Vesicular Stomatitis: No Outbreaks In 1999?

According to veterinarians, there are two possible reasons why there have been no reported cases of equine vesicular stomatitis (VS) this year. The first possible reason is that there is actually no disease occuring, the second, is that there might be cases of VS out there, but they remain unreported.

Factors inherent in the virus or in the host population in this year might have affected the absence of the disease in the Southwest this year. These factors range from environmental to ecological, possibly even meteorological. Variables within the virus itself, having to do with how, when, where, and why the infection is hosted, also could be the cause of the apparent absence of the disease.

A touchier subject is the possibility that there are cases of EVS progressing in horses around the country, but are unreported, for reasons ranging from the horse owner not recognizing the onset of the disease to farms fearing the economic repurcussions of a quarantine. “Legally, owners don't have to report--the veterinarians do,” said Colorado State University Research Associate, Elizabeth Mumford, DVM, MS.

Vesicular stomatitis is a sporadic infectious viral disease characterized by blister-like lesions in the mouth and on the lips, nostrils, teats, and coronary bands. How the disease spreads is not fully known; insect vectors and movement of animals could be responsible. Signs of the disease can last from seven to 10 days. The horse might lose weight drastically, but usually will gain it back after oral lesions heal. Clinical signs of the disease have been reported to appear three to 14 days after exposure to an affected animal.

"The signs can look like other diseases. It can look like sunburn, trauma, or lots of other things. Some owners may not ever have a veterinarian come," said Mumford. Owners might think that the symptoms indicate something minor that they feel does not warrant the cost of a veterinary farm call.

A quarantine period can disrupt or wipe out an entire show season, or season of training, buying, and selling horses. Therefore farms might knowingly have a horse with VS, but have chosen not to report it to the veterinarian.

Mumford stresses how extremely important it is to report cases of VS to veterinarians. VS research in progress will attempt to solve the mysteries of this disease, but that research requires information from the field; a problem for researchers if there are, in fact, unreported cases of the disease. "Unless we have all the information available as to where the virus is occuring, our hands are somewhat tied in terms of being able to perform effective field research," she said.

The Morris Animal Foundation and the CSU Center for Veterinary Epidemiology and Animal Disease Surveillance Systems (CVEADSS) are funding the research of VS. The three-year studies are based in Colorado and New Mexico on 20 different premises. All of the premises have had VS occur in their horses in the past. Research follows the same group of horses, trying to identify any disease and changes in the horses' antibody status. Also, the studies should help researchers understand and prevent exposure in non-outbreak areas.

The Colorado study is in its second year, the New Mexico study in its first. Both studies are in their data collection phase, with no current report or speculation about the results. According to Mumford, the veterinarians' and researchers' primary concern is the possibility of unreported cases, and letting horse owners know how important it is to recognize, report, treat, and respond to the disease.

Owners can help by learning how to recognize symptoms of VS outlined briefly above. Read more on our site about Vesicular Stomatitis.

Proceed and contact your veterinarian for an examination if you suspect VS, or if there are unreported cases of VS in your area, please contact the state veterinarian and inform them of the prevalence.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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