Coccidiosis • rabbits:InA guide for the differential diagnosis of Eimeria species

Regional Station, Indian Veterinary Research Institute, Palampur, Himanchal Pradesh 176 061

K P Jithendran 1

Cocddiosis caused by different speciesof the protozoan parasite) Eimeria is one the most importantdiseases affecting all age groups and is a major cause of morbidity and mortality in rabbits. Incommercially reared rabbits) coccidiosisoccurs in subclinical form leading to growth retardation andalterred feed conversion.Studies on coccidiosisas a clinical entity has been well studied in rabbits butinformation on coccidial species and differential diagnosis is hardly attempted. The presentcommunication is an insight into the problem) the causative agent) diffirentical diagnosisand preventivemeasuresfor control of rabbit coccidiosis.

U ABBIT production has already.R.attained commercial status inmany parts of the world includingIndia and has the potential tobecome one of the major livestockspecies. This industry is picking upfor wool production in hilly areas ofHimachal Pradesh, Uttarakhand andJammu & Kashmir and lately inSikkim and Arunachal Pradesh and asa broiler industry in areas oftemperate and subtropical climate inWest Bengal, Asom, Manipur,Andhra Pradesh, Tamil Nadu, Keralaand Karnataka. In many tribal andbackward areas rabbits are blazing anew trail in the field of self-employment and picked up as cottageindustry by small and marginalfarmers. Among diseases of rabbits,coccidiosis caused by different speciesof the protozoan parasite, Eimeria isone of the most important diseasesaffecting all age groups and is amajor cause of morbidity andmortality In commercially rearedrabbits, coccidiosis occurs insubclinical form leading to growth

1 Present address: Principal Scientist, Centralinstitute of Brackishwater Aquaculture, 75Santhome High Road, Chennai, Tamilnadu

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retardation and altered feedconversion. Studies on coccidiosis asa clinical entity has been well studiedin rabbits but information oncoccidial species and differentialdiagnosis is hardly attempted. Thepresent communication is an insightinto the problem, the causative agent,

A German Angora rabbit

differential diagnosis and preventivemeasures for control of rabbitcoccidiosis.

The parasiteThe coccidia of the genus Eimeria

are members of the subphylumApicomplexa and the family

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Eimeriidae. Though more than 25species of Eimeria are reported tocause coccidiosis in rabbits, only 11species were isolated in pure cultureand are well characterised withoutambiguity. These species are E. stiedai,E. perforans, E. media, E. magna, E.irresidua, E. intestinalis, E. exigua, E.vejdovskyi) E. coecicola, E. flavescens andE. piriformis) listed in the order inwhich they parasitize thegastrointestinal (GI) tract, the firstone being in the liver. Many otherreported species of Eimeria fromrabbit has been considered assynonyms by various workers. Mixedinfections with 2 or more species ofEimeria are the rule in nature invarious combinations.

Life cycleRabbit coccidiosis is initiated by

oral ingestion of the sporulatedoocysts by the susceptible hosts andthe infection develops into the diseasein young rabbits primarily, whereasadults are mostly carriers. Sinceinfection occurs in specific part of anorgan on a specific type of cells,coccidiosis has been classified in twotypes: intestinal coccidiosis andhepatic coccidiosis. The life cycle inepithelial cell, in general, is the samefor all Eimeria species. The Eimeriaspecies parasitizing rabbits undergo acomplex life cycle, having bothintracellular and extracellular stages,and asexual and sexual reproduction,which is quite similar to that ofEimeria species parasitizing otherhosts like chickens. The onlypeculiarity of the life cycle of rabbitEimeria species is that two types ofschizonts, which later on develop intomicrogamont and macrogamont forthe formation of oocysts, can bedistinguished even at the firstschiwgony. The prepatent period isquite precise for a particular species.It is 16-18 days for E. stiedai, 5-6days for E. perforans and E. media, 7days for E. magna and 9-11 days forall the remaining intestinal coccidialspecies. In all the intestinal types, the

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patent phase lasts for 5-32 days,whereas in E. stiedai it is 21-30 daysand mortality generally occurs duringthis period.

