Why Researchers Can't Control Mosquitoes

Continuing the practice of flooding saltwater marshes without wiping out the habitat for other species is one of the primary goals of the mosquito association, which operates under the auspices of the federal Environmental Protection Agency. The program has been somewhat successful, but as anyone who has visited Florida in the summer knows, millions of mosquitoes are doing just fine, thank you.

Death by Infection and Death Traps

Barnard's lab has made some progress in a couple of promising areas. For example, some viruses have been known to kill mosquitoes, but scientists have been frustrated in their efforts to come up with a way of transmitting the virus to the mosquitoes.

Researchers at the lab have, for the first time, figured out a way to do that. By blending certain chemicals with the virus, Barnard says, they have transmitted a virus that kills some mosquitoes, specifically the mosquitoes in the Culex genus that carry St. Louis encephalitis. That is the most common disease transmitted to humans by mosquitoes in the United States. Mild infections can cause headaches and fever, but severe cases can cause convulsions, paralysis, or even death.

Entomologist James J. Becnel of the Gainesville lab says that in a field test case, the treatment killed 60 percent to 70 percent of the mosquito larvae over a 48 to 72 hour period.

So far, the tests have indicated that the virus is not harmful to other organisms, including humans, but more testing is needed.

Another idea is to come up with a means of attracting mosquitoes to a designated area where they could be ambushed. That's just what Barnard and other researchers have been trying to do, and with some success.

Mosquitoes are guided to their targets by several factors, including sight, infrared radiation, and exhaled carbon dioxide. So the researchers have been zeroing in on specific "attractants" that could be used to lure mosquitoes into a trap. Old socks work quite well, provided they've been worn long enough. Limburger cheese is pretty good. But carbon dioxide is very effective.

That means a mosquito can smell your breath from a long ways away. So Barnard and his colleagues are developing a sniff-and-die trap. Carbon dioxide and other attractants are released near the trap, which works a little like a sophisticated vacuum cleaner. The bug sniffs the scent, zeros in, and gets captured by the wind from a small fan, forcing it into a bag.

You'll probably be able to buy one of these gizmos one of these days soon, but don't expect it to cure the mosquito problem. Even Barnard admits it might only work well in a back yard, or another urban setting, where the mosquito population is relatively low.

"It's not going to work very well where you've got a horrendous number of mosquitoes," he says.

It sure won't solve the problem for the Yukon, where horrendous is an understatement. And incidentally, our problem there was one of poor timing. A hot spell, following a rainy summer, was all the bugs needed to ruin ours.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska. He will not have a new column for the week beginning Aug. 20.

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