Insecticide resistance status and mechanisms in Aedes aegypti populations from Senegal

Abstract

Aedes aegypti is the main epidemic vector of arboviruses in Africa. In Senegal, control activities are mainly limited to mitigation of epidemics, with limited information available for Ae. aegypti populations. A better understanding of the current Ae. aegypti susceptibility status to various insecticides and relevant resistance mechanisms involved is needed for the implementation of effective vector control strategies. The present study focuses on the detection of insecticide resistance and reveals the related mechanisms in Ae. aegypti populations from Senegal. Bioassays were performed on Ae. aegypti adults from nine Senegalese localities (Matam, Louga, Barkedji, Ziguinchor, Mbour, Fatick, Dakar, Kédougou and Touba). Mosquitoes were exposed to four classes of insecticides using the standard WHO protocols. Resistance mechanisms were investigated by genotyping for pyrethroid target site resistance mutations (V1016G, V1016I, F1534C and S989P) and measuring gene expression levels of key detoxification genes (CYP6BB2, CYP9J26, CYP9J28, CYP9J32, CYP9M6, CCEae3a and GSTD4). All collected populations were resistant to DDT and carbamates except for the ones in Matam (Northern region). Resistance to permethrin was uniformly detected in mosquitoes from all areas. Except for Barkédji and Touba, all populations were characterized by a susceptibility to 0.75% Permethrin. Susceptibility to type II pyrethroids was detected only in the Southern regions (Kédougou and Ziguinchor). All mosquito populations were susceptible to 5% Malathion, but only Kédougou and Matam mosquitoes were susceptible to 0.8% Malathion. All populations were resistant to 0.05% Pirimiphos-methyl, whereas those from Louga, Mbour and Barkédji, also exhibited resistance to 1% Fenitrothion. None of the known target site pyrethroid resistance mutations was present in the mosquito samples included in the genotyping analysis (performed in > 1500 samples). In contrast, a remarkably high (20-70-fold) overexpression of major detoxification genes wasobserved, suggesting that insecticide resistance is mostly mediated through metabolic mechanisms. These data provide important evidence to support dengue vector control in Senegal.

High DDT resistance without apparent association to kdr and Glutathione-S-transferase (GST) gene mutations in Aedes aegypti population at hotel compounds in Zanzibar

“…Several genes of the family cytochrome P450 and glutathione-S-transferases (GSTes) have been associated with pyrethroid and DDT resistance in Ae . aegypti populations [ 35 , 67 , 68 ]. For instance, a study by Helvecio et al [ 69 ] found that several SNPs in GSTe2 correlated with temephos resistance in Ae .…”

“…aegypti resistance to DDT and presence of GSTe2 SNPs observed (L111S, C115F, P117S, E132A, I150V, E178A, and A198E). In Senegal, Sene et al [ 68 ] also reported higher phenotypic resistance to DDT and permethrin in Ae . aegypti but, similar to this study, no kdr mutations were detected.…”

Mosquito population structure, pathogen surveillance and insecticide resistance monitoring in urban regions of Crete, Greece

“…Each extraction pool was comprised of up to 30 mosquitoes of the same species, collected from the same or neighbouring municipalities and from the same collection date. The concentration and purity of the extracted (pooled) RNA was determined by spectrophotometry using a NanoDrop 2000c spectrophotometer (Thermo Fisher Scientific, Waltham, MA, US) and its integrity was confirmed via 1% w/v agarose gel electrophoresis as previously described [ 49 ].…”

“…albopictus and Cx . pipiens pools, based on the method described by [ 49 ] ( S1 and S2 Tables) . WNV-specific detection analysis was performed in all pools (regardless of the respective Pan-Flavivirus assay outcome) with a multiplex Real Time one step RT-PCR TaqMan assay that simultaneously detects and differentiates WNV-lineage 1 from WNV-lineage 2 [ 55 ].…”

Dengue vectors in Africa: A review

“…The susceptibility status of the targeted vector populations to the used insecticides were generally not studied [ 81 ]. Insecticides susceptibly tests should be always done before insecticide spraying operations [ 82 ]. To the best of our knowledge, larviciding using abate and larvivorous fishes to control dengue vectors were only used in Cabo Verde.…”