Malaria risk rises in Africa with arrival of invasive mosquito species

In Africa, where more than 95% of the 627,000 global malaria (or malaria) deaths occurred in 2020, the disease was endemic, mainly in rural areas, through the mosquito species ‘Anopheles gambiae’, prevalent on the continent.

However, another species, Anopheles stephensi, the main vector of malaria in cities in India and Iran, has been detected in Africa since 2012, causing outbreaks in Djibouti and Ethiopia.

Unlike Anopheles gambiae, Asian mosquitoes can breed in urban water tanks and thus breed during dry seasons, and are resistant to common insecticides.

If ‘Anopheles stephensi’ spread across the entire African continent, more than 126 million people in 44 cities would be at risk of contracting malaria, according to a 2020 scientific model.

Djibouti was the first African country to discover Anopheles stephensi disease, in 2012, when it was on the verge of eliminating malaria, with only 27 cases recorded that year.

The World Health Organization (WHO) said malaria cases have risen in this country since the arrival of the new carrier, with about 73,000 infections recorded in 2020.

A study presented Tuesday at the annual meeting of the American Society of Tropical Medicine and Hygiene reported an outbreak of malaria in neighboring Ethiopia.

In Dire Dawa, Ethiopia’s second-largest city, more than 2,400 cases were recorded between January and May – the dry season when malaria is traditionally rare – compared to just 205 cases in all of 2019.

“Anopheles stefanese mosquitoes are responsible for the increased pollution,” said Fitsum Jerma Tadesse, a molecular biologist at the Armauer Hansen Research Institute, based in Addis Ababa.

Sudan also appears to have been affected, as according to preliminary data presented at the meeting, “Anopheles stephensi” was identified in 64% of the 60 test sites spread across nine regions.

“In some cases, up to 94% of households have ‘Stevensie’ mosquitoes,” Hamouda Kafi, a medical entomologist and head of the vector management department at the Sudanese Ministry of Health, said in a statement.

In July, the Nigerian Institute of Medical Research confirmed, for the first time, the presence of Anopheles Stephens in West Africa.

Mosquitoes could have been detected in Somalia, according to the World Health Organization, which launched an initiative in September to contain the spread of the species in Africa.

The threat of Anopheles stevensii in Africa is no longer likely but proven, said Sarah Zohdi, a disease ecologist with the US Centers for Disease Control.