Largest genetic study of Anopheles gambiae highlights spread of insecticide resistance

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The largest genetic study of mosquitoes has revealed the spread of insecticide resistance between regions in Africa and has uncovered several rapidly evolving resistance genes. It is hoped these findings could lead to genetic tools for monitoring resistance and managing insecticide use.

The study, published recently in Nature, was part of the Anopheles gambiae 1000 genomes project (Ag1000G). Led by the Wellcome Trust Sanger Institute (Cambridge, UK) in collaboration with 20 other institutions, the project was established in 2014 to sequence the genomes of mosquitoes collected from across Africa.

The researchers discovered that the A. gambiae mosquitoes collected in Africa were genetically more diverse than previously thought, which may explain the rapid evolution of resistance.

Mosquito control efforts have previously relied on insecticide-treated bed nets and insecticide spraying, making evolution of resistance a threat to malaria control in Africa, as author, Martin Donnelly (Liverpool School of Tropical Medicine, UK) explained: “We know that mosquito populations are rapidly evolving resistance to insecticides, which is a serious threat to the future of malaria control in Africa. We have been able to see that a diverse array of genes linked to insecticide resistance are under very strong selection, confirming that they are playing an important role in the evolution of insecticide resistance in natural mosquito populations. Our study highlights the severe challenges facing public efforts to control mosquitoes and to manage and limit insecticide resistance.”

There is research ongoing into novel control strategies, for example, using CRSPR–Cas9 to make mosquitoes infertile. However, the team commented that gene drive might be unlikely to work in these mosquitoes due to the high genetic variability, although their work did highlight less variable targets that potentially could be more suitable.

Author, Mara Lawniczak from the Wellcome Trust Sanger Institute, commented: “The diversity of mosquito genomes was far greater than we expected. Such high levels of genetic variation poise mosquito populations to rapidly evolve in response to our efforts to control them whether that be with insecticides or any other control measure, including gene drive.”

Lead author, Alistair Miles, (University of Oxford, UK and the Wellcome Trust Sanger Institute) concluded: “The data we have generated are a unique resource for studying how mosquito populations are responding to our current control efforts, and for designing better technologies and strategies for mosquito control in the future. More data will be needed to fill in the geographical gaps and study how mosquito populations change over time and in response to specific control interventions. However, this study demonstrates a clear path towards building a new and much-needed source of intelligence to support the campaign to eradicate malaria in Africa.”

Sources: www.eurekalert.org/emb_releases/2017-11/wtsi-lgs112817.php

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