Seroprevalence of antibodies to Sarcocystis neurona in horses residing in northern Colorado

• Published in: Journal of equine veterinary science Vol. 19; no. 2; pp. 122 - 126
• Main Authors: Tillotson, Kirsten, McCue, Patrick M., Granstrom, David E., Dargatz, David A., Smith, Mary O., Traub-Dargatz, Josie L.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1999
• Subjects: age differences; antibodies; breed differences; gender differences; geographical variation; horses; Sarcocystis; seasonal variation; seroprevalence; Colorado
• ISSN: 0737-0806; 1542-7412
• DOI: 10.1016/S0737-0806(99)80102-6

Summary Objective: To determine the seroprevalence of antibodies to Sarcocystis neurona in horses residing in northern Colorado during 1995 and 1996. Design: Prevalence survey. Sample Population: Aliquots of serum were collected from 608 equids from samples submitted to the Veterinary Diagnostic Laboratory at Colorado State University for testing for antibodies to equine infectious anemia (EIA). Procedure: Sera were analyzed for the presence of antibodies to S. neurona using Western blot analyses. Information regarding age, gender, breed, county of origin and quarter of the year when the sample was collected was recorded for each animal from the EIA form. Data were analyzed using chisquare analysis and multiple logistic regression. Results: Seroprevalence was 33.6%. Gender and county of origin were not associated with seroprevalence. Variables that were associated with seropositivity included age, breed, and quarter of the year. Seroprevalence increased with age. The highest seroprevalence, 66.6%, was found in the group that represented ponies and non-horse equids. Stock breeds had a seroprevalence of 32.6% and hot-blooded breeds had a seroprevalence of 27.9%. Seroprevalence was lowest during the coldest months (20.1%). Clinical Implication: Data from this sample population indicate that exposure of horses to S. neurona in northern Colorado is less than that reported for eastern regions of the United States. The overall seroprevalence is similar to that reported in horses from eastern Oregon. Although additional data are necessary, this finding suggests that areas of lower seroprevalence in the Rocky Mountain states corresponds to areas of lower opossum density. The results of this survey further support the conclusion that although a negative serum antibody test for S. neurona in a horse with neurologic signs may help rule out equine protozoal myeloencephalitis (EPM) as a diagnosis, a positive serum test result alone, especially in a clinically normal horse, does not lead to a definitive diagnosis of EPM.