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A net for all reasons
Long-lasting insecticide-treated mosquito nets are the most widely used intervention for preventing transmission of malaria by anopheline mosquitoes. Their effectiveness is threatened by the development of resistance to pyrethroid insecticides enabling the mosquito to survive contact with the net. Olyset Duo is a new type of bed net treated with pyrethroid and a new insecticide, pyriproxifen, that disrupts the maturation of eggs in the ovaries of blood-fed mosquitoes. Ngufor and colleagues evaluated the capacity of the Olyset Duo net to control pyrethroid-resistant mosquitoes in laboratory tests and under household conditions in West Africa. The Olyset Duo net killed more pyrethroid-resistant mosquitoes than did the standard pyrethroid net and also sterilized any mosquitoes that survived exposure to the net. By preventing mosquito reproduction, the new net has the potential to reduce mosquito populations and malaria transmission in areas of high pyrethroid resistance.
Olyset Duo is a new long-lasting insecticidal net treated with permethrin (a pyrethroid) and pyriproxyfen, an insect growth regulator that disrupts the maturation of oocytes in mosquitoes exposed to the net. We tested the Olyset Duo net against pyrethroid-resistant Anopheles gambiae mosquitoes, which transmit malaria parasites, in laboratory bioassays and in a trial in Benin using experimental huts that closely resemble local habitations. Host-seeking mosquitoes that entered to feed were free to contact the occupied nets and were collected the next morning from exit traps. Surviving blood-fed mosquitoes were observed for effects on reproduction. Control nets were treated with pyrethroid only or pyriproxyfen only, and nets were tested unwashed and after 20 standardized washes. The Olyset Duo net showed improved efficacy and wash resistance relative to the pyrethroid-treated net in terms of mosquito mortality and prevention of blood feeding. The production of offspring among surviving blood-fed A. gambiae in the hut trial was reduced by the pyriproxyfen-treated net and the Olyset Duo net both before washing (90 and 71% reduction, respectively) and after washing (38 and 43% reduction, respectively). The degree of reproductive suppression in the hut trial was predicted by laboratory tunnel tests but not by cone bioassays. The overall reduction in reproductive rate of A. gambiae with the Olyset Duo net in the trial was 94% with no washing and 78% after 20 washes. The Olyset Duo net has the potential to provide community control of mosquito populations and reduce malaria transmission in areas of high insecticide resistance.
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