Abstract
BackgroundBesides feeding on blood, females of the malaria vector Anopheles gambiae sensu lato readily feed on natural sources of plant sugars. The impact of toxic secondary phytochemicals contained in plant-derived sugars on mosquito physiology and the development of Plasmodium parasites remains elusive. The focus of this study was to explore the influence of the alkaloid ricinine, found in the nectar of the castor bean Ricinus communis, on the ability of mosquitoes to transmit Plasmodium falciparum.MethodsFemales of Anopheles gambiae and its sibling species Anopheles coluzzii were exposed to ricinine through sugar feeding assays to assess the effect of this phytochemical on mosquito survival, level of P. falciparum infection and growth rate of the parasite.ResultsRicinine induced a significant reduction in the longevity of both Anopheles species. Ricinine caused acceleration in the parasite growth rate with an earlier invasion of the salivary glands in both species. At a concentration of 0.04 g l−1 in An. coluzzii, ricinine had no effect on mosquito infection, while 0.08 g l−1 ricinine-5% glucose solution induced a 14% increase in An. gambiae infection rate.ConclusionsOverall, our findings reveal that consumption of certain nectar phytochemicals can have unexpected and contrasting effects on key phenotypic traits that govern the intensity of malaria transmission. Further studies will be required before concluding on the putative role of ricinine as a novel control agent, including the development of ricinine-based toxic and transmission-blocking sugar baits. Testing other secondary phytochemicals in plant nectar will provide a broader understanding of the impact which plants can have on the transmission of vector-borne diseases.Graphical abstract
Highlights
Besides feeding on blood, females of the malaria vector Anopheles gambiae sensu lato readily feed on natural sources of plant sugars
Coluzzii susceptibility to P. falciparum At a concentration of 0.04 g l−1, ricinine had no effect on An. coluzzii infection rate (LRT X2 = 0.06, df = 1, P = 0.81, Fig. 1a, left panel) or intensity (LRT X2 = 0.5, df = 1, P = 0.48, Fig. 1b, left panel)
Our results demonstrated that the consumption of ricinine in glucose solution decreased the lifespan of both An. gambiae and An. coluzzii, increased An. gambiae susceptibility to infection at a concentration of 0.08 g l−1 and accelerated parasite development in both mosquito species
Summary
Females of the malaria vector Anopheles gambiae sensu lato readily feed on natural sources of plant sugars. When ingested through a blood meal, the drugs or antibodies inhibit parasite development, thereby reducing or blocking malaria transmission from the mosquito to a human host [4]. Besides blood-feeding, the delivery of a transmission-blocking agent into a mosquito host can occur through mosquito sugar-feeding and/or contact [5,6,7]. Regarding the latter delivery route, Paton et al [8] showed that Anopheles exposure to atovaquone through treated surfaces before or shortly after Plasmodium falciparum infection can result in a full parasite arrest in the mosquito midgut
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