Knockdown Resistance Mutations in the Voltage-Gated Sodium Channel of Aedes aegypti (Diptera: Culicidae) in Myanmar

Abstract

Simple Summary Knockdown resistance (kdr) mutations in the voltage-gated sodium channel (VGSC) of mosquitoes confer resistance to pyrethroid insecticides. Analysis of kdr mutations in Aedes aegypti mosquitoes collected from five different townships in the Mandalay area, Myanmar, revealed high levels of validated kdr mutations in domains II and III of vgsc. Moreover, high frequencies of concurrent kdr mutations were also detected. The results of this study suggest that kdr mutations associated with pyrethroid resistance are widespread in the Ae. aegypti population of the study area. Our results provide a valuable molecular basis to understand the pyrethroid resistance status of the Ae. aegypti population in the area and underscore the need for an effective vector control program in Myanmar. Aedes aegypti is an important mosquito vector transmitting diverse arboviral diseases in Myanmar. Pyrethroid insecticides have been widely used in Myanmar as the key mosquito control measure, but the efforts are constrained by increasing resistance. Knockdown resistance (kdr) mutations in the voltage-gated sodium channel (VGSC) are related to pyrethroid resistance in Ae. aegypti. We analyzed the patterns and distributions of the kdr mutations in Ae. aegypti in the Mandalay area of Myanmar. The segment 6 regions of domains II and III of vgsc were separately amplified from individual Ae. aegypti genomic DNA via polymerase chain reaction. The amplified gene fragments were sequenced. High proportions of three major kdr mutations, including S989P (54.8%), V1016G (73.6%), and F1534C (69.5%), were detected in the vgsc of Ae. aegypti from all studied areas. Other kdr mutations, T1520I and F1534L, were also found. These kdr mutations represent 11 distinct haplotypes of the vgsc population. The S989P/V1016G/F1534C was the most prevalent, followed by S989P/V1016V and V1016G/F1534C. A quadruple mutation, S989P/V1016G/T1520I/F1534C, was also identified. High frequencies of concurrent kdr mutations were observed in vgsc of Myanmar Ae. aegypti, suggesting a high level of pyrethroid resistance in the population. These findings underscore the need for an effective vector control program in Myanmar.