Kentucky Reports Fourth Equine WNV Case of 2012

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.

Two of the other three affected Kentucky horses were also euthanized. One, confirmed positive late last week, is undergoing treatment and is reportedly responding well.

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 87 cases of WNV in U.S. horses in 2011; only one case was reported that year in Kentucky.

About the Author

Erica Larson, News Editor

Erica Larson, News Editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in three-day eventing with her OTTB, Dorado, and enjoys photography in her spare time.

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