Equine protozoal myeloencephalitis (EPM): Seroprevalence and risk factors for Sarcocystis neurona infection in Michigan horses

This thesis describes two studies regarding the diagnostic testing and epidemiology of equine protozoal myeloencephalitis (EPM). EPM is a neurological disease of horses and ponies caused by the Apicomplexan protozoan parasite Sarcocystis neurona. In the first study, it was determined that infection status was significantly associated with reactivity to the 30 and 16 kDa protein bands on immunoblots treated with bovine Sarcocystis cruzi antibodies prior to loading the equine samples (P < 0.001, Fisher's Exact test). Using this criteria, the S. cruzi antibody blocked western blot test had a sensitivity of 100% and a specificity of 98%.; The second study was a seroprevalence study of equine antibodies to S. neurona. Sera from 1,121 Michigan equids were tested by the western blot test for antibodies to S. neurona. The true seroprevalence was 60%, and prevalence was positively associated with opossum abundance. In logistic regression analyses, age was positively associated with the likelihood of infection, exposure to pasture was associated with increased risk of infection and feeding of sweet feed was associated with decreased likelihood of testing positive.