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Kenyan Mosquitoes Not Insecticide Resistant - 2004-06-28

Mosquitoes in Kenya have not developed widespread resistance to insecticide, as feared, after a major trial of insecticide-treated bed nets. That's the word from another new study in the American Journal of Tropical Medicine and Hygiene. But the researchers caution that insecticide resistance may still develop into a more serious problem. A study involving some 55,000 people in Kenya found that insecticide-treated bed nets reduced mosquito populations and malaria transmission by 90 percent or more.

But there has been concern that those benefits will not last, as mosquitoes develop resistance to the insecticide. The latest research found that the percentage of mosquitoes with one resistance trait doubled over the course of the study but was still only about eight percent.

Study author Nora Besansky at Notre Dame University says that's not enough to be a problem. "We were very encouraged by this result. Whatever resistance is out there at the moment doesn't seem to be affecting the ability of the bed nets to kill, or at least drive away, the mosquitoes," she says.

But Professor Besansky cautions that resistance to the insecticide may become a problem in the future because evolution does not stand still. She says researchers need to be vigilant for resistance, because if the insecticide currently used fails, there are no others available as cheaply.