Second case of West Nile confirmed in Washington

A 10-year-old Pasco, Wash., mare was recently euthanized after contracting West Nile virus. It is the second case in horses in the state this year.

Published on October 10, 2013 5:47PM

A 10-year-old mare has been euthanized in Washington state after contracting West Nile virus.

According to the Washington Department of Agriculture, the horse, from north Pasco, Wash., was not vaccinated for the disease and had not left the state.

Washington State University’s Animal Disease Diagnostic Laboratory in Pullman, Wash., reported the test results to the state veterinarian the week of Oct. 7.

“A killing frost will reduce the likelihood of further cases for the year,” acting state veterinarian Paul Kohrs said in a press release. “Horse owners in areas of the state where this disease will overwinter should consider vaccinating for West Nile in 2014 at least a month before the onset of the mosquito season.”

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

The Pasco horse is the second confirmed case of West Nile virus in a horse this year. The other case was in a horse pastured in Outlook, Wash., in Yakima County. It was reported in late September.

Washington had 72 West Nile virus cases in 2009 and none in 2010 or 2011. A horse pastured near Grandview, Wash., was euthanized after it became ill with the disease in 2012.

West Nile virus is fatal in horses in approximately one-third of the cases where clinical signs are apparent. Most horses do not become ill and show no symptoms. Symptoms include loss of coordination, loss of appetite, confusion, fever, stiffness and muscle weakness, particularly in the hindquarters.

Veterinarians who learn of potential West Nile virus cases should contact the state veterinarian’s office at 360-902-1881.


Washington State Department of Agriculture:

Washington State Department of Health:


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