Insecticide susceptibility and feeding behavior in Anopheles arabiensis and Culex quinquefasciatus after ITN introduction Southern Zambia

The mosquito Anopheles arabiensis is the major vector of Plasmodium falciparum in Macha, Zambia. The arboviral and filarial vector Culex quinquefasciatus is also present in high numbers throughout the Macha region. A major portion of Zambia’s current malaria control program relies on long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) with insecticides. Insecticide resistance in mosquito populations has the potential to lessen and even eliminate the effectiveness of these control methods. In order to characterize the insecticide susceptibility of disease vector mosquitoes in Macha, CDC bottle bioassays and LLIN survival assays were used to test F1 offspring of field-collected adult An. arabiensis, as well as Cx. quinquefasciatus from eggs collected from oviposition traps. High levels of resistance to DDT, pyrethroids, malathion, and deltamethrin-treated net material were detected in Cx. quinquefasciatus, and low levels of resistance to DDT and deltamethrin-treated net material were detected in An. arabiensis. Molecular assays revealed that the knock-down resistance (kdr) allele was frequent in the Cx. quinquefasciatus population, with 13% homozygous for kdr and 47% heterozygous. However, there was no significant correlation between kdr genotype and survival in LLIN bioassays. Continued monitoring and assessment of these mosquito populations is necessary in order to determine levels of resistance and appropriately modify vector control operations.