Vesicular Stomatitis
Vesicular stomatitis is a viral disease that primarily affects cattle,
horses, and swine. The virus that causes vesicular stomatitis has a
wide host range. This disease also occasionally affects sheep and goats.
Many species of wild animals, including deer, bobcats, goats, raccoons,
and monkeys, have been found to be susceptible hosts. Humans can also
become infected with vesicular stomatitis when handling affected animals.
Vesicular stomatitis is most likely to occur during warm months in
the Southwest, particularly along riverways and in valleys. The Southwestern
United States experienced a vesicular stomatitis outbreak from May 1998
through January 1999. It is essential that veterinarians and livestock
owners be on the alert for animals displaying clinical signs characteristic
of the disease.
In affected livestock, vesicular stomatitis 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 and show signs of lameness. Severe weight loss usually follows,
and in dairy cows, a severe drop in milk production commonly occurs.
Affected dairy cattle can appear to be normal and will continue to eat
about half of their feed intake.
While vesicular stomatitis can cause economic losses to livestock producers,
it is a particularly
significant disease because its outward signs are similiar 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 vesicular stomatitis are
also similar to those of swine vesicular disease, another foreign animal
disease. The only way to tell these diseases apart is through laboratory
tests.
Veterinarians of the U.S. Department of Agriculture’s Animal
and Plant Health Inspection Service (USDA–APHIS) work to keep
vesicular stomatitis from becoming established in the United States
because of its similarity to other diseases of concern, its negative
impact on livestock production, and its public health implications.
Vesicular stomatitis is recognized internationally as a reportable disease.
Exports of U.S. livestock and animal products would be restricted if
vesicular stomatitis were allowed to spread in this country.
Epidemiology
Vesicular stomatitis has been confirmed only in North and South America.
It is known to be an endemic disease in the warmer regions of the Western
Hemisphere, but outbreaks of the disease occasionally occur in temperate
geographic areas.
How vesicular stomatitis spreads is not fully known; insect vectors,
mechanical transmission, and movement of animals are probably responsible.
One type of vesicular stomatitis virus is known to be spread by phlebotomine
sandflies. Once introduced into a herd, the disease apparently moves
from
animal to animal by contact or exposure to saliva or fluid from ruptured
lesions.
Humans can contract vesicular stomatitis when handling affected animals
if proper biosafety methods are not followed. Prevalence of this disease
in humans may be underreported because it may often go undetected or
be misdiagnosed. In people, vesicular stomatitis causes an acute influenzalike
illness with symptoms such as fever, muscle aches, headache, and malaise.
Clinical Signs
In affected livestock, the incubation period for vesicular stomatitis
ranges from 2 to 8 days. Often, excessive salivation is the first sign.
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.
In horses, these lesions generally occur on the upper surface of the
tongue. In cattle, the lesions usually appear on the hard palate, lips,
and gums, sometimes extending to the muzzle and nostrils. Dairy cattle
often suffer from teat lesions and subsequent mastitis. Affected pigs
usually first show signs of lameness caused by foot lesions.
The morbidity rate for vesicular stomatitis varies considerably within
species. For example, about 5 to 10 percent of affected herds generally
show clinical signs of the disease. Up to 80 percent of dairy cattle
herds have become affected by vesicular stomatitis. If there are no
complications such as secondary infections, then affected animals recover
in about 2 weeks. Vesicular stomatitis does not generally cause animals
to die.
Recommended Actions
There is no specific treatment or cure for vesicular stomatitis. Owners
can protect their animals from this disease by avoiding congregation
of animals in the vicinity where vesicular stomatitis 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.
When a definite diagnosis is made on a farm, the following procedures
are recommended:
• Separate animals with lesions from healthy animals, preferably
by stabling. Animals on pastures apparently are affected more frequently
with this disease.
• As a precautionary measure, do not move animals from premises
affected by vesicular
stomatitis—unless they are going directly to slaughter—for
at least 30 days after the last lesion found has healed.
• Implement onfarm insect control programs that include the elimination
or reduction of insect breeding areas and the use of insecticide sprays
or insecticide-treated eartags on animals.
• Use protective measures when handling affected animals to avoid
human exposure to this disease.
Report Suspicious Cases
Veterinarians and livestock owners who suspect an animal may have vesicular
stomatitis or any other vesicular disease should immediately contact
State or Federal animal health authorities.
Additional Information
For more information, contact:
USDA, APHIS,
Veterinary Services
Emergency Programs
4700 River Road, Unit 41
Riverdale, MD 20737-1231
Telephone (301) 734-8073
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