Vesicular stomatitis is a viral disease that more commonly affects horses living in warmer climates. [1][2]

The disease typically results in blister-like lesions (referred to as vesicles) forming in and around the mouths of horses and other farm animals. This condition is usually self-limiting, meaning it resolves without medical intervention. [2][3][4]

A diagnosis of vesicular stomatitis can be made using specialized tests on collected blood or samples of active skin lesions. [1][2] Contact a veterinarian if vesicular stomatitis is suspected in your horse, as it is a reportable disease. [4]

Since no vaccines exist, strict biosecurity measures are critical to prevent its spread through the herd. Key measures include implementing proper disinfection and quarantine protocols, as well as controlling insect populations. [1][2][3][4]

Vesicular Stomatitis in Horses

Vesicular stomatitis (VS) is an infectious viral disease that belongs to the family of viruses known as Rhabdoviridae. [1][2]

Two viruses of the VS group are particularly significant in horses in the United States: vesicular stomatitis viruses (VSV) New Jersey and Indiana, named after the locations where they were first isolated in the early 1900s. [2]

VS is most common in warmer climates. In the southwestern United States, like California and Colorado, outbreaks of the disease are sporadic. This is in contrast to other, warmer climates like South America, Central America, and Mexico, where the disease is endemic, meaning it is always present. [1][2][3][4][5][6]

The disease is typically seasonal and is most prevalent in the summer to early fall (May to October). Vesicular stomatitis can affect all mammals, including farm animals such as cattle, pigs, sheep, goats, and llamas. [2][3][4]

The disease causes blister-like lesions on the body, known as vesicles. These lesions are typically found in and around the mouth. The inflammation caused by these blisters is referred to as stomatitis, which is where the name vesicular stomatitis is derived. [1]


Clinical signs can appear within 2-8 days of the initial infection. Many horses may exhibit a fever and drooling before other clinical signs develop. [2][7]

The most striking clinical signs associated with vesicular stomatitis are the blistering and ulceration caused by the disease. Blisters, ulcers, and eventually crusting lesions develop on hairless areas of the skin and the mucous membranes (nose, eyes, and gums). [2][3][4]

Lesions are most commonly found on the horse’s: [2][3][4]

  • Mouth
  • Lips
  • Tongue
  • Muzzle
  • Nose
  • Ears

Less commonly affected areas include: [2][3][4]

  • Coronary bands around the hoof
  • Udder or teats
  • Penis sheath and prepuce
  • Ventral abdomen

Lesions may appear as small spots, or they can coalesce and become large areas of erosions or ulcerations. [2]

Other Signs

Other more general clinical signs that may be noted secondary to these lesions include: [3][4]

A low percentage of infected animals do not develop clinical signs. [2][8][9]