Investigating the relationship between insecticide resistance, underlying molecular mechanisms and malaria prevalence in Anopheles gambiae s.l. from Guinea

Abstract

The threat of insecticide resistance across sub-Saharan Africa is anticipated to severely impact the continued effectiveness of malaria vector control. We investigated the effect of carbamate and pyrethroid resistance on Anopheles gambiae s.l age, Plasmodium falciparum infection and characterized molecular resistance mechanisms in Guinea. Pyrethroid resistance was intense, with survivors of ten times the insecticidal concentration required to kill susceptible individuals. The L1014F kdr allele was significantly associated with mosquito survival following deltamethrin or permethrin treatment (p=0.003 and p=0.04, respectively). N1575Y and I1527T mutations were identified in 13% and 10% of individuals, respectively, but neither conferred increased pyrethroid tolerance. Partial restoration of pyrethroid susceptibility following synergist pre-exposure suggest a role for mixed-function oxidases. Carbamate resistance was lower and significantly associated with the G119S Ace-1 mutation (p=0.001). Oocyst rates were 6.8% and 4.2% among resistant and susceptible mosquitoes, respectively; survivors of bendiocarb exposure were significantly more likely to be infected (p=0.03). Resistant mosquitoes had significantly lower parity rates; however, a subset of intensely pyrethroid-resistant vectors were more likely to be parous (p=0.042 and p=0.045, for survivors of five and ten times the diagnostic dose of insecticides, respectively). Our findings emphasize the need for additional studies directly assessing the influence of insecticide resistance on mosquito fitness.