Levels of Insecticide Resistance to Temephos, and Associated Mechanisms in <i>Culex pipiens</i> Mosquitoes from Central Tunisia

Abstract

Five populations of Culex pipiens collected in central Tunisia were evaluated for their susceptibility to temephos. The resistance level was high for samples # 5 (>50-fold), and low, not exceeding 4-fold in the other resistant samples. LC 50 showed the susceptibility of sample # 2. The CYP450 enzyme was found related to temephos resistance in three samples. In fact, the addition of Pb to temephos bioassays completely suppressed the resistance in samples # 1 (RR 50 =0.84, p>0.05, RSR=3.0) and 5 (RR 50 =1.5, p>0.05, RSR=37.1). The temephos resistance level of sample # 3 decreased slightly (RR=1.9, p<0.05, RSR=1.7). The biochemical assays detected elevated esterases in all studied samples with different frequencies to be involved the recorded resistance to temephos. However, synergists bioassays did not suggested any esterase activity. The insensitive AChE 1 could be responsible partly in the resistance to temephos insecticide (OP). In fact, Mortalities due to propoxur (< 25%) were recorded in two resistant samples and (>75%) were recorded in the most susceptible samples. There is an urgent need to replace the insecticide temephos for continued control of Culex pipiens in Tunisia.

Resistance development and insecticide susceptibility in Culex pipiens pipiens, an important vector of human diseases, against selection pressure of temephos and its relationship to cross-resistance towards organophosphates and pyrethroids insecticides

“…In the present study, both chemical and synergism tests did not revealed any over-produced esterases to be involved in the recorded resistance to OPs insecticides. These detoxification enzymes were involved in the resistance to chlorpyrifos and temephos insecticides in Tunisian Culex pipiens 14,21,22. This correlation was found also in other mosquito's species including Aedes aegypti 15.…”