The country’s first case of Vesicular Stomatitis (VS) since 1998 was confirmed Wednesday, May 19, on a premise with nine horses and eight head of cattle near Balmorhea, in Reeves County in west Texas. VS is a viral disease that occurs sporadically in the U.S., usually in southwestern states. The disease can affect horses, cattle and pigs, and occasionally, sheep, goats and deer, causing blisters to form in the animal’s mouth, on teats or along the hooves, resulting in excessive salivation, lameness or oozing sores.

The clinical signs of VS can cause concern because they mimic those of a highly contagious foreign animal infection¬foot-and-mouth disease (FMD)¬which has been eradicated in the U.S. since 1929. Laboratory tests must be run to differentiate between the two diseases, when cattle, pigs, sheep or other cloven-hooved animals develop signs of the disease. Unlike FMD, VS also can affect horses and other members of the equine family. Although the disease does not affect food safety, infected livestock are withheld from slaughter until they recover.

“We always launch a disease investigation when blisters or sores are reported in livestock, to determine if foot-and-mouth disease has been introduced into the U.S.,” said Dr. Max Coats, deputy director for Animal Health Programs for the Texas Animal Health Commission (TAHC), the state’s livestock and poultry health regulatory agency. “Because horses are not susceptible to FMD, we knew, in this case, that the animals had vesicular stomatitis (VS), or possibly had come in contact with poison or a toxic plant. The National Veterinary Services Laboratory (NVSL) in Ames, Iowa, has confirmed that the three horses in Reeves County have VS.”

Dr. Coats said researchers have determined that VS outbreaks are started by a virus transmitted by arthropods, such as ticks, mites, biting midges, mosquitoes or house flies. Following an incubation period of two to eight days, infected animals may develop clinical signs of disease. The outbreak then can be perpetuated by biting insects that carry the disease from infected to healthy livestock. VS-infected animals also can spread the virus if their saliva or the fluid from ruptured blisters contaminates equipment or feed shared by herd mates. Sick animals should be isolated until they heal, he said.

Dr. Coats noted that all livestock on the affected ranch in Reeves County will remain quarantined for several weeks, until they no longer pose a health threat to other livestock. 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.

“VS is rarely fatal, and infection usually runs its course in a couple of weeks,” commented Dr. Coats. “Infected livestock may need supportive care to prevent secondary infections where blisters have ruptured. The affected animals also may lose condition, because they will avoid eating as long as their mouth is sore. Lesions can also occur along hooves, resulting in temporary lameness.”

“The only thing ‘regular’ about VS is its irregularity,” he said. “Thirteen years passed between a l982-83 outbreak of VS and one in l995 that involved infection on more than 365 ranches in five states. These affected states were New Mexico, Colorado, Arizona, Utah and Texas, where infection was confined to only one premise.”

“Texas was spared in May l997, when the disease was detected in Arizona in horses. By late fall, when the outbreak ended, infection had been detected on 380 ranches in four states; Arizona, Colorado, New Mexico and Utah,” he continued. “Prior to the today’s case, VS was most recently confirmed in l998, in Texas’ Reeves County, and in New Mexico.”

“As a biosecurity measure, ranchers and veterinarians should wear rubber or latex gloves when handling potentially infected animals, and they should wash their hands thoroughly afterward. Humans reportedly may contract VS and develop flu-like symptoms that can last four to seven days,” warned Dr. Coats.

"If your livestock develops blisters, erosions or sores, don’t pass it off as another case of VS,” Dr. Coats said. “It is extremely important that we collect samples and have laboratory tests run to determine the cause of illness. Report these signs of disease to your private veterinary practitioner or the TAHC immediately. The TAHC hotline number is operational 24 hours a day at 1-800-550-8242, and a TAHC or U.S. Department of Agriculture veterinarian always is on call to take reports and work with your private veterinarian at no charge.”

“If you plan to ship horses or other livestock out of state, contact the state of destination prior to transporting the animals,” urged Dr. Coats. “Because VS has been confirmed in Texas, some states may require our shipments of livestock to undergo additional inspections or testing. Producers and veterinarians may contact the TAHC at 1-800-550-8242, if they need contact information for animal health officials in other states.”