An unusual malaria outbreak linked to an invasive mosquito | Science

Scientists have linked invasive mosquitoes to an unusual malaria outbreak in Ethiopia. Anopheles stephensiA native of South Asia, it was first identified in Africa a decade ago in the Republic of Djibouti, which borders Ethiopia. It has since spread to at least four other countries in southern Africa. Now, amid long-standing questions about whether the insect’s presence significantly boosts malaria cases on the continent, researchers have confirmed that mosquitoes living close to people’s homes are more likely to contract the disease during the unusually dry season.

The finding, reported today at the American Society of Tropical Medicine and Hygiene (ASTMH) meeting in Seattle, is the most direct evidence that the invasive insect is linked to the rise in malaria, says Martin Donnelly, an evolutionary geneticist at the Liverpool Tropical School. Non-study medicine (LSTM). “This is a big step forward” in understanding how Moment. Stephens Malaria is likely to make the fight against malaria much more difficult in Africa, where it kills more than half a million people every year, most of them children under the age of 5.

Unlike most mosquitoes that transmit the parasites that cause malaria in Africa, Moment. Stephens is a city dweller. Most African mosquitoes lay their eggs in rainy season ponds, but it thrives in artificial water sources such as cisterns and clean drinking water barrels. This allows the insect to remain active during dry seasons, which traditionally provide a respite from disease.

Malaria cases in Djibouti and elsewhere increased at the same time Moment. Stephens was identified, but scientists weren’t sure whether the new mosquito or other factors were to blame. To better understand the role of the invasive insect, Fitsum Tadesse, a molecular biologist at the Armauer Hansen Research Institute in Addis Ababa, Ethiopia, and colleagues tracked malaria cases in Dire Dawa, eastern Ethiopia. year In 2019, a total of 205 incidents occurred in the city throughout the year. This year, Dire Dawa recorded more than 2,400 cases in the first half of the year.

Tadesse and colleagues tested family members of 80 malaria patients and compared them with family members of 210 people without the disease. They found that household members of malaria patients were 5.6 times more likely to be infected than members of control households. Malaria-infected households have more mosquito breeding habitats within 100 meters of their homes than control households, the team reports today at the ASTMH meeting. Most importantly, 97% of adult mosquitoes were collected Moment. Stephens.

The finding is an important confirmation of this Moment. Stephens It’s responsible for the sudden increase in malaria cases, says Marianne Sinka, an entomologist at the University of Oxford who studies malaria-carrying mosquitoes but was not involved in the study.

Anne Wilson, an epidemiologist tracking the spread Moment. Stephens Agrees with – but not involved – colleagues in LSTM in Sudan and Ethiopia. He says the new species was the prime suspect in the outbreaks, but there was no direct evidence. Again, he says, more research is needed to confirm the species’ role in other regions.

The rise of invasive mosquitoes is bad news for malaria control across Africa. It can thrive not only in areas that are safe from malaria epidemics, but also in its strains. Moment. Stephens Those found in Africa are also resistant to most commonly used insecticides, so bed nets treated with them do not kill insects. And they prefer to rest in animal shelters – barns or stables – rather than human homes, which makes them difficult to target. Tadesse is suspicious Moment. Stephens already more widespread than six known African countries, traveling in cargo containers. “You can probably find it in all corners of the continent.”

Public health officials have stepped up efforts to research and control mosquitoes, with the World Health Organization announcing a new initiative in September to stop its spread. Creative approaches will be needed, Donnelly says. Moment. Stephens it likes to feed on livestock, he notes, so treating livestock with insecticides can help. The most promising strategies target water sources, most experts agree. One tactic is to keep cisterns, wells, and other water storage areas closed to prevent adults from laying eggs in them. Another option is to add an insecticide that targets immature mosquitoes in the larval stage.

Wilson notes that these approaches can have side benefits. Mosquitoes inside Aedes the breed that transmits dengue and other diseases also breed in cisterns and wells, so control methods can help control these diseases as well.

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