Plus or

Panacur. Many dogs will have shed numerousTrichuris eggs into their premises by the timethey are treated, and those eggs may remainviable for years. Therefore, placing these dogson long-term treatment/preventive therapywith a compound such as milbemycin oximemay be prudent. In addition, appropriate fecalexaminations as described previously should beconducted 1 and 3 months after treatment toevaluate initial success and then once or twiceannually to check for possible reinfection.

Taenia spp infections can be treated orallywith products containing praziquantel,epsiprantel, or fenbendazole. Dogs and catsacquire Taenia spp tapeworms after eatingmetacestode-infected prey or animal carcasses,and thus infections will likely recur unless petsare prohibited from hunting and scavenging.

A positive Giardia spp fecal antigen testresult necessitates an initial round of treatmenteven in asymptomatic dogs and cats. Althoughmost animal strains of Giardia spp are notinfective to immunocompetent human hosts,11

all cases in pets must be treated as potentiallyzoonotic. Currently, no drugs are approved by the FDA for treatment of giardiasis in dogsand cats. Metronidazole, fenbendazole, and the combination of praziquantel, pyrantelpamoate, and febantel are commonly used.Although metronidazole has historically beenthe most common extra-label treatment,reports of efficacy failures are common. Inaddition, metronidazole has other propertiesthat can be both positive and negative whentreating clinical diarrhea. Metronidazole iseffective against anaerobic infections, has anti-inflammatory properties, and is an effectivemedication for diarrhea associated with coli-tis.12 Therefore, metronidazole therapy oftenfirms up loose stools regardless of the cause ofthe diarrhea. Veterinarians often report to usthat they diagnose giardiasis based on a pre-sumptive identification of cysts or trophozoitesand rapid response (cessation of loose stools) tometronidazole therapy. Then, when they stopthe therapy, giardiasis (diarrhea) returns.Thinking that this indicates either treatmentfailure or recurrence of infection, they increasethe dose or frequency of administration.However, once therapy ceases, diarrhea mightrecur yet again. Many of the fecal samples sub-mitted to the Kansas State UniversityDiagnostic Parasitology Laboratory as Giardiasuspects are often heavily laden with variousyeasts but no Giardia cysts. Use of metronida-


12

Only six of 27 participants wereable to recover and identify Giardiacysts from a known positive sample.

zole may therefore lead to a misdiagnosis ofgiardiasis.

We recommend the use of fenbendazole (50mg/kg) or the combination of praziquantel,pyrantel pamoate, and febantel (5, 5, and 25mg/kg, respectively) for 3 to 5 days for thetreatment of giardiasis in dogs.2,13 It has alsobeen suggested that metronidazole (25 mg/kgbid) may be used in combination with fenben-dazole.11 Cats may be treated with either fen-bendazole (50 mg/kg sid) or metronidazole (25mg/kg bid) for 5 days.11 In addition, all dogsand cats in the household should be treated,and animals should be bathed after the lasttreatment to remove infective cysts from thehaircoat.

After treatment, fecal examinations and/orfecal antigen tests should be repeated to deter-mine the success of therapy. Persistently posi-tive fecal antigen test results can confoundevaluation of treatment success. Although pub-lished data are currently lacking, communica-tion with manufacturers and our experienceindicate that the SNAP Giardia Test Kit mayremain positive in some dogs for 1 to 3 weeksafter successful treatment.

n CONCLUSIONBecause of the inability of 1.18-SG ZnSO4

flotation solution to consistently recover heav-ier parasite eggs, it may be prudent for manyveterinary practices to conduct routine fecalexaminations using 1.27-SG Sheather’s sugarsolution and a centrifuge. Veterinary practicesshould also consider the routine use of ahydrometer so that the proper SG of theirflotation solution can be assured. If giardiasis isencountered in the practice area, fecal exami-nations should include an in-clinic Giardia sol-uble fecal antigen test, such as the SNAPGiardia Test Kit. The difficulty we noted in theability of veterinarians, veterinary technicians,and veterinary students to identify Giardiacysts in our studies is likely reflective of the sit-uation in many practices. Therefore, the SNAPGiardia Test Kit likely will improve a clinic’sability to arrive at a correct diagnosis. In addi-tion, the proper recovery and identification of

parasites should allow for a more targeted ther-apeutic approach.

