Impact of field‐realistic doses of glyphosate and nutritional stress on mosquito life history traits and susceptibility to malaria parasite infection

Abstract

Glyphosate is the world's most widely used herbicide. The commercial success of this molecule is due to its nonselectivity and its action, which would supposedly target specific biosynthetic pathways found mainly in plants. Multiple studies have however provided evidence for high sensitivity of many nontarget species to glyphosate and/or to formulations (glyphosate mixed with surfactants). This herbicide, found at significant levels in aquatic systems through surface runoffs, impacts life history traits and immune parameters of several aquatic invertebrates' species, including disease‐vector mosquitoes. Mosquitoes, from hatching to emergence, are exposed to aquatic chemical contaminants. In this study, we first compared the toxicity of pure glyphosate to the toxicity of glyphosate‐based formulations for the main vector of avian malaria in Europe, Culex pipiens mosquito. Then we evaluated, for the first time, how field‐realistic dose of glyphosate interacts with larval nutritional stress to alter mosquito life history traits and susceptibility to avian malaria parasite infection. Our results show that exposure of larvae to field‐realistic doses of glyphosate, pure or in formulation, did not affect larval survival rate, adult size, and female fecundity. One of our two experimental blocks showed, however, that exposure to glyphosate decreased development time and reduced mosquito infection probability by malaria parasite. Interestingly, the effect on malaria infection was lost when the larvae were also subjected to a nutritional stress, probably due to a lower ingestion of glyphosate.

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

“…Mosquitoes were collected in the field and maintained in insectary under standard conditions (26 ± 1 • C, 70% ± 5% RH, and 12 h light/12 h dark photoperiod) since August 2017. In a previous study, we showed that the mosquito line used here was not resistant to imidacloprid (LC50: 30 µg/L; see [48]). Mosquito eggs used in this study were obtained by feeding 50 females on one healthy bird (Serinus canaria).…”

“…We observed no effects of this pesticide on any of the parameters examined in this study. Based on the analysis of survival rates of Culex pipiens larvae 72 h after exposure to different doses of imidaclopird, we demonstrated in a previous study that the mosquito line used in this experiment was not resistant to this pesticide (concentrations of imidaclopird that kills 50% of the test animals (LC 50 ): 30 µg/L, see [48]). The fact that no effect was observed in the present study is probably explained by the low concentrations of imidacloprid used (3 µg/L in water and 0.8 µg/Kg in sugar solution).…”

“…It is thus not possible to rule out that these rearing conditions mask a potential effect of exposure to low concentrations of imidacloprid. A recent study conducted on the same biological system showed that exposure to a low dose of glyphosate associated with nutritional stress tends to increase the probability of being infected by avian malaria parasite [48].…”

“…[42][43][44]). Numerous biotic and abiotic stresses can impact the life history traits and the immunocompetence of these vectors, and ultimately impact the transmission of pathogens [45][46][47][48][49]. Here we assessed the consequences of larval and/or adult exposure to imidacloprid, one of the most widely used pesticides worldwide, on Culex pipiens life history traits and susceptibility to avian malaria parasite infection.…”

Ecological Effects on the Dynamics of West Nile Virus and Avian Plasmodium: The Importance of Mosquito Communities and Landscape

“…For example, the interactions between pathogens and mosquitoes may be determined by the presence of pollutants derived from human activities. Culex pipiens larvae fed a standard diet had higher avian Plasmodium prevalence when exposed to the herbicide glyphosate [ 136 ]. In addition, antibiotics, and other personal care products in waters in which mosquitoes breed may affect mosquito development and the epidemiology of mosquito-borne pathogens [ 137 ].…”