A mosquito said to be a major vector for malaria infections has been found to be developing a resistance to the insecticide DDT.
Scientists at the University of Glasgow have uncovered the mutation for the first time in the Anopheles funestus mosquito, found in Eastern and Southern Africa.
The discovery of ‘knock-down resistance’ (kdr) – a major insecticide resistance mechanism in insect pests – may be linked to widespread contamination and historic stockpiles of DDT.
Once used widely in agriculture, DDT is now banned, but continues to affect the environment.
The discovery of the kdr mutation was found while the researchers were conducting whole-genome sequencing across multiple mosquito populations in Tanzania in order to better understand genetic variation in their populations.
When the researchers observed the unexpected resistance to DDT within one group, further analysis revealed the resistance to be linked with novel kdr mutations.
This finding suggests that prolonged environmental contamination may have exerted selective pressure on the mosquitoes, driving the emergence of this resistance.
Currently, chemical insecticides are central to the control of agricultural pests and disease vectors, such as mosquitoes.
The control of Anopheles mosquitos through the distribution of over 2.9 billion insecticide-treated bed nets (ITNs) has helped avert an estimated 633 million cases of malaria, a disease that still kills 600,000 yearly.
However, the widespread use of insecticides for agricultural pest and disease vector control also has detrimental consequences, including direct lethal and sub-lethal effects on human and animal health.
A key obstacle to sustainable malaria control is the evolutionary arms race between mosquitoes and insecticide-based mosquito control.
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Joel Odero, the lead author and PhD student at the University of Glasgow School of Biodiversity, One Health and Veterinary Medicine, and research scientist at Ifakara Health Institute said: “Our discovery raises concerns for the effectiveness of current malaria control methods, which rely heavily on insecticides.
“Understanding the development of insecticide resistance is key to combating malaria, a disease that kills hundreds of thousands of people annually, mostly in Africa.
“The research highlights how environmental legacies such as DDT pollution can shape modern public health challenges. The emergence of new resistance mechanisms could threaten decades of progress made in reducing malaria transmission and mortality.”
Francesco Baldini, University of Glasgow School of Biodiversity, One Health and Veterinary Medicine, added: “Our discovery sheds light on the far-reaching and unintended consequences of historical insecticide use, highlighting how past environmental contamination can shape the evolution of vector populations and impact current public health interventions.”
Fredros Okumu, University of Glasgow and Ifakara Health Institute, said: “An urgent follow-up study is required to monitor the evolution of vector DDT resistance and determine whether this type of resistance could occur in other insecticide families which are currently being rolled out in products across the African continent.”
The paper, ‘Discovery of knock-down resistance in the major African malaria vector Anopheles funestus,’ is published in Molecular Ecology.
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