Atypical Myopathy Kills Hundreds of European Horses

The deadly disease atypical myopathy has claimed hundreds of equine lives in Europe over the past few weeks.

As of Nov. 27, 310 cases “compatible with a diagnosis of atypical myopathy” had been reported to the Faculty of Veterinary Medicine in Liege, Belgium, and the French surveillance center for equine pathologies (RESPE), which monitor European equine outbreaks, RESPE reported. The vast majority of the cases resulted in death.

Of the cases, there were 109 in Belgium, 81 in France, 40 in Great Britain, 37 in Germany, 22 in The Netherlands, 11 in Switzerland, eight in the Czech Republic, and two in Ireland.

Because case reporting is voluntary the reported figures might not represent all actual cases, said Gaby van Galen, DVM, MSc, Dipl. ECEIM, of the Faculty of Health and Medical Sciences at the University of Copenhagen in Denmark and a member of the Atypical Myopathy Alert Group network. Some reports have indicated as many as 50 horses died from the disease in western Germany alone, where the outbreak was at first rumored to be the result of malicious poisoning. Veterinary investigations, however, dispelled the poison theory and confirmed atypical myopathy in many of the affected horses.

A study released in June 2013 revealed that European atypical myopathy is caused by toxins in the Acer pseudoplatanus tree. Commonly called the “sycamore” or “maple sycamore” tree in the United Kingdom and other parts of Europe, it's not to be confused with the American sycamore tree in the United States; There, seasonal pasture myopathy (SPM)—which is very similar to European atypical myopathy—is caused by the Acer negundo, or box elder, tree. Both the European sycamore and the American box elder produce seeds containing hypoglycin A, which contains a toxic metabolite, said Dominique Votion, DVM, PhD, of University of Liege in Belgium, who led the international study.

To protect horses from atypical myopathy, European owners are encouraged to keep their horses out of pasture containing Acer trees, van Galen said. But as seeds can blow in the wind, it’s safest to keep horses stabled during the high-risk season if any Acer trees or nearby, she added.

“However, we know that that can create welfare issues, keeping horses indoors all the time, so solutions are not simple," she said. "The one thing we can say at this point is that the best method of prevention for atypical myopathy is keeping the horses indoors.”

Horse owners who keep their horses outdoors can try to limit the risks by cleaning up dead leaves and seeds, she said.

The highest risk for atypical myopathy happens in the fall, although minor outbreaks have occurred in the spring.

About the Author

Christa Lesté-Lasserre, MA

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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