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First floods, now pesky mosquitoes for Midwest
2008-07-03
CHICAGO - First came the floods -- now the mosquitoes. An explosion of pesky insects are pestering clean-up crews and just about anyone venturing outside in the waterlogged Midwest. In some parts of Iowa there are 20 times the normal number, and in Chicago up to five times more than usual. The good news is these are mostly floodwater mosquitoes, not the kind that usually carry West Nile virus and other diseases. But they are very hungry, and sometimes attack in swarms with a stinging bite. Heavy rain followed by high temperatures creates ideal conditions for these bugs, whose eggs hatch in the soil after heavy rains. Scientists call them nuisance mosquitoes. You could call that an understatement. "About 3 p.m. the bugs come out pretty bad. They're all over the place," Bill Driscoll, a flood cleanup worker in Palo, Iowa, said this week. "We've been burning through the repellent with the volunteers." In Lisbon, Iowa, about 20 miles east of flood-ravaged Cedar Rapids, biker Larry Crystal said mosquitoes have made his rides miserable. "Every time I stop to rest at a rest area these buggers just find a way to bite me all over my neck area between my helmet and jacket," he wrote on a bikers' blog. "They seem to be very aggressive, they're even coming into my helmet, finding any bits of skin," Crystal told The Associated Press. "They're just going at it." Some mosquito surveillance traps in Iowa have up to 20 times more mosquitoes than in recent years, said Lyric Bartholomay, an Iowa State University insect expert. For example, last week, 3,674 mosquitoes were counted in Ames-area traps, compared with 182 for the same week last year, Bartholomay said Wednesday. Trap quantities are just a tiny snapshot of the true numbers of mosquitoes flying around. In Iowa, the main culprit is the Aedes trivittatus, a common nuisance mosquito with "a voracious appetite and they hurt when they feed on you," she said. A relative called Aedes vexans is doing much of the biting in Chicago's suburbs, hit by recent heavy rains, said Mike Szyska of the Northwest Mosquito Abatement District. Mosquito numbers in northwestern suburbs peaked last week at about five times higher than normal for this time of year, Szyska said. Complaints and requests for insecticide spraying have the district "working day and night. We're extremely busy," he said. Right now there's no evidence of higher than normal numbers of Culex mosquitoes, more commonly associated with West Nile virus. Several states have found evidence of West Nile, but only a few cases, which tend to start occurring later in July. But health authorities say that could change with drier weather, which Culex mosquitoes prefer, so they're advising people to take precautions. Culex mosquitoes breed in stagnant water and sludge in protected areas like ditches, storm drains or backyard bird baths and discarded tires, Szyska said. "One thing that we're warning people with the flooded homes, as they're gutting them and getting rid of debris, make sure you dispose of that kind of stuff correctly," said Howard Pue of Missouri's Department of Public Health. In the meantime, the explosion of floodwater mosquitoes has left many people feeling like mosquito magnets. And about 10 percent of the population actually qualifies, according to entomologist Jerry Butler, a professor emeritus at the University of Florida. These are the people who get covered in bites while their porch partners or biking buddies are left unscathed. Many of them get exaggerated skin reactions to the bugs -- hard red welts or hives that can itch for days. Children are more susceptible to these reactions, which can cause a lot of discomfort but generally are not dangerous, said Dr. Anju Peters, an allergy specialist at Chicago's Northwestern Memorial Hospital. Her 7-year-old daughter got several bites and broke out in hives last week inside the family's Chicago home when an outside door was left open for just a few minutes, Peters said. Some people have allergies to mosquitoes, developing limited but severe skin reactions that researchers call "skeeter syndrome." Some can develop potentially dangerous, widespread reactions including wheezing, and, rarely, life-threatening throat-swelling and breathing problems. Research is under way to develop skin tests and treatment for these allergies using mosquito saliva. Because tests are not widely available, allergic reactions to mosquitoes are underdiagnosed and undertreated, according to the University of Manitoba's Dr. Estelle Simons, a leading mosquito allergy expert. Whether true allergies or normal reactions to mosquito saliva, the bumps and itching can sometimes be eased, though not prevented. Using over-the-counter antihistamines such as Zyrtec and Claritin throughout mosquito season or after a bite can help, doctors say. Sweat and carbon dioxide given off by the skin and from breathing are among the best known mosquito magnets, said Butler, who has long studied which odors and substances attract mosquitoes. Mosquitoes often target larger people, who tend to give off more carbon dioxide, he said. And alcohol is another lure, "so people who have been drinking are going to be more attractive" to the bugs, he said. Alcohol in lotions and perfumes also attracts mosquitoes, as do some cosmetic fragrances including lavender, Butler said. Also, he said, there's evidence that people with very high cholesterol levels often are mosquito magnets. Butler said mosquitoes need fats like cholesterol but can't make them so get them by feeding on others. ___ On the Net: Iowa State: http://www.ipm.iastate.edu West Nile: http://www.cdc.gov/ncidod/dvbid/westnile/index.htm
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