New data shows the spread of an invasive species of malaria mosquito in Africa that poses a potential threat to millions of city dwellers, researchers warn on Tuesday.
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Caused by five species of parasites transmitted through the bites of infected mosquitoes, malaria (or malaria) remains a scourge, particularly for African children, despite the recent introduction of a vaccine. It is manifested by fever, headache, muscle aches, then by cycles of chills, fever, and sweating.
In Africa, which accounted for more than 95% of the 627,000 global deaths in 2020, malaria spreads mainly in rural areas via the continent’s predominant Anopheles gambiae mosquito.
Another species, Anopheles stephensi, long the main vector of malaria in Indian and Iranian cities, however, can reproduce in urban water reservoirs and therefore thrives during the dry season. It is also resistant to common insecticides.
According to a 2020 model, if this mosquito spread in Africa, more than 126 million people in 44 cities would be at risk of malaria.
In Djibouti, the first African country to detect Anopheles stephensi in 2012 when it was close to eradicating malaria with just 27 cases that year, malaria has skyrocketed since the pathogen’s arrival. According to the World Health Organization, around 73,000 cases were registered there in 2020.
And a malaria outbreak in neighboring Ethiopia was caused by the same mosquito, according to a non-peer-reviewed study presented Tuesday at the annual meeting of the American Society of Tropical Medicine and Hygiene in Seattle, United States.
In Dire Dawa, the second largest city in Ethiopia, located in the east on the railway line between Addis Ababa and Djibouti, 205 malaria cases were registered in 2019. This year, more than 2,400 cases were nothing between January and May only.
However, this epidemic occurred during the dry season, when malaria is traditionally rare.
Faced with the rise in cases, “researchers rushed to investigate,” one of them, Fitsum Girma Tadesse, a molecular biologist at the Armauer Hansen Research Institute in Addis Ababa, told AFP. They quickly determined that “Anopheles stephensi mosquitoes are responsible for the increase in contamination”.
These malaria-carrying mosquitoes have also been found in nearby water reservoirs.
This species’ preference for open water reservoirs, common in African cities, “makes them unique,” Fitsum Girma Tadesse said.
Sudan also seems to be affected. According to other preliminary data presented in Seattle, Anopheles stephensi mosquitoes were identified at 64% of the 60 test sites spread across nine regions.
“In some cases, up to 94 percent of households have Stephensi mosquitoes nearby,” Hmooda Kafy, a medical entomologist and head of the vector management department at the Sudan Ministry of Health, said in a statement.
The findings come after the Nigerian Institute of Medical Research first confirmed the presence of Anopheles stephensi in West Africa in July.
For Sarah Zohdy of the US Centers for Disease Control, it was “surprising” that attention was focused on the Horn of Africa.
In recent months, the threat of Anopheles stephensi in Africa has gone from being “potential” to being proven, noted this disease ecology expert, who works with the United States Presidential Malaria Initiative, a partner in the Ethiopian study.
“There is now evidence that the world needs to take action against this phenomenon,” she stressed, also calling for increased surveillance to know exactly how far Anopheles stephensi has spread across the African continent. According to the WHO, which launched an initiative in September to stop its spread in Africa, had it been detected in Somalia.
Because it can thrive in urban water reservoirs, “we are transforming ourselves from a seasonal disease into one that can exist year-round,” which the researcher says poses “a major threat” to advances in malaria control.
Malaria deaths more than halved between the turn of the century and 2017 – thanks largely to insecticide-treated bed nets, testing and medication – before the Covid-19 pandemic halted that decline.