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Sunday, August 29, 2010

Vesicular Stomatitis

There's an equine disease called Vesicular Stomatitis (VS) that occurs from time to time in the USA. It is also called "False Hoof and Mouth Disease", as the symptoms mimic Hoof and Mouth Disease.

Some importing countries require testing for VS for six months after a case of VS has been reported in the USA. Others require the test for every shipment, irregardless of how long it has been since the USA had a case of the disease.

At the current time, all horses being exported from the USA to or through the European Union must be tested for VS, as there were some cases of the disease that were reported at a ranch on the Arizona/Mexico border in the Spring of 2010.

The testing medium that is used for VS for horses being exported is, unfortunately, not a very reliable test and it is fairly common to get "inconclusive" results. Another term for this type of result is "toxic". On rare occasions there will even be a false positive result. Usually the animal in question will test negative with a new blood draw.

However, there are times when the toxic or false positive results come back again and again for the same animal. When that happens, the animal cannot be shipped to a country requiring VS testing.

We've asked a number of veterinarians what could cause the toxic or false positive results and, while no one knows for sure, there are several theories. The most commonly held observation that veterinarians have shared with us is that there may be a correlation between certain vaccinations and toxic or false positive VS results.

In particular, Rabies vaccinations may play a role. VS is a "rabido virus", as is Rabies, so the testing medium may pick up the Rabies vaccine in the blood and mistake it for VS.

If you plan to ship an equine from the USA, it is probably wise to postpone giving any vaccinations before sending the animal to quarantine. Any and all vaccinations that are required by the importing country will be given after the horse or donkey arrives at our facility.

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