Kentucky animal health officials have confirmed the commonwealth’s eighth case of equine West Nile virus (WNV), this time in Bourbon County, according to a statement from Equine Programs Manager E.S. "Rusty" Ford.

According to the statement, issued the evening of Aug. 27, a 15-month-old Standardbred filly was euthanized after developing clinical signs of WNV. Ford said the signs were first noted on Aug. 15 and included lethargy, pain and stiffness in her neck, and rear limb ataxia (incoordination, which began after about 24 hours of illness). The filly did not respond to treatment, Ford said, and was euthanized after the ataxia progressed into recumbency.

The filly had no WNV vaccination history. Ford noted in the statement that none of the animals with confirmed WNV cases in Kentucky this year were current on vaccinations.

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%