Vesicular Stomatitis

Vesicular stomatitis is a viral disease that primarily affects horses 

and cattle. It occasionally affects swine, sheep, goats, llamas, 

alpacas, and people who handle affected animals. Vesicular 

stomatitis is found only in the Western Hemisphere, where it is 

endemic in warmer climates and occurs sporadically in more 

temperate areas. 

Vesicular stomatitis is not endemic within the United States and 

is federally reportable. In the past decade, the southwestern and 

western United States experienced several vesicular stomatitis 

outbreaks introduced from Mexico. Outbreaks usually occur 

during the warmer months, often along waterways. In some years, 

only a few premises in a single State were affected. In other years, 

multiple States and many premises were involved. 

Veterinarians and livestock owners in these regions should be 

aware that vesicular stomatitis can potentially occur in their area. 

You should also be on the alert for animals displaying clinical 

signs of the disease. 

Economic Impacts

Although vesicular stomatitis does not normally kill affected 

animals, it can cause economic losses for livestock producers 

by preventing animal movements and impacting international 

trade. Farms with affected animals are quarantined until 14 days 

after lesions appear on the last case at that location. 

Quarantine periods can be lengthy if the disease continues to 

spread within the premises. Some countries may stop imports of 

certain animals and their products when cases are reported in 

the United States. 

Vesicular stomatitis clinical signs can look like those of several 

other diseases. One of those diseases, foot and mouth disease 

(FMD), is a foreign animal disease that would cause devastating 

economic consequences if found in the United States. The only 

way to tell these diseases apart is through laboratory testing. It’s 

important to quickly test any animal with clinical signs to identify 

which disease is causing illness.

Clinical Signs 

The incubation period for vesicular stomatitis is 2 to 8 days. The 

first sign of illness is often excessive salivation. If you look inside 

the mouth, you will see blanched and raised vesicles or blisterlike lesions on the inner surfaces of the lips, gums, tongue, and/

or dental pad. These blister-like lesions can also form on the lips, 

nostrils, coronary band, prepuce, vulva, and teats. The blisters 

will swell and break open, which causes mouth pain, discomfort, 

and reluctance to eat or drink. This can cause severe weight loss. 

If the coronary bands of the hooves are affected, lameness can 

occur. You may also notice a rise in body temperature before or at 

the same time lesions first appear. 

Dairy cattle often suffer from teat lesions, followed by mastitis. 

A severe drop in milk production is common. Some affected 

dairy cattle can appear normal with no clearly visible signs of 

illness but may only eat about half of their normal feed intake. If 

there are no complications such as secondary infection, affected 

animals typically recover in about 2 weeks. 

In horses, vesicular lesions generally occur on the upper surface 

of the tongue, lips, corners of the mouth, and gums, as well as 

around the nostrils. The lesions in horses may also appear as 

crusting scabs on the muzzle, lips, ears, coronary bands, sheath, 

udder, or underside of the abdomen. Affected pigs usually first 

show signs of lameness caused by foot lesions. 

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Disease Spread

How vesicular stomatitis spreads is not fully understood. Insects, 

animal movements, and moving the virus on objects are all 

factors. The most common method of transmission is through 

biting insects. Black flies, sand flies, and biting midges have all 

been shown capable of transmitting the virus, but other insects 

may also be involved. Once the disease is introduced into a herd, 

it may move from animal to animal by contact or exposure to 

saliva or fluid from ruptured vesicles. 

Vesicular Disease in Humans 

People can get vesicular stomatitis after coming into contact 

with lesions, saliva, or nasal secretions from infected animals. 

The disease causes an acute influenza-like illness with symptoms 

such as fever, muscle aches, headache, and malaise. To avoid 

exposure to this disease, use personal protective measures when 

handling affected animals. 

Recommended Actions 

There is no specific treatment or cure for vesicular stomatitis. 

Good sanitation and quarantine practices on affected farms 

usually contain the infection. 

Once a definitive diagnosis is made on a farm, the State 

Veterinarian will determine specific quarantine procedures. The 

following procedures are also recommended: 

• Separate animals with lesions from healthy animals, 

preferably by stabling. Animals on pastures tend to be 

affected more frequently with this disease.

• Do not move animals from premises affected by vesicular 

stomatitis until at least 14 days after the onset of lesions in 

the last case.

• Implement on-farm insect control programs that include 

eliminating or reducing insect breeding areas, manure 

management practices, and using insecticides or other 

insect prevention strategies on animals and around facilities.

• Use personal protective measures when handling affected 

animals to avoid human exposure to this disease.

Report Suspicious Cases

If you suspect an animal may have vesicular stomatitis or any 

other vesicular disease, immediately contact State and Federal 

animal health authorities. You can’t diagnose the disease based 

on clinical signs alone. Samples must be tested at a facility 

approved by the U.S. Department of Agriculture’s (USDA) National 

Veterinary Services Laboratories. 

A diagnosis can be based on antibody tests using serum samples 

from the animal and/or by detecting virus from swabs of lesions, 

blister fluid, and tissue (flaps, biopsies). It can generally be made 

within a few days.

Additional Information 

For information on any current vesicular stomatitis outbreaks or 

summaries of the most recent past outbreaks, go to www.aphis.

usda.gov/animalhealth/vesicular-stomatitis 

To speak with someone from USDA’s equine health team, call 

(970) 494-7391.