Evaluation of Temephos Resistance and Identification of Both Metabolic and Target-Site Resistance Mechanisms Involved in Three Field Populations of Culex pipiens pipiens (Diptera: Culicidae) from Tunisia

Abstract

Culex pipiens pipiens is an important vector responsible for West Nile virus outbreaks that have recently affected many areas of Tunisia, and the use of vector control insecticides is the most powerful and widely applied system for the control of the disease. Our purpose was to measure the impact of mosquito control on temephos resistance status of Culex pipiens pipiens. An evaluation of resistance to temephos in three field-collected populations of Culex pipiens pipiens between 2003 and 2005 was conducted in northern and southern Tunisia. The three collected populations showed low resistance ratio for temephos insecticide in all studied samples which ranged from 1.52-fold in sample #1 to 0.50-fold at the LC50 level in sample #2. The use of two synergists showed that the increased detoxification by the Cytochrome P450 (CYP450) was involved in the temephos resistance in sample #1. Biochemical assay demonstrated that detoxification esterases were involved in the recorded resistance although they were not detected using synergist bioassays. Altered AChE gene was detected in all field populations. The low resistance observed in Tunisian populations of Culex pipiens pipiens is particularly interesting because it leaves a range of tools useable by vector control services.