Equine Health: Vesicular Stomatitis

(From the June/July issue of Western Horse & Gun Magazine)

During 2014’s peak travel season for horse owners, the state of Colorado had more than 370 premises under quarantine for equine vesicular stomatitis. Surprisingly most of the equine events in the state went on without a hitch, and the final quarantines were released in late January.

Vesicular stomatitis (VS) can often be a scary disease, mostly because of its appearance and some of the effects from the sores and lesions horse owners find around their horses’ muzzles. While the 2015 travel season starts to heat up, it’s important to understand the disease and how you can prevent it from happening to you

An Ugly Looking Disease
Vesicular stomatitis is a viral disease that is more commonly found in the southwestern United States, affecting mostly horses, cattle, and swine. It is identified by formations of lesions (blisters) typically found on the tongue, lips, and around the mouth or nose. The blisters can also be found on the udder or sheath or along the coronary band.

The lesions look very painful, but experts do not see long-term effects from them very often

“Occasionally horses will have lesions along the coronary band around the foot that can cause some problems that can be lasting,” explains Keith Roehr, DVM, Colorado state veterinarian. “Most horses that have blisters on their nose or lesions on their tongues will heal up within a number of weeks and are pretty much back to normal.”

Because the blisters will appear on the inside of the horse’s mouth or around the lips, they can cause the horse to lose weight due to difficulty eating or drinking, and just the stress from the pain. But Roehr explains that with an ample amount of time to heal, horses usually make a full recovery and will return to normal.

Unlike highly transmitted diseases like equine herpesvirus, VS does not invade the bloodstream or neurologic system of the horse. Instead, it resides in the blisters and on the skin surface after the blisters rupture.

There are only a few different ways that VS can be transmitted from horse to horse. The hardest way to prevent transmission is via vectors such as biting flies—black flies, sand flies, and Culicoides (biting midges).

Horse-to-horse transmission can occur when another horse comes into contact with an infected horse’s open lesions. Remember that the virus essentially lives in the blisters, which will ooze and eventually rupture. This can increase the risk for transmission.

The third threat of transmission occurs when your healthy horse comes into contact with contaminated equipment such as shared water troughs, feed buckets, or surfaces like grooming and tie areas.

Diagnosis and Treatment
Vesicular stomatitis might be one of the easiest to discover early because of the blisters. Other signs that your horse might be affected by the virus include excessive slobbering and a fever of 102-104°F in the acute phase of the disease.

Other signs include geldings and stallions having difficulty urinating, due to the lesions being around the sheath, and lameness due to the lesions appearing around the coronary band.

However, just because your horse has lesions doesn’t necessarily mean he has VS, so work with your veterinarian to have laboratory tests pulled for confirmation. If your horse has VS, your veterinarian will report the disease for tracking, which will also place your property on a hold or quarantine order pending lab results. A quarantine can typically last 21 days after the last horse’s lesions are healed (which can take seven to 10 days).

Treatment of VS is difficult because there are no antivirals available to give to horses at this time. Roehr says the best owners can do is make sure the horse is comfortable and staying hydrated and getting proper nutrition. A soft bran mash is often more preferred by horses with VS because it’s easier to eat. If your horse starts to get dehydrated, veterinary treatment will be required for intravenous fluids.

Keep the blisters clean to help prevent bacterial infections with the open sores. Work with your veterinarian on the best cleaning and treatment protocol if your horse is diagnosed with VS.

Proper biosecurity protocols such as disinfecting water troughs, feed buckets, and walls regularly, and quarantining infected horses will help prevent transmission. When you’ve handled a horse infected with VS, wear gloves and be sure to wash your hands with soap and water should you come in contact with an infected horse. Have a change of clothes at the barn to change into as well.

When you’re traveling this summer, check the state veterinarian websites of the states you’re hauling through and hauling to for updates on their VS status. Some states will require recent veterinary health checks and certificates whether you’re only traveling within your state or to other states.

“Last summer, most of the events in Colorado that were operating during the VS outbreak had some screening processes,” explains Dr. Roehr. “Even if the horses didn’t cross the state line, they had to have a certificate of veterinarian inspection within three to five days of the event so we knew that a veterinarian seen that horse very recently, and that reduced the risk of exposure to other horses quite a bit.”

Horse owners can practice good insect control during outbreaks by using flysheets, masks, and sprays to help prevent being bitten. Using fly predators, which are insects that feed on other insects, is inexpensive and helps control the fly population on your farm.

It’s hard for veterinarians to predict if VS will be an issue during a typical travel season because the disease is typically not a yearly occurrence in the United States. The first cases usually occur in late June and July, so Roehr suggests owners and exhibitors keep watch for horse health updates and work with their veterinarians as they prepare for their events.

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