Resistance to the pyrethroid deltamethrin has increased in An. gambiae s.s. since 2011, possibly due to the scale-up in distribution of long-lasting insecticide-treated bed nets. Resistance management strategies are recommended using different classes of insecticides for IRS, and including the distribution of new-generation bed nets.

The main vector of malaria Anopheles gambiae maintains the transmission of malaria over long periods of time, because of the exceptional longevity and great ability to adapt to various environments. The aim of this study is to understand the impact of the predefined egg laying delay that characterizes long dry seasons on reproductive dynamics, feeding habit, and mortality rate of An. gambiae gravid females. For this purpose, gravid females of An. gambiae awaiting laying, previously fed with blood were kept under observation in cages for several weeks. Then, at the end of predefined periods of observation, these gravid females were individually made to lay eggs, and the development cycle of eggs was studied in comparison with eggs laid in the normal conditions (controls). In addition, the behaviour of feeding and mortality rate were studied in gravid females kept in cages, without laying, for several weeks. The results obtained show that the average egg-laying number of the control females varies little from that of the females obliged to retain their eggs in abdomen for several days. The hatching rate was 86.2% in no retention batches and 31% in a 50-day retention batches. The adults' emergence rate was 77.7% in no eggs retention batches and 18.3% for eggs laid after 50 days of retention. In the batches of eggs with 20 days of retention, the emergence rate decreased significantly 0.89 times compared to control batches. The feeding rate of gravid females increased from 96.7% at the 1 blood meal to 12.5% at the 10. In addition, the mortality rate of gravid females awaiting for laying is 0.36 times lower than that of no gravid females.

Background The SEMOS gold mine in Sadiola, southwestern Mali, has been implementing a malaria vector control programme for 15 y using indoor residual house spraying and sporadic larval control. Periodic screening of the vector populations have been carried out over the years to provide information to the control programme, mainly on vector species present and their insecticide resistance status. The data from five entomological surveys, carried out in 2006, 2011, 2014, 2016 and 2018, are presented. Methods Adult mosquitoes were collected resting on walls inside houses and on verandas. Insecticide susceptibility assays were carried out and mosquitoes subsequently identified by species using molecular assays. Results The major malaria vector mosquitoes, Anopheles gambiae and Anopheles arabiensis were abundant at each sampling period with Anopheles coluzzii and Anopheles funestus being rare or absent. Anopheles rivulorum was identified in 2006 and Anopheles leesoni in 2016. The presence of Anopheles rivulorum-like, identified for the first time in 2018, was not screened for in previous surveys. Insecticide susceptibility bioassays showed resistance in both A. gambiae and A. arabiensis to pyrethroids, carbamates and dichlorodiphenyltrichloroethane over the 12 y. Conclusions This is the first record of A. rivulorum-like west of Côte d'Ivoire. Resistance levels to the three classes of insecticides were variable but appeared to decrease after pyrethroids were discontinued for house spraying.