Kentucky animal health officials have confirmed the commonwealth’s fourth case of equine West Nile virus (WNV) in 2012, according to a statement from Kentucky Equine Programs Manager E.S. "Rusty" Ford.

The affected horse–a 2 ½-year-old Arabian colt from Scott County–first showed signs of disease on Aug. 14 when his owner noticed an abnormal gait that progressively worsened. The colt was presented for veterinary examination on Aug. 17; clinical signs at presentation included lethargy, moderate rear limb ataxia (incoordination), proprioceptive deficits (lack of physical awareness of limbs and their placement), and poor tail tone. Ford’s statement indicated that the horse was treated, but did not respond, became recumbent, and was subsequently euthanized.

Ford’s statement also noted the colt was vaccinated against the virus in March, but did not receive a subsequent booster. He had no previous vaccination history.

"The attending veterinarian suspects the colt’s immunity had likely been compromised by other health-related factors," Ford said in the statement