Vesicular Stomatitis In Arizona
Vesicular stomatitis (VS) has been identified in three horses on a farm in Arizona. This is a reportable disease in the US and Canada that makes periodic appearances in various states. Last year it was found in Texas and New Mexico. The farm where the virus was discovered has been quarantined. The owners were advised to separate affected animals unaffected animals, implement on-farm insect control programs and use protective measures when handling affected animals to avoid human exposure to the disease. All good pieces of advice.
Vesicular stomatitis is caused by a virus from the Rhabdoviridae family (the same family as rabies virus) and is highly infectious. The most obvious clinical signs of infection are blisters and sores on the lips, gums, tongue and nostrils. Infection is rarely so severe as to be fatal, but the blisters can be quite painful such that affected horses may not eat. In addition to being a highly infectious disease among horses, a major concern with VS is that it can infect swine and cattle as well, in which infection looks very similar to Foot and Mouth Disease - a tremendously important foreign animal disease in these other species. Horses infected with VS must be strictly quarantined, from both other horses and other livestock, to contain the virus. The virus is shed in the fluid from the blisters, so controlling exposure to insects which may mechanically transfer virus from one animal to another (just by flying from nose to nose), and preventing transmission via people's hands or other equipment is very important. Some insect species also serve as biological vectors of the virus. There is no specific treatment, but most animals will recover with supportive care in a few weeks. People can be infected by VS, but clinical signs are typically limited to flu-like illness and occasionally mild stomatitis (inflammation of the mouth) and the disease is self-limiting.
The Canadian Food Inspection Agency (CFIA) has implemented the following import restrictions to help prevent the disease from getting into Canada:
- No horses originating from Arizona will be allowed into Canada
- Any horse coming to Canada from the US must have been out fo Arizona for at least 21 days
- Any Canadian horse going into Arizona will either have to be out of Arizona a minimum of 21 days before returning or it will require an import permit and an inspection within 15 days by a USDA accredited veterinarian, and a negative ELISA test for VS.
I have to wonder about the allowance for horses to come back from Arizona is less than 21 days - it doesn't make sense to me that a horse in Arizona can be inspected and tested for VS and still considered virus-free up to two weeks later. The 21-day minimum "layover" between Arizona and coming back to Canada makes much more sense, as any horse that encounters VS should develop clinical signs of infection within this time frame. If they're still lesion-free three weeks after leaving Arizona, then it's fairly safe to say they're VS-free.
By far the best thing to do for the next several weeks - until they've identified the source of the virus and have the situation well contained - is to keep your horses out of Arizona.
Image: Lesions on the lips of a horse with vesicular stomatits (source: http://wyovet.uwyo.edu/)
