Genomic study traces invasive malaria mosquito spread from Asia to Africa
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A genomic surveillance study published in Science has traced the invasion route of Anopheles stephensi, an urban malaria mosquito, from South Asia to Africa. The mosquito, first detected in Djibouti in 2012, has since spread across the Horn of Africa, Yemen and Kenya, carrying insecticide resistance from Asia.
Invasion Route
The study, led by Liverpool School of Tropical Medicine, analyzed mosquitoes collected across Asia, Africa and the Middle East. Results show An. stephensi originated in South Asia, likely coastal Pakistan or northern India, with Djibouti serving as the bridgehead for invasions into Yemen, Ethiopia and possibly Sudan. Sudan's flat terrain aided spread, while the Ethiopian Highlands slowed movement into Kenya, creating distinct genetic subpopulations.
Insecticide Resistance
Insecticide resistance driven by detoxification enzymes is widespread across all invasive populations, the study found. Lead author Tristan Dennis noted that resistance to insecticides used in bed nets and indoor spraying was introduced from Asia, meaning the mosquito arrived in Africa pre-adapted to resist main vector control tools. The findings highlight the need for alternative strategies like larval source management and novel insecticides.
Genomic Resource
The study created a freely available genomic data resource in partnership with the MalariaGEN Vector Genome Observatory. This resource supports development of cheaper surveillance tools, including resistance diagnostics and ancestry markers to track new invasions. Co-author Elfatih Malik called it a reminder that public health threats do not respect borders, urging sustained surveillance and regional partnerships.
What's Next
The genomic resource is expected to aid monitoring of An. stephensi spread across Africa. It remains unclear whether current vector control programs can adapt quickly enough to contain the insecticide-resistant mosquito.
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Genomic study traces invasive malaria mosquito spread from Asia to Africa
