Genetic variation in the sensitivity of Anopheles gambiae to DEET

While mosquitoes have rapidly evolved resistance to a variety of insecticides, increased resistance or insensitivity to the commonly used insect repellant N,N-Diethyl-meta-toluamide (DEET) has only rarely been observed.  However, widespread use of DEET and other repellants may impose strong selection for insensitivity in mosquitoes and other target insects.  Here we show that the African malaria mosquito Anopheles gambiae harbors highly heritable variation in its sensitivity to DEET.  Approximately 10% of the female mosquitoes in the N’Gousso laboratory colony were insensitive to DEET, and would take blood meals from mammalian hosts that had had DEET applied to the skin. From this starting laboratory population we were able to rapidly select more fully insensitive and sensitive lines.  Such a strong phenotypic response to artificial selection suggests that there is substantial natural genetic variation in the sensitivity of individual Anopheles gambiae to DEET.  Whole genome resequencing of the sensitive and insensitive lines should reveal the specific sites of genetic variance underlying the DEET-resistance phenotype.  Our work suggests that the effectiveness of large-scale repellant use is likely to be compromised by the rapid evolution of resistance in mosquito populations as well as other pestiferous insect populations.