Equid Blog : Horse Health & Diseases : University of Guelph : Ontario Veterinary College : Equine Infectious Diseases

Earlier this summer, the Canadian Food Inspection Agency imposed quarantine restrictions on certain US states because of vesicular stomatitis. Texas is now (again) considered vesicular stomatitis free, since the previous cases have resolved and no new cases have been identified. Accordingly, import restrictions on horses coming from or through Texas have been lifted. 

Restrictions have been reduced for horses from New Mexico. Horses from non-infected counties can get import permits if they:

• Have been inspected and had no signs of vesicular stomatitis within 10 days of export.
• Have not been to or through an infected county within 21 days.
• They are from a farm at least 25 km from any quarantined farm.
• The have a negative ELISA test within 10 days of export.

(Image source: www.signs-up.com)

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Not long after the first reported case of vesicular stomatitis (VS) of 2009 in Texas, the disease has now also been identified in De Baca County, New Mexico. It's not too surprising, because infectious diseases tend not to pay attention to state boundaries, and New Mexico tends to be one of the first states affected by VS during outbreak years. Reportedly, only a single horse has been infected in New Mexico so far, and the farm involved has been quarantined.

This will presumably result in many regions placing travel or import restrictions on horses from New Mexico, as was done with horses from Texas. Previously in some years when this disease has been detected in the US, it has been contained to a single state. During other years, multi-state outbreaks involving large numbers of horses have occur. Only time will tell what this year will bring.

People that live in or adjacent to areas where vesicular stomatitis is present should closely observe their horses for signs of this disease, including:

• Drooling
• Lesions in the mouth, ranging from raised, white lesions to blisters. After lesions rupture, ulcerated areas are present.
• Swelling, inflammation and lesions around the coronary band (these are less common than mouth lesions).

This disease is primarily spread by insects, so direct contact with an infected horse is not required for disease transmission. Therefore, even closed herds need to be on the lookout. If signs consistent with vesicular stomatitis are found, movement of horses on and off the property should immediately cease and a veterinarian should be contacted as soon as possible.

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The Canadian Food Inspection Agency (which, despite the name, is not only in charge of food inspection) has announced import restrictions on horses from Missouri and Texas. Horses that have been in those states in the past 21 days or who have passed through those states during transportation are being flagged because of concerns regarding exposure to piroplasmosis and vesicular stomatitis, respectively. Canadian horses traveling to those states will have to wait until the restrictions are lifted or will have to be moved to a non-affected state for 21 days before being eligible to come home.

If these two outbreaks spread beyond these two particular states, it's fairly certain that these restrictions will be expanded.

There's still no word on the location of the two horses that were "busted out" of their piroplasmosis quarantine in Missouri. It's surprising how little information as been forthcoming on this matter.

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Vesicular stomatitis (VS) has been identified in a horse in south Texas. This viral disease is highly infectious and is a concern for various reasons.

Horses are often the first animals affected when an outbreak of VS develops. A quick response can help prevent the virus from spilling over into other species. It's a particular concern in cattle and sheep because VS can look very similar to foot and mouth disease, a tremendously important foreign disease that can have a devastating economic impact (just ask anyone from the UK).  Even though it is not usually fatal, vesicular stomatitis can also result in severely decreased production in food animals, and therefore also have a significant economic impact.

The impact of VS on infected horses varies. It causes painful blisters (most commonly on the upper surface of the tongue, surface of the lips and around nostrils, corners of the mouth and the gums) which can limit the use of the horse for a period of time (although infected horses can't compete anyway because the must be strictly quarantined). Some horses may be too sore to eat or drink normally, and therefore require supportive care. In unusual situations, the lesions are so severe that euthanasia is elected.

Vesicular stomatitis is a reportable disease in the US, and identification of this case has prompted a rapid outbreak investigation and response. The last outbreak, in 2006, was contained to 17 horses and 12 cattle in Wyoming. A much larger outbreak in 2005 infected livestock on at least 445 premises in 9 states. To help keep this virus contained, restrictions on livestock movement are promptly implemented. Infected animals and their herdmates are quarantined, neighbouring farms may be investigated and/or quarantined, and people are put on the alert to look for more cases. A fast response and cooperation of horse owners is critical. A major concern is  that people may have horses that develop vesicular stomatitis but don't tell anyone because that want to avoid being quarantined. This type of situation can prevent containment of the problem and lead to ongoing transmission and even bigger problems in the long run. Good communication and cooperation are essential.

Image from: http://www.newsinfo.colostate.edu

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