Entomological baseline data on malaria transmission and susceptibility of Anopheles gambiae to insecticides in preparation for Indoor Residual Spraying (IRS) in Atacora, Benin

To implement indoor residual spraying (IRS), the department of Atacora was selected in Benin. Entomological surveys were performed before IRS implementation. Mosquitoes were sampled by Pyrethrum spray catch and were identified morphologically and by molecular methods. The Plasmodium falciparum circumsporozoite indices were measured by enzyme linked immunosorbent assay (ELISA). Molecular detection of pyrethroid knock down resistance and that of insensitive acetylcholinesterase were performed. Susceptibility status of Anopheles gambiae was determined using World Health Organization (WHO) bioassay tests to various insecticides. A. gambiae s.l. was the main species harvested in houses (81.71%) and A. gambiae s.s is practically the only member that was found. Both M and S forms were in sympatry, but the molecular S form was predominant (94.42%). A. gambiae s.l were susceptible to bendiocarb but fully resistant to organochlorine (DDT), permethrin and deltamethrin. Entomological inoculation rate vectors (EIR) was 6 infectious bites per man per month on average during the study period. The average of kdr and Ace-1 allelic frequency were 78 and 3%, respectively. A. gambiae s.l is characterized by a high endophilic behavior in Atacora, which is a good criterion for IRS implementation. The susceptibility to bendiocarb add to the low Ace-1 mutation frequency found in A. gambiae populations could lead to the use of bendiocarb for IRS.