April 2003

Contact: Rocky Beach,
WDFW Wildlife Diversity
(360) 902-2510

West Nile virus (WNV) was first reported in the United States in 1999 in New York. Since that time, the virus has spread across the country, and in 2002 the first animal cases were identified in Washington state-a raven in Pend Oreille County, a crow in Snohomish County and two horses, one in Island County and one in Whatcom County.

State agencies, including the Washington Department of Fish and Wildlife (WDFW), are working together to minimize public health risks from the disease.

To date (April 2003), there have been no cases of humans acquiring the disease in Washington state. The Washington Department of Health offers more information on WNV human health issues on its website and on its toll-free telephone line: 1-866-78VIRUS (1-866-788-4787).

Horses also can be affected by the virus. Horse owners can visit the state Department of Agriculture's website for additional information.

Impacts to fish and wildlife
Protecting Washington fish and wildlife is a key mandate of the Washington Department of Fish and Wildlife (WDFW). The department is concerned with the impact of West Nile virus on wildlife populations directly from the disease and seeks to ensure that the potential impact on fish and wildlife from pesticides used to control mosquitoes is minimized.

At least 140 species of birds, including songbirds, hawks, owls, eagles, waterfowl, woodpeckers and hummingbirds, have tested positive for West Nile virus in the United States. At least 77 of those species are found in Washington. Corvids (ravens, crows, jays, magpies, etc.) are the group most commonly affected by the virus. (See http://www.nwhc.usgs.gov/research/west_nile/wnvaffected.html for a list of wildlife species that have tested positive for West Nile virus elsewhere in the United States). Besides birds, some free-ranging mammal species, including caribou, squirrels, wolves, bear, and deer, have tested positive for the virus.

Thousands of wild birds, and many fewer wild mammals, have died from WNV since 1999. There is no way to accurately predict the number of wildlife deaths that might occur in the future, but it is anticipated that more bird deaths will occur in Washington.

WDFW is working closely with the state Department of Health, the lead state agency for WNV investigations, to document the identity and distribution of species impacted by West Nile virus in Washington. WDFW's ongoing wildlife research, survey and monitoring efforts are expected to produce information on whether certain species are being impacted.

Although scientists are working to develop vaccines that could potentially be administered to wild animals, it is not feasible to capture a significant portion of Washington's wild animals for multi-dose vaccinations. Some zoo facilities, however, have vaccinated their captive birds against the virus.

Reporting dead birds
The presence of dead birds in an area may be an indicator that WNV is present. Public health workers in Washington conduct dead bird surveillance from late spring to fall, when mosquitoes are most active. If you find a dead bird, or if you notice more dead birds in an area than you consider normal, please take the following actions:

• Report the information promptly to your local health department. Birds that have been dead less than 48 hours provide the best samples for testing.
• Be prepared to share information about the bird(s) such as the specific location it was found, including the distance to the nearest town, road or other landmark. Also provide your name and phone number.
• It is best to leave the bird in place on the ground and report its location. If you choose to collect the specimen, use a shovel or wear gloves to place it in two plastic bags. Keep the specimen in an ice chest or refrigerator that is not used for food or place plastic bags of ice or cool packs over the bird and cover it with a bucket. Do not handle wildlife with bare hands.

Game birds
Transmission of WNV directly from birds to humans is extremely rare and appears to require blood-to-blood contact between birds and humans. Although waterfowl and other game birds do not appear to develop concentrations of WNV in their blood high enough to infect humans, as a precaution hunters should wear gloves when handling and cleaning game. If a hunter's skin is broken while cleaning game, he/she should thoroughly wash the area with soap and water. As always, it is strongly recommended that wild game be thoroughly cooked before it is eaten.

Mosquito control
WNV is a mosquito-borne disease. Certain mosquito species become infected after biting infected birds, the primary carriers of the disease, and then may transmit the virus to other birds and mammals. There are extremely rare instances of transmission by other means, such as bird-to-bird or bird-to-human. To date, more than 40 of the 165 species and subspecies of mosquitoes in North America have been found to carry WNV.

The best protection from WNV is to avoid mosquito bites by staying indoors at dawn and dusk when mosquitoes are the most active; wearing long sleeves, long pants and a hat in mosquito-infested areas, and using mosquito repellant when necessary.

