The discovery of a novel knockdown resistance (kdr) mutation A1007G in the Voltage-Gated Sodium Channel (vgsc) on Aedes aegypti (Diptera: Culicidae) from Malaysia



Background: The usage of insecticide rendered the successful vector control program with the high usage of the pyrethroid. However, the intensive and extensive use of pyrethroid, causing resistance in Aedes aegypti and hampered the control program. Knockdown resistance (kdr) resulting from the Voltage-Gated Sodium Channel (vgsc) is one of the mechanisms of resistance in pyrethroid group insecticide. Investigating the phenotypic status of Ae. aegypti mosquitoes is a lead in knowing the current resistance status and as an indicator of the genotypic resistance. In this study, we investigate the resistance in phenotypic and genotypic of Ae. aegypti with a new kdr mutation point, A1007G was detected.

Methods: Using the adult bioassay, we tested the phenotypic resistance from the Selangor state against 0.75% permethrin, 0.05% deltamethrin with and without the addition of PBO synergist. Permethrin-resistant and deltamethrin-resistant, including susceptible samples, were subjected to genotyping analysis on mutation point in domain II and domain III of Voltage-Gated Sodium Channel (vgsc).

Results: Adult bioassay revealed that the Ae. aegypti was highly resistance toward 0.75% permethrin and 0.05% deltamethrin. The bioassay with the presence of PBO synergist showed an increment of mortality rate, but the status of Ae. aegypti is still resistance towards both insecticides. Genotyping result showed that three common kdr mutations (S989P, V1016G, and F1534C) have existed in the Ae. aegypti population. Luckily, a new mutation on A1007G was also detected in this population, and this is the first time reported.

Conclusions: This study has brought a piece of information on the current resistance status in Ae. aegypti in Malaysia. The detection of new mutation point of A1007G has added the knowledge on the resistance in mosquitoes. Thus, this study will aid the decision in using the insecticide usage in vector control program before this invaluable insecticide rendered ineffective in killing mosquitoes.

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