Equine Protozoal Myeloencephalitis (EPM): Treatment
Equine protozoal myeloencephalitis (EPM) continues to be an elusive disease to prevent, diagnose, and treat.
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.Horse feed, hay, or pasture that is contaminated by opossum feces is then unintentionally consumed by a horse; the ingested sporocysts penetrate and infect a horse's leukocytes (white blood cells, predominantly monocytes) and endothelial cells that line the blood vessels. It is speculated that, like a "Trojan horse," the parasites cross the horse's blood-brain barrier by hiding in the leukocytes, then they are released within the central nervous system (CNS) tissues, where they inflict their damage.
Although POSITIVE EPM test results do not confirm current infection with EPM, it may prompt us to pursue empirical treatment based on the horse's clinical signs and history.
Empirical treatment involves administration of a medication called Marquis for a period of at least 28 days. If a positive response to therapy is observed within the first 28 days, then we strongly recommend continuing treatment until additional improvement is not evident for at least 10 days. In other words, we recommend discontinuing therapy only after the response has "plateaued" for a period of 10 or more days. This often occurs within the initial 28-day period. In some cases, it takes longer than 28 days to reach the "10-Day-Plateau". This practice has resulted in far less incidence of EPM recurrence in our experience.
A 28-day supply of Marquis costs approximately $794.84.
For more information about Marquis, please click HERE.