Freeze Stops European Atypical Myopathy Reports

The largest outbreak of equine atypical myopathy in Europe has ended with freezing winter temperatures, with a record number of 371 reported cases, according to a group of researchers in Belgium.

Atypical myopathy (AM) causes severe generalized weakness and stiffness, often ending in death. Urine becomes coffee-colored, and blood workups show significant increases in plasma levels of creatine kinase.

France, Germany, and Belgium were most affected, with 124, 92, and 64 cases, respectively, but Ireland, The Netherlands, Denmark, Switzerland, the U.K., and Luxembourg also reported instances of AM in autumn 2009.

"Atypical myopathy is not a reportable disease, and given its high mortality rate, the horses often die even before they are diagnosed. So these numbers are certainly underestimated," said Gaby van Galen, DVM, MSc, Dipl. ECEIM who, along with Dominique Votion, DVM, PhD, collect data via the Atypical Myopathy Alert Group based at the University of Liège. The group consists of veterinarians, owners, and veterinary medical schools throughout Europe who report cases.

Survival rate for the fall 2009 epidemic was 24%, which was "higher than previously thought," said van Galen. "It's important to be aware that some horses suffering from AM do survive," she said. "Moreover, survivors seem to recover completely."

Despite the terms "epidemic" and "outbreak," AM is not a contagious disease, van Galen said. It appears to be caused by a yet-undetermined agent in pastures--a plant, bacteria, fungus, or some other toxin. However, freezing temperatures consistently end all fall epidemics, suggesting that the causative agent is killed or inactivated by the cold.

Spring epidemics also occur but are usually less widespread, van Galen said. Preventive measures should be taken for the upcoming season, including nutritional supplementation, regular vaccinations and deworming, and stabling, especially for horses most at risk: young, old, those animals not being regularly worked, and stallions.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.