Horses on a total of three sites in Texas and four premises in New Mexico are known to be infected with vesicular stomatitis (VS), a painful blistering disease of livestock such as horses, sheep, swine, and deer. 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 are the first to be confirmed since l998.
 
“The most recent confirmed cases in Texas involve three horses on a ranch near Denver City, in Yoakum County, about 80 miles southwest of Lubbock, and one horse near Del Rio, in Val Verde County about 150 miles west of San Antonio,” said Dr. Bob Hillman, Texas state veterinarian and head of the Texas Animal Health Commission (TAHC), the state’s livestock and poultry health regulatory agency. The country’s first VS cases this year were confirmed May 19, in three horses, which are confined to their ranch in Reeves County, in far west Texas.
 
To prevent animal-to-animal disease transmission, the 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, a process that usually takes two or three weeks. Prior to quarantine release, the animals will be re-examined by a state or federal regulatory veterinarian, to prevent the spread of disease to other premises.

Dr. Steve England, 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.
 
“During an active year for VS, it is not unusual for this unpredictable disease to be found scattered across several counties and states,” said Hillman. “We urge owners and private veterinary practitioners to report clinical signs of the disease to their state veterinarians’ offices. A disease investigation will be conducted, with laboratory tests run at the National Veterinary Services Laboratory in Ames, Iowa. There is no charge for these services.”
 
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 may place additional testing requirements or restrictions on livestock originating from states with infection. The TAHC has directed private veterinary practitioners to carefully inspect animals for VS, and 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.”
 
The TAHC hotline is operational 24 hours a day at 800/550-8242, with a TAHC or USDA veterinarian always on call to take reports and work with veterinary practitioners. In New Mexico, producers should make reports to the New Mexico Livestock Board at 505/841-6161