The Washington State Department of Agriculture (WSDA) has confirmed five new cases of West Nile virus in horses, bringing to six the number of cases so far this year and now surpassing the total number in the state for all of 2014.

The first case of West Nile virus in a horse this year was reported July 21 and involved an unvaccinated Quarter horse gelding in Kennewick. The horse’s condition continues to improve.

Veterinarians reported four new cases since then, all confirmed as positive for West Nile virus by the Washington State University’s Animal Disease Diagnostic Laboratory in Pullman. They include:

• A two-year-old unvaccinated Andalusian stud colt from Harrah, Yakima County. The horse’s condition is improving.
• A four-year-old unvaccinated Andalusian stud in Kennewick, Benton County. It has been euthanized.
• A three-year-old unvaccinated Quarter horse gelding in Mesa, Franklin County. The horse died.
• A nine-year-old Appaloosa mare in Othello, Adams County. It is unclear if it was vaccinated, but appears to be recovering.
• A three-year old Azteca male in Mabton, Yakima county. The horse was not vaccinated and appears to be recovering.

Washington had five confirmed cases of horses with West Nile virus last year, with the first case reported Aug. 19, 2014. The affected horses were in Benton, Franklin, Grant, Okanogan and Yakima counties.

West Nile virus is spread by mosquitoes that have fed on infected birds. The disease sickens people, horses, birds and other animals, but it does not spread directly from horses to people or other animals. Although most horses do not become ill, in about a third of the cases in which the horse shows symptoms, the disease can be fatal. Horses that do become ill can show loss of coordination, loss of appetite, confusion, fever, stiffness, and weakness, particularly in their hindquarters.

It is not too late to have your horse vaccinated for the disease. To reduce the risk, horse owners should also try to keep horses indoors at dawn and dusk, when mosquitoes are prevalent, and remove sources of standing water, such as old tires or bird baths.

Veterinarians who learn of potential West Nile virus cases in horses or other animals should call the State Veterinarian’s Office at (360) 902-1881. The state Department of Health maintains statistics of positive cases of West Nile virus in humans, horses, birds and mosquito samples.