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State veterinarian urges horse owners to vaccinate against West Nile virus

OLYMPIA – Horse owners should take advantage of the availability of vaccines to prevent West Nile virus, a potentially fatal disease in horses, according to Washington’s state veterinarian.

Although the first confirmed case of West Nile virus (WNV) in a Washington horse didn’t occur until August in each of the past two years, there is no guarantee it will take that long for WNV to show up in 2008. Last year, all eight cases of horses with WNV occurred in Yakima County and were confirmed in August or September. In previous years, there have been horses in Western Washington as well.

“Seven of the eight horses in 2007 cases were not vaccinated and the other horse didn’t have an up-to-date vaccine,” said Dr. Leonard Eldridge,” state veterinarian.

Eldridge is again urging horse owners to vaccinate their horses against WNV. He also is recommending that horse owners take measures to reduce mosquito populations. Precautions include removing standing water from yards and barns and changing water in troughs or bird baths that could be a source of mosquito breeding.

West Nile virus is spread by the bite of an infected mosquito and can infect people, horses, many types of birds, and other animals. Horses with WNV do not spread the disease. Mosquitoes get infected when they feed on an infected bird.

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

WNV is fatal in about one-third of all horses that contract it, although most horses 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.

“Older, sick or weak horses have much less chance of survival if infected,” Eldridge said. “Vaccinating your horse or getting the proper booster shots promptly is the best way to help protect your animal and prevent greater expenses from treating your horse after the disease is acquired. A spring dose of vaccine, even in previously vaccinated horses, is necessary to maintain protective immunity in most horses.”

Horse owners should consult with their veterinarians for vaccination recommendations and WNV control measures. The American Association of Equine Practitioners recommends WNV vaccine injections. The vaccine requires two doses four to six weeks apart, and immunity will not be achieved until five weeks after the second vaccine. An annual booster shot should be considered prior to the start of the mosquito season.

A chart listing WNV cases for humans, birds and animals is maintained on the state Department of Health’s Web site at  www.doh.wa.gov/WNV. No cases have been reported for 2008.
 

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