Adams County horse the first infected with West Nile Virus this year

Vesicular stomatitis and West Nile viruses have been confirmed in Colorado horses, the Colorado Department of Agriculture said July 21.

West Nile was confirmed in an Adams County horse and vesicular stomatitis in horses in Boulder County and in two Weld County locations.

“Strict fly control is an important factor to inhibit the transmission of vesicular stomatitis. 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,” State Veterinarian Keith Roehr said in a news release.

Colorado is the second state in the U.S. to confirm vesicular stomatitis virus this year. The first cases were diagnosed in Texas. The three Colorado locations where the infected animals were found have been quarantined and nearby farms and ranches are being investigated, according to an agriculture department news release.

In addition to horses, mules, cattle, bison sheep, pigs and camelids are susceptible to the virus. The clinical signs of the disease include blisters, 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.

West Nile Virus

The first reported equine case of West Nile 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 West Nile can be amplified and carried by infected birds and then 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 West Nile are similar to 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.

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