Intestinal localisation of thedevelopment of Eimeria spp.Generally,Eimeria species are very

host and site specific. The specific siteof development for each Eimeriaspecies of the rabbit may vary thoughfor some species, some parts of theendogenous development takes placein another site of the intestine. Thegross lesions within the gut and theirintensity depend upon the dose ofoocysts ingested. However, hostspecificity,developmental site,prepatent and patent periods, andpathogenicity varies from species tospecies. Gross lesions within the gutare most visible when gamogonyoccurs. Although, overlaps in thepreferred sites of development occur,macroscopic intestinal lesions can beused, in association with othercriteria, in the species identification(Table 1). Only E. jlaoescens, E.coecicola and E. piriformis completetheir development in the caecum,vermiform appendix and colon,respectively.In hepatic coccidiosis, theparasite completes its development inthe bile ducts of the liver.

Signs and symptomsThe main clinical symptoms in the

affected animals include diarrhoea,anorexia, progressive loss of conditionand emaciation before death. Thegross lesions within the gut and theirintensity depend on the dose of theoocysts ingested and the age of theanimals. The intestinal form ofcoccidiosis mainly affects younganimals of 6 weeks to 5 months. Thesymptoms of the disease includereduced weight gain; poor feedconversion, diarrhoea, anaemia andgrowth retardation. In intestinalcoccidiosis, the disturbances in waterand electrolyte balance occur in theparasitized part of the intestine beforethe appearance of the macroscopic

lesions and are essentiallycharacterised by a loss of water andsodium. The loss of sodium iscompensated by the exchange ofpotassium from the blood, therebyleading to hypokalaemia and causingdeath of the animal. The coccidia,which parasitize the ileum, caecum orcolon cause pathognomic lesions,which are more characteristic of theorgans, involved than of the parasitespecies. In hepatic coccidiosis, whichaffects rabbits of all ages, the parasitecompletes its development in the bileduct epithelial cells. While mostinfections are mild, severe infectionscan result in progressive emaciation,liver enlargement with slightly raisedwhite nodules (1-3 mm dia), or cordsdevelop on it, which later on tend tocoalesce and thereby interfere withliver function. The animal ischaracterized by thirst, wasting of theback and hind quarters, withenlargement of abdomen. The animalsmay have diarrhoea and their mucousmembranes may be icteric. This formof coccidiosis fW1S either as a chroniccourse for several weeks before death.

PathogenicityCoccidia are specific pathogenic

agents. They are highly contagious;induce same lesion and samesymptoms with low prognosis. Theduration of detectable lesions doesnot exceed 3 or 4 days and theirintensity depend on the dose of theinfection. The coccidiosis in rabbitscan be classified into 4 types whenclinical parameters like body weightgain, diarrhoea and mortality aretaken to consideration. These arenon-pathogenic (E. coecicola), slightlypathogenic (E. perforans) E. exigua) E.vejdovskyi), moderately pathogenic (E.media) E. magna) E. irresidua, E.piriformis) and very pathogenic (E.mtestinahs, E. flavescens). The causativeagent of hepatic coccidiosis,E. steidai,can also be classified as moderatelypathogenic (Table 2). In fieldconditions, pathogenicity of E. magnaand E. irrsidua is enhanced by bad

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hygienic conditions or intercurrentinfections like Escherichia coli. Animalsthat survive the disease may acquirespecies specific and in some instancesstrain specific immunity.

Diagnostic methodsA diagnostician may find low

graded infection in any healthy rabbiton faecal examination or animpression smear of the liver for thepresence of coccidia. Here careshould be taken to differentiate fromrabbit specific yeasts. The degree ofinfection can be assessed by faecalfloatation and by counting thecoccidian oocyst per gram (OPG) offaeces. However, an infection ofpathogenic significance is oftenaccompanied by diarrhoea, decrease inweight gain or loss of weight anddistinctive lesions. Many workersmake little efforts to differentiatebetween the different species found inrabbits. E. steidai found in liver, isless difficult to identify.

