First report of field evolved resistance to agrochemicals in dengue mosquito, Aedes albopictus (Diptera: Culicidae), from Pakistan

Abstract

BackgroundAgrochemicals have been widely used in Pakistan for several years. This exposes mosquito populations, particularly those present around agricultural settings, to an intense selection pressure for insecticide resistance. The aim of the present study was to investigate the toxicity of representative agrochemicals against various populations of Aedes albopictus (Skuse) collected from three different regions from 2008-2010.ResultsFor organophosphates and pyrethroids, the resistance ratios compared with susceptible Lab-PK were in the range of 157-266 fold for chlorpyrifos, 24-52 fold for profenofos, 41-71 fold for triazofos, and 15-26 fold for cypermethrin, 15-53 fold for deltamethrin and 21-58 fold for lambdacyhalothrin. The resistance ratios for carbamates and new insecticides were in the range of 13-22 fold for methomyl, 24-30 fold for thiodicarb, and 41-101 fold for indoxacarb, 14-27 fold for emamectin benzoate and 23-50 fold for spinosad. Pair wise comparisons of the log LC50s of insecticides revealed correlation among several insecticides, suggesting a possible cross resistance mechanism. Moreover, resistance remained stable across 3 years, suggesting field selection for general fitness had also taken place for various populations of Ae. albopictus.ConclusionModerate to high level of resistance to agrochemicals in Pakistani field populations of Ae. albopictus is reported here first time. The geographic extent of resistance is unknown but, if widespread, may lead to problems in future vector control.

Insecticide resistance and its underlying mechanisms in field populations of Aedes aegypti adults (Diptera: Culicidae) in Singapore

“…RR 50 was scaled as follows: RR 50 < 1 (susceptible), RR 50 = 1 to 10 (low resistance), RR 50 = 11 to 30 (moderate resistance), RR 50 = 31 to 100 (high resistance), and RR 50 > 100 very high resistance [24].…”

Isolation and efficacy of entomopathogenic fungus (Metarhizium anisopliae) for the control of Aedes albopictus Skuse larvae: suspected dengue vector in Pakistan

“…albopictus larvae as immature stage of the vectors which is the most perfect stage for the bio-control agents [21,22] , it is also reported to be resistant to all groups of chemicals which are extensively used in the Agriculture Sector of Pakistan [23] .…”

Monitoring the diversity of malaria and dengue vector in Karachi: studying variation of genera and subgenera of mosquitoes under different ecological conditions

“…subpictus as the actual carriers of malaria in urban and rural areas of Karachi. Aedes aegypti is the only carrier of dengue fever in Karachi, while Aedes albopictus has been reported as a carrier of dengue fever in many parts of the Punjab province (Khan et al 2011). …”