Factsheet

Veterinary Services 

APHIS

June 2005

Vesicular Stomatitis:

Questions and 

Answers

Vesicular stomatitis (VS) is a viral disease that 

primarily affects horses, cattle, and swine and 

occasionally sheep, goats, llamas, and alpacas. 

Humans can also become infected with VS when 

handling affected animals, but this is a rare event. VS 

has been confirmed only in the Western Hemisphere. 

It is known to be an endemic disease in the warmer 

regions of North, Central, and South America, but 

outbreaks of the disease in temperate geographic 

parts of the Hemisphere occur sporadically.

Outbreaks in the Southwestern United 

States usually occur during warm months, often 

along waterways and in valleys. The Southwest 

experienced a VS outbreak from May 2004 through 

January 2005. Animals in Texas, New Mexico, and 

Colorado were involved. A total of 294 premises in 

43 counties were affected in these three States (see 

map). There could be another outbreak in 2005, and 

it is essential that veterinarians and livestock owners 

be on the alert for animals displaying clinical signs 

characteristic of VS.
Erosions and exudate in the nostrils.

Q. What are the clinical signs of VS?

A. In affected livestock, VS causes blisterlike lesions 

to form in the mouth and on the dental pad, tongue, 

lips, nostrils, hooves, and teats. These blisters swell 

and break, leaving raw tissue that is so painful that 

infected animals generally refuse to eat or drink. If 

the hooves are affected, the animal may show signs 

of lameness. Severe weight loss usually follows, 

and in dairy cows, a severe drop in milk production 

commonly occurs. Some affected dairy cattle can 

appear to be clinically normal and will continue to 

eat about half of their normal feed intake. Lesions in 

horses may also be expressed as crusting scabs on 

the muzzle, lips, or ventral abdomen.

Q. How is the disease spread?

A. How VS spreads is not fully known; insect vectors, 

mechanical transmission, and movement of animals 

are all factors. Once VS is introduced into a herd, the 

disease may move from animal to animal by contact 

or exposure to saliva or fluid from ruptured lesions.

Q. Can humans contract VS?

A. Humans rarely contract VS when handling affected 

animals but can become infected. To avoid exposure 

to this disease, use protective measures when 

handling affected animals. In people, VS causes an 

acute influenzalike illness with symptoms such as 

fever, muscle aches, headache, and malaise.

Q. Why is it so important to recognize animals 

with VS promptly?

A. VS is recognized internationally as a reportable 

disease. What this means is 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 U.S. animals. Interstate 

movement of animals is also impacted. Premises 

containing affected animals are quarantined until 21 

days after the lesions in the last affected animal have 

healed. These quarantine periods may be quite long. 

 While VS can cause economic losses to livestock producers, it is a particularly significant disease 

because its outward signs are similar to (although 

generally less severe than) those of foot-and-mouth 

disease, a foreign animal disease of cloven-hoofed 

animals that was eradicated from the United States 

in 1929. The clinical signs of VS are also similar to 

those of swine vesicular disease, another foreign 

animal disease. The only way to tell these diseases 

apart is through laboratory testing.

Q. What are clinical signs of VS? How does the 

disease progress in affected animals?

A. In affected livestock, the incubation period 

for VS ranges from 2 to 8 days. Often, excessive 

salivation is the first sign that an animal is affected. 

Body temperature may rise immediately before or 

at the same time lesions first appear. Initially, close 

examination of the mouth reveals blanched and 

raised vesicles. If there are no complications such 

as secondary infections, affected animals recover in 

about 2 weeks. VS does not generally cause animals 

to die.

 Clinical signs of VS and other vesicular diseases 

include:

• Excessive salivation

• Swollen lips

• Blanched skin and raised or broken vesicles of 

various sizes around and in the mouth:

Horses: Upper surface of the tongue, surface of 

the lips and around nostrils, corners of the mouth, 

and the gums.

Cattle: Tongue, lips, gums, hard palate, and 

sometimes the muzzle and the area around the 

nostrils.

Pigs: Snout.

• Lesions involving feet of horses and cattle are 

not commonly seen in the Southwestern United 

States. However, if lesions do occur, lameness 

may be noted as a clinical sign.

• Foot lesions and lameness are frequent in pigs.

• Teat lesions may occur in dairy herds. Loss 

of production and mastitis in dairy herds due 

to secondary infections may be a secondary 

complication.

Cow drooling from mouth lesions.
Erosions—ruptured vesicles—of the gums.

