VESICULAR STOMATITIS

As of June 15, (press time), there has been a foreign animal disease outbreak of Vesicular Stomatitis (VS) identified in New Mexico. Suspected cases have been investigated in Las Cruces, Cliff, and Las Lunas, New Mexico. Other locales will probably be involved within the next few weeks. The majority of premises investigated have involved horses; however, cattle cases have been investigated and cattle are equally susceptible to the disease.

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 affected animals. These vesicles or 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 lasting 9 days (range 3-14 days) usually. 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. The 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 affected 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 10 years. The last outbreak of VS in this country was in 1982 & 1983. At that time, it caused major economic losses in California, mainly in dairy cattle. The VS virus is thought to be spread by the bites of various insects and outbreaks 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 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 the sporadic nature of the disease and the fact that most all affected animals recover.

If you see blister or any of the other common signs of VS, salivation, lameness, or mammary vesicles, contact your 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. If the current outbreak in New Mexico expands to other states, restrictions on the movement of cattle, horses, and/or swine coming into California may go into effect. It is very important to consider the possibility of coming into contact with VS infected animals when shipping cattle or horses into areas where VS outbreaks are occurring, such as is currently the case in New Mexico. Your veterinarian and the State Veterinarian's office will be receiving frequent updates on the current outbreak in New Mexico.

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.

John Maas, DVM, MS
Diplomate, ACVN & ACVIM
Extension Veterinarian
School of Veterinary Medicine
University of California-Davis