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  • Special Report: The Drought of '99

  •   Asian Tiger Mosquito Spreads Trouble

    The Asian Tiger mosquito population has not been reduced by the drought. (New Orleans Mosquito and Termite Control)
    By Susan Saulny
    Washington Post Staff Writer
    Sunday, August 8, 1999; Page C1

    They are brazen biters, efficient disease carriers, and hunt by day, not just at night. Stealthy and resilient, they have thwarted most scientific efforts at control and eradication.

    They will try to eat you alive.

    But these mosquitoes are not your garden-variety bloodsuckers. This new pest plaguing parts of the Washington region is called the Asian Tiger, and it is wreaking havoc on bare skin from Baltimore to Virginia Beach.

    It is especially prevalent in inner-Beltway communities in Prince George’s County, where it has found one favorite habitat in abundance – old tires. But researchers caution they are sure that Asian Tigers are all over the metropolitan area.

    How bad a bug is it? It’s so tough that this summer’s drought, which has curbed other mosquito populations, has done nothing to tame it. Instead, “they’re spreading and worsening,” said Jeannine M. Dorothy, an entomologist in the Maryland Department of Agriculture’s Mosquito Control division. “There’s really no way we can control it.”

    And that’s a problem because the Asian Tiger poses a potential health threat. In laboratory settings, it has been found to be a successful disease bearer, or “vector,” able to transmit maladies affecting humans such as encephalitis, Dengue fever and yellow fever, as well as dog heartworm. Outside the laboratory, there have been no reported fatalities connected to the Asian Tiger.

    “We keep watching it. We monitor it,” said Duane J. Gubler, director of vector-borne infectious diseases at the Centers for Disease Control in Fort Collins, Colo. “So far, there is no evidence that it is involved in human disease transmission.”

    The Asian Tiger defies most mosquito stereotypes. It will breed in anything that holds water, even the tiniest amounts, such as flowerpots, tires, old soda cans and clogged rain gutters. It bites more often than standard-issue mosquitoes do. It has nothing against sunshine.

    Researchers in New Orleans tried for almost a decade to breed a cannibal mosquito to try to check the Asian Tiger population. They were not successful. Other experts around the country also are studying the mosquito’s habits and trying to find ways of controlling it.

    And to make matters worse, the Asian Tiger is out-competing the area’s native mosquito, which is a much less aggressive pest.

    “They’re tearing us up. And we just basically gonna keep getting ate alive,” said Quayshawn Briscoe, 20, a resident of Fairmount Heights, one area of inner-Beltway Prince George’s that has a dense population of Asian Tigers.

    So named because of white stripes on its legs and thorax, the Asian Tiger is believed to have arrived in Houston around 1985 via a shipment of tire castings from Japan. They quickly swept up the coast of the southeastern United States, transported mostly in scrap tires. Asian Tigers were found around a tire recycling plant in Baltimore in the late 1980s and showed up around the same time in Prince George’s.

    Scientists describe Asian Tigers as skittish, making them hard to kill by the traditional method of death by big slap.

    “There are some mosquitoes that will just sit on you, but the Asian Tiger is hard to kill because it’s very flighty,” said Stephen Sackett, field operation supervisor for the New Orleans Mosquito Control Board, which has been researching the insect for more than a decade. “The Asian Tiger will come in quick, bite and fly off.”

    Insect repellent creams and sprays for the body do work, Dorothy said, but there is little else anyone can do.

    “Mosquito control programs cannot adequately control this species because of its habits,” Dorothy said. “All we can do is inform the public. You’ll never get rid of them, but you can cut the numbers.”

    How? By getting rid of standing water, however little, anywhere.

    Dorothy and her small staff spend a lot of time posting in business windows signs that warn “The Tiger’s In Town!” The poster has a menacing-looking tiger head in the middle and gives tips about how to keep mosquitoes from breeding around the home: “Get rid of unnecessary containers.” “Change birdbath and wading pool water once a week.” “Keep ornamental pools stocked with minnows.” “Keep shrubs and grass well-trimmed.”

    While traditional mosquito-control efforts target swamps, ponds and large bodies of stagnant water and most likely include nighttime neighborhood spraying (because most mosquitoes come out at dusk), “There’s no way to go around treating every flowerpot, birdbath and kiddie pool for the Asian Tiger,” said Kim Largen, the gypsy moth and mosquito control branch chief in Prince William County.

    Largen said the mosquitoes were first noticed in Prince William in 1997.

    “Now, pretty much anywhere we look we’re finding them,” she said.

    Dorothy is investigating the unproven idea that copper might kill Asian Tiger larvae. She said cemetery workers in Louisiana noticed that bronze vases in which families leave flowers to honor the dead don’t incubate mosquitoes eggs the way ceramic and cement vases do.

    To test the hypothesis that copper leaching into the water kills the Asian Tigers, Dorothy has set up little experiments in Cheverly, Bladensburg and other small Prince George’s towns. Her control tires have stagnant water in them; others hold copper tubing, old pennies and water.

    “I hope it works,” she said. “If it does, we will be able to say, ‘You can control Asian Tigers and it only costs pennies a year.’. . . But for now when people call and ask me, ‘How do you get rid of them?‘ I have to say I wish I knew.”

    © 1999 The Washington Post Company

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