Equine Herpesvirus Myeloencephalopathy Outbreak Update

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An outbreak of equine herpesvirus-1 apparently originated at the National Cutting Horse Association (NCHA) Western National Championships, held April 29 through May 8 in Odgen, Utah. According to a USDA situation report (PDF), as of May 19, a total of 997 horses were reportedly exposed to EHV-1 (either at the NCHA event or through contact with horses exposed at the event); 21 cases of EHV-1 infection and 12 cases of EHM have been confirmed; and 7 horses died or were euthanized.

To limit the potential spread of EHV-1 and to alleviate horse owners' fears of exposure, a number of events in many states have been postponed or canceled and two veterinary teaching hospitals have closed to non-emergency equine and camelid cases.

The American Association of Equine Practitioners (AAEP) has developed resources about EHV-1, EHM and the current outbreak, including updates and a FAQ for veterinarians and FAQs and resources for horse owners.

EHV-1 at a glance:

• Equine herpesvirus myeloencephalopathy (EHM) is caused by equine herpesvirus-1 (EHV-1). The virus most commonly causes respiratory infection, and not all infected horses will develop EHM;
• EHV-1 is a normally occurring virus found in the equine population; this outbreak is not being caused by a new virus or a new strain of a virus;
• Signs of EHM in horses may include nasal discharge, incoordination, weakness of the rear limbs and hind end, lethargy, urine dribbling, and decreased tail tone;
• Llamas and alpacas can also be infected with EHV-1 and may develop neurologic disease; Currently, there is no equine vaccine that has a label claim for protection against EHM;
• There is no specific treatment that has been proven effective for EHM;
• If your horse has potentially been exposed to an infected horse (or through contact with people or equipment that have been in contact with an infected horse), or is showing signs that could indicate EHM, quarantine your horse and other potentially exposed horses and contact your veterinarian.

For more information, visit the AVMA blogpost on this subject.