Pirimiphos-methyl Resistance in Culex pipiens (Diptera: Culicidae) in Southern Tunisia

Pirimiphos-methyl is an organophosphorus insecticide having a fast action with less toxicity for humans and environment. The aim of this study was to investigate the pirimiphos-methyl resistance of three populations of Culex pipiens in southern Tunisia. Three Culex pipiens samples were collected in 3 localities (South east, south west, and extreme south) of southern Tunisia between March 2002 and October 2005. The susceptibility of the third population (extreme south) of Culex pipiens to pirimiphos-methyl was not considered due to control-level mortality. Both other studied samples were resistant to pirimiphos methyl and to propoxur. A significantly correlation was observed between the mortality due to propoxur and the LC₅₀ of pirimiphos methyl (P<0.01) showed an insensitive acetylcholinesterase (AChE). The characterization of Esterase phenotypes confirmed the previous studies which showed the major implication of esterases in the resistance to organophosphorus insecticides. Our results can improve current control and mosquito surveillance strategies.