Relationship between Wolbachia infection in Culex quinquefasciatus and its resistance to insecticide

Many studies have been done on the various factors affecting resistance to insecticides. The relationship between Wolbachia bacteria and resistance to insecticides is one of the factors that has attracted a lot of attentions. Wolbachia are obligatory intracellular endosymbionts that naturally occur in a wide range of arthropods and nematodes, including the mosquito Culex quinquefasciatus. Initially, the presence of bacteria was proved by molecular assays. Then the resistance level of this species was evaluated in adults against DDT 4.0% and deltamethrin 0.05% using the standard WHO guideline. After elimination of Wolbachia by tetracycline and its proof by molecular assays, the susceptibility tests were conducted again on uninfected line. Finally, the two lines were compared in terms of responding to insecticides. The findings indicated that there is no significant correlation between susceptibility of two lines in response to DDT 4.0% while they represented a significant correlation for deltamethrin (P =0.00). We propose that Wolbachia bacteria increase the susceptibility to deltamethrin but they show neutral effect on DDT susceptibility in Cx. quinquefasciatus. However, more studies on other vectors and insecticides still need to be done.