Kentucky, California Report more WNV-Positive Horses

Animal health officials in Kentucky and California have reported additional cases of West Nile virus (WNV) in resident horses, bringing the states' totals to five and six cases, respectively.

In Kentucky, Equine Programs Manager E.S. "Rusty" Ford issued a statement yesterday (Aug. 21) afternoon indicating a yearling Arabian filly from Shelby County was confirmed WNV-positive earlier that day. Ford said the owner noticed partial paralysis of the filly's lower lip and tongue, in addition to dysphagia (difficulty swallowing).

The filly received treatment, Ford said, and as of Aug. 21 was eating, drinking, and moving around well.

The filly was reportedly vaccinated in early spring, though not documented, and did not receive a booster, Ford said. She had no previous vaccination history.

"This is the second young horse diagnosed in Kentucky within the past 24 hours and in each case the patient reportedly received (at best) partial vaccination against West Nile virus," Ford said in his statement. "This information does serve as evidence that to maximize meaningful immunity requires vaccinating in accordance with and following the vaccine manufacturers' labeled instruction."

Of the five confirmed cases in Kentucky, two are recovering and three have been euthanized.

In California, the state Department of Food and Agriculture (CDFA) confirmed two additional WNV cases on Aug. 17: an unvaccinated yearling filly from Yolo County and an unvaccinated 2-year-old filly from Fresno County. Both horses are recovering, according to a CDFA statement.

Of the six confirmed cases, five are recovering and one has been euthanized.

"The CDFA urges horse owners to consult their veterinarian concerning a WNV vaccination program to ensure maximum protection of their horses," the statement said.

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.

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 eventing with her OTTB, Dorado.

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