Comparison of Susceptibility Status of laboratory and field populations of Aedes aegypti against Temephos in Rawalpindi

Abstract

In Pakistan, application of the larvicide temephos to the aquatic breeding sites of Aedes aegypti is a key part of the dengue control strategy. Throughout Pakistan no data is available on the susceptibility status of Ae. aegypti to temephos. The aim of the study was to examine the susceptibility status of Ae. aegypti against temephos and compare and estimate the resistance ratios of both laboratory and field populations on the basis of median lethal concentration LC50 and LC95. Larval bioassays were carried out according to WHO method on the field population of Ae. aegypti from three different localities (Rawal Town, Pothohar Town and Cantonment) of Rawalpindi. The laboratory reared susceptible strain of Ae. aegypti provided by the insectarium of Medical Entomology and Disease Vector Control (MEDVC) department was used as reference for comparison. The LC50 values of all field populations of Ae. aegypti were recorded as 0.024 mg/L for Rawal Town, 0.019 mg/L for Pothohar Town and 0.025 mg/L for Cantonement showing resistance ratios RR50 of 6.32, 5 and 6.58 respectively. Similarly LC95 values were recorded as 0.26 mg/L for Rawal Town, 0.23 mg/L for Pothohar Town and 0.25 mg/L for Cantonement showing resistance ratios RR95 of 9.29, 8.21 and 8.93 respectively. Our results indicated that all the field populations of Ae. aegypti were resistant to temephos, compromising its field effectiveness. This comparative data of resistance ratios RR50 and RR95 on the temephos susceptibility of Ae. aegypti could help public health services to design more effective vector control measures.