Evidence of multiple mechanisms providing carbamate and organophosphate resistance in field An. gambiae population from Atacora in Benin

Background: insecticide resistance in anopheles gambiae s.l is a major concern to malaria vector contro programmes. in west africa,resistance is mainly due to target-site insensitivity arising from a single point mutation metabolic-based resistance mechanisms have also been implicated and are currently being investigated in wes africa. the aim of this study is to better understand the origins of carbamate and organophosphate resistance i an. gambiae population from atacora,benin in west africa methods: anopheles mosquitoes were reared from larvae collected in two districts (kouandé and tanguiéta) of th atacora department. mosquitoes were then exposed to who impregnated papers. four impregnated papers wer used: carbamates (0.1% bendiocarb,0.1% propoxur) and organophosphates (0.25% pirimiphos methyl,1 fenitrothion). pcr assays were run to determine the members of the an. gambiae complex,as well as phenotype for insensitive acetylcholinesterase (ache1). biochemical assays were also carried out to detect any increase in th activity of enzyme typically involved in insecticide metabolism (oxidase,esterase and glutathion-s-transferase) results: 769 female of an. gambiae mosquitoes from kouandé and tanguiéta were exposed to bendiocarb propoxur,pirimiphos methyl and fenitrothion. bioassays showed resistance with low mortality to bendiocar (78.57% to 80.17%),propoxur (77.21% to 89.77%),and fenitrothion (89.74% to 92.02%). on the other hand,the sam populations of an. gambiae from kouandé and tanguiéta showed high susceptibility to pirimiphos methyl wit recorded mortality of 99.02% and 100% respectively. the low rate of ace-1r allele frequency (3.75% among survivor and 0.48% among dead) added to the high proportion of homozygous susceptible specimens which survived th who bioassays (8/28),suggest that the ace-1 mutation could not entirely explain anopheles gambiae resistance t carbamate and organophosphate. biochemical assays suggest that resistance in this population is mediated b metabolic resistance with elevated level of gst,mfo and nse compared to a susceptible strain an. gambia kisumu conclusions: anopheles gambiae populations resistance from atacora is multifactorial and includes target-sit mutation and metabolic mechanism. the co-implication of both resistance mechanisms in an. gambiae s.l may be serious obstacle for the future success of malaria control operations based on llins and irs. © 2014 aïkpon et al.