Abstract
Insecticide resistance across sub-Saharan Africa may impact the continued effectiveness of malaria vector control. We investigated the association between carbamate and pyrethroid resistance with Anopheles gambiae s.l. parity, Plasmodium falciparum infection, and molecular insecticide resistance mechanisms in Guinea. Pyrethroid resistance was intense, with field populations surviving ten times the insecticidal concentration required to kill susceptible individuals. The L1014F kdr-N1575Y haplotype and I1527T mutation were significantly associated with mosquito survival following permethrin exposure (Prevalence Ratio; PR = 1.92, CI = 1.09–3.37 and PR = 2.80, CI = 1.03–7.64, respectively). Partial restoration of pyrethroid susceptibility following synergist pre-exposure suggests a role for mixed-function oxidases. Carbamate resistance was lower and significantly associated with the G119S Ace-1 mutation. 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. Pyrethroid resistant mosquitoes had significantly lower parity rates than their susceptible counterparts (PR = 1.15, CI = 1.10–1.21). Our findings emphasize the need for additional studies directly assessing the influence of insecticide resistance on mosquito fitness.
Highlights
Malaria remains a leading cause of morbidity and mortality in the tropics, where it is estimated to have resulted in ~445,000 deaths in 2016 alone[1]
A total of 3962 female An. gambiae s.l. mosquitoes were captured from six sites in Maferinyah subprefecture, in Forecariah Prefecture (Senguelen = 766; Yindi = 755; Maferinyah Centre I = 660; Madinagbe = 608; Fandie = 608 and Moribayah = 565) over 25 days by manual aspiration from houses and human landing catches (HLCs)
We cannot entirely discount natural variation in parity, which may have increased over the sampling period at the beginning of the rainy season. These findings present a comprehensive overview of the current levels of insecticide resistance and underlying target site mutations present in Maferinyah, Guinea, an area of high malaria transmission
Summary
Malaria remains a leading cause of morbidity and mortality in the tropics, where it is estimated to have resulted in ~445,000 deaths in 2016 alone[1]. A recent large-scale, multi-country trial reported no association between malaria disease burden and pyrethroid resistance, with evidence that LLINs continued to Bureau for Global Health, Office of Infectious Disease, United States Agency for International Development, Washington DC, United States of America. Laboratory studies suggest that fitness costs associated with insecticide resistance may influence malaria transmission either by directly reducing mosquito life span[16] and/or fecundity[17], altering host seeking, feeding and mating behaviours[18,19,20] or by impairing parasite development inside vectors[21,22,23]. Because the current vector control strategy relies almost exclusively on LLIN use[26], nationwide pyrethroid resistance is of concern[27]. To better inform future malaria control efforts in Guinea, there is a need to characterize levels of operationally-significant insecticide resistance, as well as determine the effect this phenomenon has on the vectorial capacity of local mosquitoes to transmit malaria
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