Insecticidal effectiveness of nicotine from Nicotiana tabacum against species of Anopheles gambiae complex and Anopheles funestus group (Diptera: Culicidae) from the Luapula Province of Zambia

Abstract Background One of the main challenges affecting malaria control initiatives in sub-Saharan Africa is the swift and widespread emergence of insecticide resistance. Consequently, there is a need to explore alternative insecticides for controlling malaria vectors. This study investigated the effectiveness of tobacco extract on wild Anopheles mosquitoes during the dry season (October–November 2021) in Chebele village, Mwense District, Luapula Province, Zambia. Methods Wild Anopheles larvae were collected using the pipetting and dipping method along the Mwense stream and reared to the F 0 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). The solvent extraction method was used to extract tobacco compounds from tobacco leaves. Filter papers were impregnated with clothianidin (1.55% w/v; SumiShield ® 50WG) following standardized PMI-AIRS procedures. Clothianidin was used as a positive control, while distilled water served as a negative control. Non-blood-fed, 2–3-day-old female wild Anopheles mosquitoes were exposed to clothianidin (1.55% w/v) 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 the World Health Organization (WHO) bottle bioassay. The insectary-reared Kisumu strain ( An. gambiae sensu stricto) was used as a reference for the bioassays. Results Morphological identification of adult mosquitoes collected from 73 households showed that 98.03% were Anopheles funestus s.l. (n = 199), 1.48% were Anopheles gambiae s.l. (n = 3), and 0.49% were Culex species (n = 1). The bioassays were conducted on live wild adult Anopheles mosquitoes reared from field-collected larvae to F 0 adults prior to species determination, following World Health Organization guidelines; thus, efficacy outcomes reflect the total tested Anopheles population. Subsequent PCR analysis confirmed Anopheles funestus sensu stricto (s.s.) (n = 93; 46%) and Anopheles gambiae s.s. (n = 81; 40%) as the dominant members of the An. funestus group and An. gambiae complex, respectively. Tobacco extract (83.3% v/v) and clothianidin (1.55% (w/v) were found to have knockdown effect at 80 min of 94.05% (95% CI 90.50–97.70%) and 100.00% (95% CI 97.40–100.00%), respectively. Results showed that both clothianidin and tobacco extract elicited 100% mortality in adult wild Anopheles mosquitoes and the Kisumu strain after 24 h. The estimated LC 50 for tobacco extract on wild Anopheles mosquitoes was estimated at 38.77% v/v (95% CI 9.99–55.91% v/v), as determined by probit analysis. Conclusion Nicotiana tabacum leaf extract demonstrated insecticidal activity against wild An. gambiae s.s. and An. funestus s.s. under laboratory conditions, supporting its potential for further investigation as a plant-based vector control candidate. Additional field evaluations and formulation standardization are required before operational application can be considered.