Audrey Lenhart, PhD, MPH
Chief, Entomology Branch, Division of Parasitic Diseases and Malaria (DPDM),
Centers for Disease Control and Prevention (CDC)
Learn about the threat of A. stephensi, an invasive malaria vector spreading in Africa. Explore its behaviour challenges in control, and the need to act now for global malaria elimination.
Sub-Saharan Africa accounted for 94% of global malaria cases and 95% of global malaria deaths in 2022. Significant progress in malaria control has been made over the past 20 years, largely due to highly effective mosquito control tools targeting native species prevalent across rural Africa.
Invasive A. stephensi threatens Africa
However, Anopheles stephensi (A. stephensi) — a mosquito native to the Indian subcontinent and an important malaria vector in both urban and rural settings — is gaining a foothold in sub-Saharan Africa. This invasive malaria vector presents a threat to global malaria elimination, and its establishment there could alter the landscape of malaria in Africa, causing a shift from a primarily rural disease to one with a significant urban component.
Since 2012, this vector has been detected in eight African countries and continues to spread. Recent modelling estimates indicate an additional 126 million people could become at risk of malaria if this vector becomes established in key urban centres. Significant increases in malaria associated with this vector have already been detected in Djibouti, Ethiopia and Sudan.
Recent modelling estimates indicate an additional
126 million people could become at risk of malaria
if this vector becomes established in key urban centres.
Challenges in controlling A. stephensi
In addition to thriving in non-rural settings, little is known about how best to control this mosquito. The two most widely used tools to control malaria vector mosquitoes are insecticide-treated bed nets and the spraying of residual insecticides on the walls inside houses. These interventions efficiently target mosquitoes that bite and rest inside houses, especially mosquitoes that bite during the night.
However, the limited data that exist on the behaviour of A. stephensi in Africa suggest that it does not share the same preference for indoor, nighttime biting as the native African malaria vectors. In addition, these invasive mosquitoes are resistant to many of the commonly used insecticides.
Collaborative approaches urgently needed
Anopheles stephensi is an acute threat that requires a coordinated preparedness, detection, and response strategy to protect human health. We urgently need to better understand how these invasive populations are being introduced and move over space and time.
Countries at the highest risk must be equipped to detect and rapidly respond to these mosquitoes by deploying vector control tools that target the unique behaviours of this invasive species. A coordinated, multisectoral approach is crucial to adequately address this threat to global malaria elimination and mitigate additional risks.