State veterinarian urges owners to vaccinate horses against West Nile virus

  • Written by Washington State Dept. of Agriculture

 OLYMPIA – As the weather warms up across the state and mosquitoes become more prevalent, the Washington State Department of Agriculture is advising horse owners to make sure their horse’s vaccination is current for protection against West Nile virus.

In August 2012, a two-year-old gelding pastured near Grandview was euthanized after it became ill following a bite from a mosquito infected with West Nile virus. The horse was not vaccinated for the disease.

“It was the only West Nile equine case reported to us last year, but there’s no way to predict the virus won’t return in force this year,” State Veterinarian Leonard Eldridge said. “Outbreaks still present a risk.”

Although most horses infected with the mosquito-borne illness do not become ill, West Nile virus is fatal in about one-third of all horses that show symptoms.

Horses that do become ill show a loss of coordination, loss of appetite, confusion, fever, stiffness and muscle weakness, particularly in the hindquarters.

Infected horses do not spread West Nile virus to other horses or animals.

To protect their livestock, horse owners should take measures to reduce mosquito populations, including:
• Removing standing water from yards and barns that can serve as a breeding ground for mosquitoes.
• Removing old tires and garbage that may be rain soaked.
• Changing water at least weekly in troughs or bird baths.
• Keeping horses in stalls or screened areas during the early morning and evening hours when mosquitoes are the most active and feeding.
• Placing fans inside barns and stalls to maintain air movement.

Veterinarians who learn of potential West Nile virus cases in horses or other animals should contact the State Veterinarian’s Office at (360) 902-1881.

State and local health departments, mosquito control districts, other state agencies and volunteers work together on environmental monitoring and prevention measures for the virus.

Visit the websites of the state Department of Health at or the U.S. Department of Agriculture at for more information.

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