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Deadly Equine Virus Outbreak Traced to Utah Competition

Deadly Equine Virus Outbreak Traced to Utah Competition

Strain of DNA virus hits 14 horses in 6 states, Canada; 5 animals are dead and horse owners are urged to closely monitor animals.

Just as the spring horse show season moves into full swing, owners and trainers are encouraged to monitor their horses for symptoms of a potentially serious disease that is easily spread from horse to horse or through shared equipment.

The warning follows an outbreak of equine herpesvirus myeloencephalopathy at a competition in Utah April 29-May 8, in which horses from other states competed. Since then, the virus appears to have spread to several other states, according to a Kansas State University veterinarian.

As of May 18, a total of 14 confirmed or suspected cases have been reported in the United States, including five deaths. The states reporting confirmed or suspected cases by that date included California, Colorado, Idaho, New Mexico (suspected), Utah (suspected), Washington, and Alberta, Canada.

There have been no confirmed or suspected cases reported in Kansas so far (as of May 18), said Beth Davis, associate professor of clinical sciences in K-State's College of Veterinary Medicine.

"Equine herpesvirus 1, or EHV-1, is one of a large group of DNA viruses causing potentially serious disease in horses and other species," Davis said. "EHV-1 can cause different forms of disease, including abortion in mares, respiratory infection and neurological symptoms. The most recent outbreaks have involved the EHV-1 respiratory/neurological form of the virus, or equine herpesvirus myeloencephalopathy (EHM)."

The virus is contagious and is spread by direct horse-to-horse contact, but also by contaminated hands, equipment and tack, said Davis, who serves as K-State's section head for equine medicine and surgery. The virus also can spread for a short time through the air within the stall and stable environment.

Horses infected with the neurologic strain of EHV-1 might have a fever as well as nasal discharge, incoordination, hindend weakness, recumbency, lethargy, urine dribbling and diminished tail tone.

Currently there are no EHV-1 vaccines that have been proven to prevent against the development of EHM, Davis said. She recommends that horse owners contact their local veterinarian or the K-State Large Animal Desk , 785-532-5700, to discuss potential vaccine recommendations that may be implemented to help limit the severity of disease, should their horse become exposed to the virus.

"If horse owners notice that a horse develops fever, respiratory or neurological signs, they should call us or their local veterinarian and not move the horse or horses in the immediate area," Davis said. "We are also urging horse owners in this situation to alert those who have horses in the adjacent vicinity to cease all movement in or out of the facility until a diagnosis is confirmed by testing. If horses are exposed and then travel to a new stable or show, the infection can spread to other horses at the new location."

Davis is encouraging horse owners who have questions or notice such symptoms to contact their veterinarian or K-State's Large Animal Desk at 785-532-5700. She has developed a fact sheet, available on the website: Click on the link under the photo or on "Timely Topics" on the left side.

Information about this group of DNA viruses is also available on the American Association of Equine Practitioners website: Specific information about EHV-1 is available at and frequently asked questions/answers are available at

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