Colorado has become the second state in the country to have a confirmed case of vesicular stomatitis (VS). Four horses on two Weld County premises tested positive for the disease and have been placed under quarantine. The horses involved in these index cases have no history of travel.

 Vesicular stomatitis virus
Vesicular stomatitis virus

On July 17th, the National Veterinary Services Laboratory reported a positive test on samples submitted from four horses in Weld County. The initial Colorado disease investigation was performed by one of the field veterinarians from the State Veterinarian’s Office at the Colorado Department of Agriculture. Previous positive cases of vesicular stomatitis in 2014 have been diagnosed in the southern area of Texas near the Mexico border and more recently in Bastrop and Travis Counties just south of Austin, TX.

“Vesicular stomatitis can be painful for animals and costly to their owners,” said State Veterinarian, Dr. Keith Roehr. “The virus typically causes oral blisters and sores that can be painful causing difficulty in eating and drinking.”

Veterinarians and livestock owners who suspect an animal may have VS or any other vesicular disease should immediately contact State or federal animal health authorities. Livestock with clinical signs of VS are isolated until they are healed and determined to be of no further threat for disease spread. There are no USDA approved vaccines for VS.

While rare, human cases of VS can occur, usually among those who handle infected animals. VS in humans can cause flu-like symptoms and only rarely includes lesions or blisters. 

VS susceptible species include horses, mules, cattle, bison, sheep, goats, pigs, and camelids. The clinical signs of the disease include vesicles, erosions and sloughing of the skin on the muzzle, tongue, teats and above the hooves of susceptible livestock. Vesicles are usually only seen early in the course of the disease. The transmission of vesicular stomatitis is not completely understood but components include insect vectors, mechanical transmission, and livestock movement. For more infectious disease news and information, visit and “like” the Infectious Disease News Facebook page