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.