A progressive, infectious (Pasq) neurological disease of horses, endemic in the USA (EPM8) and only encountered elsewhere in imported equids (EPM 3). EPM is one of the most frequently diagnosed neurological conditions of the Western Hemisphere (Furr) and the principal differential for multifocal, asymmetric progressive CNS disease (Pasq). As it can resemble any neurological disorder, EPM must be considered in any horse with neurological signs if it resides in the Americas or if it has been imported from that area (EPM 8). The disease is not contagious (Pasq).