Ecology: How malaria mosquitos survive dry season

Mosquitoes in the western Sahel region of Africa may be able to survive the dry season by entering a state of dormancy known as aestivation, a paper published in Nature Ecology and Evolution suggests. The findings may have implications for public health interventions to control malaria.

Africa accounts for 94% of all global malaria cases and deaths, and it is important to understand how mosquito vectors of malaria survive. The long duration of the dry season in the western Sahel region should be inhospitable to Anopheles coluzzii mosquitoes, however, adult mosquitoes reappear at the start of the wet season too rapidly to be the result of a new generation. Prior explanations for their emergence days after the onset of rains included long-distance migration and aestivation, however the evidence for aestivation has been mostly circumstantial and no estimate of its relative contribution to the persistence of malaria mosquitoes has been available.

To explore the role that aestivation plays in mosquito persistence during the dry season, Roy Faiman, Alpha Seydou Yaro and colleagues used deuterium isotopes to mark mosquito larvae during the breeding season at two villages in Mali. When the authors sampled adult mosquitoes after the seven-month-long dry season, they found that around 20% of the adult population were marked with the isotopes. This suggests that local aestivation is occurring and contributes to the mosquito population at the beginning of the wet season.

The authors conclude that their findings may aid our understanding of how insects survive in arid habitats and also have important implications for mosquito control and malaria elimination strategies.