Vesicular stomatitis Q and A

A horse with vesicular stomatitis shows blisters in the mouth area.
A horse with vesicular stomatitis shows blisters in the mouth area.

What is vesicular stomatitis?

It is a viral disease that affects mostly cattle, horses, and swine; and occasionally sheep, goats, llamas, and alpacas.

What are the symptoms?

The incubation period for vesicular stomatitis ranges from 2 to 8 days. The first sign is often excessive salivation. Close examination of the mouth initially reveals blanched and raised vesicles or blister-like lesions. These blister-like lesions can form in the mouth and on the dental pad, tongue, lips, nostrils, hooves, and teats. The blisters swell and break, leaving raw tissue that is so painful that infected animals show signs of lameness and generally refuse to eat or drink. Severe weight loss may follow. Body temperature may rise immediately before or at the same time as lesions first appear. Dairy cattle often suffer from teat lesions and subsequent mastitis; a severe drop in milk production commonly occurs. Some affected dairy cattle can appear to be normal with no clearly visible symptoms but may only eat about half of their normal feed intake.

Does it affect horses any differently to other animals?

In horses, vesicular lesions generally occur on the upper surface of the tongue, the lips, around nostrils, corners of the mouth, and gums. Lesions in horses may also be expressed as crusting scabs on the muzzle, lips, or ventral abdomen.

Can humans catch the disease?

Yes. People can become infected when handling infected animals, but this is a rare. It causes an acute influenza-like illness with symptoms such as fever, muscle aches, headache, and malaise. To avoid exposure to this disease, individuals should use protective measures when handling affected animals.

Where is the disease found?

It has been confirmed only in the Americas. It is an endemic disease in the warmer parts of North, Central, and South America, but outbreaks in the temperate northern parts of the Americas occur sporadically. Before the current cases in Texas and New Mexico, the last reported cases in the United States were in Wyoming in 2006. Outbreaks in the US usually occur in the warmer months, often along waterways and in valleys.

How does the disease spread?

This is not fully understood. Biting flies are known to play a part and it can also be spread by mechanical transmission and movement of animals. Once the disease is introduced into a herd, it can move from animal to animal by contact or exposure to saliva or fluid from ruptured lesions.

Mouth blisters in a horse with vesicular stomatitis.
Mouth blisters in a horse with vesicular stomatitis.

What is the cure?

There is no specific treatment or cure. Owners can protect their animals from the disease by avoiding congregating animals in the vicinity where the disease has occurred. Mild antiseptic mouthwashes may bring comfort and more rapid recovery for an affected animal. Good sanitation and quarantine practices on affected farms usually contain the infection until it subsides and soon ends.

How long does it take animals to recover?

If there are no complications such as a secondary infection, affected animals typically recover in about a fortnight.

Can animals die from the disease?

Not usually.

What practices are recommended on infected properties?

Separate animals with lesions from healthy animals, preferably by stabling. Animals on pastures apparently are affected more frequently. Do not move animals from affected premises unless they are going directly to slaughter, for at least 21 days after the last lesion has healed. Implement on-farm insect control programmes. Use protective measures when handling affected animals to avoid human exposure.

What do you do if you think an animal has the disease?

Contact state or federal animal health authorities. Diagnosis of the disease cannot be made based on clinical signs but requires testing of samples at a facility approved by the US Department of Agriculture’s National Veterinary Services Laboratories, in Ames, Iowa. A diagnosis can be based on antibody tests using fluid samples from the animal and/or by isolation of the virus from swabs of lesions, blister fluid, and tissue flaps. A diagnosis can be made within a few days for antibody detection or in slightly over a week for virus detection in swabs, fluids, and tissues.

Why is a correct diagnosis important?

The disease is significant because its outward signs are similar to those of foot-and-mouth disease, a 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. Some lesions in livestock can be caused by contact with toxic plants, so testing can also eliminate vesicular stomatitis as the cause.

How serious is an outbreak?

It is recognised internationally as a reportable disease. What this means is that there are serious economic and regulatory repercussions associated with the diagnosis. When the disease is detected in the US, many countries take action to block international trade of US animals. Interstate movement of animals is also impacted. Premises containing affected animals are quarantined until 21 days after the lesions in the last affected animals have healed. As a result, quarantine periods can be lengthy.

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