Malaria Interventions Targeting Older Mosquitoes Could Prevent Insecticide Resistance, Researchers Say
Malaria interventions that target older mosquitoes, which are more likely to transmit malaria, could prevent the development of insecticide resistance, Pennsylvania State University researchers Andrew Read and Matthew Thomas write in a perspective piece published Tuesday in the journal PLoS Biology, the Independent reports.
According to the perspective piece, a mosquito contracts malaria by feeding on blood, and the parasite takes about 10 to 14 days to migrate to the insect's salivary glands, after which the mosquito can transmit malaria to humans. Read, biology and entomology professor at Pennsylvania State, said "It is one of the great ironies of malaria. Most mosquitoes do not live long enough to transmit the disease." He added, "To stop malaria, we need to kill only the old mosquitoes." However, current insecticides target all mosquitoes, which "imposes an enormous selection in favor of insecticide-resistant mosquitoes," Read said. According to the Independent, insecticide resistance also can spread quickly among mosquito populations, thus rendering the chemicals ineffective as malaria interventions.
However, slow-acting insecticides that target mosquitoes at a later stage in their life cycle are less likely to contribute to insecticide resistance because they allow younger mosquitoes to continue breeding, the Independent reports. Thomas, a professor at Pennsylvania State, said he is working with colleagues to develop a "fungal pesticide that kills mosquitoes late in life." Thomas said public health workers could use the insecticide to spray walls or treat insecticide nets, which would allow mosquitoes to become "infected by the fungal spores." According to Thomas, the fungi would take 10 to 12 days to kill a mosquito. Therefore, the insecticide would affect only older insects, thus reducing the need for mosquitoes to develop resistance. According to the scientists, research on malaria and mosquito lifespan in Africa and Papua New Guinea indicates that killing mosquitoes later in life reduces the number of infectious bites by about 95% (Connor, Independent, 4/7).
The perspective piece is available online.