Abstract
BackgroundThe main goal of this study was to assess the blood feeding behaviour and the contribution Anopheles coluzzii and Anopheles gambiae, 2 sibling species of An. gambiae sensu stricto. present and living in sympatry in 2 regions of northern Benin targeted for indoor residual spraying (IRS).MethodsThe study was carried out in 6 districts of 2 regions of Benin (Alibori and Donga). Human landing catches (HLC) performed inside and outside of the households and pyrethrum spray captures (PSC) carried out in bedrooms were used to sample vector populations (An. gambiae and An. coluzzii). Collected mosquitoes were analysed to estimate the human biting rate indoors and outdoors, the circumsporozoite antigen positivity, and the anthropophagic index using ELISA methodology. Polymerase chain reaction was used to estimate the frequency of the knockdown resistance (kdr) L1014F and the ace-1 mutations, 2 markers associated respectively with pyrethroids and carbamate/organophosphate insecticide resistance.ResultsA higher blood feeding rate was observed in An. gambiae compared to An. coluzzii as well as, a non-pronounced outdoor biting behavior in both species. The latter showed similar anthropophagic and sporozoite rates. However the analysis indicates a seasonal difference in the contribution of each species to malaria transmission associated with shifts in resting behaviour. Anopheles coluzzii females accounted for most of the detected infections: 86% in Alibori and 79% in Donga, during the dry season versus 14.4% and 21.2%, respectively for An. gambiae during the same period. This relationship was reversed in Donga during the rainy season (66% for An. gambiae against 34% for An. coluzzii). Results also indicated lower frequencies of kdr L1014F and ace-1 in An. coluzzii versus An. gambiae.ConclusionDespite similarity in some parameters related to malaria transmission in both surveyed species, An. coluzzii is potentially a more important malaria vector because of high density in the region. It is also characterized by lower frequencies of the ace-1 mutation than is An. gambiae. The ongoing use of pirimiphos methyl (organophosphate) for IRS should continue to show a good impact in Alibori and Donga because of the very low level of the ace-1 mutation in both species.
Highlights
The main goal of this study was to assess the blood feeding behaviour and the contribution Anopheles coluzzii and Anopheles gambiae, 2 sibling species of An. gambiae sensu stricto. present and living in sympatry in 2 regions of northern Benin targeted for indoor residual spraying (IRS)
Akogbéto et al Malar J (2018) 17:307 for IRS should continue to show a good impact in Alibori and Donga because of the very low level of the ace-1 mutation in both species
Distribution of Anopheles gambiae complex in the two regions All samples of An. gambiae s.l. collected by Human landing catches (HLC) and pyrethrum spray captures (PSC) were used for species identification
Summary
The main goal of this study was to assess the blood feeding behaviour and the contribution Anopheles coluzzii and Anopheles gambiae, 2 sibling species of An. gambiae sensu stricto. present and living in sympatry in 2 regions of northern Benin targeted for indoor residual spraying (IRS). The main goal of this study was to assess the blood feeding behaviour and the contribution Anopheles coluzzii and Anopheles gambiae, 2 sibling species of An. gambiae sensu stricto. Anopheles gambiae sensu lato (s.l.) is a complex of 8 species, which contribute differently to malaria transmission. An. gambiae sensu stricto (s.s.), the nominotypical member, is comprised of 2 species based on molecular evidence: Anopheles coluzzii (the An. gambiae molecular ‘M form’) and An. gambiae (the ‘S form’) [1]. Heterogeneity in the vector capacity of each species is due to a highly diverse bio-ecology: feeding on humans or cattle, resting indoors or outdoors. Other sibling species of An. gambiae complex play a role, albeit a lesser role, in malaria transmission, for example, Anopheles melas in West Africa [6,7,8]. The main factor of vector competence of a mosquito to a parasite is its ability to offer a suitable physicochemical environment for the development of the parasite during the sporogonic cycle
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