n REFERENCES1. Zimmer JF, Burrington DB: Comparison of

four techniques of fecal examination for detect-ing canine giardiasis. JAAHA 22:161–167,1986.

2. Payne P, Dryden M, Ridley R, et al: Evaluationof the efficacy of Drontal Plus andGiardiaVax to eliminate cyst shedding in dogsnaturally infected with Giardia spp. JAVMA220(3):330–333, 2002.

3. Dryden MW, Payne PA, Ridley R, Smith V:Comparison of common fecal flotation tech-niques for the recovery of parasite eggs andoocysts. Vet Ther 6(1):15–28, 2005.

4. Dryden MW, Payne PA, Smith V: Accuratediagnosis of Giardia spp and proper fecal exam-ination procedures. Vet Ther 7(1):4–14, 2006.

5. David ED, Lindquist WD: Determination ofthe specific gravity of certain helminth eggsusing sucrose density gradient centrifugation. JParasitol 68:916–919, 1982.

6. O’Grady MR, Slocombe JOD: An investigationof variables in a fecal flotation technique. Can JComp Med 44:148–154, 1980.

7. Barr SC, Bowman DD, Hollis NE: Evaluationof two procedures for diagnosis of giardiasis indogs. Am J Vet Res 53:2028–2031, 1992.

8. Zajac AM, Johnson J, King SE: Evaluation ofthe importance of centrifugation as a compo-nent of zinc sulfate fecal flotation examinations.JAVMA 38:221–224, 2002.

9. Hopkins RM, Deplazes P, Meloni BP, et al: Afield and laboratory evaluation of a commercialELISA for the detection of Giardia coproanti-gens in humans and dogs. Trans R Soc Trop MedHyg 87(1):39–41, 1993.

10. Dryden MW, Gaafar SM: Whipworm infectionin small animals. Comp Anim Pract 2(5):1722,1988.

11. Companion Animal Parasite Council: Con-trolling Internal and External Parasites in Dogsand Cats: 2005 CAPC Guidelines. Available atwww.capcvet.org; accessed May 2006.

12. Drugs used in treatment of chronic colitis, inKahn CM (ed): The Merck Veterinary Manual,ed 9. Available at www.merckvetmanual.com;accessed May 2006.

13. Zajac AM, LaBranche TP, Donoghue AD, et al:Efficacy of fenbendazole in the treatment ofexperimental Giardia infection in dogs. Am JVet Res 59:61–63, 1998.


13

Standard Centrifugation Fecal Examination: A Step-by-Step Guide*

14

1 2

Mix 2 to 5 g of feces with approxi-mately 10 ml of flotation solution in adisposable cup until the consistency isuniform.

3

Strain the mixture.

4

Pour the strained mixture into a 15-mlcentrifuge tube.

5

Fill the tube with flotation solution toform a slight positive meniscus; do notoverfill the tube.

6

Place a coverslip on top of the tube.

8

Remove the tube and let it stand for10 minutes.

9

Lift the coverslip directly upward andplace on a glass microscope slide.Examine the entire area under thecoverslip at 10× magnification.†

*All images ©2006 Veterinary Learning Systems.†You may wish to use the 40× objective to confirm the diagnosis and make measurements; with practice, however, most parasites can beidentified at 10× magnification.

7

Put the tube in the centrifuge, makesure the centrifuge is balanced, andspin at 1,200 rpm (280 ×g) for 5 minutes.

