[Evidence of very high resistance to chlorpyrifos and permethrin in Culex pipiens populations in Tunisia].

Resistance to two organophosphorous insecticides (temephos and chlorpyrifos) and one pyrethrinoid (permethrin) was studied in larvae of five Culex pipiens samples collected in Gafsa, Telalsa, Sayada, Monastir et Sfax. Large variations in the tolerance to these insecticides was observed between samples. Gafsa sample was the most susceptible and disclosed little difference when compared to the susceptible reference strain. In contrast, at LD95 the resistance ratio (RR) was 8 folds with temephos, 9000 folds with chlorpyrifos, and 1500 folds with permethrin in the Sfax sample. These results are discussed in relation to resistance mechanisms and mosquito control.