Sporulation of oocysts andshipmentThe sporulation time of oocyst is

one of the most important criterionsin the identification of the species. Itis mainly influenced by populationdensity of the oocysts, oxygen tensionand ambient temperature. Incontrolled conditions, the sporulationtime varies from 22 hours for E.perforans to 70 hours for E. pirifonniswhen the oocysts are incubated at20°C. Live oocysts may be desired byresearchers to verify species diagnosisand to characterize different strains.Oocysts sporulate within 48 hr ifmaintained at 27°C in petri dishes.The sporulation time varies accordingto the species, but in practice theduration varies from 24 hr for E.exigua and E. perforans) 72 hr for E.intestinalis, E. coecicola and E.pirifonnis and 48 hr for the otherspecies. Oocysts remain viable formany weeks at room temperature andmany months under low temperature.After sporulation the material may be

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Table 1. Macroscopic lesions of digestive tract and liver of rabbits by different Eimeria spp.

Species Post-mortem lesions

E. media Non-specific lesions of the duodenum (the endogenous development takesplace in the jejunum and the ileum)

Non-pathogenic lesions of vermiform appendix in heavy infection.

Lesions on the jejunum and more pronounced on the ileum, dose dependentlesion

Lesions occur on the jejunum and to a lesser extent on the ileum

Marked lesions on the caecum and colon

Marked lesions on the ileum and on the lower part of the jejunum

Only the colon (proximal and distal). Pathological lesions consist of catarrhalinflammation of the small intestine.

Lesions of the biliary ducts white nodules and the liver hypertrophy

Lesions only on the ileum and the distal part of the jejunum

No pathogenicity associated with this species. Moderate to severe intestinalinflammation mainly in ileum.

Mild to moderate lesions in duodenum and ileum.

E. coecicola

E. magna

E. irresidua

E. f1avescens

E. intestinalis

E. piriformis

E. stiedai

E. vejdovskyi

E. exigua

E. perforans

Table 2. Pathogenicity of different species of rabbit coccidiosis

Pathogenicity

Non pathogenic

Slightly pathogenic

Species

E. coecicola

E. perforansE. exigua, E. vejdovskyi,

E. media, E. magna,E. stiedai, E. irresidua,E. piriformis,

E. intestinalis, E.f1avescens

Severe decrease of growth,Severe diarrhoea, high mortality.

Mildly pathogenic orpathogenic

Symptoms

No sign of disease

Slight decrease of growth,no diarrhoea, no mortality

Decrease of growth, diarrhoeadose dependant mortality

Highly pathogenic

Table 3. Morphological features of Eimeria spp. of rabbits

Species Length (mm) Breadth (mm) Shape Index(mean ± SO) (mean ± SO) (mean length/width)

E. steidai 34.00 ± 2.44 20.20 ± 1.46 1.68E. perforans 18.64 ± 1.80 14.60 ± 0.96 1.28E. media 30.62 ± 1.40 17.09 ± 1.24 1.79E. magna 36.49 ± 3.58 23.41 ± 2.14 1.56E. irresidua 32.40 ± 3.64 18.60 ± 1.48 1.74E. intestinalis 29.37 ± 1.73 19.49 ± 1.70 1.51E. coecicola 38.80 ± 1.49 24.92 ± 1.26 1.56E. piriformis 30.62 ± 1.40 17.12 ± 1.21 1.79E. exigua 18.0' 16.0 1 1.10E. vejdovskyi 31.5 2 19.1 2 1.65E. f1avescens 30.02 21.0 2 1.43

stored in a bottle, leaving half of the .bottle left empty to provide neededair space.

difficult to differentiate and mayrequire the help of a specialist.Sporulation time, morphology andmorphometric parameters are used forspecific identification in rabbits.Morphology of the sporulated oocystsis an important criterion in

Differential diagnosis of sporulatedEimeria oocysts in rabbitsThe oocysts of coccidian are often

