Vesicular Stomatitis (VS) is a viral disease that causes painful blistering of the gums, tongue and occasionally the udder, sheath or coronet band. Horses usually have a mild fever, salivation and may go off feed and act depressed for several days.
VS is thought to be transmitted by biting insects and occurs during insect season. VS is also thought to be spread by direct contact between saliva of infected animals and other horses. However, the precise means of spread is not entirely known.
Up to now, VS has occurred exclusively in the Americas. More frequent and severe outbreaks have occurred since the late 1990’s. The disease is more common in southern Mexico and Central and South America. It is likely that a warmer climate in the last 15 years has favored the presence of the disease in North America, and is at least partly responsible for more frequent outbreaks here.
Because of its resemblance to Foot & Mouth Disease (another viral disease that has had a major impact on the livestock industry), VS is closely regulated by the USDA. For this reason, VS is a reportable disease, meaning that if a horse has or is suspected of having this disease, vets are required to report it to agricultural authorities (usually the State Veterinarian). These authorities may investigate the case as part of a larger effort to monitor equine health and coordinate with other states and the USDA APHIS in preventing the spread of illness or disease on a national and international level.
VS is a zoonotic disease, meaning that it can be transferred from an infected horse to humans. It usually causes flu or cold-like symptoms in humans. If you have been exposed to a horse with (or suspected of having) VS you should contact your doctor.
Diagnosis is by oral examination by a veterinarian, along with blood tests and tests of swabs of the area for virus.
This disease is usually self-limiting, meaning that horses usually recover on their own with little or no treatment. This disease usually lasts about a week.
Treatment revolves around monitoring to be sure horses are eating and drinking until the problem resolves on its own. NSAIDS (phenylbutazone or similar) may be given to help with pain and inflammation. Some vets recommend oral rinsing but usually this is not necessary and it increases human exposure. Feeding moistened or soft feeds may help horses during the painful early phase.
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Prognosis & Relevant Factors
The prognosis for horses with VS is good to excellent. Most recover fully in about 10-14 days.
Pastured horses have a much higher rate of disease than stabled horses. It is unclear why this is but may relate to exposure to the infecting insects or to grazing itself.
The infection rate is high in a group of horses but many horses do not show signs of disease. This relates to the immunity of some horses versus others. Usually 20%-30% of horses in a group will show signs of disease.
Horses less than one year of age have a lower incidence of infection than older horses.
VS is generally a summer-time problem. Colder weather in fall and early winter usually ends an outbreak.
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Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health