Effect of Neonicotinoid Exposure on the Life History Traits and Susceptibility to Plasmodium Infection on the Major Avian Malaria Vector Culex pipiens (Diptera: Culicidae)

Abstract

Culex pipiens complexes play an important role in the transmission of a wide range of pathogens that infect humans, including viruses and filarial worms, as well as pathogens of wildlife, such as the avian malaria parasite (Plasmodium spp.). Numerous biotic and abiotic stresses influence vector-borne pathogen transmission directly, through changes in vector density, or indirectly by changing vector immunocompetence, lifespan, or reproductive potential. Among these stresses, mosquito exposure to sublethal doses of pesticides could have important consequences. In addition to being exposed to pollutants in aquatic breeding sites, mosquitoes can also be exposed to chemicals as adults through their diet (plant nectar). In this study, we explored the impact of mosquito exposure at the larval and adult stages to one of the most commonly used pesticides, imidacloprid, a chemical belonging to the class of the neonicotinoids, on a set of life history traits ranging from development time to fecundity. We also studied the impact of this pesticide on the susceptibility of mosquitoes to infection by the avian malaria parasite, Plasmodium relictum. Surprisingly, we observed no effects of imidacloprid on any of the parameters examined. This result highlights the fact that Culex pipiens mosquitoes do not appear to be susceptible to imidacloprid when exposure doses are close to those measured in the field.

Implications of Sublethal Insecticide Exposure and the Development of Resistance on Mosquito Physiology, Behavior, and Pathogen Transmission

“…Many studies that investigated the effects of sublethal concentrations of pesticides on larval mosquitoes have reported that the physiology of an individual is not reset during metamorphosis to enable it to negate these effects in adults [80,81]. The effects of physiological stressors during the immature developmental stage on the adult can also be difficult to interpret, as they may have multiple outcomes, such as longer development times, male-biased sex ratios, and higher emergence rates and body sizes [82][83][84][85] or they offer null impacts, depending on the xenobiotics [86,87].…”

“…Studies have been carried out considering the interaction between adult mosquitoes derived from exposed larvae and malaria-causing parasites [86,87,94]. For instance, the exposure of Culex pipiens to the neonicotinoid imidacloprid did not affect the life history traits of individuals nor the susceptibility of adults to infection by avian malaria parasite (Plasmodium gallinaceum) [86]. The exposure of larvae of Cx.…”