Abstract
Insecticide resistance raises concerns for the control of vector-borne diseases. However, its impact on parasite transmission could be diverse when considering the ecological interactions between vector and parasite. Thus we investigated the fitness cost associated with insecticide resistance and Plasmodium falciparum infection as well as their interactive cost on Anopheles gambiae survival and fecundity. In absence of infection, we observed a cost on fecundity associated with insecticide resistance. However, survival was higher for mosquito bearing the kdr mutation and equal for those with the ace-1R mutation compared to their insecticide susceptible counterparts. Interestingly, Plasmodium infection reduced survival only in the insecticide resistant strains but not in the susceptible one and infection was associated with an increase in fecundity independently of the strain considered. This study provides evidence for a survival cost associated with infection by Plasmodium parasite only in mosquito selected for insecticide resistance. This suggests that the selection of insecticide resistance mutation may have disturbed the interaction between parasites and vectors, resulting in increased cost of infection. Considering the fitness cost as well as other ecological aspects of this natural mosquito-parasite combination is important to predict the epidemiological impact of insecticide resistance.
Highlights
Has been characterized in many insect species and has demonstrated conserved resistant mutations[11]
The fitness cost associated with insecticide resistance has been characterized on a large range of life history traits: such as development time, mortality and predation avoidance in larvae, flight and host-seeking activities, male reproductive success, fecundity, survival and susceptibility to infection in adults[8,16,17,18,19,20,21,22,23,24,25]
Most research has focused on the direct consequences of mosquito adaptation to the insecticides to assess the entomological efficacy of vector control, but they do not necessarily take into account the ecological complexity of the natural vectorial systems in order to predict its epidemiological impact
Summary
Has been characterized in many insect species and has demonstrated conserved resistant mutations[11]. In the natural avian malaria system, Culex pipiens-P. relictum, a decreased fecundity and an increased survival was observed[33] as well as a stress-dependent cost on survival[34,35] These studies showed that Plasmodium infection is more likely to imply a cost when mosquitoes experience unfavorable environmental conditions. P. falciparum infection reduces the ability of resistant vectors to survive insecticide exposure[37] This illustrates complex interactions between insecticide resistance, exposure to insecticide and malaria parasite transmission. The strains shared a common genetic background to avoid any confounding effect due to other resistance mechanisms or any other mutations that are not in linkage disequilibrium We compared these life history traits between Plasmodium infected and unexposed mosquitoes from each strains and demonstrated that the cost of infection is higher in the resistant vectors than in the susceptible ones
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