Point mutation in the transcript of these domains results in insecticidal resistance which generally termed kdr (knock down resistance) mutation. It is a transmembrane protein, present in neuronal axons, containing four homologous domains (I–IV), each with six transmembrane segments (S1–S6) with a circular radial arrangement in which a central ion pore is formed 12.
Largely used DDT and synthetic pyrethroids targets Voltage Gated Sodium Channel ( vgsc) gene in mosquito vectors, altering its gating properties and finally producing a knockdown effect 10, 11. One of the major ways of gaining such resistance is the target site insensitivity in which the targeted site for insecticide is altered through point mutations. As the uses of chemical insecticides increased sharply, development of resistance against these insecticides occurs simultaneously. Mosquitoes have acquired insecticide resistance as a result of the indiscriminate application of insecticides directly targeted at them, as well as indirect exposure to insecticides sprayed on agricultural fields 9. In India, DDT, malathion, deltamethrin, lambda-cyhalothrin, cyfluthrin, alpha-cypermethrin, bifenthrin, and cyphenothrin are used under the National Center for Vector Borne Diseases Control (NCVBDC) for control of malaria and other vector borne diseases 8. Chemical insecticides particularly synthetic pyrethroids are the prime armament in vector population reduction as it has less toxicity to mammals and less persistent in environment 7. Due to the emergence and spread of new Dengue serotypes and the lack of protective vaccines, vector control is the sole way for global management of mosquito borne diseases 6. The temperature and relative humidity in the northern part of West Bengal are ideal for the growth and reproduction of Aedes mosquitoes, which has led to a number of dengue epidemics in recent years 5. West Bengal is a Dengue endemic state of India and all four Dengue virus serotypes has been identified from this region 4. albopictus has been linked to Zika virus infections in the large extent of India 3. and thus it emerged as a potential threat to global public health as well as global economy, particularly in tropical and subtropical countries like India 1, 2. The Asian tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae), is an epidemiologically important vector for the transmission of a variety of viral infections such as Dengue fever, Chikungunya, Yellow fever, Zika etc. The findings of the current study will help to uncover the mechanisms underlying insecticide resistance and hence to reduce errors in vector control measurements. Studied populations were found 81% homozygote susceptible (1534F/F), 12.5% heterozygote (1534F/C) and 6% homozygote resistant (1534C/C) for F1534C kdr mutation. A total of 200 successful amplification followed by partial sequencing of vgsc gene further revealed the presence of F1534C kdr mutation in both phenotypically susceptible and resistant mosquito specimen.
albopictus from the studied region were found resistant against DDT and synthetic pyrethroids, among them only one population possessed F1534C kdr mutation. albopictus from northern part of West Bengal, India including a novel T1520I mutation. Here, we describe the occurrence of F1534C kdr mutation in wild population of Ae. In Aedes albopictus, at least four such kdr (knock down resistance) mutations had already been documented.
Mutations in the Voltage Gated Sodium Channel gene ( vgsc) serve as the primary machinery behind this resistance development. Development of insecticide resistance in Aedes mosquitoes however, poses severe threat to insecticide-based vector management programme. Control of Dengue vectors largely depends upon synthetic pyrethroids. Dengue is the most rapidly spreading vector-borne disease with an estimated 100–400 million cases each year.
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