Vesicular Stomatitis in Colorado

Vesicular stomatitis (VS) has been confirmed in three horses on two farms in Colorado, resulting in the quarantine of affected premises and transportation restrictions on Colorado livestock to two other states. One affected farm with two VS horses is in Las Animas County, which is on the southeast border of the state, and one Douglas County horse is affected in Central Colorado. Veterinarians suspect VS in an additional two Las Animas animals, a beef cow and a horse, on a separate premise from the equine cases.

According to Wayne Cunningham, DVM, MS, Colorado state veterinarian, the index (first) case, which occurred on the Las Animas site with two affected horses, began showing clinical signs of VS on June 27. Signs included blister like lesions on the mouth, tongue, and nostrils. This horse and the others in Las Animas County, "Are backyard horses, were not traveling, and were staying in one spot," said Cunningham. "The one horse in Douglas County had been to New Mexico a week or so prior."

The suspected bovine case is located five to six miles away from the other Las Animas premises. Blood samples have been sent to the USDA's Plum Island foreign animal disease laboratory in New York. "I think that will be a confirmed case--it will be tomorrow or Thursday before we hear (results)," said Cunningham. "The reason we (sent this sample to Plum Island) is because we have to differentiate vesicular stomatitis from foot and mouth disease (FMD). You can't tell them apart clinically, but certainly it's most likely VS. We just want to err on the side of caution."

Horses are not affected by the foreign animal disease FMD, which infects cloven-hooved livestock. Foot and mouth disease could have devastating ramifications to national and international movement of livestock. Since horses have shown VS in Las Animas County, it is expected that VS is what is ailing the cow.

Spread of VS probably occurs through insect vectors (arthropods such as ticks, mites, biting midges, mosquitoes, or house flies) and mechanical transmission (on shared buckets, brushes, water tanks, etc.). The disease can be spread if the saliva or fluid from ruptured blisters of an infected animal contaminates shared feed or equipment. Incubation of the virus ranges from two to eight days, and excessive salivation is often the first sign. Blanched and raised vesicles in the mouth of affected animals are often noted, and these lesions generally occur on the upper surface of the tongue on horses.

Cunningham's staff has put out media releases and is working with the state extension service and the Colorado Veterinary Medical Association to help educate horse owners and livestock producers on preventing eruption of the disease in their livestock.

"All of the premises are quarantined," said Cunningham. "The way we work with that is when the last lesion is healed on the last animal, we count 30 days and then release the quarantine. So (the quarantine release) depends on how rapidly they heal."

At press time, only Kentucky (see and Idaho (horses being imported into the state from Colorado, New Mexico, and Texas will need a VS-free permit) had placed restrictions on animals from Colorado.

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.

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