A horse near Spokane is the first reported victim of West Nile virus in Washington state this year, officials say.
The Animal Disease Diagnostic Laboratory at Washington State University reported the positive test results for the 10-year-old quarter horse from Four Lakes, Wash., according to the state Department of Agriculture.
The horse was not vaccinated for the disease. It is reported to have coordination problems with its rear legs and muscle tremors, but is improving, according to the department.
West Nile virus is spread by mosquitoes that have fed on infected birds. The disease sickens people, horses, birds and other animals, but does not spread directly from horses to people or other animals.
It’s unknown whether the horse was infected at home or while traveling, said Mike Louisell, spokesman for the department.
The disease is fatal to horses in about one-third of the cases in which clinical signs appeal. Most horses that are infected do not become ill and show no symptoms. Horses that do become ill can display a loss of coordination and appetite along with confusion, fever, stiffness and muscle weakness, particularly in their hindquarters.
Last year, WSDA confirmed 27 equine West Nile virus cases. Of those, seven horses died or were euthanized. Benton, Franklin, Grant, Kittitas, Lincoln, Okanogan, Pend Oreille, Spokane, Stevens and Yakima counties all reported cases. Spokane had the most, with eight cases.
More than 30 cases have been reported in some years, Louisell said.
The state recommends vaccinating horses in the spring or obtaining an annual booster shot. Horse owners can reduce mosquito populations and possible breeding areas by removing stagnant water sources and keeping horses inside during insect feeding times, typically early morning and in the evening. They can also consider equine-approved mosquito repellent, place fans inside barns to maintain air movement and avoid leaving incandescent bulbs on at night, as they attract mosquitoes.
“This is one of those risks that is very well-tracked,” he said.
Veterinarians who learn of potential West Nile virus cases in horses or other animals should contact the state veterinarian’s office at 360-902-1878.