Anopheles gambiae (s.l.) is found where few are looking: assessing mosquito diversity and density outside inhabited areas using diverse sampling methods

Patric Stephane Epopa,Frederic Tripet,Abdoul Azize Millogo,Catherine Matilda Collins,Ace R North,Roch K Dabiré,Mark Quentin Benedict,Samantha OʼLoughlin,Georges Anicet Ouédraogo,Abdoulaye Diabaté

doi:10.1186/s13071-020-04403-9

Abstract

BackgroundOne of the promising current approaches to curb malaria lies in genetic vector control, the implementation of which will require an improved understanding of the movement of genetic constructs among mosquito populations. To predict potential gene flow from one area to another, it is important to begin to understand mosquito dynamics outside of the commonly-sampled village areas, and thus how genes may move between villages. This study assessed the presence and relative abundance of mosquitoes in a 6-km corridor between two villages in western Burkina Faso.MethodsThe area surrounding the villages was mapped and the road between them was used as the basis of a transect along which to sample. Five collection points were placed along this transect. To investigate both larval and adult mosquito presence, multiple sampling approaches were used surrounding each point: searching for larval sites in an area of 500 m radius, swarm sampling, human landing catches (HLC), CDC light traps and backpack aspiration catches of potential resting sites. Sampling took place twice: in September and October 2015.ResultsAdult mosquitoes from six species of Anopheles and three other genera were found along the whole transect. Anopheles gambiae (s.l.) was the most abundant followed by Anopheles nili and Anopheles coustani. Larvae of Anopheles spp. were found in small pools of surface water along the whole transect, though their presence increased with human proximity. HLC and aspiration were the most efficient methods of collecting adult mosquitoes along the whole transect, indicating that there are both host-seeking and resting mosquitoes well away from core village areas. In contrast, swarms of male mosquitoes, thought to be the principle mating locations of Anopheles spp. mosquitoes in West Africa, were only found close to the core village areas.ConclusionsThis preliminary study indicates that Anopheles spp. mosquitoes are both present and breeding in low human-density areas along transit axes and provides both a relative evaluation of methods for use in these areas and evidence that gene flow between Sahelian population centres is likely. More robust and structured studies are nevertheless needed to come with stronger conclusions.

Highlights

One of the promising current approaches to curb malaria lies in genetic vector control, the implementation of which will require an improved understanding of the movement of genetic constructs among mosquito populations
Substantial research efforts focus on new vector control approaches or tools, such as genetic vector control [5,6,7], entomopathogenic bacteria or fungi [8, 9], and indoor mosquito traps [10, 11] to complement the strategies in current use
The collection point (CP) were originally selected from satellite images of the area and their precise locations were determined after ground-truthing with specific criteria

Summary

Introduction

One of the promising current approaches to curb malaria lies in genetic vector control, the implementation of which will require an improved understanding of the movement of genetic constructs among mosquito populations. In a global context of increasing mosquito resistance to the main insecticide classes used in public health [1, 2], malaria control programmes in many sub-Saharan countries face reduced efficiency of their insecticide-based vector control tools. Gene flow is predominantly intraspecific [12] and is essentially the product of mosquito movement from one place to another for bloodfeeding, mating or larval development site-seeking, or because of environmental factors such as wind or human-borne [13] As some of these proposed tools have potential for area-wide implementation, understanding gene flow via mosquito movement between neighbouring locations will be essential for predicting spread and cost-effectiveness

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Conclusion