Make sure all necessary equipment is onhand: Centrifuge, conical test tubes andrack, flotation solution, applicator sticks,disposable cup, strainer, and microscope.

As stated in this excellent article by Dryden and col-leagues, conducting fecal examinations accurately is amust in veterinary practice. Frequent and accurate fecal

examinations are necessary for several reasons:Gastrointestinal (GI) parasites remain common in dogsdespite the availability of many excellent broad-spectrumagents;1 certain GI parasites, such as Toxocara, Ancylostoma,Dipylidium, Giardia, Cryptosporidium, and Toxoplasma, areimportant zoonotic agents and may require the use of specif-ic parasite control products; and pet owners often do notadminister broad-spectrum agents regularly even wheninstructed to do so by veterinarians. Veterinarians and petowners may believe that fecal examinations are unnecessarybecause they think that well cared for pets are not exposed toparasites or they presume the animals are receiving heartwormor flea preventives that have additional broad-spectrum activ-ity against GI parasites. I agree with the authors’ admonitionthat failure to monitor parasite control strategies using appro-priate fecal examination procedures can result in potentiallyserious pet and human health issues.

Common fecal examination procedures used to diagnoseGI parasites include direct smear, sedimentation, simple flota-tion, centrifugal flotation, and fecal ELISA. Dryden et al pro-vide excellent overviews of the comparable performance andstrengths and weaknesses of each of these procedures. Theyalso include data from their clinical and teaching laboratoriesand conference “wet labs” to support their conclusions andrecommendations. Several points they raised are worthy ofcomment. Their results provide the clear message that cen-trifugal flotation is superior to either direct smear or simpleflotation when attempting to recover fecal stages of commonGI parasites. They demonstrated significantly increased ratesof recovery of roundworm, hookworm, whipworm, tape-worm, and Physaloptera ova when using centrifugation. Thesesame results were demonstrated in exercises conducted withveterinarians, veterinary technicians, and students. Results ofthe studies indicate that centrifugation can be performed withequal accuracy using either a swinging bucket or fixed-anglecentrifuge. I also have emphasized these points.2 Ova ofTrichuris vulpis and Taenia spp can be especially difficult to

recover by fecal flotationbecause of their densityand their intermittent orerratic passage in feces.Again, the data present-ed here support the useof centrifugation forgreater sensitivity whenexamining feces forthese parasites.

Giardia is a particu-larly problematic para-site for several reasons.Both trophozoites andcysts are sometimes dif-ficult to recover fromfeces, even in animalswith clinical giardiasis.While it is true thattrophozoites are morelikely to be observed indiarrheic feces and cystsin formed feces, I haveobserved exceptions tothis claim. Becausetrophozoites are boundby a single unit mem-brane, they are fragile and easily destroyed or damaged bydense flotation solutions. Thus, direct examination of feces(direct smear) may result in better recovery of trophozoites;however, direct smears are less sensitive than centrifugal flota-tion because of the small amount of feces examined. Cysts,on the other hand, may be difficult to detect because of inter-mittent passage in feces or because veterinarians or trainedstaff may not recognize them. The recent introduction of afecal ELISA for detection of a Giardia-specific protein infeces (SNAP Giardia Test Kit) has greatly improved our capa-bility to confirm or rule out giardiasis as a potential cause ofclinical diarrhea in dogs and cats. Initial data supporting sen-sitivity and specificity of the test are very encouraging. In the


15

Commentary

A Strategic Approach to Diagnosing and TreatingGastrointestinal ParasitesByron L. Blagburn, MS, PhDDepartment of PathobiologyCollege of Veterinary MedicineAuburn UniversityAuburn, Alabama

FIGURE 1. Iodine-stainedtrophozoite of Giardia sp from adirect smear.

