A horse with West Nile virus was euthanized at Grandview in Yakima County.

The state Agriculture Department said Tuesday the horse was pastured and had not traveled outside the area. It was not vaccinated for the virus. The disease was confirmed by testing at the Washington Animal Disease Diagnostic Laboratory in Pullman.

No human cases of West Nile virus have been confirmed this year in Washington, although there have been more than 1,100 in 38 other states.

The virus is spread by mosquitoes and kills about one-third of the infected horses. Washington had 72 cases of West Nile virus in horses in 2009, but none in the next two years.