Colorado Has Additional Vesicular Stomatitis Case; First West Nile Virus Case in 2014

The Colorado Department of Agriculture has two important updates involving Colorado’s horse community; vesicular stomatitis and the West Nile virus have been confirmed in Colorado horses.

“Strict fly control is an important factor to inhibit the transmission of vesicular stomatis. Although the insect vectors for transmission of West Nile Virus and VS in horses are different, one of the most important disease prevention practices for both diseases is insect control for both the premises and the individual animals,” said State Veterinarian, Dr. Keith Roehr.

Vesicular Stomatitis (VS)

A third Colorado premises has a confirmed diagnosis of vesicular stomatitis and a number of other premises in the surrounding area are being investigated. The third confirmed premises is located in Boulder county and has been placed under quarantine. Last week, four horses on two Weld County premises were placed under quarantine after testing positive for VS. Colorado is the second state in the country to have VS; previous positive cases in 2014 have been diagnosed in Texas.

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.

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.

Additional information including tips for livestock owners and veterinarians can be found by visiting and clicking on “Vesicular Stomatitis Virus” or call the Colorado State Veterinarian’s Office at 303-869-9130. To view the current location of cases and other important updates and information you can visit

West Nile Virus (WNV)

The first reported equine case of WNV in Colorado has been diagnosed in an Adams County horse. This case was diagnosed by Colorado State University Veterinary Diagnostic Laboratory in Fort Collins.

The transmission of the disease varies from year to year and depends on a number of factors, including mosquito numbers. The WNV can be amplified and carried by infected birds and spread locally by mosquitoes that bite those birds. The mosquitoes can then pass the virus to humans and animals.

Infected horses may display symptoms including head tilt, muscle tremors, stumbling, lack of coordination, weakness of the limbs or partial paralysis. The clinical signs of WNV are consistent with other important neurological diseases such as equine encephalitis, rabies, and equine herpes virus; therefore it is important to work with your veterinarian to get an accurate diagnosis through laboratory testing. Horse owners should also consult their private practicing veterinarian to determine an appropriate disease prevention plan for their horses.

Vaccines have proven to be a very effective prevention tool. Horses that have been vaccinated in past years will need an annual booster shot. However, if an owner did not vaccinate their animal in previous years, the horse will need the two-shot vaccination series within a three to six week period.

In addition to vaccinations, horse owners also need to reduce the mosquito populations and their possible breeding areas. Recommendations include removing stagnant water sources, keeping animals inside during the bugs’ feeding times, which are typically early in the morning and evening, and using mosquito repellents.

For complete and updated information concerning new WNV equine case information including numbers and location of test positive horses visit:






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