FIGURE 2. Iodine-stained cyst ofGiardia sp from centrifugal flotationin zinc sulfate.

present publication, the authors provide convincing evidencethat a combination of centrifugal flotation using zinc sulfateand fecal ELISA greatly increases our likelihood of positivelyidentifying Giardia-positive samples. The use of zinc sulfateis suggested because it causes less distortion to Giardia organ-isms within cysts than does sucrose solution (Figure 1). I findthat using iodine to stain either direct smears or fecal flotationpreparations enhances the internal structure of both cysts andtrophozoites and helps to distinguish Giardia cysts from yeastsand plant remnants (Figure 2).

Dr. Dryden and colleagues discuss several broad-spectrumagents that are effective in treating and controlling GI para-sites. However, different strategies must be used dependingon the parasites recovered. Table 1 summarizes selecteddewormers with activities against ascarids, hookworms,whipworms, tapeworms, Giardia, and combinations thereof.Some are strategic dewormers; that is, they are used once toremove the target parasites and then at subsequent strategicintervals to eliminate migrating parasites or to maintain thehost free of parasites. Others are used monthly for heartwormprevention or flea control and also possess additional activityagainst certain GI parasites. I agree with the authors’ com-ments on the lack of approved products for treatment of giar-diasis and that treatment with metronidazole alone often has

limited success. I concur that efficacy can be improved byusing either fenbendazole or a combination of febantel,pyrantel pamoate, and praziquantel. Also, as Dryden and col-leagues mention, metronidazole may be used in combinationwith fenbendazole or febantel, pyrantel pamoate, and prazi-quantel to achieve enhanced efficacy against Giardia; thecombination of febantel, pyrantel pamoate, and praziquantelcould also prove efficacious against other parasites.

In summary, available data support centrifugal flotation asbeing the most reliable method of recovering ova and cysts ofGI parasites, including tapeworms and whipworms. Use ofcentrifugal flotation in combination with the Snap GiardiaTest Kit increases the likelihood of diagnosing Giardia infec-tions. Several broad-spectrum agents are available for thetreatment and control of major GI parasites. A combinationof febantel, pyrantel pamoate, and praziquantel is effectiveagainst Giardia as well as important nematode and cestodeparasites.

REFERENCES1. Blagburn BL, Lindsay DS, Vaughn JL, et al: Prevalence of canine

parasites based on fecal flotation. Compend Contin Educ Vet18:483–509, 1996.

2. Blagburn BL, Butler JM: Performing centrifugal fecal flotation.Vet Med, July 2006, in press.


16

Table 1. Summary of Selected Dewormers

Parasite Dewormer Regimen

Ascarids and/or hookworms Febantel/pyrantel pamoate/praziquantel Single dose; follow-up doses discretionaryPyrantel pamoate praziquantel (cats only) Single dose; follow-up doses discretionaryPyrantel pamoate Single dose; follow-up doses discretionaryFenbendazole Daily for 3 days; follow-up doses discretionaryMilbemycin oxime Single dose followed by monthly administrationa

Milbemycin oxime/lufenuron Single dose followed by monthly administrationa,b

Ivermectin/pyrantel pamoate Single dose followed by monthly administrationa

Selamectin (cats only) Single dose followed by monthly administrationa,b

Ascarids, hookworms, and Febantel/pyrantel pamoate/praziquantel Single dose; follow-up doses discretionarywhipworms; whipworms Fenbendazole Three daily doses; follow-up doses discretionaryonly; or combinations Milbemycin oxime Single dose followed by monthly administrationa

that include whipworms Milbemycin oxime/lufenuron Single dose followed by monthly administrationa,b

Ascarids, hookworms, Febantel/pyrantel pamoate/praziquantel Single dose; follow-up doses discretionarywhipworms, and tapeworms, or combinations that include whipworms and tapeworms

Ascarids, hookworms, Febantel/pyrantel pamoate/praziquantel Daily for 3–5 dayswhipworms, and tapeworms, or combinations that include GiardiaaMonthly administration necessary for effective heartworm prevention.bMonthly administration necessary for effective heartworm prevention and flea control.

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