Equine protozoal myeloencephalitis (EPM) continues to be an elusive disease to prevent, diagnose, and treat. In this special collection of three articles this month, we will delve into the often-contentious world of EPM research to share what practitioners and those studying the disease have discovered.

What is EPM?

Equine protozoal myeloencephalitis describes an infection of the central nervous system with an intracellular (they cannot reproduce outside their host cell) protozoan parasite known as Sarcocystis neurona. 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). S. neurona is contained in the muscles in the form of sarcocysts, which once ingested by the opossum will mature and pass in their infective stage (sporocysts) in opossum feces