Insecticidal effectiveness of nicotine from nicotiana tabacum against sub-species of anopheles gambiae s.l (Insecta: Diptera: Culicidae).

One of the main issues affecting malaria control initatives in sub-Saharan Africa is the swift and widespread emergence of insecticide resistance. Consequently, there is a need to explore alternative insecticides for the control of malaria vectors. This study investigated the effectiveness of tobacco extract on wild Anopheles mosquitoes during the October-November 2021 dry season in Chebele village in Mwense district of Luapula Province in Zambia. Wild Anopheles larvae were collected using pipetting and dipping method along Mwense stream and raised to F1 progeny. Wild Anopheles mosquitoes were identified using morphological taxonomic keys. Specimens belonging to the Anopheles gambiae complex and Anopheles funestus group were further identified by multiplex Polymerase Chain Reaction (PCR). Solvent extraction method was used to extract tobacco extract from tobacco leaves. A protocol was followed to
impregnant filter papers with 0.132g/ml clothianidin (SumiShield® 50WG), a chemical used as an indoor residual spraying insecticide in Zambia, as a positive control while distilled water as a negative control. Non-blood-fed 2 to 3 day old female wild Anopheles mosquitoes were exposed to clothianidin (0.132g/ml) and tobacco extract at different concentrations (25% v/v, 33.3% v/v, 50% v/v, 62.5% v/v, 71.43 v/v and 83.3% v/v) using WHO bottle bioassay. The laboratory reared Kisumu strain An. gambiae sensu stricto mosquitoes were used as reference for insecticide susceptibility tests. Two hundred and three (203) indoor biting mosquitoes were collected from 73 households using Prokopack Aspirator in order to determine the mosquito species in the study area. Morphological
identifications revealed that 96.06% were An. funestus s.l (n=195) , 0.99% were An. gambiae s.l (n=2) and 0.493% were Culex species (n=1). PCR results on wild mosquitoes indicated that An. funestus sensu stricto (s.s) (n=93;46%) and An. gambiae s.s (n=81;40%) were the dominant species within the An. funestus group and Anopheles gambiae complex, respectively. One hundred and forty two (142) wild female Anopheles species were exposed to clothianidin for
80 minutes and these were identified morphologically as An. funestus sensu lato (s.l) (n=108; 76.1%), An. gambiae s.l (n=30; 21.1%), An. pretoriensis (n=3;2.1%) and An. rufipes (n=1;0.7%). Similarly, 168 wild Anopheles species were exposed to tobacco extract and mosquitoes were identified morphologically as An. funestus s.l (n=96;57.1%), An. gambiae s.l (n=64;38.1%), An. coustani (n=1;0.6%) and An. rufipes (n=7;4.2%). Tobacco extract and clothinanidin recorded
100% mortality rate at 24 hours post exposure time. These results suggests that the tobacco extract can be considered as an alternative bioinsecticide for the control of malaria vectors.