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Malaria Mosquitoes Sterilised by Bed Nets

The use of a new combination of chemicals on insecticide-treated bed nets (ITNs) could maintain the long-term effectiveness of the world’s best weapon against malaria infection.

“We know that ITNs dramatically reduce malaria infection and deaths in endemic regions by forming a protective barrier,” said A/Prof Greg Devine of the QIMR Berghofer Medical Research Institute. “At the moment, though, only pyrethroid insecticides are approved by the World Health Organisation for ITNs, and there have been worrying signs that mosquitoes are developing pyrethroid resistance, potentially undermining the effectiveness of the nets.”

However, a study published in PLOS ONE has now shown that combining a pyrethroid insecticide with a powerful chemosterilant known as PPF makes adult mosquitoes sterile. “Resistant mosquitoes spend more time at the nets, get a bigger dose of the PPF and are sterilised. Over time, that reduces the proportion of pyrethroid-resistant insects in the population,” Devine said.

“PPF doesn’t kill adult mosquitoes, so we don’t want to use it on its own because even a sterile mosquito might transmit malaria. But when you combine PPF with pyrethroids it ensures that those really important mosquito-killing insecticides retain their efficacy. That’s crucial for the continued success of malaria control in large parts of sub-Saharan Africa where insecticide resistance is now emerging.”

PPF is already available for mosquito control, and is approved as safe for humans.

“What this finding might do is get us off the treadmill … where for decades we’ve developed insecticides, used them universally because they’re effective, and then seen mosquitoes develop a resistance to them,” Devine said. “By combining the chemicals we can prevent the development of resistance, protect effective chemistries and conserve the sustainability of our best malaria control tools.”