GRANDVIEW - A horse near the Lower Valley city of Grandview was euthanized recently when it tested positive for the West Nile virus.
The two-year-old gelding had no history of travel out of the area and was not vaccinated for the virus, state officials said.
The Washington Animal Disease Diagnostic Laboratory in Pullman reported the positive test results to the state veterinarian's office.
The West Nile virus is spread by mosquitoes that have fed on an infected bird. The disease can sicken people, horses, many types of birds and other animals. It is not spread from horses to other animals.
No human cases of the virus have been confirmed in Washington in 2012. According to the Centers for Disease Control and Prevention, 1,118 human cases have been reported in 38 states this year.
The West Nile virus is fatal in about one-third of all horses that show clinical signs, although most horses do not become ill and show no symptoms at all. Those that do become ill display loss of coordination, loss of appetite, confusion, fever, stiffness and muscle weakness, particularly in the hindquarters.
Washington led the nation with 72 cases of the virus in horses in 2009, but no cases were detected in Washington horses in the past two years.
Washington's state veterinarian continues to urge owners to vaccinate their horses against the disease.
Veterinarians who learn of potential West Nile virus cases in horses or other animals should contact the state veterinarian's office at (360) 902-1881.