Five Premises Under VS Quarantine in Wyoming

The USDA has reported the detection of vesicular stomatitis (VS) in nine horses on five premises in eastern Wyoming. Vesicular stomatitis, which normally moves up from the Southwest along waterways, has not appeared elsewhere in the country this year. This has lead researchers to believe VS might have overwintered in Wyoming, and they're trying to figure out how.

Vesicular stomatitis is a viral disease that primarily affects horses, cattle, and swine, but it can also affect sheep and goats. The disease causes blister-like lesions in the mouth and on the dental pad, tongue, lips, nostrils, hooves, prepuce, and teats of livestock. When the blisters break, they can leave raw, painful areas that can precipitate lameness and reluctance to eat. Animals with VS should be isolated from other livestock to ensure that troughs and feed buckets are not shared. Affected farms are encouraged to increase their insect control measures because biting flies such as Culicoides midges might be responsible for carrying the disease.

The two affected counties--Converse and Natrona--border one another, and the affected premises (one in Converse and four in Natrona) are situated near waterways. Donal O'Toole, MVB, MRCVS, PhD, Dipl. ECVP, FRCPath, director of the Wyoming State Veterinary Laboratory and head of the Department of Veterinary Sciences at the University of Wyoming in Laramie, said VS typically moves up out of the southwestern United States and appears in other states before springing up in Wyoming. This year there was no warning.

"The virus isolate from the first horse to come up positive in Natrona this year has been compared by the USDA to isolates from from Wyoming and Montana last year," said O'Toole. "Although I don't know the specific details, I understand it is a close match. The inference is that vesicular stomatitis virus somehow managed to overwinter in Wyoming in 2005-06.

"This is an interesting situation since in the past we've always assumed this disease comes out of Central America or Mexico and moves north in big jumps we don't understand," he added. "The similarity of the current isolate suggests that some years the virus can hang around in the U.S. and pop up the following year."

O'Toole said that several USDA officials were investigating what the overwintering host might be. They hoped to find some clues before the first frost--which usually occurs in September--that would kill off any potential insect vectors.

Livestock officials take signs of vesicular disease in livestock very seriously because animals with VS can appear as if they're suffering from foot and mouth disease (which horses cannot contract). That disease could cause major national and international ramifications on livestock sales and transportation.

Agriculture officials in Florida and Kentucky have placed restrictions on animals being shipped from Wyoming (Florida: and Kentucky:

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More