Equine Protozoal Myeloencephalitis - Causes

Causes

EPM is caused by the parasite Sarcocystis neurona. In order to complete its life cycle this parasite needs two hosts, a definitive and an intermediate. In the laboratory, raccoons, cats, armadillos, skunks, and sea otters have been shown to be intermediate hosts. The opossum is the definitive host of the disease. Horses most commonly contract EPM from grazing or watering in areas where a possum has recently defecated. However, horses cannot pass the disease among themselves. That is, one horse cannot contract the disease from another infected horse. The horse is the dead-end, or aberrant, host of the disease.