Search

Background Mass distribution of insecticide treated nets (ITNs) is the principal malaria vector control strategy adopted by Niger. To better inform on the most appropriate ITNs to distribute, the Niger National Malaria Control Programme (NMCP), with the support of the U.S. President’s Malaria Initiative and its partners, conducted insecticide resistance monitoring in sixteen sites selected across the country. Methods The susceptibility of Anopheles gambiae sensu lato (s.l.) to chlorfenapyr and pyrethroid insecticides was investigated in nine sites in 2019 and fifteen sites in 2020, including eightfrom the previous year. The susceptibility status, pyrethroid resistance intensity at 5 and 10 times the diagnostic concentrations, and piperonyl butoxide (PBO) synergism with diagnostic concentrations of deltamethrin, permethrin and alpha-cypermethrin were assessed using WHO bioassays. Two doses (100 and 200 µg/bottle) of chlorfenapyr were tested using the CDC bottle assay method. Species composition and allele frequencies for knock-down resistance (kdr-west and kdr-east) and acetylcholinesterase (ace-1) mutations were further characterized using polymerase chain reaction (PCR). Results High resistance to all pyrethroids tested was observed in all sixteen sites during both years. Pre-exposure to PBO substantially increased susceptibility with average increases in mortality from 30 to 70% for deltamethrin, 0 to 60% for permethrin, and 5 to 70% for alpha-cypermethrin. Susceptibility to chlorfenapyr (100 ug/bottle) was recorded in all sites except in Tessaoua and Magaria where susceptibility was recorded at the dose of 200 ug/bottle. The kdr-e allele, investigated for the first time, was detected in the country. Both kdr-w and kdr-e were present in all 15 sites surveyed in 2020, at frequencies between 0.46–0.81 and 0.41–0.87, respectively. An. coluzzii was the predominant malaria vector species in the 16 sites surveyed for insecticide susceptibility followed by An. gambiae s.s. and An. arabiensis. Conclusion The data collected showed high resistance to pyrethroids with the involvement of various resistance mechanisms, which will guide the NMCP in making evidence-based decisions to better adapt vector control strategies and insecticide resistance management in Niger, starting with the introduction of new generation ITNs such as interceptor G2 and PBO ITNs for mass distribution campaigns, by targeting sites where the vector population showed susceptibility to chlorfenapyr or increased mortality using PBO synergism.

Une etude transversale a ete realisee dans la ville de Niamey pour tester lefficacite des deux larvicides sur des populations imaginales sauvages deCx pipenset dAn. gambiae s.lselon la methode de lOMS 2005. Les larvicides testes etaientBacillus thuringiensis(Bactivec),Bacillus sphaericus(Griselesf) et une combinaison de Bactivec + Griselesf. Les taux de mortalite et les analyses ont ete realises sur le logiciel R. Les taux de mortalite induits par les doses 5 ppm, 10 ppm, 100 ppm et 1000 ppm de Bactivec ont varie de 98% a 100%, superieurs au seuil de sensibilite definis par lOMS. La dose 5 ppm des deux autres formulations (Griselesf et Bactivec + Griselesf) a induit des mortalites inferieures a 90% contrairement a celle de Bactivec. ChezAn. gambiae, les DL50 et DL95 ont ete de 0.67 ppm et 3.00 ppm respectivementcontrairement aux deuxautres formulations (Griselesf et Bactivec+ Griselesf) qui ont presente des DL50 comme suit:Griselesf: DL50 = 1,99ppm et Bactivec+ Griselesf: DL50 = 1,35ppm, et DL95comme suit: Griselesf: DL95 = 13,64ppm et Bactivec+ Griselesf: DL50 = 9,63ppm). La situation a ete differente avec les larves deCulex pipiensoù les DLBactivec+ Griselesf avec une DL50 de 0,503 ppm et une DL95 de 0,81 ppm. Les deux biolarvicidesont presenteune activite larvicide variant dune espece de moustique a une autre. Le Bactiveca eteplus efficace chez les larves danopheles contrairement au Griselesf qui etait plus efficace sur les larves deCulex sp. La combinaison des deux biolarvicides (Bactivec+Griselesf) a ete plus efficace contre les especesde Culex sp. &nbsp