Anopheles stephensi, the mosquito from Asia that threatens Africa

Published on : 16/09/2020 – 22:55

Already established in the city of Djibouti a few years ago, a mosquito native to Asia and well adapted to the urban environment has been spotted in Ethiopia and Sudan. Its geographical area could extend further into Africa, exposing 126 million people living in urban areas to the risk of malaria, according to a study published on September 14 in the scientific journal PNAS.

Anopheles stephensi. This is the name of this species of mosquito that is widespread in Asia and which, more recently, has also made its home in the Horn of Africa. Until 2011, it was raging in some countries in Southeast Asia, the Indian subcontinent and the Middle East. Since then, it has been reported in Djibouti in 2012, Ethiopia (2016) and Sudan (2019). The expansion of this malaria-carrying insect is a cause for concern.

While Djibouti had not been confronted with an epidemic of malaria since 1999, here it is that from 2012, the capital had to deal with outbreaks of increasingly important cases. An alert for the rest of the continent, because as indicated in a study published in the journal Proceedings of the National Academy of Sciences (PNAS), this mosquito has the ” ability to survive and proliferate in urban areas », Unlike the other main vectors of malaria, which prefer rural and peri-urban areas, such as the species Anopheles gambiae, dominant in Africa.

Eggs in water tanks

In Asia, Anopheles stephensi is the main vector of malaria in urban areas. ” It has adapted very well to large Indian metropolises », Specifies Carlo Costantini, researcher entomologist at the Institute of research for the development (IRD). ” Females deposit their eggs in cement tanks to store water. Few species can colonize this kind of artificial roost “. For Anopheles gambiae for example, it is the puddles of rain that act as breeding sites. Those of the cities are too dirty or polluted for this species, even if it seems little by little to adapt to it.

The mosquito Anopheles stephensi is also distinguished by its behavior vis-à-vis its guests. It stings at dusk, most often outdoors, unlikeAnopheles gambiae, which stings in the dead of night, usually indoors. Yes Anopheles stephensi colonized African cities, ” the main tool in the fight against malaria transmission – sleeping under an insecticide-treated mosquito net – would be ineffective », Pointe Carlo Costantini.

126 million inhabitants threatened

There is great fear to see this city mosquito gain ground in Africa. The authors of the study published in PNAS mapped the places where it could be established, via a model taking into account different parameters (temperature, precipitation etc.) Result: out of 68 African cities with more than one million inhabitants , 44 cities would be highly adapted to the insect – like Mombasa in Kenya or Lagos in Nigeria. 126 million people who are today spared the risk of contracting malaria could be exposed.

For the World Health Organization, the spread of this mosquito is ” a major potential threat in the fight against malaria in Africa », While the burden of the disease is already very heavy: 400,000 people succumb to it each year on the continent.

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