Isotopic evidence that aestivation allows malaria mosquitoes to persist through the dry season in the Sahel

In the Sahel region of West Africa, An. coluzzii mosquitoes appear to survive the dry season locally, but the relative contribution of this subpopulation to the persistence of the species in the Sahel has remained unknown. Here the authors use stable isotope tracking to determine the fraction of mosquitoes that undergo aestivation, a state of dormancy that allows them to persist through the dry season and maintain yearly malaria transmission. Data suggest that the malaria vector mosquito Anopheles coluzzii persists during the dry season in the Sahel through a dormancy mechanism known as aestivation; however, the contribution of aestivation compared with alternative strategies such as migration is unknown. Here we marked larval Anopheles mosquitoes in two Sahelian villages in Mali using deuterium (H-2) to assess the contribution of aestivation to persistence of mosquitoes through the seven-month dry season. After an initial enrichment period, 33% of An. coluzzii mosquitoes were strongly marked. Seven months following enrichment, multiple analysis methods supported the ongoing presence of marked mosquitoes, compatible with the prediction that the fraction of marked mosquitoes should remain stable throughout the dry season if local aestivation is occurring. The results suggest that aestivation is a major persistence mechanism of An. coluzzii in the Sahel, contributing at least 20% of the adults at the onset of rains. This persistence strategy could influence mosquito control and malaria elimination campaigns.

Automated summary

The study finds that aestivation is a major persistence mechanism for Anopheles coluzzii mosquitoes in the Sahel region, allowing them to survive during the dry season and maintain a stable population at the onset of rains. This finding could have implications for mosquito control and malaria elimination efforts.