ANTIBODIES TO TOXOPLASMA GONDII IN SASKATCHEWAN CATS, SHEEP AND CATTLE P. N. Nation and J. R. Allen* INTRODUCTION

SEVERAL SEROLOGICAL TESTS have been developed to aid in screening for and diagnosis of toxoplasmosis. Screening tests are performed to indicate whether or not a given animal or group of animals has been exposed to Toxoplasma gondii. Thus an indication of the prevalence of toxoplasmosis in a given population is obtained. Only one serum sample per animal is needed for a screening test. Diagnostic tests are used to indicate whether or not an individual is suffering from acute toxoplasmosis. For such tests, serum samples taken at two week intervals are needed (7). A significant rise in antibody levels between the first and second samples indicates current toxoplasmosis. The serological tests for toxoplasmosis include the indirect fluorescent antibody (IFA) test, the Sabin-Feldman dye test, and the indirect hemagglutination (IHA) test. The indirect hemagglutination test measures IgG antibodies which appear two weeks or so after initial infection. Thus this test will not detect antibody immediately upon infection because IgM is the first antibody formed (7). This test is also less sensitive than the IFA or dye tests (5), but these disadvantages must be considered against the advantages. One of these is that there is no need to maintain live Toxoplasma organisms for this test, a requirement of the Sabin Feldman dye test which carries with it the risk of infection of laboratory personnel. Equipment required for this test is neither expensive nor as elaborate as that required for the IFA test, a factor which makes it practical from the standpoint of the private practitioner and the smaller diagnostic laboratory. The IHA test can be performed fairly quickly, only a small volume of serum is needed, and commercial kits are available which contain all the necessary reagents and control sera. The principle of the indirect hemagglutination test for toxoplasmosis is that a test serum containing IgG antibodies against T. gondii will agglutinate sheep erythrocytes stabilized *Departinent of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N OWO. CAN. VET. JOUR., vol. 17, no. 12, December, 1976

and coated with a soluble T. gondii extract. With the IHA test, a titre of 1/64 is the lowest considered significant. Therefore, in surveys for Toxoplasma antibodies using the IHA test, sera are screened at this dilution. Exact titres can be determined by further titration of sera found to be positive at the dilution of 1/64. MATERIALS AND METHODS Serum samples were obtained from 149 cattle, 58 sheep and 118 cats presented to the Department of Clinical Studies at the Westem College of Veterinary Medicine for a variety of clinical conditions or for elective surgery. A further 44 sera of clinically normal sheep were obtained from the University of Saskatchewan sheep flock. All sera were screened for antibodies to Toxoplasma gondii at a dilution of 1/64 using the International Biological Laboratories Inc. indirect hemagglutination test for toxoplasmosis.1 The method described by International Biological Laboratories (8) was followed using microdilution equipment for all steps. RESULTS None of the 149 bovine or 102 ovine sera tested positive for Toxoplasma gondii antibodies at the 1/64 dilution level. Of the 118 feline sera, four gave positive reactions when

screened at a dilution of 1/64. Of these titration revealed: one to be positive at 1/64, questionable at 1/128, and negative at 1/256; a second to be positive at 1/128, questionable at 1/256, and negative at 1/512; and the third to be positive to a dilution of 1/4096, the highest dilution tested. There was not enough serum left for titration of antibody levels of the fourth sample. Therefore, according to this survey, the prevalence of Toxoplasma gondii antibody levels is nil for sheep and cattle and 3.4% in cats. DISCUSSION Previous surveys of serum antibody levels of

