The Washington State Department of Agriculture is urging horse owners to make sure their horses are vaccinated to protect against West Nile virus, which can be fatal.
Warmer weather after a rainy spell could mean mosquitos, which can spread the disease after feeding on infected birds.
While only two cases of West Nile virus were confirmed last year in Eastern Washington, the number has been much higher in previous years, with 72 cases reported in 2009, according to state officials.
"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 in a statement. "It can take up to four weeks for the immunity offered by the initial series of vaccinations to be fully protective."
Most horses do not become ill and show no symptoms at all. But in a third of the cases with critical symptoms, the horses die, according to state officials. Horses that do become ill will often lose coordination and appetite and suffer from confusion, fever, stiffness and muscle weakness, particularly in their hindquarters.
The virus does not spread from horses to people or other animals.
Department of Agriculture officials advise people to keep their horses indoors during dawn and dusk, a peak time of mosquito activity, and to get rid of any standing water nearby including places where rain water can be stored, such as in old tires or bird baths.
Veterinarians who learn of potential West Nile virus cases should call the State Veterinarian's Office at 360-902-1881.
For more information, go to http://agr.wa.gov/foodanimal/animalhealth/diseases/west nilevirus.