Twenty-three cases of equine atypical myopathy (EAM) have been reported this spring to the University of Liège, in Belgium, and the RESPE (Réseau d’Epidémio-Surveillance en Pathologie Equine, or the Epidemiological Surveillance Network for Equine Diseases), according to a May 2 notice from the Atypical Myopathy Alert Group.

According to the alert, 18 cases have been identified in France, four in Great Britain, and one in New Zealand.

Atypical myopathy, a seasonal, pasture-associated muscle disorder, presents a particular challenge to veterinarians. The disease is characterized by a generalized complete degeneration of muscle fibers, which leads to sudden death due to the collapse of the cardiorespiratory system in more than 90% of cases. The economic impact is often devastating.

Affected horses can either die acutely or show profuse sweating, muscle fasciculation (twitching), weakness, pigmenturia (urine discoloration), reluctance to move, recumbency (inability to stand), difficulty breathing, and death after 12-72 hours. Since the etiology is unknown, no effective prophylaxis (preventive treatment) exists and affected horses can only be treated symptomatically