Detection of pyrethroid resistance mutations and intron variants in the voltage-gated sodium channel of Aedes (Stegomyia) aegypti and Ae. (Stegomyia) albopictus mosquitoes from Lao People's Democratic Republic

In Lao People's Democratic Republic (PDR), Aedes aegypti (Linnaeus 1762) and Ae. albopictus (Skuse 1894) mosquitoes (Diptera: Culicidae) are vectors of arboviral diseases such as dengue. As the treatment for these diseases are limited, control of the vectors with the use of pyrethroid insecticides is still essential. However, mutations in the voltage-gated sodium channel gene (vgsc) giving rise to pyrethroid resistance is threatening vector control programs. Here, we analyzed both Ae. aegypti and Ae. albopictus mosquitoes collected in different districts of Laos (Kaysone Phomvihane, Vangvieng, Saysettha and Xaythany) for vgsc mutations commonly found throughout Asia (S989P, V1016G and F1534C). Sequences of the vgsc gene showed that the F1534C mutation was prevalent in both Aedes species. S989P and V1016G mutations were detected in Ae. aegypti from each site and were always found together. In addition, the mutation T1520I was seen in Ae. albopictus mosquitoes from Saysettha district as well as in all Ae. aegypti samples. Thus, mutations in the vgsc gene of Ae. aegypti are prevalent in the four districts studied indicating growing insecticide resistance throughout Laos. Constant monitoring programmes and alternative strategies for controlling Aedes should be utilized in order to prolong the effectiveness of pyrethroids thereby maximizing vector control