On May 18, the National Veterinary Services Laboratories in Ames, Iowa, confirmed three cases of vesicular stomatitis in a herd of horses in west Texas. It is the first vesicular stomatitis outbreak in the United States since 1998.

According to the Department of Agriculture, a foreign animal disease investigation was initiated at the facility in Balmorhea, Texas, on May 10 to examine several horses with tongue lesions, and U.S. Department of Agriculture officials confirmed the diagnosis after several rounds of testing. The facility has been quarantined, and animals will be re-examined by a state or federal veterinarian before the quarantine is lifted, according to the Texas Animal Health Commission.

Dr. Max Coats, the deputy director of Animal Health Programs for the commission, said in a statement that the commission always investigates reports of blisters or sores in livestock because these may be signs of foot-and-mouth disease. In this case, the commission could rule out FMD because horses are not susceptible to the disease, he said.

Vesicular stomatitis outbreaks occur periodically in the United States. The disease can cause great concern when livestock are affected because its clinical signs mimic those of FMD in susceptible species, and FMD has not been seen in the United States since 1929, according to the commission. When cattle, pigs, sheep, or other cloven-hooved animals develop signs such as sores and blisters, laboratory tests must be run to differentiate between the two diseases.

The virus that causes vesicular stomatitis is transmitted by arthropods. It also may be passed from animal to animal when saliva or the fluid from ruptured blisters contaminates equipment or feed. Humans may also contract vesicular stomatitis and develop flu-like symptoms.

More information about vesicular stomatitis is available at the USDA Animal and Plant Health Inspection Service's Web site, www.aphis.usda.gov/lpa/pubs/fsheet_faq_notice/fs_ahvs.html.