New malaria mosquito emerges in African cities, and experts are worried

[Gert van der Hoek]

January 28, 2021

A new malaria mosquito is emerging in African cities, with potentially devastating consequences for those living there, according to a new study.

The larvae of Anopheles stephensi -- India's main mosquito vector of malaria -- are now "abundantly present" in locations across Africa, researchers from The Netherlands' Radboud University Medical Center and Ethiopia's Armauer Hansen Research Institute said. Vectors are living organisms that can transmit infectious pathogens between humans, or from animals to people.

This mosquito species only appeared in Africa a few years ago. Now, this invasive insect is "abundantly present" in water containers in cities in Ethiopia -- and highly susceptible to local strains of malaria, researchers have said.Most African mosquitoes that can transmit malaria are known to breed in rural areas. However, experts were already concerned this particular mosquito has found a foothold in urban areas, including cities in Ethiopia, Sudan and Djibouti, which researchers said could increase the malaria risk for urban populations.

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[Gert van der Hoek]

New malaria mosquito is emerging in African cities

NEWS RELEASE 27-JAN-2021

A new urban mosquito is widespread in the Horn of Africa and is highly susceptible to local malaria parasites

Larvae of a new malaria mosquito species are abundantly present in water containers in cities in Ethiopia. The mosquito, Anopheles stephensi, is the main malaria mosquito in India but only appeared on the African continent a few years ago. It has now been found in cities and towns in urban settings in Ethiopia, Sudan, and Djibouti. Researchers from the Radboud university medical center and the Armauer Hansen Research Institute in Ethiopia showed that the invading mosquito species is highly susceptible to local malaria strains. Malaria can therefore become an increasing problem for urban areas in Ethiopia and elsewhere in Africa.

In Africa, malaria is traditionally been a rural disease with towns and cities associated with much lower levels or absence of malaria. This is due to the fact that most African malaria mosquitoes breed in rural areas. However, the introduction of Anopheles stephensi may increase the malaria risk for urban populations. Over recent years there have been increasing reports of the Asian mosquito species Anopheles stephensi in the Horn of Africa. Anopheles stephensi can reproduce particularly well in man-made containers with clean water. This makes Anopheles stephensi a notorious mosquito species for urban malaria

The Asian mosquito appears to be particularly susceptible to African malaria

A mosquito species only poses a health risk if it can spread local malaria parasites. "That is why we performed mosquito feeding experiments with the blood of Ethiopian malaria patients. This allowed us to determine whether the local malaria parasite can develop in the new mosquito," explains Professor of Epidemiology of Tropical Infectious Diseases Teun Bousema of Radboud university medical center in Nijmegen. "To our surprise, the Asian mosquito turned out to be even more susceptible to local malaria parasites than our Ethiopian mosquito colony. This mosquito appears to be an extremely efficient spreader of the two main species of malaria".

With this important puzzle piece, concerns about urban malaria in Africa are increasing. In 2019, the World Health Organization (WHO) already sounded the alarm about the possible consequences of the invasion of Anopheles stephensi in Africa. With this new findings, these concerns seem justified. "An aggressive approach to target this mosquito is now a top priority," concludes dr. Fitsam Tadesse. "Only if we act quickly can we prevent the spread to other urban areas on the continent. We must target the mosquito larvae in places where they now occur and prevent mosquitoes from spreading over long distances, for example via airports and sea ports. If that fails, the risk of urban malaria will rise in large parts of Africa."