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For Expert Comment: MU Veterinarian Warns of Regional Horse Herpes Outbreak, Advises Vigilance

May 18th, 2011

Story Contact: MU News Bureau, 573-882-6211,

The views and opinions expressed in this “for expert comment” release are based on research and/or opinions of the researcher(s) and/or faculty member(s) and do not reflect the University’s official stance.

COLUMBIA, Mo. – University of Missouri veterinarians are notifying horse owners that a regional outbreak of equine herpes myeloencephalopathy, also known as EHV-1, is occurring in states to the west of Missouri. There are no confirmed cases reported in Missouri.

The outbreak of this infectious disease has been traced to the National Cutting Horse Associations’ Western National Championships in Odgen, Utah, which happened from April 30 to May 8, 2011. Currently, EHV-1 has either been confirmed or is suspected in horses in at least nine different states and Canada. Any horse that was at the Odgen show or in contact with horses at that show should be closely monitored.

“We don’t want to unnecessarily alarm anyone, but this virus is highly contagious and can spread rapidly between horses,” said Philip Johnson, professor in the Department of Veterinary Medicine and Surgery in the MU College of Veterinary Medicine. “Horse owners should be vigilant and informed about the disease. Substantial efforts are under way in the affected states to track the extent of the infection.”

The clinical signs typically start with a fever of 102 degrees Fahrenheit or higher, Johnson said. Other symptoms include:

• nasal discharge from both nostrils                                                 • urine dribbling
• unusual tiredness                                                                           • reduced tail tone
• weakness                                                                                       • difficulty/inability standing
• leaning                                                                                            • recumbency

In addition to horse-to-horse contact, disease transmission also occurs through horse aerosol sprays (forced air from the nose), contaminated hands of horse workers, equipment, tack and food. Current vaccines do not prevent the neurological manifestation of this infection.

Horses that are suspected of carrying EHV-1 should be immediately isolated and tested on-site by a veterinarian. For diagnostic corroboration, veterinarians will obtain nasal swabs and blood samples from suspected horses and any other horses that may have been in contact. Veterinarians employ various treatment strategies when faced with this disease. Some severely infected animals ultimately are unable to stand and must be subjected to euthanasia.

EHV-1 cannot be transmitted to humans or cattle, as the virus is very specific to equine species such as horses, mules and donkeys. Llamas and alpacas can be affected as well.

Horse owners are encouraged to contact their veterinarians with questions or concerns. Veterinarians in the MU Veterinary Medicine Teaching Hospital are available to help veterinarians identify and provide consultation for the treatment of affected animals. The MU Veterinary Medical Diagnostic Lab is conducting the lab testing to determine the presence of the virus. MU Equine Ambulatory veterinarians are available to visit horse owners close to Columbia, Mo.

To contact the MU Veterinary Hospital during normal business hours, Monday-Friday 8:00 a.m. – 5:00 p.m., call (573) 882-7821. For emergencies after hours and on weekends, please call (573) 882-4589.