~ 31 ~ International Journal of Mosquito Research 2016; 3(6): 31-35 ISSN: 2348-5906 CODEN: IJMRK2 IJMR 2016; 3(6): 31-35 © 2016 IJMR Received: 06-09-2016 Accepted: 07-10-2016 Anju Viswan K Biopesticides & Toxicology Laboratory, Department of Zoology, University of Calicut, Malappuram District, Kerala, India Pushapalatha E Biopesticides & Toxicology Laboratory, Department of Zoology, University of Calicut, Malappuram District, Kerala, India Azhahianambi P Department of Veterinary Parasitology, Madras Veterinary College, Vepery, Chennai, Tamil Nadu, India Correspondence Anju Viswan K Biopesticides & Toxicology Laboratory, Department of Zoology, University of Calicut, Malappuram District, Kerala, India Application of synthetic insecticide and change in detoxifying enzyme levels in Culex quinquefasciatus Say Anju Viswan K, Pushapalatha E and Azhahianambi P Abstract The mosquito populations are increasing day by day in Chennai, one of the filarial endemic regions in Tamil Nadu, India due to the unplanned growth of cities, increased and improper usage of insecticides, development of resistance in target insects etc. Continuous and extensive uses of chemical insecticides lead to selection of resistant mosquitoes in the environment. The early detection of resistance in vector mosquitoes will help the local government to plan and select appropriate alternative control measures or insecticides for effective control. Quantitative metabolic enzymes assay have been commonly used in the detection of insecticide resistance because it is very sensitive and gives results rapidly even at low frequencies. Elevation in detoxifying enzyme levels indicates the status of insecticide resistance. The present study compares the detoxifying enzyme levels of Culex quinquefasciatus Say of Chennai with laboratory population. The results shows the samples collected from the Chennai corporation shows 1.85, 1.79, 1.71 and 1.48 fold increase in α and β esterases, GST and MFO levels respectively. The % remaining activity of AChE in Propoxur inhibited fraction was 89.84 in field population indicates the organophosphate and carbamate resistance. The study highlights rise of multiple insecticide resistance in Cx. quinquefasciatus of Chennai and the urgent need to rapidly implement resistance management strategies by improving vector control measures using alternative ecofriendly techniques. Keywords: Cx. quinquefasciatus, insecticide resistance, α and β esterases, glutathione-S-transferase, mixed function oxidases, acetylcholinesterase 1. Introduction The rapid urbanization in most of the developing countries has resulted in breeding of the culicine species, especially the filarial vector Culex quinquefasciatus Say (Diptera: Culicidae). Culex quinquefasciatus is one of the major domestic pests in urban areas and carry Wuchereria bancrofti, the lymphatic filarial worm and many arboviruses [1] . National Health Mission Tamil Nadu reported that In Tamil Nadu, 13 districts are said to be endemic to filariasis, and Chennai is one among them. As per the reports of Directorate of Public Health and Preventive Medicine Chennai, in 2005 the microfilarial rate was 0.38% and dropped to 0.07% in 2011 and rose again to 0.11% in the year 2015. Last few years a multi fold increase in mosquito numbers reported in Chennai corporation area. In Chennai, pyrethrum and malathion is used during the fogging operations and temephos for spraying as larvicide. The use of synthetic insecticides to control insect vectors has led to selection of resistant insect population and hence the control measures fails to work properly. The major metabolic enzymes involved in resistance in mosquitoes include Cytochrome P450 mediated monooxygenase, non-specific esterases, acetylcholinesterases [2] and glutathion-s-transferase [3] . Quantitative metabolic enzymes assay have been commonly used in the detection of insecticide resistance because it is very simple, sensitive and gives results rapidly even at low frequencies [4,5] .The elevated levels of esterases contribute the resistance of mosquitoes towards organophosphates, carbamates and pyrethroids [6] . Glutathione –S- transferase involved in the resistance towards organophosphates, organochlorines and pyrethroids [7-9] . The increased levels of mixed function oxidases are responsible for the resistance in mosquitoes to organophosphates, organochlorines, carabamates and pyrethroids; the widely using four major classes of insecticides [10] . The insensitive acetylcholinesterase plays a major role in organophosphate and carbamate resistance [11, 12] . The present study is to investigate the potential resistance mechanisms involving carboxylesterases, mixed function oxidases, glutathione-S-transferase and insensitive