Beware of EVA in Horses


Equine Viral Arteritis is nothing for horse owners to sneeze at, especially as breeding season is just around the corner. In particular, Texas equine producers, veterinarians and livestock health officials have become increasingly concerned about Equine Viral Arteritis (EVA), which has been detected in New Mexico and Utah this year. A viral disease of horses, donkeys and other equine animals, EVA causes mares to abort, can cause mild to severe respiratory disease in some horses and may also cause some stallions to become chronically infected and shed the virus in semen. While EVA has been encountered rarely and is not a reportable disease in Texas, regulations have been implemented in some states, including Kentucky, New York and Colorado.
While some infected equine exhibit no signs of disease, owners should be alert and notify their accredited private veterinary practitioner if horses or foals develop signs of EVA, including fever, depression, diarrhea, coughing or nasal discharge, or swelling of the legs, body or head. Laboratory testing is necessary to confirm a diagnosis, as other equine diseases can present similar clinical signs.
“EVA is not currently a reportable disease in Texas,” says Dr. Bob Hillman, Texas’ state veterinarian and head of the Texas Animal Health Commission (TAHC), the state’s livestock and poultry health regulatory agency. “However, we urge veterinarians and horse owners to report suspected and confirmed cases of EVA to the TAHC to ensure we have the most accurate picture of the disease in the state and can provide up-to-date information to veterinarians and equine owners.”
Horses can be infected by inhaling the equine arteritis virus, through natural service of a mare by a carrier stallion, artificial insemination of a mare with semen from a carrier stallion, or by being exposed to bedding or other objects contaminated with the virus. Stallions that shed the equine arteritis virus in their semen can infect unvaccinated mares, causing a respiratory disease and abortion. Acutely infected horses spread the infection to other horses via the respiratory route. A pregnant mare may also be infected through contact with acutely infected horses and may abort. Cleaning and disinfection of stalls, trailers and equipment can reduce the risk of EVA exposure.
“Know the EVA status of stallions, semen shipments and mares before they are introduced onto your farm. Consult your accredited private veterinary practitioner about vaccination protocols for brood mares, stallions and colt foals, and ensure that good biosecurity measures are followed,” Hillman says.

Links to additional information about EVA may be accessed at the TAHC’s web site at



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