The effect of larval cigarette exposure on the life history of the major malaria vector Anopheles arabiensis (Diptera: Culicidae)

Abstract

Anopheles arabiensis typically breeds in clean, temporary bodies of water. This species, however, is adapting to breeding in polluted water. This has the effect of pollutants being non-insecticidal forms of selection pressure driving insecticide resistance. Cigarette butts are common plastic pollutants which are complex toxicants that would include nicotine pollutants. This is of concern as the neonicotinoid clothianidin is suggested as a potential vector control insecticide. As such, there is a risk that larval exposure to cigarette pollution could alter the efficacy of this insecticide. This study aimed to examine the effect of larval cigarette exposure on the life history of laboratory-reared An. arabiensis, as well as elucidate the role of nicotine in these effects. Two laboratory strains of An. arabiensis were used, the insecticide susceptible SENN and the resistant SENN-DDT strain. The effects of cigarette and nicotine exposure on key life history traits were assessed. SENN-DDT laid more eggs in cigarette-polluted water than SENN but developed significantly slower in polluted water. Larval cigarette selection increased adult longevity in SENN-DDT, but reduced longevity in SENN. Larval selection did not alter neonicotinoid tolerance in males of either strain, or female SENN. Nicotine selection increased tolerance to both neonicotinoids, but cigarette selection only increased clothianidin tolerance in SENN-DDT females. Insecticide resistant An. arabiensis therefore had an advantage in cigarette polluted environments. Selection for cigarette tolerance only increased neonicotinoid tolerance where insecticide resistance was already present. Therefore, larval cigarette exposure may only have a limited effect on neonicotinoid efficacy for malaria control.