Impact of specifics phytochemicals in nectar on insecticide resistance of the mosquito Anopheles gambiae

Nectar is the main energy source for mosquitoes, and its phytochemicals contribute to the physiological maintenance of nectar-feeding insects. However, their role in shaping insecticide resistance phenotypes remains poorly understood. To address this, we investigated how specific dietary components affect resistance in Anopheles gambiae s.l. We conducted three experiments in which Anopheles gambiae s.l. females were fed their assigned diets from emergence and exposed to 0.25% or 5% deltamethrin in WHO tube tests at 4–5 days old. In the first experiment, mosquitoes were fed sucrose, glucose, fructose, or trehalose at low (1.97 kcal) or high (19.7 kcal) concentrations. Mortality was highest in mosquitoes fed trehalose (84.1 %), followed by fructose (74.1 %), sucrose (67.9 %), and glucose (67.1 %). Lower concentrations resulted in higher mortality (87.1 %) than higher concentrations (59.2 %). No interaction between sugar type and concentration was detected. In the second, mosquitoes were fed 10% glucose supplemented with 0, 50, or 200 ppm caffeine. Mortality increased with caffeine concentration, from 11.4% (0 ppm) to 15.3% (50 ppm) and 41.0% (200 ppm). In the last, they fed 10% glucose with or without vitamin C and/or hydrogen peroxide. Mortality was higher without vitamin C (32.5%) than with it (20.4%), and higher with hydrogen peroxide (34.6%) than without (18.1%). No interaction between the two compounds was detected. Overall, our study highlights the potential of specific phytochemicals to enhance insecticide efficacy when strategically incorporated into vector control tools.