UNIVERSITY PARK, Pa. -- It Is No Secret That West Nile Virus -- Which Causes A Potentially Fatal Form Of Encephalitis -- Is An Invasive Species That Found Its Way To North America From Africa. But Most People Don't Realize, According To Entomologists In Penn State's College Of Agricultural Sciences, That Some Of The Mosquitoes That Spread The Disease Also Are Unwanted Invaders From Another Continent.

West Nile virus, which first was found in the United States in 1999 in New York, is carried by birds and spread by mosquitoes. It now has been seen in nearly every county in Pennsylvania, according to entomologist Steve Jacobs, who notes that scientists have been surprised at how rapidly it has disbursed here.

"It is unusual that West Nile has spread so far inland," he says. "It's a problem in Eastern Europe too, where it has been for a very long time, repeatedly introduced by migratory birds coming from Africa. I would never have guessed that it would have gone as far as it has here.

"There is very little we can do to stop something like this," Jacobs adds. "All we can do -- once the virus is spread throughout the state or the country -- is to educate the public to wear insect repellents and recognize the disease so they can seek treatment. But in terms of general health risks to the public, West Nile is well down the list. I think many people believe the risks of dying from West Nile are much higher than they are."

One of the people immersed in the educational effort to cope with West Nile virus in Pennsylvania is entomologist Louise Bugbee. A Penn State Cooperative Extension agent, she coordinates state-funded mosquito-control efforts for Lehigh County, educates municipal workers and the public about West Nile virus, and does mosquito surveillance and research.

"I help people understand how to eliminate mosquito-breeding areas," she says. "That's important because the 2002 West Nile virus outbreak in North America was the largest encephalitic disease arboviral epidemic ever documented in the Western Hemisphere, and it was the largest West Nile virus outbreak ever documented, according to the U.S. Centers for Disease Control."

Ironically, the West Nile virus situation has been exacerbated by other invasive species. "There are a lot of mosquito-borne diseases out there, but not every mosquito can be a vector for every disease," says Bugbee. "There are two species of mosquitoes not indigenous to Pennsylvania that we are concerned about as vectors for West Nile. They came into the southern part of this country we think in old tires to be retread from Southeast Asia. They have thrived in our climate.

"We know that Ochlerotatus japonicus can survive the winters in Pennsylvania -- we are finding lots of them," she adds. "Another mosquito brought into this country in the last 20 years that we are concerned about in the West Nile cycle is Aedes albopictus. So far they have not been seen too much in Pennsylvania, but they are in New Jersey and eventually they will expand into this state, too. The native Culex species of mosquitoes also can be a vector for West Nile."

Jacobs points out that with modern commerce -- the whole world is less than 24 hours away -- a host of diseases and pests arrive in the United States every day, especially with the importation of exotic plants. The division of the U.S. Department of Agriculture responsible for animal and plant inspection has its hands full, he points out.

"There is a tremendous amount of stuff coming in from many ports and federal inspectors use beagles and other dogs to look for pathogens," Jacobs says. "But you can't have a dog that is trained to look for everything. Dogs find insects, drugs, explosives and certain kinds of plants. Each exotic plant and animal produces its own chemical signature."

West Nile virus certainly is not the first exotic disease to arrive. According to Jacobs, bubonic plague was brought to California from China around the turn of the century, and yellow fever and malaria were not far behind.

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EDITORS: Contact Louise Bugbee by phone at (610) 391-9840 or by e-mail at lmb19@psu.edu.

Writer/Editor: Jeff Mulhollem Office: 814-863-2719