The Kentucky State Veterinarian's office announced today (Aug. 3) that a Henderson County horse has tested positive for West Nile virus (WNV). The horse has since been euthanized.
"Results of diagnostic testing received yesterday (Aug. 2) from Murray State University's Breathitt Veterinary Center, confirms the diagnosis of West Nile virus having affected a horse in Henderson County, Ky.," according to a statement from Kentucky Equine Programs Manager E.S. "Rusty" Ford. "This marks the first West Nile diagnosis of an equine within Kentucky made during 2012."
Ford's statement relayed that the unvaccinated yearling Thoroughbred filly began showing clinical signs of disease--including lethargy, fever, and rear limb ataxia (incoordination)--on July 30. Her clinical signs progressed through the night, Ford's statement read, and she became recumbent the following day. She was euthanized on Aug. 1.
Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia (hypersensitivity to touch and sound); changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia. Equine mortality rate can be as high as 30-40%.
The USDA Animal and Plant Health Inspection Service reported 83 cases of WNV in U.S. horses in 2011; only one case was reported that year in Kentucky.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.