Repellent Elicits Olfactory Fatigue

Decades of experience have established that DEET, or N,N-diethyl-m-toluamide, is highly effective at repelling mosquitoes and other insects. In turns out, however, that shortly after exposure to the substance, some mosquitoes are desensitized to DEET’s repelling effect, according to researchers in England (PLoS One, DOI: 10.1371/journal.pone.0054438). James G. Logan of London School of Hygiene & Tropical Medicine and colleagues evaluated electrophysiologic responses elicited by DEET exposure in Aedes aegypti mosquitoes, a variety known for biting during the day and transmitting dengue fever. The team observed that three hours after a brief exposure to DEET, the mosquitoes were not as deterred by the presence of DEET from approaching human skin, heat, and other attractants. The group determined that the reduced aversion to DEET is nongenetic in origin and correlates with a decrease in sensitivity of odor receptors on mosquitoes’ antennae. The findings, which have implications for effective use of the repellent, suggest that mosquitoes become desensitized to odors in a manner similar to the way humans acclimate to smells, but likely because of a very different mechanism, Logan says.