Warmer weather following a rainy spell could trigger an active mosquito season, which is why the Washington State Department of Agriculture is advising horse owners to make sure their horses are vaccinated to protect against West Nile virus.
The disease is potentially fatal to horses and is spread by mosquitoes that have fed on infected birds. While West Nile virus can sicken people, horses, birds and other animals, it does not spread from horses to people or other animals.
Two cases of West Nile virus were confirmed last year in Eastern Washington, however the number has been much higher in previous years, with 72 cases reported in 2009.
“With mosquito season approaching, now is the time to schedule a visit with your veterinarian for an initial series of vaccine injections if your animals have never been vaccinated before, or for an annual booster injection,” said Acting State Veterinarian Paul Kohrs. “It can take up to four weeks for the immunity offered by the initial series of vaccinations to be fully protective.”
West Nile virus is fatal to horses in about a third of the cases where clinical signs are apparent, although most horses do not become ill and show no symptoms at all.
Horses that do become ill often display loss of coordination, loss of appetite, confusion, fever, stiffness and muscle weakness, particularly in their hindquarters.
To reduce the risk, WSDA advises owners to keep horses indoors during the peak mosquito activity times of dawn and dusk, eliminate any sources of standing water nearby and even check areas where rain water may accumulate, like old tires or bird baths.
Veterinarians who learn of potential West Nile virus cases should contact the State Veterinarian’s Office at (360) 902-1881.