Health officials are issuing a West Nile Virus warning for this spring and summer for the disease's common targets: horses and humans.
Oregonians are advised to take steps to control mosquitoes - the carriers of the virus - and horse owners are urged to vaccinate their animals.
State Veterinarian Don Hansen of the Oregon Department of Agriculture says it is very likely that more cases of the disease will be reported in Oregon this year than last, and urged owners of horses to take steps to protect them.
Oregon became one of the last states to report the presence of West Nile Virus when the disease was confirmed in 2004. The final tally for 2006 showed detections of the virus in 73 humans, 35 horses and 25 birds.
"Vaccinating horses against the disease provides good protection," Hansen said. "For those who have already vaccinated their horses several months past, a booster shot now will strengthen protection. It is important for horse owners to vaccinate animals before the mosquito season gets into high gear."
The vaccine for horses is available through local veterinarians and many veterinary supply stores.
Insect control on individual animals remains a good preventive measure against the virus. Insect repellents applied to animals according to label directions will reduce risk.
For humans, screening windows at night and controlling exposure to mosquitoes at dusk and dawn limit the possibility of infection.
Reduction of mosquito breeding sites is also effective in controlling the spread of the disease. It is important to eliminate any source of stagnant water: puddles, pools, wheelbarrows, birdbaths, tires and any other place where water can stand for 72 hours or more is a potential breeding site.
Infected wild birds are the source of West Nile Virus. Mosquitoes that bite infected birds and then can transmit the infection to horses and humans. The disease does not transmit from horse to horse or human to human. A bite by an infected mosquito is the only known route of transmission.
A low percentage of mosquitoes carry the virus and a low percentage of horses bitten by infected mosquitoes become ill. But a horse showing signs is a serious situation. The disease causes inflammation of the brain and about one-third of affected horses die. Symptoms include stumbling, lack of coordination and weakness.