Several new cases of vesicular stomatitis (VS) have been confirmed in horses in Texas and Colorado over the past week. The Colorado Department of Agriculture also reported diagnoses of VS in two cattle earlier this month, and several states have modified their livestock import requirements to prevent spread of the disease.

Since the last USDA situation report on August 6, 64 new premises have been confirmed for VS infections in Colorado, 62 due to infections in equines and two with infections in cattle. In Texas, the latest report showed 11 new premises with infected equines and one with infected cattle.

So far this year, a total of 186 VS-positive premises have been identified, with 133 in Colorado and 53 in Texas. On May 28, the Texas Animal Health Commission (TAHC) announced confirmation of the nation’s first case of VS this year in horses in Kinney County.

Vesicular stomatitis virus (VSV) is classified as a rhabdovirus, and there are two serotypes of VSV – New Jersey and Indiana. Outbreaks this year have involved the New Jersey serotype. Infection with one serotype is not cross-protective for the second serotype. Clinical signs of VS, which can affect equines, cattle, bison, sheep, goats, pigs and camelids include vesicles, erosions, and sloughing of the skin on the muzzle, tongue, teats and above the hooves.

Insect vectors are the primary source of transmission of VS although mechanical transmission occurs in some species. Fly control is a key component in preventing spread of the virus.

Rarely, VS can affect humans, typically those who are in contact with infected animals. In humans the disease typically causes flu-like symptoms. Find more information about the disease on the University of Wisconsin’s Vetmed website.

Several states have modified their requirements for importing livestock in an effort to prevent the spread of VS. TAHC has compiled information states have provided on enhanced entry requirements they are imposing on Texas livestock (including cattle and horses) due to the recently announced VS cases. View the list of states and their requirements here.

Veterinarians and livestock owners who suspect an animal could have VS should contact state or federal animal health authorities. Livestock with clinical signs of VS typically will be quarantined until they clear the virus and present no further threat to transmit the disease.

USDA provides weekly situation reports, maps and other information on VS online.