The largest genetic study of mosquitoes has found their ability to resist insecticides is evolving rapidly and spreading across Africa, putting millions of people at higher risk of contracting malaria.

British scientists who led the work said mosquitoes’ growing resistance to control tools such as insecticide-treated bed nets and insecticide spraying, which have helped cut malaria cases since 2000, now threatens “to derail malaria control” in Africa.

“Our study highlights the severe challenges facing public efforts to control mosquitoes and to manage and limit insecticide resistance,” said Martin Donnelly of the Liverpool School of Tropical Medicine, who worked on the study with a team from Britain’s Wellcome Trust Sanger Institute.

Latest World Health Organization (WHO) data show that 216 million people were infected last year with the malaria parasite, which is transmitted by blood-sucking Anopheles mosquitoes.

The disease killed 445,000 people in 2016, the majority of them children in sub-Saharan Africa.

To understand how mosquitoes are evolving, the researchers sequenced the DNA of 765 wild Anopheles mosquitoes taken from 15 locations across eight African countries. Their work, published in the journal Nature on Wednesday, created the largest data resource on natural genetic variation for any species of insect.

Analyzing the data, the scientists found that the Anopheles gambiae mosquitoes were extremely genetically diverse compared with most other animal species. This high genetic diversity enables rapid evolution, they said, and helps to explain how mosquitoes develop insecticide resistance so quickly.

The genome data also showed the rapid evolution insecticide resistance appeared to be due to many previously unknown genetic variants within certain genes. The scientists said these genetic variants for insecticide resistance were not only emerging independently in different parts of Africa, but were also being spread across the continent by mosquito migration.

Michael Chew, an infection and immunobiology expert at Britain’s Wellcome Trust global health charity which helped fund the research, said the findings underlined the importance of pushing scientific research ahead to tackle malaria.

“This species is a major transmitter of malaria and the unexpectedly high genetic diversity found by scientists poses fresh questions for those in malaria research and control programs,” he said in a statement.

“Global efforts to tackle malaria through effective vaccines, insecticides and the best drug combinations require urgent, united action by scientists, drug companies, governments and the WHO.”
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