Since it was first identified in New York City in 1999, West Nile virus has spread to 28 other states, including Maine.

As a result, the Maine Bureau of Health has stepped up public education efforts about the virus, which is spread to humans and some animals by the bite of an infected mosquito. That bite can lead to an infection called encephalitis, or swelling of the brain, the bureau states.

However, some of these efforts aimed at reducing the risk of contracting the disease have drawn quick clarifications from Maine Audubon.

On its Maine West Nile Virus Web site, the bureau instructs homeowners to reduce or eliminate all standing water on the property to curb mosquito populations.

That advice, however, was quite upsetting to Sally Stockwell, Maine Audubon’s director of conservation, because it could result in damage to vernal pools and other wetlands.

“Vernal pools – small, ephemeral wetlands that provide habitat for several amphibian species – should not be drained!” Stockwell said.

Vernal pools are extremely important breeding sites for spotted and blue-spotted salamanders, four-toed salamanders, wood frogs and fairy shrimp. Additionally, beneficial predators that control mosquito populations call these pools home.

“Vernal pools are the source of many species that form the basis of the food chain for the surrounding forestland, and they should not be drained on account of West Nile virus,” she added.

Although the bureau states that mosquitoes get the virus from biting infected birds, Stockwell said the mosquitoes that breed in vernal pools are typically spring-emerging species that feed on mammals.

Maine has about 40 different types of mosquitoes, but most of the nuisance pests don’t transmit the virus.

The bird-biting mosquitoes, members of the Culex species, are the virus carriers and they breed primarily in containers, not wetlands, Stockwell said.

That’s why homeowners should be drilling holes in the bottom of recycling containers and in tire swings, and overturning plastic wading pools, flower pots and wheelbarrows to remove unnatural standing water instead of filling in vernal pools.

Maine’s first known brush with West Nile virus came in the fall of 2001 when seven dead birds tested positive for the virus.

According to the Bureau of Health’s avian surveillance update, out of 554 birds tested between March 30 and Sept. 26, 2002, 65 birds tested positive for the virus.

Thirty-seven were found in Cumberland County, 10 in Androscoggin County, seven in Penobscot County, six in York County, two in Waldo County, and one each in the counties of Hancock, Lincoln and Somerset.

For more information on landscaping and vernal pool protection, contact Maine Audubon at 781-2330 or To learn more about the West Nile virus in Maine, visit the Bureau of Health’s Web site at

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