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Increase of West Nile Virus Cases in Horses

UDAF officials are urging horse owners to vaccinate their horses to protect them from the West Nile Virus (WNV) due to an increase in cases. Four horses have tested positive for the virus since August 16, 2022.

“The West Nile Virus continues to be a threat to horses in Utah,” said state veterinarian, Dr. Dean Taylor. “It is important that horse owners get their horses vaccinated annually to protect against this disease.”

The four horses that tested positive for WNV were located in Duchesne and Uintah counties. Three of the four horses were euthanized as a result of contracting the disease.

WNV is spread by mosquitoes and affects people, birds, and horses. The disease can be prevented in horses with a yearly vaccination in the spring or early summer. Horse owners can also protect their horses by removing standing water on their property where mosquitoes may breed or by using insect repellant on their horses to prevent mosquito bites. The disease cannot be spread from horses to other horses or people.

In horses, WNV causes fever, incoordination, and other neurological signs. Around one-third of horses that contract WNV will die or be euthanized due to the disease. For more information about WNV, visit for a map of all reported human and animal cases of WNV and other mosquito-borne diseases.