Abstract
BACKGROUND: Literature on the seroprevalence of antibodies to the causative agents of equine protozoal myeloencephalitis (EPM) in Canada is limited. HYPOTHESIS/OBJECTIVES: To determine the prevalence of serum antibodies against Sarcocystis neurona and Neospora hughesi in apparently healthy horses without signs of neurologic disease which have always resided in Alberta, Canada, using commercially available immunodiagnostic tests. ANIMALS: Samples from 116 healthy horses were obtained from a biobank containing horse serum collected across Alberta in 2021 and 2022. Samples were selected based on owner survey responses, and only horses that had always resided in Alberta were included in the study. METHODS: This cross-sectional study analyzed serum samples for anti-S neurona (SarcoFluor and rSnSAG2/4/3 ELISA) and N hughesi (NeoFluor and NhSAG1 ELISA) antibodies. A subset of 30 samples underwent additional testing by S neurona western blot. RESULTS: For anti-S neurona antibodies, 26/116 horses were positive on indirect fluorescent antibody test (IFAT), 4/116 on ELISA, and 5/30 on western blot; however, none of the horses were positive on all 3 of the tests. For anti-N hughesi antibodies, 18/116 were positive on IFAT and 2/116 on ELISA, with no horses positive on both tests. CONCLUSIONS AND CLINICAL IMPORTANCE: These findings suggest possible exposure of Alberta horses to S neurona and N hughesi. However, the commercially available tests had low sensitivities and poor agreement in this study group of apparently healthy horses.