Washington Confirms First Equine WNV Case since 2009

West Nile virus (WNV), a potentially fatal disease in equines, was confirmed in a Yakima County horse. The 2-year-old gelding has been euthanized.

The horse, who was pastured near Grandview, had no history of travel out of the area and was not vaccinated against WNV. The Washington Animal Disease Diagnostic Laboratory in Pullman reported the positive test results to the state veterinarian's office.

WNV is spread by mosquitoes that have fed on an infected bird. The disease can sicken people, horses, many types of birds, and other animals. It is not spread from horses to other animals.

No human cases of WNV have been confirmed in Washington in 2012. According to the Centers for Disease Control and Prevention, 1,118 human cases have been reported in 38 states this year.

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%.

Washington led the nation with 72 WNV cases in horses in 2009, but no cases were detected in Washington horses in the past two years. Washington's state veterinarian continues to urge owners to vaccinate their horses against the disease.

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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