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Vesicular Stomatitis (VS) Overview

Vesicular Stomatitis (VS) is classified as a rhabdovirus since it has a rod-like shape when examined under a microscope.  Signs and symptoms very closely resemble those of Hoof and Mouth disease, which was eradicated from the United States in the late 1920's.  Diagnosing horse ailments requires a vet. (Click here for a list of Florida veterinarians)
Vesicular Stomatitis VS Transmission: Vesicular Stomatitis usually occurs between late spring and early fall. The seasonal time frame of outbreaks lends to the theory that insects serve as vectors.  Phlebotomine sandflies are responsible for the spread of one type of VS.  In addition, mechanical vectors such as shared feed tubs and water troughs, or exposure to saliva or fluids from lesions can increase transmission potential of VS.  People can become infected and pass the virus between horses.  The virus cannot, however, pass through intact skin; it is opportunistic, and thus may enter through a break in the skin or a wound.  This may be an important consideration if horses are being vaccinated in the vicinity of infected animals.
Vesicular Stomatitis VS Symptoms: The incubation period for the disease can vary from two to eight days.  The horse may develop a fever at the time that blisters begin to form on the tongue, gums or hoof area.  Unfortunately, the blisters often go unnoticed until the horse goes off feed due to painful lesions left after the blisters have burst.  Then, by the time the lesions are discovered and the animal quarantined, the entire herd may have already been exposed.  The most common signs in horses include frothing or drooling from the mouth and blisters or lesions as a result of broken blisters.  Occasionally, a horse may show lameness or develop laminitis if he has ulcers in the hoof area.  Infrequently, this can result in the sloughing of his hoof.  Vesicular Stomatitis is rarely deadly, and horses without secondary bacterial infections will usually recover within two weeks. This can result in decreased milk production, painful milking, depression, loss of appetite and potentially serious cases of mastitis.
Vesicular Stomatitis VS Treatment: There is a vaccination made specifically for horses, but the State Veterinarian controls distribution of the vaccine. Since the vaccination is comprised of killed virus, a vaccinated horse's serum will show positive for both serology tests.  Therefore, a vaccinated horse will test positive and may have the same limitations of an infected horse.  An owner must have proof of identification and excellent vaccination records to avoid travel limitations on his/her vaccinated horse.  Horses are rarely vaccinated, except in the case where an outbreak has occurred in the vicinity.