Insecticide resistance status of indoor and outdoor resting malaria vectors in a highland and lowland site in Western Kenya

• Published in: PloS one 2021-03, Vol.16 (3), p.e0240771
• Main Authors: Owuor, Kevin O, Machani, Maxwell G, Mukabana, Wolfgang R, Munga, Stephen O, Yan, Guiyun, Ochomo, Eric, Afrane, Yaw A
• Format: Article
• Language: English
• Subjects: Animals; Anopheles - drug effects; Anopheles - genetics; Behavior; Bioassays; Biology and Life Sciences; Cages; Collections; Control; Culicidae; Data analysis; Deltamethrin; Drug therapy; Editing; Eggs; Entomology; Enzymes; Funding; Genetic aspects; Indoor environments; Insect Proteins - genetics; Insect Proteins - metabolism; Insecticide resistance; Insecticide Resistance - genetics; Insecticides; Insecticides - pharmacology; Kenya; Laboratories; Malaria; Malathion; Medical research; Medicine and Health Sciences; Metabolism; Microbiology; Mosquito Control; Mosquito Vectors - genetics; Mosquitoes; Mutation; Organophosphates; Outdoors; Oviposition; Peptidyl-Dipeptidase A - genetics; Peptidyl-Dipeptidase A - metabolism; Permethrin; Pesticide resistance; Piperonyl Butoxide - pharmacology; Prevention; Progeny; Public health; Pyrethroids; Reviews; Sea level; Social Sciences; Sucrose; Vector-borne diseases; Vectors; Voltage-Gated Sodium Channels - genetics; Voltage-Gated Sodium Channels - metabolism; Yaw
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0240771

Long Lasting Insecticidal Nets (LLINs) and indoor residual spraying (IRS) represent powerful tools for controlling malaria vectors in sub-Saharan Africa. The success of these interventions relies on their capability to inhibit indoor feeding and resting of malaria mosquitoes. This study sought to understand the interaction of insecticide resistance with indoor and outdoor resting behavioral responses of malaria vectors from Western Kenya. The status of insecticide resistance among indoor and outdoor resting anopheline mosquitoes was compared in Anopheles mosquitoes collected from Kisumu and Bungoma counties in Western Kenya. The level and intensity of resistance were measured using WHO-tube and CDC-bottle bioassays, respectively. The synergist piperonyl butoxide (PBO) was used to determine if metabolic activity (monooxygenase enzymes) explained the resistance observed. The mutations at the voltage-gated sodium channel (Vgsc) gene and Ace 1 gene were characterized using PCR methods. Microplate assays were used to measure levels of detoxification enzymes if present. A total of 1094 samples were discriminated within Anopheles gambiae s.l. and 289 within An. funestus s.l. In Kisian (Kisumu county), the dominant species was Anopheles arabiensis 75.2% (391/520) while in Kimaeti (Bungoma county) collections the dominant sibling species was Anopheles gambiae s.s 96.5% (554/574). The An. funestus s.l samples analysed were all An. funestus s.s from both sites. Pyrethroid resistance of An.gambiae s.l F1 progeny was observed in all sites. Lower mortality was observed against deltamethrin for the progeny of indoor resting mosquitoes compared to outdoor resting mosquitoes (Mortality rate: 37% vs 51%, P = 0.044). The intensity assays showed moderate-intensity resistance to deltamethrin in the progeny of mosquitoes collected from indoors and outdoors in both study sites. In Kisian, the frequency of vgsc-L1014S and vgsc-L1014F mutation was 0.14 and 0.19 respectively in indoor resting malaria mosquitoes while those of the outdoor resting mosquitoes were 0.12 and 0.12 respectively. The ace 1 mutation was present in higher frequency in the F1 of mosquitoes resting indoors (0.23) compared to those of mosquitoes resting outdoors (0.12). In Kimaeti, the frequencies of vgsc-L1014S and vgsc-L1014F were 0.75 and 0.05 respectively for the F1 of mosquitoes collected indoors whereas those of outdoor resting ones were 0.67 and 0.03 respectively. The ace 1 G119S mutation was present in