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====Description====

====Description====

Equine protozoal myeloencephalitis (EPM) is a common neurologic disease of horses in the Americas; it has been reported in most of the contiguous 48 states of the USA, southern Canada, and several countries in Central and South America. In other countries, EPM is seen sporadically

Equine protozoal myeloencephalitis, or EPM, is a disease cause by a protozoal infection of the central nervous system of horses.  Equine protozoal myeloencephalitis (EPM) is a common neurologic disease of horses in the Americas; it has been reported in most of the contiguous 48 states of the USA, southern Canada, and several countries in Central and South America. In other countries, EPM is seen sporadically

EPM was discovered in the 1960s by Dr. Jim Rooney. The disease is considered rare, though recently, an increasing number of cases have been reported. Research at the University of Kentucky has labeled the opossum as the definitive host of the disease.

 

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First descrobed 1964 by Dr. Jim Rooney, called segmental myelitis, focal myelitis encephlaitis, toxoplasma-like encephalitis. 1976 Dubey suggested caused by Sarcocystis member.  S.neurona was eventually cultured form spinal cord of affected horse and so namedbecuase it developed within neurons.  This and similar organsism have been cultured form several ataxic horses, zebra, domestic cat, Canadian lynx, sea otter, straw-nekced ibis, mink, raccoon and sunk.  The disease is considered rare, though recently, an increasing number of cases have been reported. Research at the University of Kentucky has labeled the opossum as the definitive host of the disease.

 

Neospora hughesi has recently been shown to also cause EPM in the horse but is probably reltively unimportant.

 

====Aetiology and Epidemiology====  

====Aetiology and Epidemiology====  

Most cases of EPM are caused by an Apicomplexan protozoan, [[Sarcocystis|Sarcocystis neurona]] . Horses are infected by ingestion of S neurona sporocysts in contaminated feed or water. The organism is assumed to undergo early asexual multiplication (schizogony) in extraneural tissues before parasitizing the CNS. Because infectious sarcocysts are not formed, the horse is considered an aberrant, dead-end host for S neurona . All Sarcocystis spp have an obligate predator-prey life cycle. The definitive (predator) host for S neurona is believed to be the opossum ( Didelphis virginiana ). Opossums are infected by eating sarcocyst-containing muscle tissue from an infected intermediate (prey) host and, after a brief prepatent period (probably 2−4 ωκ), infectious sporocysts are passed in the feces. Nine-banded armadillos, striped skunks, raccoons, sea otters, Pacific harbor seals, and domestic cats have all been implicated as intermediate hosts; however, the importance in nature of each of these species is unknown. A few cases of EPM, both in the Americas and Europe, are associated with Neospora hughesi , an organism that is closely related to S neurona . The natural host(s) of this organism have not yet been identified.   

Most cases of EPM are caused by an Apicomplexan protozoan, [[Sarcocystis|Sarcocystis neurona]] . Horses are infected by ingestion of S neurona sporocysts in contaminated feed or water. The organism is assumed to undergo early asexual multiplication (schizogony) in extraneural tissues before parasitizing the CNS. Because infectious sarcocysts are not formed, the horse is considered an aberrant, dead-end host for S neurona . All Sarcocystis spp have an obligate predator-prey life cycle. The definitive (predator) host for S neurona is believed to be the opossum ( Didelphis virginiana ). Opossums are infected by eating sarcocyst-containing muscle tissue from an infected intermediate (prey) host and, after a brief prepatent period (probably 2−4 ωκ), infectious sporocysts are passed in the feces. Nine-banded armadillos, striped skunks, raccoons, sea otters, Pacific harbor seals, and domestic cats have all been implicated as intermediate hosts; however, the importance in nature of each of these species is unknown. A few cases of EPM, both in the Americas and Europe, are associated with Neospora hughesi , an organism that is closely related to S neurona . The natural host(s) of this organism have not yet been identified.