WNV Confirmed in Yakima Co., Wash., Horse

WNV Confirmed in Yakima Co., Wash., Horse

West Nile virus is spread by mosquitoes that have fed on infected birds.

Photo: Photos.com

A case of West Nile virus (WNV) has been confirmed in a Yakima County, Wash., horse. The 7-year-old Quarter Horse gelding was recently pastured in Outlook, Wash., and had no history of travel out of the area. He has no vaccination history.

The Washington Animal Disease Diagnostic Laboratory in Pullman reported the positive test results to the state veterinarian’s office on Sept. 25. It is the only confirmed case of WNV in a Washington horse this year. Washington had 72 equine WNV cases in 2009, but none in 2010 or 2011. Last year, a horse pastured near Grandview was euthanized after it became ill with the disease.

West Nile virus is spread by mosquitoes that have fed on infected birds. The disease sickens people, horses, birds, and other animals, but it does not spread from horses to people or other animals.

WNV is also a viral disease transmitted to horses by infected mosquitoes. 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 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 state veterinarian’s office recommends spring as the best time to vaccinate horses against WNV or obtain booster shots. Veterinarians who learn of potential WNV cases in horses or other animals should contact the state veterinarian’s office at 360/902-1881.

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