Towards the elimination of malaria in the Union of Comoros: geographical insight on control actions and maintenance factors

Résumé En

Introduction: Malaria has long been endemic in the Union of Comoros. Since 2007, the Comorian government has been conducting a national strategy for eradicating malaria by 2016. Between 2010 and 2014, the number of malaria cases has radically fallen by more than 90%. This study aims at describing the spatial patterns of the epidemiology of malaria and at identifying risk factors through a geographical approach. Method: Monthly cases, as reported by the “Programme National de lutte Contre le paludisme” (PNLP) from 2010 to 2014, were geo-referenced in the three islands (i.e. Grande Comore, Moheli and Anjouan) at two different scales: by sanitary district and by health center. In Grande Comore, malaria cases confirmed by microscopic exam during the active control from 2012 to 2014 were geo-localized at the village scale. Data on environmental factors, including meteorology and land use (analyzed by remote sensing of SPOT 5 satellite images) but also information on malaria control actions were integrated into a spatial database. We realized statistical and spatial analyses to show the relationships between this dataset and malaria information.Results: The mapping of malaria incidence reveals spatial and temporal variations between and within islands. In the 7 districts of Anjouan and in 2 of the 3 districts of Moheli, the incidence is less than 1 case per 100,000 inhabitants in 2014. In contrast, the incidence remains higher in every health district of Grande Comore with more than 4 cases per 100,000 inhabitants in 2014. This is consistent with the reduction of prevalence of Plasmodium falciparum that decreased from 24% in 2012 to 2 in 2014 in Grande Comore. Also, Long before the two other islands, Moheli has benefited from a campaign of indoor insecticide spraying and a population mass treatment by Artequick and Primaquine between 2007 and 2009. In addition, we highlight spatial relationships between malaria incidences and environmental factors in Grande Comore.Conclusion: This study clarifies the impact of control actions on malaria epidemiology and the environmental factors that contributed to its maintenance.