Molecular Drivers of Insecticide Resistance in Malaria Vectors

Presenting to an audience of some 600 online attendees at the Global Mosquito Resistance Management Summit, Professor Charles S. Wondji of The Liverpool School of Tropical Medicine opened his presentation by outlining the dangers of vector resistance in Africa. Wondji reported that vector control has successfully reduced malaria cases by 70 percent since 2000 but increasing insecticide resistance in malaria vectors poses new challenges. He gave a startling example where resistant mosquitoes often survive inside the very bed nets designed to kill them.

“What’s happened in central Africa is not the same as in southern or east Africa. So that means that it’s not one size fits all in terms of implementing control programs.”

Wondji provided an overview of the genetic basis of resistance and its external drivers in Africa, including agricultural practices. Because the agricultural sector uses the same limited insecticides as the public health sector, he explained, vectors often develop resistance before the insecticides are even used for public health.

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He went on to highlight the importance of minimizing vector resistance, which — if not managed correctly — could lead to increased mortality upwards of 260,000 malaria deaths per year.

Wondji then illustrated the design of a DNA-based diagnostic tool used to detect one resistance mechanism, the p450 allele. He demonstrated the role this tool plays in a bed net experiment in Cameroon, which revealed the efficacy of PBO-based nets to block p450 resistant mosquitoes. He warned, however, that when mosquitoes develop double resistant alleles, the effect is additive and the percentage of vector survival increases.

Wondji concluded with more hopeful findings that rotating insecticides can, in many cases, restore susceptibility of the vector populations. He recommended methods like mixture rotation and mosaics to limit the frequency of resistance.