Equine Atypical Myopathy

Equine atypical myopathy (EAM) is a muscle disease seen in pastured horses in Europe. Seemingly healthy horses develop muscle deterioration characterized by weakness, trembling, reluctance to move, and sweating. As the illness progresses, horses become recumbent, have difficulty breathing, and may die within 12 to 72 hours of becoming ill. About 90% of fatalities from EAM are due to collapse of heart and lung function. The disease is most often seen in autumn in young horses kept at pasture without grain supplementation.

Though no specific cause of the disease has been identified, studies in Switzerland have found a connection between Clostridium sordellii and EAM. C. sordellii toxin and its characteristic cell damage were found in the muscles of horses with EAM but not in their healthy pasturemates. The same toxin is responsible for gas gangrene syndrome in cattle and sheep (black leg) as well as toxic shock syndrome in humans.