New malaria mosquito threatens mass outbreaks in Africa

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Africa only has a few months to respond to an invasive malaria mosquito that thrives in cities before the situation gets out of hand, experts warn.

Scientists predict that more than 125 million urban residents across Africa will be at higher risk of malaria from a type of Asian mosquito that is moving rapidly across the continent.

The Anopheles stephensi mosquito is one of the few malaria mosquitoes that thrives in urban areas because it finds clean water to lay its eggs.

Malaria is traditionally seen as a rural disease. In Africa, city centers can be completely free from malaria transmission, according to experts from the London School of Hygiene and Tropical Medicine (LSHTM).

However, the invading mosquito could drastically change the location and movement of malaria in Africa, where 94 percent of malaria deaths worldwide are recorded, mostly among children under five.

“I think it’s really pretty scary,” says Jo Lines, professor of malaria control and vector biology at LSHTM. “It’s part of our duty as a [scientists] to say, “Look, something is happening here.” If we don’t scream now, it will be too late. “

New research, led by Marianne Sinka, a senior postdoctoral fellow at Oxford University, suggests that An. stephensi may already be adapting to its new environment and will be active all year round.

“The more you see, the more you find. We don’t really understand the scale of the threat yet, but it’s not looking good for the past few years. “

Louisa Messenger, London School of Hygiene and Tropical Medicine

“If it continues to invade the African continent in an uncontrolled manner, there is a very real possibility of a mass malaria outbreak,” says Sinka’s team. “In a continent that is struggling to improve and strengthen its health systems, such a huge burden could be catastrophic. Targeted vector monitoring is therefore urgently required. “

New threat

Sinka’s research is a warning bell, says Louisa Messenger, an assistant professor at LSHTM. “The main conclusions and observations are very striking. The numbers are very dramatic when they translate into reality, “Messenger told SciDev.Net.

In 2012, an unusual urban malaria outbreak was reported in the horn of Africa’s city of Djibouti, with Ethiopia and Sudan also reporting cases. This was An’s first recorded appearance. Stephensi in Africa.

Up until last year, the World Health Organization had issued a vector alert warning that the mosquito appeared to be spreading from Djibouti to neighboring countries.

According to Messenger, the mosquito probably arrived via ships calling at ports in East Africa. The transmission mapping shows that the mosquito’s spread follows the main routes that heavy vehicles use to carry goods.

“The idea of ​​An. stephensi to africa is particularly worrying; Over 40 percent of Sub-Saharan Africans live in urban environments, ”write Sinka and co-authors in their article published in PNAS (September 14).

“Mosquitoes can be much more difficult to control in urban settings, but people may have better access to health care and treatment. Therefore, it is difficult to gauge the consequences of this invading mosquito,” Sinka told SciDev.Net.

Researchers are working quickly to understand the extent to which An is spreading. stephensi.

“The more you search, the more you find,” says Messenger. “We don’t really understand the extent of the threat yet, but things haven’t been looking good for the past few years.”

Entomologist Fredros Okumu, scientific director at the Ifakara Health Institute in Tanzania, agrees that the study’s results are significant. “The best at the moment [strategy] is to assess the extent of its spread and its role in the transmission of malaria, ”says Okumu.

Call to action

Governments must move to control An. stephensi within “a few months or a year, but no longer, after which it will be too late, it will have spread too far,” says Lines.

In 1930, the world did not react quickly to the invasion of Brazil by the African mosquito Anopheles gambiae, which resulted in a severe malaria epidemic in 1938. Lines said the Brazilian crisis should serve as both a warning and an example of success – When a comprehensive management plan was passed, Gambiae was wiped out in Brazil.

“The sooner you make this decision, the cheaper it is,” says Lines.

“This is an emerging infectious disease disaster that we can still prevent – but only if we act decisively now.”

Messenger says bed nets and insecticide sprays hold action, but they won’t hold back against the mosquito spread. “To push back, you have to think of more source reduction,” she says.

Integrated strategies that include household behavior change and monitoring programs, as well as conventional control measures, can work, Messenger and colleague Lines say.

“We have options [we need] The coordination, the money and the political will do it, ”says Messenger.

This piece was produced by SciDev.Net’s English desk for sub-Saharan Africa.

References

Marianne Sinka and Others A New Malaria Vector in Africa: Predicting Anopheles Stephensi Area of ​​Expansion and Identifying Urban Population at Risk (PNAS, September 14, 2020)

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