Variation in Anopheles distribution and predictors of malaria infection risk across regions of Madagascar

Romain Girod,Christopher D. Golden,Marcia C. Castro,Luciano M. Tantely,Benjamin L. Rice,Gauthier N. Emile,Hervet J. Randriamady,Nicholas J. Arisco

doi:10.1186/s12936-020-03423-1

Abstract

BackgroundDeforestation and land use change is widespread in Madagascar, altering local ecosystems and creating opportunities for disease vectors, such as the Anopheles mosquito, to proliferate and more easily reach vulnerable, rural populations. Knowledge of risk factors associated with malaria infections is growing globally, but these associations remain understudied across Madagascar’s diverse ecosystems experiencing rapid environmental change. This study aims to uncover socioeconomic, demographic, and ecological risk factors for malaria infection across regions through analysis of a large, cross-sectional dataset.MethodsThe objectives were to assess (1) the ecological correlates of malaria vector breeding through larval surveys, and (2) the socioeconomic, demographic, and ecological risk factors for malaria infection in four ecologically distinct regions of rural Madagascar. Risk factors were determined using multilevel models for the four regions included in the study.ResultsThe presence of aquatic agriculture (both within and surrounding communities) is the strongest predictive factor of habitats containing Anopheles larvae across all regions. Ecological and socioeconomic risk factors for malaria infection vary dramatically across study regions and range in their complexity.ConclusionsRisk factors for malaria transmission differ dramatically across regions of Madagascar. These results may help stratifying current malaria control efforts in Madagascar beyond the scope of existing interventions.

Highlights

Deforestation and land use change is widespread in Madagascar, altering local ecosystems and creating opportunities for disease vectors, such as the Anopheles mosquito, to proliferate and more reach vulnerable, rural populations
Anopheles coustani was dominant in the SE, High plateau (HP), and West coast (WC), while An. gambiae was dominant in the Southwest
The average number of peridomicile habitats varied by region, with larger numbers on average existing in HP (2.82 habitats) and SE (2.71 habitats) compared to SW (0.24 habitats) and WC (0.37 habitats)

Summary

Introduction

Deforestation and land use change is widespread in Madagascar, altering local ecosystems and creating opportunities for disease vectors, such as the Anopheles mosquito, to proliferate and more reach vulnerable, rural populations. Agricultural expansion and associated changes in land use, such as deforestation for food production, can create new microhabitats and alter the distribution or density of species, including mosquitoes These changes can increase the number of suitable larval habitats for mosquito species, including Anopheles mosquitoes, the Arisco et al Malar J (2020) 19:348 behaviour and resource access, here referred to as socioeconomic factors, play key roles in mediating malaria risk. Examples of these socioeconomic factors include bed net use, health and housing infrastructure, baseline health status, and treatment/prevention access [11, 12]. Communities living in western dry forests experience more seasonal transmission while those living in eastern moist forests experience more consistent transmission throughout the year [23]

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