Because mosquitoes lay their eggs in or near some sort of water, and larvae require water to survive, property owners can reduce mosquito-breeding areas by reducing or eliminating standing water including:

• Emptying anything that holds standing water-old tires, buckets, plastic covers and toys.
• Making sure roof gutters drain properly and cleaning clogged gutters each spring and fall.
• Fixing leaky outdoor faucets and sprinklers.
• Cleaning and change the water in bird baths, fountains, wading pools and animal troughs at least twice a week. Where feasible, pools can be aerated with underwater pumps to keep water moving.

Planting native vegetation and installing nest boxes can help attract mosquito-eating birds and bats. However, property owners should avoid introducing non-native fish or wildlife in an attempt to control mosquitoes. While it is permissible to release some fish commonly available in pet stores into small, contained backyard pools and ponds, non-native fish should not be released into open or partially contained waters that may occasionally flood into natural water bodies. Some non-native species, including so-called mosquito fish, Gambusia affinis, can be major pests when introduced outside their natural range. Gambusia are aggressive and have been known to feed on eggs, larvae and juvenile native fish and amphibians. Because of these negative impacts on native species, Gambusia is a regulated species in Washington state, and may not be introduced without a fish stocking permit issued by WDFW.

Under WDFW policy, transfer/stocking permits may only be issued to organized mosquito control districts, the U.S. Army Corps of Engineers, and local or state health departments; permits may not be issued to private individuals. To protect the Olympic mudminnow, a state sensitive species, Gambusia stocking is prohibited in Clallam, Jefferson, Kitsap, Grays Harbor, Mason and Thurston and portions of Lewis County that drain into the Chehalis river. For information on fish stocking permits contact the WDFW regional office in your area.

In seeking to control mosquitoes, it is important to realize that natural water bodies such as wetlands contain numerous natural mosquito predators, such as birds and frogs. Mosquitoes can actually increase if wetlands are drained or destroyed. Wetlands also help clean polluted run-off water, prevent floods and help protect drinking water supplies.

Besides direct effects from WNV itself, fish and wildlife can also be negatively impacted by some chemical mosquito control measures. While some pesticides that target mosquito larvae (larvicides), such as Bacillus thuringiensis israelensis or Bti, are believed to have a negligible effect on wildlife, other larvae control chemicals can pose a risk to fish, amphibians and other invertebrates, and compounds used to control adult mosquitoes ("adulticides") may impact those animals as well as reptiles, birds and mammals.

The Washington Department of Fish and Wildlife supports an Integrated Pest Management approach to mosquito control that emphasizes taking steps to reduce mosquito exposure, and using Bti to target mosquito larvae if chemical control is necessary.

The application of pesticides to natural waters, including Bti, is regulated by the Washington departments of Ecology and Agriculture. The Department of Agriculture oversees label compliance and issues professional licenses to those who apply pesticides, while Ecology issues permits for uses of aquatic pesticides to assure water quality is protected.

Related websites:

Washington Department of Health
http://www.doh.wa.gov/ehp/ts/zoo/wnv/wnv.html

Centers for Disease Control and Prevention
http://www.cdc.gov/ncidod/dvbid/westnile

BIRDNET
http://www.nmnh.si.edu/BIRDNET/

U.S. Geological Survey National Wildlife Health Center
http://www.nwhc.usgs.gov/research/west_nile/west_nile.html

U.S. Geological Survey National Biological Information Infrastructure
http://westnilevirus.nbii.gov

Cornell University Center for the Environment
http://www.cfe.cornell.edu/erap/WNV

National Audubon Society
http://www.audubon.org/bird/wnv/Workshop.html

Portland Audubon Society
http://www.audubonportland.org/wnv.html

American Bird Conservancy
http://www.abcbirds.org/pesticides/west_nile_position_statement

Smithsonian Institute West Nile Virus Wildlife Health Workshop
http://www.serc.si.edu/migratorybirds/current_events_fin.htm

Rutgers University
http://www.rci.rutgers.edu/~insects/mosbiol.htm

University of Florida Cooperative Extension Service
http://edis.ifas.ufl.edu/ig122

Northwest Coalition for Alternatives to Pesticides (PDF file)
http://www.pesticide.org/westnilevirus.pdf

Department of Ecology: Preparing for WNV needn't harm the environment
http://www.ecy.wa.gov/news/2003news/2003-046.html

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