OLYMPIA, Wash --- The Washington State Department of Agriculture urges Washington horse owners to vaccinate their animals against West Nile virus as soon as possible.

State Veterinarian Dr. Brian Joseph said,” Now is the time to vaccinate for this mosquito-borne disease due to our extremely wet winter and Washington’s history of leading the nation with equine cases of the West Nile virus.”

The virus can be fatal to horses and is spread by mosquitos that have fed on infected birds. West Nile virus can infect people, horses, birds and other animals but it does not directly spread from horses to people or other animals.

Washington had 27 confirmed cases last year of infected horses, nine less than the number of confirmed cases in 2015.

The West Nile virus vaccine is effective if administered to horses before mosquito season. Last year the first reported case was in late July, reported by Washington State University’s Washington Animal Disease Diagnostic Laboratory in Pullman. There were ten counties that reported cases in 2016, Spokane County lead with eight cases.

Horses require two doses of the vaccine initially, and ten boosters at least annually.

Dr. Joseph said he advises horse owners to discuss vaccinations for West Nile virus, equine herpes virus and other diseases with their veterinarians.

Most horses that are exposed to West Nile virus display no symptoms. Horses that do often display a loss of coordination, loss of appetite, confusion, fever, stiffness and muscle weakness particularly in their hindquarters. The virus is fatal in about one-third of the cases where symptoms are evident.

To reduce the risk, WSDA advises owners to keep horses indoors during peak mosquito activity times, like dawn and dusk, use insect repellants and fly sheets to reduce exposure, eliminate sources of standing water nearby and check areas where rain water accumulates.

Veterinarians who diagnose potential West Nile Virus cases should contact the State Veterinarian’s Office at (360)902-1878.