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

This week, a premises in Boulder County Colorado was placed under quarantine after a case of VS was confirmed in a horse. The case follows confirmation of VS in four horses on two premises in Weld County Colorado a week ago.

Also this week, TAHC confirmed three new cases of VS in horses on three premises in Texas. So far this year, a total of 16 VSV-positive premises have been identified, 13 in Texas and three in Colorado. On May 28, the 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. Last week, Wyoming State Veterinarian, Dr. Jim Logan, announced that, due to cases of VS recently found in Colorado and Texas, the Wyoming Livestock Board (WLSB) is now requiring that all livestock imported from any state where the disease has been diagnosed must be accompanied by a health certificate written within 10 days prior to entry into the state. Livestock animals include horses, cattle, sheep, goats and swine.

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.