Toxoplarsma gondii have revealed that infec-

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TOXOPLASMA GONDII

tion is common. In sheep and cattle, 72% were lege of Veterinary Medicine for a variety of found by the indirect immunofluorescence test clinical conditions or for elective surgery. Sera to have antibody levels in one report (2). In were obtained from a further 44 clinically northe Guelph area of Ontario, approtimately mal members of the sheep flock of the Univer50% of sheep and cattle have antibodies to T. sity of Saskatchewan. Sera were screened for gondii (9). In another report, 28% of sheep antibodies to T. gondii at a dilution of 1/64. and 29% of cattle surveyed by the indirect Toxoplas-ma antibodies were detected in four hemagglutination test in Northern California cats and none of the sheep and cattle. were found to have antibody titres using a dilution of 1/64 as the significant level (10). REsuME Of 405 sheep tested at the Hopland Field Les auteurs ont utilise l'epreuve indirecte de Station in California, 13% had antibodies to T. gondii when surveyed by the IHA test at a l'h6magglutination pour proceder a la re1/64 dilution (4). The approximate world- cherche d'anticorps seriques contre Toxowide average percentage of infected sheep is plasma gondii, chez 118 chats, 102 moutons et 149 bovins. Les echantillons de serum des 39% and that for cattle is 22% (10). Studies performed on feline serum revealed chats, des bovins et de 58 des moutons prothat 58% had serum titres demonstrated by venaient de sujets ref6res au departement de the Sabin Feldman dye test in one series in pathologie cinique du College de Medecine East Germany (6) while in another, the IFA v6terinaire de l'Ouest pour une vari6te' de contest demonstrated antibody levels in 43% of ditions cliniques ou d'interventions chirurgi200 cats (7). A third survey found the pre- cales. Les auteurs preleverent aussi des echanvalence of T. gondii antibodies to be 14% in tillons de serum chez 44 moutons sains du a stray cat population in two California coun- troupeau de l'Universite de la Saskatchewan. ties and 25% in cats presented to veterinary Ils utiliserent la dilution 1:64 des echantillons clinics in the same region (1). In another pour proc6der a la recherche des anticorps survey, T. gondii antibodies were found by the contre T. gondii. Ils ne decelerent de ces antiSabin Feldman dye test at dilutions of 1:2 or corps que dans le serum de quatre chats. more to be more common in adult stray cats in Iowa and Missouri (57.9%) than in house ACKNOWLEDGMENTS cats in Kansas City (37.5%) (3). We would like to thank Mr. Bob Norman for The prevalence of Toxoplasma infection in advice and guidance in technical aspects of animals from the Saskatoon area (bovine and the IHA test and Miss J. the McKnight for typing the ovine 0%, feline 3.4%) is much lower than in manuscript. other areas from which surveys have been reported. The reasons for this are uncertain. One REFERENCES might expect that if relatively few cats are infected, there would be a lower prevalence 1. BEHYMER, R. D., D. R. HARLOW, B. S. BEHYMER and C. E. FRANTi. Serologic diagof infection of other animal species, due to the nosis of toxoplasmosis and prevalence of position of cats in the life cycle of T. gondii Toxoplasm gondii antibodies in selected as oocyst shedders. The cold dry inland confeline, canine, and human populations. J. tinental climate of the Saskatoon region may Am. vet. med. Ass. 162: 959-963. 1973. be important by reducing animal contact dur- 2. CAMPANA-RoUGET, Y., F. LEVIrrE and A. M. ASSMAN. La toxoplasmose chez les herbiing the winter, by reducing oocyst survival, vores en Cote-D'Or. Revue Med. vet. 125: and by reducing cyst survival in carcasses, 99-104. 1974. thus reducing infection of carnivores. There may also be other unknown epidemiological 3. DUBEY, AJ. P. Feline toxoplasmosis and coccidiosis: survey of domiciled and stray cats. factors in the Saskatoon area which control J. Am. vet. med. Ass. 162: 873-877. 1973. both inter and intraspecific spread of toxo- 4. FRANTI, C. E., G. E. CONNOLLY, H. P. RIEplasmosis. MANN, D. E. BEHYMER, R. RUPPANNER, C. M. WILLADSEN and W. LONGHURST. A survey

SUMMARY

The indirect hemagglutination test was used to survey the sera of 118 cats, 102 sheep and 149 cattle for antibodies to Toxoplasma gondii. Sera of cats, cattle and 58 sheep were obtained from animals submitted to the Department of Veterinary Clinical Studies at the Western Col309

for Toxoplasma gondii antibodies in deer and other wildlife on a sheep range. J. Am. vet. med. Ass. 167: 565-568. 1975.

5. JoNEs, S. R. Toxoplasmosis, A review. J. Am. vet. med. Ass. 163: 1038-1042. 1973. 6. KUrsCHMANN, K., E. ALBREcHT and W. WmnFuHR. Studies on the occurrence of Toxoplasma gondii infection in cats. Mh. VetMed. 29: 244-246. 1974.

CANADIAN VETERINARY JOURNAL

7. MCKINNEY, H. R. A study of toxoplasma infections in cats as detected by the indirect fluorescent antibody method. Vet. Med. small Anim. Clin. 68: 493-495. 1973. 8. QUALITATIVE AND QUANTITATIVE INDIRECT HEMAGGLUTINATION TEST FOR ANTIBODIES TO

Toxoplasma gondii. Instructions for use provided with test reagents by International Biological Laboratories Inc.

9. TIzARD, I. R. and F. A. CAOLI. Toxoplasmosis in veterinarians: an investigation into possible sources of infection. Can. vet. J. 17: 24-25. 1976. 10. VANDERWAGEN, L. C., D. E. BEHYMER, H. P. RIEMANN and C. E. FRANTi. A survey for toxoplasma antibodies in Northern California livestock and dogs. J. Am. vet. med. Ass. 164: 1034-1037. 1974.

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Antibodies to Toxoplasma gondii in Saskatchewan cats, sheep and cattle.

ANTIBODIES TO TOXOPLASMA GONDII IN SASKATCHEWAN CATS, SHEEP AND CATTLE P. N. Nation and J. R. Allen* INTRODUCTION SEVERAL SEROLOGICAL TESTS have been...
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