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determination of the Eimeria species.The shape differences in the form ofshape index (ratio of average lengthand average width) are also useful incomparing the oocysts, which aresubspherical with those of elongated.The measurements and morphologicalfeatures of different Eimeria species inrabbits are shown in Table 3Influence of coecotrophy on the

artificially prolonged prepatent, patentperiods, oocysts excretion andsporulation time in the rabbit hasbeen documented. Prepatent period,of course, is difficult to determine incase of coccidiosis due to peculiarbehaviour of coprophagy. The speciesof E. media and E. coecicola aredifficult to identify within mixture astheir dimensions and other featuresoverlap between species. However,the sites of infection are different inmonospecific infections. Therefore,species diagnosis has to be based ona combination of variouscharacteristics including site ofdevelopment in the intestinal tract ofthe host, type of lesions etc. A keyfor the species identification ofsporulated oocysts of Eimeria fromrabbit is given below.

Identification of other stagesAlthough, oocysts are the most

easily recognised stage in the lifecycle, schizonts, merozoits, andgarnetocytes may also be identified inscrapings of the mucosa. In order toexamine the endogenousdevelopmental stages scrapings shouldbe examined from different locationsalong the intestinal tract. However,species identification by this or byhistological method is a matter ofspecialist's job.

Prevention and controlProphylactic medication in drinking

water and feed was found todrastically reduce oocyst productionand almost total inhibition of hepaticand intestinal lesions in rabbits.Treatment of hepatic coccidiosis isdifficult and the diseases may remainlife long. Many drugs have been triedagainst coccidiosis in rabbits such asSulpha drugs, Clopidol, Nitrofurans,Pyrimethamine, Amprolium,Monensin etc. However, the mostcommon drugs are Nitrofurans,Amprolium and Sulpha drugs. Thefollowing drugs have been found tobe effective against clinicalscoccidiosis in rabbits during thecourse of the present study in variousfarms.BIFURAN (N itrofurawne

+Furawlidone),SKF-l tablet/litre ofdrinking water for 7days.(Sulfaquinoxaline),RANBAXY- 0.05% indrinking water for 7days.

CODRINOL (P-toluensulphonyl-betamethoxyethyleurethane+Tetracycline),HOECHST-l gm/litre of drinking waterfor 7 days.

AMPROLSOL (Amprolium 20%),GLAXO-0.06 % indrinking water for 7days.16% solution(Sulphadimethylpyridin),CYANAMID-7.5 ml/litre of drinking waterfor 7 days.

PEQUIN

SULMET

SUPERCOX (Sulphaquinoxaline(18.7% w/w) andDiaveridine (3.3% w/w), WOCKHARDT-10 gm in 10 litres ofdrinking water or 100gm powder in 50 kgof final feeds to 5-7days.

The treatment should take intoaccount the possibility of re-infection especially due tocoprophagy in rabbits. Thus aminimum of 2 periods of treatmentsare recommended preferably 2 periodsof 7 days each with a pause of 7days in between. Apart frommedication, good preventive hygieneis the key to successful rabbitproduction.

SUMMARY

Rabbit production for meat andwool is gaining momentum in Indiaas a micro livestock. Broiler rabbitsare reared irrespective of thegeographical locations and available inalmost all parts of the country. TheAngora rabbit which is reared mainlyfor fine wool production is, however,restricted to the hilly regions of thecountry particularly in sub-temperateclimates. Coccidiosis is a majorimpediment in rabbit production andthe most common protowan parasiticdisease affecting all age groups. Thisclinical entity is caused by almost adozen species of Eimeria withdifferential features with respect tothe clinical course, the causativeagent, differential diagnosis andpreventive measures for control ofrabbit coccidiosis.

•A success story of more wheat ...(Continued from page 14)emergence spraying of pendimethalin@ 1.5 kg a.i.zha significantlyincreased the seed yield up to 49.92q/ha and 48.67 q/ha as compared tofarmers' practice (24.33 q/ha in2001-02 and 22.06 q/ha in 2002-03).

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The increased seed yield wassignificant at both the levels, i.e. 1and 5 percent of significance. Inanother trial the number of weedswere reduced up to 51.35 per centafter one year of sowing of wheat

crop through zero-tillage seedingdevice. The major weeds werePhalaris minor; Chenopodium album)Lathyrus aphaca, Melilotus alba)Cynodon dactylon.

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