Five horses in southwest Texas have been confirmed as having the viral disease, vesicular stomatosis.
The US Department of Agriculture Animal and Plant Health Inspection Service confirmed the cases in Kinney County, southeast of Del Rio.
The horses were tested after the owner observed blistering and swelling on the animals’ muzzles and contacted their local veterinarian.
Testing at the National Veterinary Services Laboratories confirmed the virus as the New Jersey serotype.
Vesicular stomatitis can cause blisters and sores in the mouth and on the tongue, muzzle, teats or hooves of horses, cattle, swine, sheep, goats, llamas and a number of other animals.
Lesions usually heal in two or three weeks.
Because of the contagious nature of the disease, which has symptoms similar to foot and mouth disease, animal health officials urge livestock owners and caretakers to report these symptoms to their veterinarian immediately.
Most animals recover well with supportive care by a veterinarian, but some lesions can be painful.
The infected group of horses has been quarantined by the Texas Animal Health Commission.
Affected and exposed horses will be monitored by regulatory veterinarians until all lesions have healed and a decision is made to release the quarantine. This will be a minimum of 21 days, officials said.
There is no known exposure to other horses around the state, or at any equine events, state officials said.
No other cases have been identified in the immediate area or elsewhere in Texas.
“Livestock owners should use the best means possible to limit exposure of their livestock to insect bites,” the state veterinarian, Dr Dee Ellis, said.
“It is thought that insects are an important vector in the transmission of vesicular stomatitis.
“Sand flies and black flies likely play a role in the virus transmission, so controlling insects is important.
“Outbreaks are extremely sporadic and years may lapse between cases.”
The last confirmed case in Texas was in 2009.
Some states and other countries may restrict livestock movements from states with known cases of the disease. People in Texas should contact destination states or countries for their requirements before moving livestock, Ellis said.
State epidemiologist Dr Andy Schwartz said those who suspected any animal had the disease should contact their veterinarian immediately.
“VS is not highly contagious to people but it can cause flu-like illness if infected saliva gets into an open wound, eyes or mouth.
“People handling potentially infected animals should wear gloves for protection, and talk with their physician if they have questions.”