Backyard Bloodstream

Baltimore Sun

From back yard to bloodstream: The summer bug battle is rejoined

Research hasn't cut risks posed by ticks, mosquitoes

June 13, 2005|By Dennis O'Brien | Dennis O'Brien,SUN STAFF

You don't have to read the headlines to know that they're nasty creatures. And the news is still bad for those who venture outdoors this summer: We're a long way from wiping out the 60 species of mosquito that cause West Nile virus and the deer tick that carries Lyme disease.

And despite research involving garlic, catnip, eucalyptus and volunteers willing to stand in tubs full of ticks, there is no infallible system for keeping the bugs out of your back yard -- and your bloodstream.

"There's a tremendous push being made to see if we can find something. But there's not many chemicals out there as candidates," said Jerome A. Klun, an entomologist with the U.S. Department of Agriculture's research lab in Beltsville.

Beltsville researchers have been awarded $4 million in Defense Department grants to come up with repellents to protect troops from ticks and mosquitoes that transmit malaria, dengue and yellow fever overseas.

To that end, Klun and colleague John Carroll will create their own version of Fear Factor this fall when they and other volunteers douse their ankles in three kinds of repellent and step into plastic tubs filled with 100 lab-raised ticks each -- to see how many ticks ignore the repellent and crawl up their legs.

The experiment will run for six days as the researchers compare SS-220, a repellent developed by Klun and other Beltsville researchers not yet on the market, with Picaridin, a commercially available repellent, and a solution containing the popular insect repellent chemical known as DEET.

Carroll, 59, said there's no danger that the ticks are carrying Lyme disease. Not only are they lab-raised, they're also lone star ticks, a different variety from the deer ticks that transmit the disease.

Nor does the tub of ticks give him the creeps. "When I'm out in the field, it's more risky than if I'm standing in a tub and I can see what's going on," he said.

For Carroll and other bug fighters, part of the problem in finding a perfect repellent is the complexity of the bugs.

The pests have 30 million years of evolution on their side, and they've developed sensors that zero in on the carbon dioxide and other chemicals we emit. Once they sense us, they use different approaches to get into our bloodstreams.

The female mosquito -- the one that bites -- approaches like a Stealth fighter, and once it lands, a probe-like cutting apparatus in her head finds our blood, which provides protein to nourish her eggs.