Illustration of the Plasmodium falciparum parasiteCredit: THOM LEACH/ SPL /GETTY IMAGES
In March 2022 Ethiopia’s National Malaria Elimination Program called for an emergency meeting about an outbreak of malaria in Dire Dawa, the country’s second largest city, with a population of around 465,000.
In the first five months of 2022, cases of malaria reached 2,425, a 12-fold increase from 2019.
A team from Ethiopia, with international colleagues, found the cause of the outbreak to be the influx of the insecticide-resistant species of mosquito, Anopheles stephensi, which was not found in the area before 2018. The mosquito carried the malaria-causing parasite Plasmodium falciparum, which was the predominant cause behind malaria cases between 2019 and 2022.
Fitsum Tadesse, a molecular biologist who was leading an urban malaria project at the Armauer Hansen Research Institute, in other cities of Ethiopia, quickly moved to have Dire Dawa included as a study site as soon as the outbreak happened.
“I deployed my team of entomologists, laboratory technologists, phlebotomists, community health extension workers, local informal and formal leaders, and health service providers,” Tadesse tells Nature Africa.
Undermining efforts
In around three months, the team had completed data collection and embarked on laboratory work and data analysis for another two months. In their study, published in Nature Medicine, Tadesse and colleagues confirmed that the mosquito, prevalent in southern Asia is driving the spread of drug and diagnosis-resistant malaria in Africa, undermining efforts made to fight the disease.
Recent genetic experiments published in Science Advances suggest that a specific mutation in Plasmodium falciparum causes strong resistance to multiple first-line antimalarial drugs, including piperaquine (PPQ) and artemisinin.
The Science Advances study also found that one gene variant responsible for resistance to PPQ could enhance susceptibility to yet another antimalarial drug, lumefantrine and that combining the two drugs can help counter that resistance. “These [genetic crosses] will be key to identifying the genetic basis of P. falciparum resistance to first-line combination therapies, which appears to be imminent in Africa,” the researchers say in their report.
The need for collective action
The researchers behind the Nature Medicine study refer to their findings as "the strongest evidence to date for a role of Anopheles stephensi in driving an urban malaria outbreak in Africa, highlighting the major public health threat this fast-spreading mosquito poses."
Tadesse explains that the recent findings point towards new challenges in fighting malaria, which did not usually spread in urban settings and so the control programs were mostly focused on rural areas.
“It brings new challenges in settings where we normally do not see malaria. With the rapid expansion of poorly planned urbanisation, the spread of Anopheles stephensi will put many urban dwellers at risk,” he adds.
