Murray Valley Encephalitis in Horses: What We Know

Learn about this uncommon, but often deadly, virus and its impact on infected horses in Australia.

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If you’ve never heard of the Murray Valley encephalitis virus (MVEV), join the club.

Although MVEV is endemic in several areas throughout the world, clinical cases of Murray Valley encephalitis are uncommon. Nonetheless, they do occur, particularly in Australia. And the virus is remarkably similar to another common encephalitis virus: West Nile virus (WNV). To date, no cases of MVEV appear to have been reported in the United States or Canada. But Anita Barton, BVSc (Hons), from the Department of Veterinary Science at the University of Queensland, Australia, and colleagues recently studied a case of Murray Valley encephalitis in a 2-year-old Australian Stock Horse.

“Water birds are the reservoir host for MVEV, so a combination of both mosquitoes and water birds are needed to increase the prevalence of disease,” Barton explained. "Flood events are suspected to attract mosquitoes and bring hosts downstream to less endemic areas where we see an increase in Murray Valley encephalitis cases in both horses and humans."

Clinical signs of Murray Valley encephalitis in horses are primarily neurologic in nature and include depression, ataxia (incoordination), muscle fasciculations, facial paralysis, and weakness

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Written by:

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she’s worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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