Tuesday, March 24, 2009

The Not So Sweet Smell of DEET

photo by rob lee

Those darn mosquitoes! If you’ve ever gone camping or hiking, you have most likely used N,N-Diethyl-meta-toluamide, commonly known as the insect repellent DEET. So how does DEET manage to keep pesky bugs away? In the case of mosquitoes, it appears that they smell DEET directly. The hair-like sensory organs found on the antennae and maxillary palps of mosquitoes house olfactory receptor neurons (ORN) which sense smell. With increasing concentrations of DEET, increased neuronal excitation occurs within the ORNs, indicating that the act of smelling is causing a reaction and the response is dose-dependent.

Mosquitoes not only smell DEET directly, they also avoid it. When Petri dishes were set containing either solvent or DEET-treated filter paper, mosquitoes landed in the solvent-only area significantly more. Likewise, when mosquitoes were given the option to fly towards sugar-treated cotton only after passing through an area where DEET vapors were being released, they avoided landing or departed shortly after landing. This further indicates that an interaction between mosquitoes with actual odorants is not necessary for DEET-induced repellency-- the mosquitoes are able to smell DEET and avoid it.

Reference: Syed Z and Leal WS. (2008) Mosquitoes smell and avoid the insect repellent DEET. PNAS. 105(36):13195-6.

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