July 2, 2008

Mosquitoes Ravage Waterlogged Midwest

Due to the recent flooding in parts of the Midwest, explosions of pesky mosquitoes are pestering clean-up crews and just about anyone venturing outside. Areas of Iowa have reported 20 times the normal number, and in Chicago up to five times more than usual.

Fortunately, they're not the kind of mosquitoes that 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.

"They're all over the place," said Bill Driscoll, a flood cleanup worker in Palo, Iowa, said this week. "We've been burning through the repellent with the volunteers."

About 20 miles east of flood-ravaged Cedar Rapids, Larry Crystal said mosquitoes have made his motorcycle rides miserable.

"They seem to be very aggressive, they're even coming into my helmet, finding any bits of skin," said Crystal.

Lyric Bartholomay, an Iowa State University insect expert, said some mosquito surveillance traps in Iowa have up to 20 times more mosquitoes than in recent years

"Last week, 3,674 mosquitoes were counted in Ames-area traps, compared with 182 for the same week last year," said Bartholomay.

Trap quantities are just a tiny snapshot of the true numbers of mosquitoes flying around.

Bartholomay said 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.

"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.

He said mosquito numbers in northwestern suburbs peaked last week at about five times higher than normal for this time of year.

Several states have found evidence of West Nile, but no evidence of higher than normal numbers of Culex mosquitoes"”more commonly associated with West Nile virus.

However, drier weather is what Culex mosquitoes prefer, so health authorities are advising people to take precautions.

Szyska said Culex mosquitoes breed in stagnant water and sludge in protected areas like ditches, storm drains or backyard birdbaths and discarded tires.

"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.

About 10 percent of the population qualifies as so-called "Mosquito Magnets", 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.

Some people have allergies to mosquitoes, developing limited but severe skin reactions that researchers call "skeeter syndrome" that can result in potentially dangerous, widespread reactions including wheezing, and, rarely, life-threatening throat-swelling and breathing problems.

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.

He said mosquitoes often target larger people, who tend to give off more carbon dioxide.

Alcohol is another lure, "so people who have been drinking are going to be more attractive" to the bugs, he said.

Butler noted that alcohol in lotions and perfumes also attracts mosquitoes, as do some cosmetic fragrances including lavender.

"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 they get them by feeding on others.