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