A half-century after its discovery, DEET is still the unquestioned king of mosquito repellants. But researchers have discovered that under the right circumstances the mosquitoes can fight back…
From this story on Wired.com:
More than half a century after DEET’s invention, scientists still don’t know how the popular mosquito repellent works. Now, using a combination of artificially accelerated evolution and painstaking anatomical observation, researchers have answered a fundamental question about DEET’s mechanisms – and in the process showed that mosquitoes may become resistant to it. “It’s a fundamental piece of research. It will give us a lot more knowledge, rather than just going out and spraying something,” said study co-author Linda Field, a molecular biologist at England’s Rothamsted Research institute.
Field and Nina Stanczyk, a University of Nottingham biochemist, started their study by resting a DEET-sprayed arm on a mesh cage, just out of reach of female Aedes aegypti mosquitoes. (Only female mosquitoes bite; like males, they typically feed on flower nectar, but require nutrients from blood in order to lay eggs). Those that tried to feed were removed and bred separately. Within a few generations, more than half were DEET-resistant. Field cautioned that laboratory results shouldn’t be automatically extrapolated to the natural world, but a similar dynamic could well exist, especially in heavily populated areas where humans are the predominant source of blood. “If a small percentage are insensitive, they have a much better chance of getting a blood meal, and are much more likely to pass on their genes. You’d likely see a buildup of the trait,” said Field.