Equine Protozoal Myeloencephalitis (EPM)

Essay by Kenneth EllzeyJunior High, 9th gradeA+, March 1997

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Teacher has no idea what EPM is so could tell them anything and they would believe it. Complete with references. Very Informative

Equine Protozoal Myeloencephalitis (EPM)

Equine Protozoal Myeloencephalitis (EPM) is a disease among horses that damages the Central Nervous System (CNS). If not treated, it can be deadly. The protozoan, Sarcocystis neurona, infects the horse, building colonies in the brain and along the spine. Since it is a relatively 'new' disease, discoveries are occurring constantly in the research of the disease.


The first cases of EPM in North America were recorded in the 1960s. The disease was then known as 'focal or segmental myelitis/encephalitis' (the case was unknown). Judging from the literature, EPM wasn't very common in those days. In the 1970s the disease was described as equine protozoal myeloencephalitis for the first time, but the actual protozoan parasite was not known. It was (incorrectly) thought that the protozoan was Toxoplasma.

In the late 1970's and early 1980's, evidence was found that led scientists to believe that the EPM-protozoa belonged to the Sarcocystis group. In the late 1980's, the causative organism of EPM was isolated in the laboratory and determined to be a previously-undescribed species of Sarcocystis; it was named Sarcocystis neurona. It was, then, possible to conduct some accurate testing for EPM.


The parasite, S. neurona, depends on two separate hosts in order to complete its life-cycle - the opossum and wild birds. The protozoa lives in the lining of the intestine of a carnivore. It reproduces inside the intestine and gives off infective sporocysts in the feces, or droppings, of the carnivore. Sarcocystis requires a specific carnivore host for reproduction. To complete the its life-cycle, the sporocysits must be eaten by another animal (secondary host). The sporocyst migrates to the skeletal muscles and can...