Detection of Permethrin resistance in Aedes aegypti, Aedes albopictus and Culex quinquefasciatus collected from Kuala Lumpur, Malaysia

Abstract

To date, currently information on the status of pyrethroid resistance especially the permethrin resistance amongst mosquitoes of medical importance in Malaysia is limited. Hence, this study was carried out to elucidate the permethrin resistance level as well as the resistance mechanism(s) involved in Aedes aegypti (Linnaeus), Aedes albopictus Skuse and Culex quinquefasciatus Say. Three standard laboratory methods were applied: the WHO larval bioassay; the WHO adult bioassay; and the mixed function oxidases (MFOs) enzyme microassay. Three successive generations of the laboratory susceptible strains and the permethrin-selected strains of both mosquito species were tested. Another study was then conducted in order to verify the permethrin resistance mechanism(s) involved in local vectors of Kuala Lumpur where only the first generations of these colonies were utilized. The results obtained from both protocols were supportive in confirming the development of low permethrin resistance amongst almost all strains of Ae. aegypti, Ae.albopictus and Cx. quinquefasciatus employed in this study. The presence of oxidases and their roles in the permethrin resistance mechanism in these mosquito populations were also demonstrated using the synergist; piperonyl butoxide (PBO) and the MFOs enzyme microassay. In other words, the involvement of knockdown resistance (kdr) alleles was not yet detected in these mosquitoes. Furthermore, the possibility for the involvement of other resistance mechanisms claimed to be associated with pyrethoid resistance such as the non-pecific esterases and glutathione-S-transferases (GSTs) had been proposed. Additionally, a positive correlation between the level of permethrin resistance and the oxidases activity had also been established.