A case study on resistance status of Aedes species in Assam, India and strategy for reducing insecticide use

Aedes mosquitoes are vectors of several arboviruses causing Dengue haemorrhagic fever, Dengue shock syndrome , Chikungunya, Zika and Yellow fever. Dengue is one of the important Aedes borne disease in south east Asia and also endemic to certain pockets of North east India including Assam. Because of unavailability of effective vaccine, insecticides are mostly used to control the vectors for reduction of dengue incidences. The latter has resulted in development of resistance to insecticides in the dengue vectors, the degree of which varies in different regions. Hence, to determine the resistance status of dengue vector, Aedes spp. against four recommended insecticides and understand the relevant resistance mechanisms involved , susceptibility/resistance study was carried out using the standard WHO protocols in selected habitats of upper Assam located in the north eastern corner of India. Resistance mechanisms using three major detoxification enzymes were determined.The pyrethroids, Temephos, deltamethrin and permethrin showed to have caused greater resistance as compared to malathion. Resistance to permethrin was uniformly detected in mosquitoes from all areas. The resistant ratio ranged from 1.65 to 1.08 for both malathion and deltamerthrin, and from 3.15 to 1.08 for permethrin . Enhanced activity of major detoxification enzyme was observed in the resistant strains . The whole study provides important evidence to support the need for alternate strategy to control dengue in Assam. Prospective strategies for reducing insecticide use in Aedes vector prone areas will be discussed.