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West Nile virus found in Yakima horse—first WNV case in Washington reported for 2006

OLYMPIA –  West Nile virus (WNV) has been confirmed in an eight-year-old quarter horse in Yakima County, the state Department of Agriculture announced today (Aug. 18). The horse started showing signs of central nervous system problems on Aug. 11.

The positive test result was reported late Thursday by the Washington Animal Disease Diagnostic Laboratory in Pullman. The mare, which had not been vaccinated for WNV, had not left the Terrace Heights premises during the current mosquito season.

“This is the first confirmed case this year of a horse contracting West Nile virus in Washington,” said Dr. Leonard Eldridge, state veterinarian.

Last September, one horse in Yakima County was confirmed with the disease. Another horse in Thurston County and two horses in Snohomish County were believed to have contracted WNV in 2005 while in California.

“The best way to protect a horse from West Nile infection is vaccination,” Eldridge said. The vaccine requires two doses three to six weeks apart, with immunity achieved five weeks after the second vaccine. An annual booster shot should be considered prior to the start of the mosquito season.

West Nile virus is spread by the bite of an infected mosquito and can infect people, horses, many types of birds, and other animals. Humans cannot contract West Nile through contact with an infected horse and infected horses do not spread the disease to other horses or animals. Mosquitoes get infected when they feed on an infected bird.

“We may be headed for more cases of WNV in horses as birds infected with the virus move into Washington state,” Eldridge noted. The threat of WNV can be minimized by controlling mosquitoes and preventing horses from being exposed to adult mosquitoes.

Many horses and other animals contracting WNV do not become ill and show no symptoms at all. Those that do become ill show signs such as loss of coordination, loss of appetite, confusion, fever, stiffness and muscle weakness, particularly in the hindquarters. About one-third of horses that become ill die.

Veterinarians and horse owners should report potential cases of West Nile virus in horses by calling the State Veterinarian’s Office at (360) 902-1878.

More WNV information is available on the following Web sites:

• Department of Agriculture: agr.wa.gov/FoodAnimal/AnimalHealth/Diseases/WestNileVirus/default.htm
• Department of Health: www.doh.wa.gov/WNV/
• Washington State University: www.wnv.wsu.edu
   

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