Fire up the citronella-scented tiki torches, and slather on the DEET: Everybody knows these simple precautions repel insects, notably mosquitoes, whose bites not only itch and irritate, but also transmit diseases such as West Nile virus, malaria. and dengue.
Now, Johns Hopkins scientists have discovered what it is in the bugs’ molecular makeup that enables citronellal (the aromatic liquid used in lotions, sprays and candles) and DEET, to deter insects from landing and feeding on you. A better understanding of these molecular-behavioral links already is aiding the team’s search for more effective repellants.
In separate studies published, in Neuron and Current Biology, the Johns Hopkins researchers reveal how mosquitoes and other insects taste DEET—a man-made compound that’s been the most widely used insect repellent for more than 50 years—and smell citronellal, a commonly used botanical repellant.
Three taste receptors on the insects’ tongue and elsewhere are needed to detect DEET. Citronellal detection is enabled by pore-like proteins known as TRP (pronounced “trip”) channels. When these molecular receptors are activated by exposure to DEET or citronellal, they send chemical messages to the insect brain, resulting in “an aversion response,” the researchers report.
“DEET has low potency and is not as long-lasting as desired, so finding the molecules in insects that detect repellents opens the door to identifying more effective repellents for combating insect-borne disease,” said Craig Montell, Ph.D., a professor of biological chemistry and member of Johns Hopkins’ Center for Sensory Biology.