First came floods, now mosquitoes for Midwest

CHICAGO -- First came the floods -- now the mosquitoes. An explosion of pesky insects are pestering cleanup 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.

Mosquito populations won't be officially counted in Missouri until next week, according to Karen Yates, vector-borne disease program coordinator for the Missouri Department of Health and Senior Services, and Christina L. Frazier, professor of biology at Southeast Missouri State University infectious epidemiologist. They said, based on St. Louis County's self-funded counting program, the Show Me State can expect a mosquito boom.

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."

A species 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.

More vexans can be expected in Missouri, too.

"They're not called vexans for nothing. They are active biters. They will come after you ... they got their name because they are very vexing," Frazier said.

Right now there's no evidence of higher than normal numbers of Culex mosquitoes, more commonly associated with West Nile virus. Several states, including Missouri, 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.

Southeast Missourian staff writer Peg McNichol contributed to this report.