Erosions and dried exudate on the coronary band 

and heel.

Erosions on a teat.

Hyperemia and beginning erosions on the 

coronary bands.

Photos obtained from: 

<http://www.aphis.usda.gov/vs/ep/fad_training/

VESVOL7/vesindex.htm>.

Erosions—ruptured vesicles—on the tongue. Vesicles on the tongue.
Q. What should I do if I think my horse has VS?

A. If you suspect your horse has VS, notify the 

State or Federal veterinarian in your area. Diagnosis 

of VS cannot be made based on clinical signs but 

requires testing of samples at the U.S. Department 

of Agriculture’s National Veterinary Services 

Laboratories. Diagnosis of VS can be based on antibody tests using serum from the animal and/or by 

detection of virus from swabs of lesions, blister fluid, 

and tissue flaps. Diagnosis can be made within a 

few days for antibody detection in serum or in slightly 

over a week for virus detection in swabs, fluids, and 

tissues.

Q. If there is another VS outbreak this year, what 

do I need to do if I plan to travel with my horse to 

another State or country?

A. During a VS outbreak, States and countries may 

put regulations into place restricting the movement 

of animals and requiring testing of animals prior to 

movement. Each State and country has different 

requirements for movement testing. It is important 

that the animal owner become familiar with the 

regulations and testing requirements associated with 

moving an animal.

 Not all laboratories run the same antibody tests, 

so it is important to check with your laboratory to 

find out if they run the test you need to comply 

with regulations or movement restrictions. It is 

also important to contact the laboratory in advance 

to determine the samples needed, submission 

procedures, and testing cost.

 Not all VS tests are conducted on a daily basis, 

and during an outbreak of VS, there is an increased 

demand on laboratories for movement testing of 

animals. Therefore, it is important that a person 

submitting a sample to a lab for movement testing 

plan well in advance and have the sample at the lab 

at the earliest possible time based on the movement 

regulations.

For more information on testing, please visit our 

Web site at <http://www.aphis.usda.gov/vs/nvsl>. 

Q. What can we do to protect our animals?

A. There is no specific treatment or cure for VS. 

Owners can protect their animals from this disease by 

keeping their animals from congregating in the area 

where VS has occurred. Mild antiseptic mouthwashes 

may bring comfort and more rapid recovery to an 

affected animal. Good sanitation and quarantine 

practices on affected farms usually contain the 

infection until it dies out of its own accord. If you 

suspect that you have a horse with VS, do not allow it 

to come in contact with your other horses.

When a definite diagnosis of VS is made on a 

farm, the following procedures are recommended:

United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture

The U.S.Department of Agriculture (USDA) prohibits discrimination

in all its programs and activities on the basis of race, color, national 

origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to

all programs.) Persons with disabilities who require alternative

means for communication of program information (Braille, largeprint, audiotape, etc.) should contact USDA’s TARGET Center at 

(202) 720–2600 (voice and TDD).

To fi le a complaint of discrimination, write USDA, Director, Offi ce of

Civil Rights, Room 326–W, Whitten Building, 1400 Independence

Avenue, SW, Washington, DC 20250–9410 or call (202)720–5964

(voice and TDD). USDA is an equal opportunity provider and

employer.

• Separate animals with lesions from healthy 

animals, preferably by stabling. Animals on 

pastures are at an increased risk of disease.

• As a precautionary measure, do not move animals 

from premises affected by VS, unless they are 

going directly to slaughter, for at last 21 days after 

the last lesion found has healed.

• Implement on-farm insect control programs 

that include the elimination or reduction of 

insect breeding areas and the use of approved 

insecticide sprays or insecticide-treated eartags 

on animals.

Additional Information

 To see more pictures of what lesions might look 

like, please visit the following Web site: 

<http://www.aphis.usda.gov/vs/ep/fad_training/

VESVOL7/vesindex.htm>.

Additional information can be obtained from the following Web pages:

• http://www.quarterh.com/health3.htm 

• http://www.oie.int/eng/maladies/fi ches/A_A020.

HTM

• http://www.vetmed.wisc.edu/pbs/zoonoses/vsv/

vsvindex.html

• http://www.aphis.usda.gov/vs/ep/fad_training/

VESVOL7/vesindex.htm

 For more information, contact

 U.S. Department of Agriculture

 Animal and Plant Health Inspection Service

 Veterinary Services

 Emergency Management 

 4700 River Road, Unit 41

 Riverdale, MD 20737–1231

 Telephone (301) 734–8073