West Nile virus detected in horses in Washington and Kentucky

Two new equine West Nile virus (WNV) cases have been reported to the Equine Disease Communication Center in Washington and Kentucky.

In Franklin County, Washington, a 2-year-old filly tested positive and is currently recovering under veterinary care. In Washington County, Kentucky, a 3-year-old Tennessee Walking Horse mare tested positive on September 18. The mare, which was unvaccinated, exhibited symptoms including dehydration, muscle fasciculations, and lower lip paralysis; she was subsequently euthanized. This marks the first confirmed equine WNV case in Kentucky for 2026.

West Nile virus is transmitted to horses through bites from infected mosquitoes. While not all infected horses show clinical signs, symptoms can include muscle twitching, hypersensitivity to touch and sound, changes in mental activity, and spinal issues such as asymmetrical weakness. There is no cure for the virus, though supportive care can assist recovery in some cases. Equine mortality rates for the virus can reach between 30% and 40%.