West Nile virus confirmed in unvaccinated horses in Washington and Oregon

Two unvaccinated horses in the Pacific Northwest have tested positive for West Nile virus (WNV). The first case was reported in a 2-year-old horse in Benton County, Washington, while a second case was confirmed in Union County, Oregon, on August 11.

West Nile virus is transmitted to horses through bites from infected mosquitoes. While not all infected animals show clinical signs, symptoms can include depression, muscle twitching, hypersensitivity to touch or sound, and neurological issues such as asymmetrical weakness or ataxia. There is no cure for the virus, though supportive care may assist recovery. Mortality rates for horses can reach between 30% and 40%.

Health officials recommend vaccination as an effective prevention tool. Unvaccinated horses typically require a two-shot series administered three to six weeks apart, while vaccinated horses may need annual or bi-annual boosters. Additionally, owners are advised to reduce mosquito exposure by eliminating stagnant water sources.