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Vesicular Stomatitis and Horses

Author: marilyn m fisher

Let's say you buy a handsome bay Thoroughbred from a reputable source. The Coggins Test proves he doesn't have Equine Infectious Anemia, and your veterinarian assures you she's never seen such a healthy four-year-old. You put him in your pasture where he settles down to eating as much grass as he can. He makes a couple of buddies, including your dog. But just when summer begins, he gets sick-- alarmingly so.

When the vet comes, she gives you a tentative diagnosis of vesicular stomatitis.
Although it's comforting to know that most horses will recover in two weeks, if they don't have secondary bacterial infections, it's important to know about and recognize vesicular stomatitis, because it is highly contagious and thus a reportable disease.

APHIS (Animal and Plant Health Inspection Service) explains that "there are serious economic and regulatory repercussions associated with the diagnosis, and once the disease is detected in the United States, many countries take action to block international trade of US animals. Interstate movement of animals is also impacted."

Locally, all premises containing affected animals have to be quarantined for a specified period until the last affected animals have healed. These quarantine periods may be quite long. Thus, this disease has local, national, and international ramifications. This article will give a brief overview of vesicular stomatitis.

Between late spring and early fall, horses and other animals (cattle, pigs, and more rarely, sheep, llamas, alpacas and goats) may develop vesicular stomatitis. The disease is caused by a rhabdovirus, meaning that the virus appears under the microscope as rod-shaped. It is theorized that insects active during this time transmit the microorganisms for VS to horses that have a break in their skin or a wound. The incubation period (the time of the first exposure to the first signs) is anywhere from two to eight days.

The symptoms of VS look frightening to a horse owner. One early one is that the horse salivates excessively. The name of the disease, vesicular stomatitis, refers to the blisters or vesicles which develop in the horse's mouth. These blisters, filled with fluid, are on his tongue and gums. When they break and become raw, the horse refuses to eat or drink. It's too painful.

If VS has spread to his feet, he may be limping because he has ulcers in his hoof area around the coronary band, the place between his skin and the hoof where all growth occurs. His hoof may even be sloughing. Common sense dictates that a horse owner call the vet at once if a horse is displaying some or all of the above symptoms.

The vet will contact state and federal authorities and send samples for laboratory analysis to determine whether the horse actually has VS and analyze the activity of his antibodies. (There are other conditions which have some of the same symptoms.)The vet usually performs two procedures. In one, the vet takes a sample from the blisters or tissue flaps to isolate the virus. It takes about forty-eight hours to find out if the horse has VS. The vet may also decide to draw a blood sample for two serum tests to examine the antibodies of the infected horse. Samples are sent to the US Department of Agriculture's National Veterinary Services Laboratories.

Unfortunately, it is not fully known how VS migrates from one horse to another. Possibilities include:

  • those same disease-bearing insects mentioned above
  • infected communal feed tubs, water buckets, housing, equipment, and trailers
  • exposure to the saliva or fluids from the lesions of an infected

There is no specific treatment or cure for VS. The owner can use soft feeds and a gentle antiseptic mouthwash to relieve the horse's pain and to help him recover. The vet may prescribe anti-inflammatory medicine to reduce the swelling in the mouth, and antibiotics if there is a secondary infection in the ulcerated places.

In order to prevent VS from spreading to other horses, the infected horse should have a separate water source and his own feeding utensils, and he should be stabled. The owner should try to eradicate insects by setting up an insect control program, including the use of approved insecticide sprays, and/or insecticide-treated eartags. VS horses can only be transported if specific guidelines in the states where the
horses reside are followed. Moving may be allowed for slaughter or twenty-one days after the last lesions have healed.

It is rare but possible for a person to contract VS when working with infected animals. Owners should wear latex gloves and stay away from direct contact with the horse's blister fluids or saliva. A person's eyes, mouth and open wounds should not be exposed to the infection.

In humans, the disease manifests itself in flu-like symptoms like muscle aches, headache, fever and fatigue, and a general feeling of being sick. A doctor should be contacted right away. There is a horse vaccination, but its use is open to debate as to its effectiveness. How long the vaccination is effective is arguable, and because the vaccine is made up of killed virus, a vaccinated horse's serum will show positive for the two serology tests mentioned earlier. The horse will have to abide by the same conditions as an infected horse.

The horse's owner has to have proof of identification and meticulous vaccination records to avoid travel restrictions on the vaccinated horse. Horses are rarely vaccinated except if an outbreak has occurred in their vicinity. VS has been confirmed only in the Western Hemisphere, found in the warmer regions of North, Central and South America. However, it can occur in temperate regions of the hemisphere as well. In Southwestern United States, outbreaks often occur along waterways or in valleys.

There was an eruption of VS in 2005. On April 27, 2005, the first case of VS was discovered. A seven-month outbreak ensued. JAVMA News reports that "440 premises were placed under quarantine in Arizona, Colorado, Idaho, Montana, Nebraska, New Mexico, Texas, Utah, and Wyoming." 405 premises were later
released from quarantine. On April 11, 2006, The World Organization for Animal Health was informed by the United States that the 2005 VS outbreak was over. VS is indeed a serious disease, one which horse owners need to understand.

For more information on vesicular stomatitis, go to and

About the author:
Marilyn M. Fisher's first novel is The Case of the Three Dead Horses, a mystery set in Central Virginia, where she was a college English professor and administrator. Now living in Tennessee, she continues to write both fiction and prose. Her horse protection web site address is