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A species of mosquito native to Asia threatens to put tens of millions of city dwellers in Africa at greater risk of contracting malaria as the invasive insect spreads across the continent, according to a study.
Malaria, which killed 400,000 people in 2018, mainly children in Africa, is caused by parasites that about 40 species of mosquitoes spread between humans when they feed.
The Anopheles gambiae group of mosquito species are the main drivers of the spread of malaria in Africa, but these insects do not like the polluted puddles seen in cities and have not learned to deposit their larvae in freshwater tanks. urban.
For these reasons, most of the malaria transmission in Africa occurs in rural areas.
In a new study published in the Proceedings on the National Academy of Sciences (PNAS), medical entomologist Marianne Sinka of the University of Oxford traced the spread of another species, Anopheles stephensi, which originated in Asia.
This species has learned to slide through crevices to access water tanks, favoring brick and concrete ones.
“It is the only one that is really good for entering central urban areas,” Sinka told AFP.
Anopheles stephensi caused a major outbreak in the Horn of Africa in Djibouti City in 2012, a city where malaria barely existed and has since been observed in Ethiopia, Sudan and elsewhere.
Sinka and his colleagues combined the species’ location data with spatial models that identified the environmental conditions that characterize its preferred habitat: high-density urban areas where it is hot and rainfall is abundant.
Their study found that 44 cities are “very suitable” places for the insect, putting 126 million more Africans, mainly in the equatorial regions, at risk of contracting malaria, compared to today.
“That means that Africa, which already has the highest burden of malaria, could have an even greater impact,” Sinka said, with 40 percent of the continent’s population in urban areas.
Unlike African mosquitoes, which like to bite humans when it’s cold at night, Anopheles stephensi can feed at night when it’s hotter, making mosquito nets less effective.
Therefore, installing window screens, drenching the walls with insecticides, and covering the body are better ways to protect against this species.
In the long term, the most effective measure is to target the larvae: remove standing water and hermetically seal the water tanks against intrusion. These methods proved effective in India, Sinka said.
