What is vesicular stomatitis virus?

Vesicular stomatitis is a viral infection that can cause disease in a broad range of animals, primarily horses, cattle, and pigs.

What are the clinical signs of vesicular stomatitis in horses?

After a horse contracts the virus, it takes between 2 and 8 days for clinical signs to develop. Horses with vesicular stomatitis can develop blister-like lesions called vesicles on the tongue, gums, or lips, and occasionally along the coronary bands or on the udder/sheath. When the blisters rupture, the skin surface tends to slough, leaving behind areas of raw, ulcerated oral mucosa. These ulcers are quite painful, and affected horses are often observed frothing at the mouth or drooling and refusing to eat. Horses with coronary band lesions may develop lameness as the blisters rupture.

How do you treat VSV in horses?

There is no specific treatment; affected horses are managed with anti-inflammatories for pain control and supportive care to prevent weight loss. Soft feeds may encourage the horse to continue eating. If the lesions become infected, additional treatments such as mouthwash and antibiotics may be necessary, and horses that refuse to drink may require fluid therapy to prevent dehydration. The disease tends to run its course in about two weeks, and rarely causes significant illness or complications.

How is equine vesicular stomatitis spread?

There are multiple insects, including black flies, midges, and sand flies, that are known to transmit the virus. It is also possible for horses to transmit the virus via saliva or fluid from the blisters, which may take place with direct physical contact or shared equipment such as buckets, feeders, water troughs, tack, stalls, or trailers.

Vesicular stomatitis virus is endemic in parts of the world, including areas of Mexico and Central America, and periodically reoccurs throughout parts of North America in warmer seasons (summer and early fall).

Although VSV does not often cause significant disease in horses, it is a major source of concern to the animal agricultural industry because it is indistinguishable from a similar, but more problematic infection: foot and mouth disease. Both diseases can occur in cattle, with devastating economic impacts. VSV can be transmitted to cattle from infected horses, either via direct contact or insect bites. For this reason, vesicular stomatitis is a reportable disease in horses, meaning when a case is suspected, the veterinarian is required to report it to state and federal animal health authorities, who will quarantine the facility for at least 14 days. Interstate and international travel may be restricted from affected states, and competition organizers may enact restrictions as well.

How do I prevent my horse from getting VSV?

There is no vaccine to prevent VSV in horses, but preventative measures like good fly control, regular cleaning and sanitizing of feeders or shared equipment, and proper quarantine of new horses can help minimize the likelihood of infection.

Infection risk may be further reduced by removing horses from pastures with standing water and sheltering during peak times for insect bite activity, usually at dusk. Fly spray and physical barriers such as masks, boots, and sheets may also reduce insect bites.

Can humans get vesicular stomatitis from horses?

Gloves should be worn while handling an infected horse, as it is possible for the virus to be transmitted from horses to humans (people generally do not develop blisters, but may have flu-like symptoms). If the disease is suspected, it is important to isolate the affected horse(s) and notify your veterinarian.

Are there any current outbreaks of vesicular stomatitis virus?

Colorado has had previous outbreaks of VSV, although at this time, no cases have been reported within the state. Currently, there are ongoing outbreaks of VSV in California, Nevada, and Texas.