KING COUNTY, WASHINGTON - Dr. Alonzo Plough, Public Health - Seattle & King County Director, and Pam Bissonnette, King County Department of Natural Resources and Parks director, today outlined the current status of West Nile virus in the region and detailed the county's mosquito control efforts to minimize the impact of West Nile virus when it arrives in King County.

Natural Resources and Parks Director Pam Bissonnette explained how to minimize mosquitoes at stormwater ponds.

"We are fortunate to not yet have cases of West Nile virus in King County," said Plough, "but people must be vigilant in removing mosquito breeding habitats in their yards by tipping out anything that can hold standing water."

"We're doing our part at Natural Resources and Parks by monitoring our stormwater facilities, and larviciding those where the health risk is greatest," said Bissonnette. "While stormwater ponds are essential for protecting health and property from flooding and polluted runoff, they can occasionally provide habitat for mosquitoes. When such ponds are located near concentrations of people at risk and where mosquito larvae are present, our staff are applying an environmentally friendly larvicide to reduce the threat."

Nearly 500 cases have been reported to the Centers for Disease Control so far this year, with 10 deaths nationwide. Plough said that while anyone can become infected with West Nile virus and become ill, people over the age of 50 are most at risk for serious illness. In 2003, almost 10,000 people were confirmed with West Nile virus, and more than 250 people died. Most people become infected with West Nile virus in the later summer and early autumn months.

Bissonnette said that through July, DNRP staff had made roughly 350 stormwater facility site visits and treated approximately 75 facilities. The larvicides used are Bti and Bs, which are naturally occurring bacterium. They are applied in areas of the ponds or drainage structures where the mosquito larvae live. When the larvicide is ingested, it produces a toxin that crystallizes in the larval gut, resulting in death. It is not harmful to other species.

State law requires permits for larviciding in any body of water that is not fully contained, such as a lined fountain or ornamental pond. The Department of Natural Resources and Parks has found that many of their stormwater ponds do not have larvae in them, either because the ponds are dry or because they have enough water to provide habitat for fish, frogs, and other mosquito predators.

To lessen the number of mosquitoes near people's homes, residents are urged to reduce artificial habitat by removing or tipping out any source of standing water. If larger bodies of water on private property do appear to be a source of mosquitoes, homeowners may consult a Pest Control Operator who is licensed and can obtain permits to apply larvicide in water.

"We will never be able to eliminate all mosquitoes so people should protect themselves when mosquitoes are biting by wearing clothing that covers up bare skin," Plough said. Insect repellents containing the chemical N,N-diethyl-meta-toluamide (DEET) are known to be safe and effective for adults and children, but is important to read and follow the instructions on the label carefully. It is also recommended that all door and window screens be free of rips or tears.

West Nile virus is primarily a bird disease, and crows are especially susceptible. Mosquitoes become infected by feeding on an infected bird and can pass the virus to humans, horses, or other animals when they bite. As part of surveillance activities, Public Health - Seattle & King County is tracking bird deaths in the County. Residents may assist by calling to report dead birds.

Horses are at high risk for West Nile virus. Horse owners are urged to contact their veterinarian about a vaccine for West Nile virus. Other domestic pets, such as cats and dogs, are very unlikely to become ill from West Nile virus.

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