Vesicular Stomatitis Case Counts Climb in Texas and New Mexico

Horses on nine sites in Texas and four premises in New Mexico have vesicular stomatitis (VS), a painful blistering disease of livestock such as horses, cattle, sheep, swine, and deer. Because of the findings, emergency VS regulations in Florida and Kentucky have taken effect to help keep out VS. The viral disease appears spontaneously and sporadically in the southwestern United States and is thought to be transmitted by sand flies and black flies.

The VS cases this spring, which were confirmed beginning May 19, were the first to be confirmed in the United States since 1998. The infection had been confined to about 25 horses in both states. All aspects of the disease are not fully understood, because outbreaks occur infrequently. Officials have said this year's outbreak could potentially continue until late fall.

At press time (June 24) the sites under quarantine in Texas were:

  • One ranch in Reeves County in far west Texas;
  • One ranch in Yoakum County, near Denver City;
  • One ranch in Val Verde County,
  • One ranch in Uvalde County; and in South Texas,
  • Four ranches in Starr County; and
  • One ranch near Carrizo Springs in Dimmitt County.

The Texas Animal Health Commission (TAHC) requires that the VS-infected animals and the other livestock on the premise remain quarantined until 30 days after all VS blisters or lesions heal, which usually takes two to three weeks. Prior to quarantine release, the animals will be re-examined by a state or federal regulatory veterinarian.

Steve England, DVM, state veterinarian for New Mexico, said a "handful" of horses on four small premises near Carlsbad, N.M., were found to be infected since June 4. The animals remain quarantined on their premises.

Signs of VS, which include blisters, open sores or erosions in an animal's mouth, on the muzzle, teats, or hooves--mimic those of foot-and-mouth disease (FMD), an extremely dangerous and highly contagious foreign animal disease that can affect cattle, sheep, swine, and deer, but not horses. Laboratory testing is needed to differentiate between VS and FMD, or to determine if the animals had contact with a toxic plant or poison.

During a VS outbreak, animal health officials across the country might place additional testing requirements or restrictions on livestock originating from states with infection, as Florida and Kentucky have done (see for specifics on the restrictions). The TAHC has directed private veterinary practitioners to carefully inspect animals for VS and to document the exam on certificates of veterinary inspection (health papers) issued for livestock leaving Texas. A similar statement also is required on paperwork for livestock entering Texas from other states with VS infection. Hillman recommended producers or veterinarians check with each state of destination prior to shipping livestock.

"To help prevent VS, control biting flies," said England. "Keep horses and other equine animals under a roof at night and keep stalls clean to reduce exposure to flies. If you borrow equipment or tools from another rancher, disinfect them before using them. At shows, on trail rides, or other events, make sure your animals are fed and watered from their own buckets or troughs. If your horses, cattle, sheep, deer, or other livestock develop blisters or open sores indicative of VS, call your practitioner and state veterinarian's office."

In Texas, the TAHC can be reached to report possible VS 24 hours a day at 800/550-8242. In New Mexico, make reports to the New Mexico Livestock Board at 505/841-6161.

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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