Operation STING

You don8217;t have to read the headlines to know that they8217;re nasty creatures. And the news is still bad for people who venture outdoors this summer: We8217;re a long way from wiping out the 60 species of mosquito that cause the West Nile virus, and the deer tick that carries Lyme disease. 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 backyard 8212; and your bloodstream.

8216;8216;There8217;s a tremendous push being made to see if we can find something. But there8217;s not many chemicals out there as candidates,8217;8217; said Jerome A. Klun, an entomologist with the US Department of Agriculture8217;s research lab in 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 8216;Fear Factor8217; 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. They want to know how many ticks ignore the repellent and crawl up their legs. The experiment will run for six days as the researchers compare SS-220, an experimental repellent developed by Klun and other Beltsville researchers, with Picaridin, a commercially available repellent, and a solution containing the popular insect repellent chemical known as DEET.

Not only are they lab-raised, they8217;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. The challenge is the complexity of the bugs. The pests have 30 million years of evolution on their side, and they8217;ve developed unique sensors that zero in on the carbon dioxide and other chemicals we emit.

Despite years of effort, scientists still aren8217;t sure what constituents of our sweat and breath attract the insects, and what best repel them. Preliminary evidence confirms what many researchers suspect 8212; that some people are attractive to mosquitoes while others nearby remain un-nibbled. Ethane, ethanol, acetone and isoprene 8212; chemicals found in varying amounts in sweat and exhaled breath 8212; might attract mosquitoes, studies show. Some researchers are convinced that chemical changes in our sweat, often caused by our diets, play a key role.

LAT-WP