Fact Sheet No. 6: Vesicular Stomatitis
By John Maas, DVM, MS Diplomate, ACVN & ACVIM Extension Veterinarian School of Veterinary Medicine University of California-Davis

Description and Cause

Vesicular Stomatitis (VS) is a disease that is caused by a virus and it affects cattle, horses, swine, deer, and humans. The VS virus is classified as a rhabdovirus because of its bullet shape. The disease in horses, cattle, swine, and deer is characterized by vesicles or blisters. These blisters form in the mouth, on the tongue and lips, on the feet, and on the teats and mammary gland of affective animals. These vesicles of blisters tend to be large and very painful. Also, the vesicles of VS are indistinguishable from those of Foot and Mouth Disease. The disease in humans causes flu-like symptoms with the occasional blister around the nose or mouth.

The disease has an incubation period usually lasting 9 days (with a range 3-14 days). That is to say, that once the animals are exposed to the virus it takes about 9 days before the blisters are seen. The vesicles that occur in the mouth and around the lips cause excess salivation or slobbering and the animals do not want to eat or drink and therefore, lose weight. They are particularly reluctant to eat dry, rough feed. These lesions around the coronary band of the feet cause lameness and the animals are reluctant to walk. The lesions around the teats of the mammary gland cause the cows to be painful when nursed and the virus will be easily passed to the calves. Also many of the vesicles occur on the teat ends and this can lead to severe mastitis in affected cows. This is particularly of importance to dairy cattle. The disease causes economic losses due to weight loss, and mastitis.

While the percentage of cattle and other animals affected is usually very high, the number of animals that die is quite low. The main significance of VS is that:

• it is a foreign animal disease,
• it has clinical signs identical to Foot and Mouth disease,
• and it can cause significant economic losses in affecting animals.

Swine and dairy cattle have more economically significant losses than do beef cattle and horses under most circumstances. Vesicular Stomatitis seems to invade the United States approximately every ten years. The last outbreak of VS in this country was in 1982 & 1993. At that time, it caused major economic losses in California, mainly in dairy cattle.

Transmission

The VS virus is thought to be spread by the bites of various insects and out breaks occur most commonly in the summer and fall. However, the VS virus can also be spread by contact from one animal to the next. This direct, animal to animal, spread was particularly important in the last major outbreak. Most animals affected with VS recover in 2-3 weeks; however if the vesicles become infected by bacteria or fungi, recovery can take longer. One of the main considerations with VS is that it cannot easily be distinguished from Foot-and-Mouth Disease, which is an even more serious disease both for the individual animals and for the affected herds.

Treatment and Prevention

Treatment of affected animals is symptomatic. Death loss can be avoided if ill cattle or horses are offered shade, fresh water, and soft feed. Debilitated animals may be aided by broad spectrum antibiotic therapy to control secondary bacterial invaders. Vaccines for the prevention of VS are not currently licensed for use in the United States due to sporadic nature of the disease and the fact that most all affected animals recover.

If you see blisters or any of the other common signs of VS, salivation, lameness, or mammary vesicles, contact your local veterinarian to examine the animals. Your veterinarian can then contact the California State Veterinarian's office and/or the California Veterinary Diagnostic Laboratory, as needed. Avoid moving your animals into areas where VS has been confirmed or is suspected and do not move or sell suspicious animals before a diagnosis can be made.