Seasonal dynamics of Anopheles stephensi and its implications for mosquito detection and emergent malaria control in the Horn of Africa.

Invasion of the malaria vector across the Horn of Africa threatens control efforts across the continent, particularly in urban settings where the vector is able to proliferate. Malaria transmission is primarily determined by the abundance of dominant vectors, which often varies seasonally with rainfall. However, it remains unclear how abundance changes throughout the year, despite this being a crucial input to surveillance and control activities. We collate longitudinal catch data from across its endemic range to better understand the vector’s seasonal dynamics and explore the implications of this seasonality for malaria surveillance and control across the Horn of Africa. Our analyses reveal pronounced variation in seasonal dynamics, the timing and nature of which are poorly predicted by rainfall patterns. Instead, they are associated with temperature and patterns of land use; frequently differing between rural and urban settings. Our results show that timing entomological surveys to coincide with rainy periods is unlikely to improve the likelihood of detecting Integrating these results into a malaria transmission model, we show that timing indoor residual spraying campaigns to coincide with peak rainfall offers little improvement in reducing disease burden compared to starting in a random month. Our results suggest that unlike other malaria vectors in Africa, rainfall may be a poor guide to predicting the timing of peaks in -driven malaria transmission. This highlights the urgent need for longitudinal entomological monitoring of the vector in its new environments given recent invasion and potential spread across the continent.

Funder

Funder name	Awards
Wellcome Trust, United Kingdom	Sir Henry Wellcome Postdoctoral Fellowship, 224190/Z/21/Z - NIH Research–Wellcome Partnership for Global Health Research Collaborative Award and Controlling emergent An. stephensi in Ethiopia and Sudan, ref. 220870_Z_20_Z
Medical Research Council, United Kingdom	Reference MR/R015600/1 which is jointly funded by the UK MRC and the UK Foreign, Commonwealth and Development Office (FCDO) under the MRC/FCDO Concordat agreement
Bill and Melinda Gates Foundation, United States
Novo Nordisk Fonden, Denmark	The Novo Nordisk Young Investigator Award (NNF20OC0059309)
Danmarks Grundforskningsfond, Denmark	Chair grant
Eric and Wendy Schmidt Fund For Strategic Innovation	Schmidt Polymath Award (G-22-63345)
European Union / Community Jameel	EDCTP2 program
Royal Statistical Society, United Kingdom