Malaria Mosquitoes in African Cities: A New Threat

Mosquitoes that are infected with single-celled parasites of the genus Plasmodium usually live in the tropical and subtropical regions that exist in a broad band around the equator. The mosquitoes need to live in those regions because (most) of their energy needs come from plant sugars taken from the nectar of flowers. This means: no plants, no mosquitoes, and no malaria.

Until now.

A new mosquito species is changing long-held assumptions about where malaria can spread and how difficult it may be to control. Researchers have discovered that Anopheles stephensi, a malaria-transmitting mosquito native to South Asia and the Persian Gulf, has established itself in several African countries and is causing malaria outbreaks in densely populated cities. Unlike Africa's traditional malaria mosquitoes, which are mainly found in rural environments, Anopheles stephensi thrives in urban areas.

Its secret lies in its remarkable adaptability. Rather than relying on natural ponds or marshes, this mosquito breeds in artificial water containers such as rooftop tanks, barrels, buckets, and construction sites. As a result, rapidly growing cities with unreliable water supplies provide ideal breeding grounds, bringing malaria into places where it was previously uncommon.

The mosquito's first African detection was in Djibouti in 2012. Since then, it has spread silently across the Horn of Africa and Yemen, with confirmed sightings already in other countries, including Ethiopia, Sudan, Kenya, Nigeria, Ghana, Niger, and Somalia. In Ethiopia, its arrival has already been linked to dramatic increases in malaria cases in urban centres, demonstrating its ability to rapidly establish itself and fuel outbreaks.

A recent genomic study involving 645 mosquitoes from Africa, the Middle East, and South Asia has provided new insights into how this invasion occurred[1]. The research suggests that Anopheles stephensi most likely arrived in Africa through maritime trade from South Asia[2]. The mosquitoes appear to have first established a 'bridgehead' population in Djibouti before spreading into neighbouring countries. Even more concerning is that many of these mosquitoes already carried genes that make them resistant to commonly used insecticides before they reached Africa.

This insecticide resistance could significantly complicate malaria control efforts. Bed nets and indoor spraying remain two of the most effective methods for preventing malaria transmission, but their effectiveness depends on mosquitoes being susceptible to the insecticides used. If resistance continues to spread, health authorities may need to develop new strategies to keep outbreaks under control.

As African cities continue to expand, the emergence of this novel pathway to malaria shows how versatile nature is. It simply tries to survive,

[1] Dennis et al: The origin, history, and resistance architecture of an invasive urban malaria mosquito in Africa in Science – 2026. See here.
[2] Sharma, Hamzakoya: Geographical Spread of Anopheles stephensi, Vector of Urban Malaria, and Aedes aegypti, Vector of Dengue/DHF, in the Arabian Sea Islands of Lakshadweep, India in Dengue Bulletin - 2001