Russ Daly: What people should know about vesicular stomatitis

Russ Daly
Special to the Farm Forum

Because it’s fairly unusual, when the animal disease called vesicular stomatitis hits the news, livestock owners typically have a lot of questions. Currently this summer, the problematic disease has been found in horses in Texas, New Mexico, and Colorado – not the Dakotas yet. In 2015, South Dakota horses and cattle were affected in a larger outbreak, though – so we know there’s potential for this disease to hit us here.

Vesicular stomatitis (VS) most commonly affects horses, but it can hit cattle and pigs too. The main feature of the disease is the formation of blisters (vesicles) inside the mouth, on the tongue, the area where the mouth meets the lips, and sometimes (in adult females) the teats. Blisters can also appear at the junction of the hooves and skin (coronary band), causing lameness.

However, by the time affected show signs of a problem and are examined, the blisters have almost always ruptured, leaving behind raw sores in the mouth (“stomatitis”), on the tongue, and other affected parts of the body. These sores make eating and drinking temporarily very painful and difficult. Within a given infected herd, VS usually only affects a relatively small percentage of animals (10-20%).

Vesicular stomatitis is a viral disease, with the germ spread between animals by insect bites. The virus survives and multiplies well in small midges or black flies – the most common culprits.

Animals affected with the illness also are important sources of virus for others. Virus is prevalent in the mouth and other affected parts of the body: animals can catch VS by direct contact with an infected animal, or by indirect contact with feed, water, tack, or other items that were contaminated by an infected animal.

Interestingly, people can catch VS too. In people, the infection mimics influenza (headache, fever, muscle aches that resolve in a few days) rather than causing blisters as it does in animals. It usually only affects people in very close contact with the germ (i.e., people working very closely with affected animals).

Being a disease caused by a virus, there’s no specific treatment available for animals affected by VS. Good nursing care, including providing soft feeds, tending to sores, and watching for secondary bacterial infections (with appropriate antibiotic use) may help recovery. Luckily, VS is a self-limiting disease for which most animals recover fully over the course of 1-2 weeks.

Likewise, there’s no vaccine for VS, either. Managing animals, particularly horses, to minimize contact with biting flies may aid in prevention. This may include taking animals off pastures during times of peak insect activity, pasturing away from water sources, and appropriate use of insecticides.

Outbreaks of VS don’t occur every year, but when they do, it’s usually in the Western US (e.g. Texas, New Mexico, Colorado), and – because of the role of insects in its spread – during the summer months. The disease is not common at all in South Dakota, although there were quite a few Western South Dakota ranches affected in the 2015 outbreak.

Despite its self-limiting nature in animals, VS is a big concern for state and federal veterinarians. Besides its highly contagious nature, any disease that causes blisters in the mouth of livestock is a red flag. Foot and mouth disease (FMD) is the most concerning of these – a disease so contagious it could devastate the US livestock industry. Mouth blisters caused by VS can’t be visually distinguished from blisters caused by FMD, so state and federal vets take time to ensure it’s actually VS, and not something different – taking samples for confirmation once these signs are noted in an animal.

One big tipoff as to the diagnosis, however, is that horses are not affected by FMD. State and federal vets work to quarantine VS-affected animals in order to limit the disease’s spread. Restrictions on the movement of animals out of VS-affected states are commonly implemented.

If you suspect VS in one of your animals, your first call should be to your veterinarian. If VS is a possibility, they’ll contact the state veterinarian’s office, who will follow up with you and your veterinarian. It’s in the best interest of you, your animals, and your neighbors’ animals to determine whether VS might be causing what you’re seeing in your animals.