Intense rainfalls and floods reshape malaria transmission in Niger

The Sahel covers a vast semi-arid area characterized by a long dry season of about 8-9 months and a short rainy season of 3-4 months. Although arid, the Sahel is highly susceptible to vector-borne diseases, and a malaria endemic zone. After decades of drought, rainfall is increasing again, leading to a sustained increase in malaria transmission in the region. Changes in land use and urbanization are also modulating human-vector contacts and thus the incidence of malaria. Malaria control programs need to adapt to this situation. The aim of this study is to discuss the factors influencing malaria occurrence in this region, which are modulated by climate and land use.

For this study, both original epidemiological data and recent literature are analyzed to support the discussion on adaptation of control strategies.

Overall, the perennial presence of water resulting from rainfall and/or human activities are key factors in stabilizing malaria transmission in the Sahel. Indeed, recent studies show that in Niger, transmission is increasing, but also spreading during the dry season, especially in areas closed to wild water and flooding. In the same vein, malaria morbidity is no longer largely confined to children under five.

Preventive measures, including chemoprevention of seasonal malaria and indoor residual spraying, which are currently used only during the rainy season, need to be redesigned as part of a rethink of current prevention strategies. Policy-makers and national programs should adapt their strategies to better fit the future climatic context of the Sahel.