Vesicular stomatitis (VS) has been reported in a horse in Las Animas County, Colorado. It’s the first diagnosed case in the state since 2006, but it’s not particularly surprising since this viral disease is periodically identified in horses in various parts of the US, and this case may be associated with northward movement of the virus from the Rio Grande River valley in New Mexico. However, it’s noteworthy because VS is a potentially nasty disease and since it’s also reportable, diagnosis of a case is accompanied by quarantine and other other control measures.

Vesicular stomatitis typically results in vesicles (small blisters) and ulcers in the mouth, on the tongue and lips, as well as on the udder (udder lesions are more common in cattle compared to other affected species). Lesions around the coronary band of the foot can also develop. Because of these blisters, infected animals may stop eating or drinking, and may be lame. It’s a self-limiting disease, meaning it will typically resolve on its own, but animals can develop secondary problems like bacterial infections or severe foot damage, or in some situations the consequences of decreased drinking and eating may be severe, resulting in bigger or longer-term problems. A major concern is that this virus can also infect cattle and produce signs that are similar to the dreaded foot and mouth disease.

The source of infection in this case is not known, but the horse has no history of travel to areas where the disease is active, so insect-borne infection is suspected. That means that the virus must be present in other animals in the region, since blood feeding insects simply spread the virus around, they don’t act as reservoirs or amplifiers of the virus. The farm is under quarantine and presumably surveillance is underway to identify other horses that have had contact with the animals on this farm, as well as to monitor for any more cases in the area.

When something like this occurs, travel restrictions for horses (and/or other species) are typically put in place by various governments, ranging from travel bans to requiring animals from areas where the disease is present to be accompanied by a health certificate saying that the horse has no signs of disease and hasn’t be on a farm with the disease. Anyone planning travel to, from, or through, involved areas needs to be aware of this and check into transportation rules, including potential import restrictions if they want to enter Canada with a horse.

If you are in an infected region (or nearby), you can do some things to reduce the risk of your horse becoming infected by VS:

• Restrict travel and avoid areas where the disease is active.
• Avoid direct contact between horses as much as possible when visiting farms, shows or other places where horses mix.
• Take basic insect control measures to reduce exposure to biting flies (e.g. black flies).
• Avoid sharing/trading/selling tack and other items that have close contact with your (or any other) horse.

Vesicular stomatitis is zoonotic but it’s of limited concern. Human infections are rare and usually just result in flu-like illness.