Study on Resistance of Culex pipiens (Diptera: Culicidae) Populations to Fenitrothion in Northern Tunisia

Four populations of Culex pipiens were collected as larvae in Northern Tunisia to evaluate their resistance status against two insecticides: fenitrothion and propoxur.At LC50, the sample # 1 was susceptible, whereas all the other samples were resistant.The RR50 ranged from 1.08 in sample # 1 to 550 in sample # 3. The A2-B2, A4-B4 (and/or A5-B5), B12 and C1 esterases were found in collected samples and the frequencies ranged from 0.02 to 0.42.Propoxur caused a mortality of 0% in samples # 3 which showed the highest resistance levels to fenitrothion insecticide and 87% in sample # 1 which was susceptible hence the involvement of AChE 1 in the recorded resistance.Our results are essential for the development of such strategies of vector control.