On Friday, May 20, Texas joined New Mexico and Arizona as states with confirmed cases of vesicular stomatitis (VS) this spring. Two Travis County horses were hauled home May 10 from a trail ride in Arizona, where they apparently were exposed to the virus that can cause animals to develop blisters and sores in the mouth, on the tongue, muzzle, teats and hooves. The year’s first VS cases were confirmed April 27 in two horses in southwest New Mexico. Since then, infection has been detected in 17 horses on 11 premises in New Mexico, Arizona, and now, Texas.

“A number of states and countries impose strict testing, permitting and inspection requirements for livestock that originate from VS-affected areas or states. Check with the state or country of destination before hauling livestock from Texas,” said Dr. Bob Hillman, head of the Texas Animal Health Commission (TAHC), the state’s livestock and poultry health regulatory agency. Phone numbers for other states’ animal health regulatory agencies can be obtained from the TAHC’s Austin headquarters at 1-800-550-8242. Staff at the U.S. Department of Agriculture’s Austin office can be reached at (512) 916-5565 for international shipping rules or restrictions.

“VS rarely causes death, but an animal can suffer several weeks, while the lesions heal,” said Dr. Bob Hillman, who also serves as Texas’ state veterinarian. “To help prevent the spread of VS, an infected animal and the other livestock on a premises are quarantined until at least 30 days after the sores heal. Prior to releasing movement restrictions, a regulatory veterinarian will examine the affected animal to ensure healing is complete. Other livestock also will be checked. If infection is detected, the quarantine will begin anew.”

Dr. Hillman explained that the clinical signs of VS mirror those of the dreaded foreign foot-and-mouth (FMD) disease. Horses are susceptible to VS, but not FMD; however, both diseases can affect cattle, sheep, goats, swine, deer and a number of other species. “When sores or blisters are seen in FMD-susceptible animals, we must immediately rule out an introduction of foot-and-mouth disease (FMD). When horses have lesions, a VS test rules out other possible causes for blisters and sores, including toxic plants, chemicals or poison. Tests are run at no charge to the animal owner, and the VS diagnosis in horses is confirmed at the National Veterinary Services Laboratory (NVSL) in Ames, IA.”

Dr. Hillman noted that the disease occurs sporadically, but outbreaks generally follow a 10- to 15-year cycle. In l982-83, the country suffered its worst recorded VS outbreak, when infection was confirmed on 617 premises in nine states: Arizona, New Mexico, Colorado, Utah, Wyoming, Idaho, Montana, Nebraska and South Dakota.

Subsequent outbreaks in l995, l997 and l998 were limited to New Mexico, Colorado and Texas, with a few cases in Arizona. Last year, Arizona was "spared,” when Texas had 15 VS cases, New Mexico had 80, and Colorado, 199.

Livestock owners and private veterinary practitioners are urged to report suspected cases of VS to their respective state's livestock health regulatory agency:
Texas Animal Health Commission -- 1-800-550-8242 (operational 24 hours a day)
New Mexico Livestock Board -- 1-505-841-6161
Colorado Department of Agriculture, State Veterinarian's Office -- 1-303-239-4161
Arizona Department of Agriculture, State Veterinarian's Office -- 1-602-542-4293

The TAHC’s web site at http://www.tahc.state.tx.us has additional information on VS and a link to the U.S. Department of Agriculture, where situation reports, maps and movement restrictions and requirements are posted.