Anopheles stephensi is a relatively new arrival in the Horn of Africa, having migrated from its ancestral home in South Asia. Its distribution and presence in Africa is still limited, but recent published modeling (see here) shows that habitat suitability will allow continued spread into many other areas across the African continent. There is now growing concern that if we do nothing, that is exactly what will happen and An. stephensi will inexorably continue to invade more and more countries across Africa. If we are going to try and stop this species in its tracks before it advances beyond our capacity to prevent further spread, the time is NOW.

Why the growing concern about An. stephensi in Africa? Some entomologists are of the opinion that “This is no big deal, it is just another species added to the list and we already have vector control programmes in place that will deal with it”. No, unfortunately not so. There is a fundamental difference. In almost all areas of the world outside South Asia, malaria is predominantly a rural challenge, and cities are largely free of malaria (this is a whole topic of discussion it itself…as urbanization advances and standards of living improve, so malaria declines). But not so with An. stephensi. This species thrives under urban conditions, the same way Aedes aegypti does. Like Aedes, An. stephensi prefers to breed in small ponds and pools. Backyard clutter, road ruts, ornamental ponds, building site ditches and depressions all add to rainwater collection where An. stephensi breeds prolifically. Tens of thousands of congested urban dwellers are conveniently close at hand to provide blood-meals. Climate change and rapidly growing urban populations will powerfully sustain An. stephensi populations. As the WHO’s Dr Raman Velayudhan pointed out in a recent webinar on arboviruses (see here), already many cities in India are experiencing dramatic water shortages, so that they rely on daily trainloads of water being brought in to supplement exhausted city water supplies. This water has to be stored in cement tanks or water jars at households, providing yet more breeding sites for An. stephensi. Urban malaria, caused by An. stephensi, will massively expand the human population at risk, not covered by current control efforts in Africa.

The question that our public health colleagues in Africa are facing is this: Do they wearily submit to the steamroller of expanding An. stephensi into more and more African countries in the spirit of “It is too big a challenge and too expensive to fight and anyway there is no guarantee we can stop the spread and maintain the wall”, or do they make an all-out effort to stop the advance, push back the front, and maintain vigilant surveillance to prevent renewed spread? The bottom line is that to wait for greater clarity about what to do will reduce the window of opportunity that exists right now, while the frontline is still fairly confined, and will by default mean a guaranteed advance, almost certainly fairly rapidly and not in a slow steady march, but in jumps as the mosquitoes hitch a ride on buses and trains to the next city.

This urban malaria is a new challenge for Africa, requiring new control approaches, different to the decades of previous experience in rural village settings. India has enormous depth of experience in combatting An. stephensi, with impressive cadres of highly capable entomologists. We would do well to tap into that reservoir of experience and professional goodwill to assist our colleagues in Africa. APMEN, collaborating with PAMCA in Africa, could help to facilitate dialogue and skills exchange in a demonstration of South-South collaboration and support.

Leo Braack, Co-Chair: APMEN VCWG

Frederik Seelig,  Global Vector Hub Program Manager, London School of Hygiene & Tropical Medicine)

Susanta Ghosh, Retired, previous Head of India National Institute of Malaria Research (ICMR)

Htin Kyaw Thu, Program Coordinator: APMEN VCWG