Equine protozoal myeloencephalitis (EPM) is one of the most discussed diseases in the horse health industry. Many owners are familiar with the clinical signs horses display once affected, but how much do they know about Sarcocystis neurona, one of the disorder's causative agents?

During a presentation at the Advances in Equine Neurological Diseases Symposium, held Dec. 6 in Lexington, Ky., Daniel K. Howe, PhD, a molecular parasitologist at the University of Kentucky Gluck Equine Research Center, provided extensive insight into the parasite and its relationship to EPM.

Lifecycle and Infection

Howe first discussed S. neurona's two-host lifecycle–something many horse owners are familiar with. To complete its life cycle, this organism requires a definitive host (the opossum), which feeds on the muscles of a dead intermediate host (such as a raccoon, skunk, cat, or armadillo) containing S. neurona sarcocysts. Once ingested by the opossum, the parasites mature to their infective stage (sporocysts), which the opossum passes in its feces