Equine Protozoal Myeloencephalitis.

This article reviews the recent advances in understanding Equine Protozoal Myeloencephalitis (EPM), a disease in horses caused by protozoan parasites. Even though horses are commonly infected, they rarely show symptoms, and the factors influencing this frequency are still unclear. The methods for diagnosing EPM have improved and there are now FDA-approved treatments available.

Understanding Equine Protozoal Myeloencephalitis (EPM)

• The review discusses recent developments in our understanding of EPM, a disease that affects horses and is caused by two related protozoan parasites, Sarcocystis neurona and Neospora hughesi. Of these, Sarcocystis neurona is the more common cause.
• It is noted however, that although horses often become infected, they rarely manifest visible illness. The factors that determine why some horses exhibit symptoms while most do not, are not yet fully understood.

Epidemiology Studies and Disease Reproduction

• The research includes references to epidemiologic studies that have found certain risk factors associated with the development of EPM. Among those is the presence of opossums, which are known carriers of the Sarcocystis neurona parasite.
• Another risk factor identified is the occurrence of stressful health-related events in the horse’s recent history.
• Furthermore, attempts at experimentally recreating EPM in horses often result in detectable antibody responses, though these do not consistently lead to neurological disease, suggesting that additional factors are likely involved in the manifestation of illness.

Diagnosis and Treatment of EPM

• Diagnostic methods for EPM have improved significantly. Increased intrathecal antibody production against the parasite can now be detected, facilitating an earlier and more accurate diagnosis of the disease.
• The drugs Sulfadiazine/pyrimethamine (known by the brand name ReBalance), diclazuril (Protazil), and ponazuril (Marquis), can effectively treat EPM. These anticoccidial drugs have been approved by the Food and Drug Administration (FDA) for treating EPM in horses.