Investigators in Texas confirmed the country’s first case of vesicular stomatitis (VS) since 1998. Test results on Wednesday confirmed that the three affected horses at the farm near Balmorhea, Texas were indeed infected with VS. The operation has nine horses and eight head of cattle and has been quarantined.
VS is a viral disease that occurs sporadically in the U.S. — usually in southwestern states — and can affect horses, cattle and pigs, and occasionally, sheep, goats and deer. The disease causes blisters to form in the animal’s mouth, on teats, or along the hooves, resulting in excessive salivation, lameness or oozing sores.
Clinical signs of VS mimic those of a highly contagious foreign animal infection called foot-and-mouth disease (FMD). The U.S. eradicated FMD in 1929. Laboratory tests are the only way to differentiate between the two diseases. 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.," says Max Coats, deputy director for Animal Health Programs for the Texas Animal Health Commission. "Because horses are not susceptible to FMD, we knew, in this case, that the animals had vesicular stomatitis, or possibly had come in contact with poison or a toxic plant. The National Veterinary Services Laboratory in Ames, Iowa, has confirmed that the three horses in Reeves County have VS."
A virus that is transmitted by arthropods, such as ticks, mites, biting midges, mosquitoes or house flies generally starts VS outbreaks. Following an incubation period of two to eight days, infected animals may develop clinical signs of disease. Biting insects, which carry the disease from infected to healthy livestock, can then spread the disease. The virus also can be spread from aVS-infected animal’s saliva or if the fluid from ruptured blisters contaminates equipment or feed shared by herd mates. Sick animals should be isolated until they heal.
All of the 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. 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.
"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," warns Coats.
"If your livestock develops blisters, erosions or sores, don’t pass it off as another case of VS," stresses Coats. "It is extremely important that we collect samples and have laboratory tests run to determine the cause of illness."
Report any 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 is always on call to take reports and work with your private veterinarian at no charge.
Texas Animal Health Commission