West Nile Disease Update in Washington State

from Archives: Local News
Updated: Tuesday, July 28, 2009

West Nile virus surrounds county Horses in Prosser and mosquitoes in Umatilla County tested positive for the disease.



By SHEILA HAGAR of the Walla Walla Union-Bulletin

WALLA WALLA -- The first cases of West Nile virus in Washington state horses has been confirmed by state officials.

The state Department of Agriculture announced the findings Friday. One infected horse was found in Toppenish and the second in Prosser. Neither had been vaccinated for the disease.


The animal in Toppenish, an 8-year-old quarter horse mare in foal, was euthanized. The Prosser horse, a 9-year-old quarter horse gelding, is expected to recover.

State veterinarian Leonard Eldridge noted in a release the cases point out the need for horse owners to vaccinate their animals.

The disease is fatal in about one-third of all horses that show clinical signs, although most horses do not become ill and show no symptoms at all. Horses that do become sick display loss of coordination and appetite, confusion, fever, stiffness and muscle weakness, particularly in the hindquarters.

Washington state led the nation last year in confirmed cases of West Nile virus, with 41 horses testing positive, Eldridge said.

The virus has also been detected in live mosquitoes trapped is several locations in Umatilla County, officials there said Monday. Testing at Oregon State University is expected to confirm the results later this week. This is the first detection of the virus in Umatilla County this year.

"West Nile has been detected in our neighboring counties, so we have been expecting to find it here as well," said Ron Montgomery, manager of the West Umatilla Vector Control District. "We have a good surveillance system in place and it worked exactly as it was supposed to.

"The infected mosquitoes were collected from Hat Rock State Park, Cold Spring National Wildlife Refuge and near the Hermiston Wastewater Treatment Facility, as part of the districts routine arbovirus surveillance program. Field tests conducted at the district lab yielded positive results."
Aerial resources are on standby status and will be utilized if widespread detection of West Nile virus occurs" Montgomery said, adding he encourages people to continue submitting dead birds for testing so the district can track the spread of West Nile in Oregon.

West Nile virus is primarily a bird disease. Some birds, including magpies, blue jays and crows are especially susceptible. Mosquitoes become infected by feeding on an infected bird and can pass the virus to humans, horses or other hosts when they bite.

"Most people who become infected with West Nile Virus do not become ill," said Genni Lehnert, administrator of the Umatilla County Public Health Department. "Some may develop mild flu-like symptoms such as fever, headache, body aches, and occasionally swollen lymph glands or a rash. In rare cases West Nile may cause encephalitis, or inflammation of the brain. Individuals with severe or unusual headaches should seek medical care as soon as possible."

There have been no human or horse cases of the West Nile virus reported in Oregon this year.