Vesicular Stomatitis
This article is about Vesicular Stomatitis, its mode of transmission, its signs and symptoms, its treatment, and how it is prevented.
Vesicular stomatitis is a viral disease that primarily affects cattle, horses, swine and occasionally sheep and goats. Humans can also become infected with this disease when handling affected animals.
This disease usually occurs between late spring and early fall. The seasonal time frame of outbreaks lends to the theory that insects serve as vectors. Sandflies, small moth like blood sucking insects (this could be viewed in detail with an inspection microscope), are said to be responsible for the spread of one type of Vesicular Stomatitis. 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 the said disease. People can become infected and pass the virus between horses. The virus cannot, however, pass through intact skin, 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 is caused by a rhabdovirus, it has a bullet-like shape when examined under an inspection microscope. Signs and symptoms very closely resemble those of Hoof and Mouth disease, which was said to have been eradicated from the United States in the late 1920’s. Cattle tend to suffer the greatest economic losses from these diseases since they develop lesions on their teats. This can result in decreased milk production, painful milking, depression, loss of appetite and potentially serious cases of mastitis. The similarities in outward appearance between the two diseases resulted in vesicular stomatitis becoming a “reportable” disease. This means that any veterinarian or livestock owner that suspects an animal may have vesicular stomatitis must immediately contact federal authorities that deal with animal health.
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 (these organisms can be observed with an inspection microscope) infections will usually recover within two weeks.
According to scientists at Washington Animal Disease Diagnostic Laboratory, there are two tests that are used most frequently by veterinarians. The first involves isolating the virus from a swab taken from blisters or ulcers of affected animals. The virus isolation test takes about 48 hours for an answer. For the second test, the veterinarian collects a blood sample in “red top” tubes in order to run a serum test when the blood coagulates. Two different serum tests check for antibodies that the infected horse will have in his bloodstream. The Complement Fixation Test detects early antibodies. If the horse was infected previously, and is not currently positive by the Complement Fixation test, the serum will come back positive in the Serum Neutralization Test, but negative by the Complement Fixation test.
To control Vesicular Stomatitis, there is a vaccination made specifically available for horses. The vaccination is made up of killed virus, thus 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 vaccinated horse.
To prevent the spread of the disease, it is important to quarantine the horse immediately. The handler must then minimize the potential of infection by having completely separate water sources, and by decreasing potential cross contamination through shared salt blocks, or feeding utensils.
