Malaria broke out this year in the Ethiopian city of Dire Dawa, which saw more than 10 times as many cases between January and May than in all of 2019.
What made this increase in cases unusual is that it occurred outside of the rainy season, when malaria typically emerges in Africa and in an urban area; malaria is more of a rural problem on the continent. Cities aren’t immune, but they don’t typically see these types of outbreaks.
Something new and insidious has arrived in the Horn of Africa. An invasive species of mosquito called Anopheles stephensi threatens to derail two decades of progress in malaria control. And it can bring the deadly disease to more of the continent’s rapidly growing cities.
“There is a real fear that more transmission could start in these areas that traditionally don’t have as much malaria,” said Arran Hamlet, a disease modeling expert at the US Centers for Disease Control and Prevention. And they don’t have infection control strategies in place at the same level.”
The new mosquito comes at a bad time in the fight against malaria.
The native mosquitoes of Africa have become increasingly resistant to insecticides. (Anopheles stephensi is already resistant). Furthermore, the malaria parasite is not only becoming harder to kill, but also harder to detect. Malaria strains that do not show up on rapid diagnostic tests are becoming more common.
“We don’t want all three to meet: drug resistance, diagnostic resistance, and the highly efficient vector [Anopheles stephensi]said Fitsum Girma Tadesse, a molecular biologist at the Armauer Hansen Research Institute in Ethiopia.
“What if they coexist? We don’t know,” he said. “It’s really dangerous. You can’t detect the parasite. You can’t kill it with a drug. And the mosquito is smart enough to evade your [control] mechanisms”.
Fitsum and his colleagues linked Anopheles stephensi to the Dire Dawa outbreak in a study presented at the American Society for Tropical Medicine and Hygiene in Seattle this month. It is the strongest evidence yet that the mosquito is increasing malaria rates in Ethiopia.
a different mosquito
Malaria fighters started the millennium strong.
With insecticide-treated bed nets, indoor insecticide spraying campaigns, and new artemisinin-based drugs, malaria deaths fell from nearly 900,000 in 2000 to about 560,000 in 2015. But since then, progress has stalled. .
And the tools that have worked until recently won’t help much against Anopheles stephensi.
“East [mosquito] it’s different and more insidious than some of the other malaria-carrying mosquitoes we’re used to seeing in sub-Saharan Africa,” said April Monroe, an epidemiologist at the Johns Hopkins Center for Communication Programs.
Malaria mosquitoes native to Africa prefer to bite people inside their homes late at night. That is why mosquito nets and indoor spraying have been so effective.
But Anopheles stephensi bites earlier in the night. When he goes looking for food, “people aren’t in bed yet, so they don’t get the same protection” from bed nets, Hamlet said.
He also prefers to take his blood meal outdoors. Or if it does bite indoors, it doesn’t rest there, so avoid indoor insecticides.
The habitat of the new mosquito is also different. Most malaria mosquitoes live in rural areas of Africa. But Anopheles stephensi is “really highly adapted to urban areas, which is not what we normally see,” Monroe said.
It likes to lay its eggs in water storage containers, which are especially common in Africa’s rapidly growing unplanned urban areas that lack running water, Fitsum said.
Native to South Asia, Anopheles stephensi was first seen on the African continent in Djibouti in 2012.
The small nation was on the brink of eliminating malaria at the time. He recorded just 27 cases that year. In 2020, there were more than 73,000.
In addition to Djibouti and Ethiopia, the mosquito has turned up in Sudan, Somalia and Nigeria.
One study estimates that the mosquito may put an additional 126 million people at risk of malaria in African cities.
In Ethiopia alone, Hamlet and his colleagues estimate that Anopheles stephensi could increase malaria cases by 50% and cost hundreds of millions of dollars to control.
“This is possibly a cheap option compared to letting Anopheles stephensi spread across the country,” Hamlet said. “There is a huge economic burden on both individuals and the broader economy at this level of malaria rise.”
However, the last thing African countries need is a new disease vector that is costly to control.
“Most malaria-affected countries have limited resources to deal with existing prevalent diseases,” Fitsum said.
Some relatively good news is that since Anopheles stephensi breeds in the same places as the mosquitoes that transmit yellow fever, chikungunya, and dengue fever, efforts directed at one would also control the others.
Fitsum says that covering water containers with Styrofoam beads can help prevent mosquitoes from laying eggs. He advises people to tightly cover water containers and throw away unneeded ones.
And keep using mosquito nets and indoor sprays, he added. The native mosquitoes are still out there.