Tracing the origin, invasion history and resistance architecture of Anopheles stephensi: invasive threat to malaria control in Africa

The Speaker

I am a Research Associate in the Department of Vector Biology at the Liverpool School of Tropical Medicine. My research involves the design and implementation of genomic surveillance studies of populations of mosquitoes that transmit malaria to help improve malaria control. I use computational approaches to analyse large genome datasets from mosquito populations across Africa and Asia to better understand disease vector population dynamics, evolution, and insecticide resistance in malaria vectors across sub-Saharan Africa and Asia. I completed my PhD in Virus Evolution at the University of Glasgow (2014-2018), where I used computational tools to examine the long-term interactions between viruses and their hosts. During my first postdoc at the Institute of Biodiversity, Animal Health, and Comparative Medicine at the University of Glasgow (2019-2022), and current position at LSTM (2023-), I focused on population genomic and computational approaches to tackle pressing vector control challenges, including developing affordable, scalable computational frameworks for genomic surveillance that can easily be generalised to other disease vectors and invasive species. I am also an active contributor to the MalariaGEN initiative, developing open-source tools and analysis-ready data to support disease vector surveillance in Africa and Asia.

Abstract

The The invasion of Africa by the Asian urban malaria vector, Anopheles stephensi, endangers an estimated 126 million people in Africa, a rapidly urbanising continent where malaria is predominantly a rural disease. Since detection in Djibouti in 2012, An. stephensi has expanded deep into East Africa and Yemen. Building an evidence base for control of invasive An. stephensi requires an understanding of the origin and dynamics of the invasion, as well as the genomic architecture of resistance to chemical insecticides. Genomic data can reveal population histories, patterns of organism movement, and the molecular determinants of insecticide resistance, without requiring extensive vector surveillance. This is particularly valuable in regions like the Horn of Africa where traditional surveillance infrastructure may be compromised or inaccessible due to widespread geopolitical instability, conflict, and population displacement. Here, I will present a genomic surveillance study of 551 An. stephensi sampled across the invasive and native ranges in Africa and Asia. Our findings suggest a single invasive origin, most closely related to populations from Afghanistan and Pakistan, in Djibouti, which seeded separate subsequent invasions from Djibouti to Sudan, Ethiopia, and Yemen, before spreading inland in these countries. Furthermore, we find evidence of gene flow between South Asia and Africa, selection, and extensive copy number variation at gene families implicated in metabolic resistance in other mosquito vector taxa, suggesting resistance in An. stephensi is conferred by metabolic mechanisms introduced from Asia. These findings, and a companion genomic data catalogue, will form the foundation of an evidence base for surveillance and management strategies for An. stephensi.