Cross-sectional study of serum antibodies against Sarcocystis neurona in cats tested for antibodies against Toxoplasma gondii

Objective - To determine apparent seroprevalence of antibodies against Sarcocystis neurona in a population of domestic cats previously tested for antibodies against Toxoplasma gondii. Design - Cross-sectional study. Sample Population - Serum from 196 domestic cats. Procedure - Banked serum samples submitted to the Michigan State University Animal Health Diagnostic Laboratory for T gondii diagnostic testing were tested for antibodies against S neurona by use of an indirect fluorescent antibody (IFA) test and a western blot test. Submission records were analyzed to determine descriptive statistics and test for associations between positive results of a test for S neurona and other variables in the data set. Results - 10 of 196 (5%) samples yielded positive results for antibodies against S neurona by use of western blot analysis, whereas 27 samples yielded positive results by use of the IFA. No association was found between S neurona western blot test results and T gondii test results, age, sex, or the reason for T gondii testing. The S neurona IFA titer was positively and significantly associated with positive results of western blot analysis. Conclusions and Clinical Relevance - Domestic cats are not likely to play a substantial role as intermediate hosts in the natural life cycle of S neurona. Results indicate that natural infection of domestic cats may occur, and small animal practitioners should be aware of this fact when evaluating cats with neurologic disease. The S neurona IFA test had lower specificity than western blot analysis.