Unusual outbreak of malaria linked to invasive mosquitoes | Sciences

Scientists have linked an invading mosquito to an unusual outbreak of malaria in Ethiopia. Anopheles StephensNative to 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 sub-Saharan Africa. Now, amid lingering questions about whether the insect’s presence is significantly driving malaria cases on the continent, researchers have confirmed that people infected in the uncommon dry season for outbreaks were more likely to live mosquitoes near their homes.

The discovery, reported today at the American Society of Tropical Medicine and Public Health (ASTMH) meeting in Seattle, is the most direct evidence to date linking the invasive insect to increased malaria cases, says Martin Donnelly, an evolutionary geneticist at the Liverpool School of the Tropics. medicine (LSTM) who was not involved in the study. “It’s a big step forward” in understanding how to do it that. Stephensey It is likely to make malaria more difficult to control in Africa, where it kills more than half a million people each year, most of them children under the age of five.

Unlike most mosquitoes in Africa that transmit malaria-causing parasites, that. Stephensey of the city’s residents. Most African mosquitoes lay their eggs in rainy season ponds, but they thrive in artificial water sources such as cisterns and barrels of clean drinking water. This enables the insect to remain active during dry seasons, which traditionally provides a respite from disease.

In Djibouti and elsewhere, malaria cases rose at the same time that. Stephensey It was identified, but scientists weren’t sure if 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 traced malaria cases to Dire Dawa, a city in eastern Ethiopia that experienced a major outbreak earlier this year. general. In 2019, the city recorded just 205 cases for the whole 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 to family members of 210 people without the disease. They found that family members of malaria patients were 5.6 times more likely than members of the control family. The team reported today at an ASTMH meeting that malaria-affected households also had mosquito breeding habitats 100 meters more from their homes than control households. Most importantly, 97% of adult mosquitoes were collected that. Stephensey.

The discovery is an important confirmation that. Stephensey Responsible for the sudden increase in malaria cases, says Marian Senca, an entomologist at Oxford University who studies mosquitoes that transmit malaria but was not involved in the study.

Epidemiologist Ann Wilson, who has been tracking the spread of that. Stephensey In Sudan and Ethiopia with her LSTM colleagues – but who were not involved in the work – they agree. She says the new species was the prime suspect in the outbreak, but direct evidence was missing. However, she says, more studies are needed to confirm the species’ role in other areas.

The rise of invasive mosquitoes is bad news for malaria control across Africa. Not only can it thrive in areas that have been safe from malaria outbreaks, but strains that. Stephensey which have been found in Africa are also largely resistant to the most commonly used insecticides, so bed nets treated with them do not kill the insects. They prefer to rest in animal shelters – sheds or sheds – rather than human homes, which makes targeting them more difficult. Tadesse suspected of it that. Stephensey It is already becoming more widespread than the six well-known African countries, riding shipping containers. “You will likely find it all over the continent.”

Public health officials have stepped up efforts to survey and control mosquitoes, with the World Health Organization in September announcing a new initiative to stem its spread. Donnelly says creative approaches will be needed. that. Stephensey He’s fond of feeding livestock, he notes, so treating livestock with insecticides may help. Most experts agree that the most promising strategies target water sources. One approach is to keep cisterns, wells, and other water storage sites covered so that adults cannot lay their eggs in them. Another option is to add an insecticide that targets immature mosquitoes in the larval stage.

Wilson notes that these methods can have side benefits. mosquitoes in Aedes The genus, which transmits dengue and other diseases, also reproduces in tanks and wells, so control methods can help control these diseases as well.

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