kill them slowly. A pesticide that acts later in life mosquitos could fight against the resistance.
Jim Gathany / CDC
Kill 'em fast, kill' em young. This was the unofficial motto of struggle against insects for the last 50 years. But a new study suggests that, at least in the case of malaria, the strategy may be flawed. By choosing insecticides that act more slowly, or that specifically target older mosquitoes, researchers might be able to prevent the development of pesticide resistance, a problem that has long plagued efforts against malaria.
The new study, published April 6 in PloS Biology , proposes a "new thinking" on the problem of resistance, said entomologist Bart Knols of Wageningen University in the Netherlands. "You might be able to keep insecticides in business for 60, 80 years, perhaps forever," he said. Insecticides can control malaria, but only in the short term. One by one, pesticides have been abandoned because mosquitoes have developed resistance, often several years after their introduction. The reason? In areas where spraying is intense, any mutation that confers resistance, even if only partial, is extremely beneficial to mosquitoes, it spreads rapidly. Today, insecticide resistance is a major problem for malaria control worldwide. This could have been prevented, medical entomologist Andrew Read of Pennsylvania State University, University Park, and colleagues say.
This is their idea. Insecticides that kill mosquitoes early in their life cycle continue to reproduce, creating an enormous selective pressure to become resistant. But if you want to fight against malaria, it is good to let mosquitoes breed; the trick is to prevent them from transmitting malaria. - They are only in middle age from 10 to 14 days
In their paper, the team present models that show that targeting these older mosquitoes could delay the emergence of resistance decades - and still reduce the number of infectious bites by 95%. Some of the same authors co-author of an article on a late killer fungus slow action in Science in 05. But other candidates exist, and existing insecticides spray doses lower, maybe in smart combinations, can also be a way to target older mosquitoes, they write.
knols applauded the idea but said there would also disadvantages. People who have sprayed their home, for example, would not be the immediate advantage of being rid of their problem of mosquitoes. "You'd have to explain that they will still have mosquitoes, and they will still be bitten, but malaria will go down," says Knols. "This could be a tough sell."
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