Status of Resistant and Knockdown of West Nile Vector, Culex pipiens Complex to Different Pesticides in Iran

Background: West Nile virus (WNV) can cause a fatal disease in humans and it is mainly transmitted to people through the bites of infected mosquitoes. Vector control using insecticides is a very important goal. Study of Culex pipiens re-sistance towards several insecticides in the city of Tehran, Iran was evaluated. Methods: Adult females reared from field-caught larvae from southern part of Tehran and lab strain reared in the insec-tary of Tehran University of Medical Science were determined for resistant status by exposing to 4% DDT, 0.1% bendi-ocarb, 0.1% propoxur, 1% fenitrothion, 0.05% deltamethrin, 0.75% permethrin, 0.05% lambda-cyhalothrin, 0.5% etofenprox, 5% malathion and 0.15% cyfluthrin papers using the standard WHO susceptibility tests. Results: Results clearly showed resistance development of Cx. pipiens against tested insecticides. Mortalities of Cx. pipiens were less than 90% with high resistance, low knock down rate and knock down time (50%) observed against insecticides. DDT and Malathion showed the most and least lethal time (LT50) values for the field strain. The results of the knock-down test showed that DDT and deltamethrin had the most and least knockdown times (50%) for the field strain, respec-tively, while DDT and lambda-cyhalothrin had the most and least knockdown times (50%) for the lab strain, respectively. Conclusion: Resistance to mentioned insecticides in Cx. pipiens is widely distributed in southern part of Tehran. Regular implementation of susceptibility test in Cx. pipiens mosquitoes will help local public health authorities to develop new and better control strategies.