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Background: Triatomines, which are the vectors of Trypanosoma cruzi, have been considered to be exclusive blood feeders for more than 100 years, since the discovery of Chagas disease., Methods: We offered artificial sugar meals to the laboratory model-insect Rhodnius prolixus, which is considered a strict haematophagous insect. We registered feeding by adding colorant to sugar meals. To assess putative phytophagy, fruits of the tomato Solanum lycopersicum were offered to R. prolixus and the presence of tomato DNA was assessed in the insects using PCR. We also assessed longevity, blood feeding and urine production of fruit-exposed triatomines and control insects., Results: All instars of R. prolixus ingested sugar from artificial sugar meals in laboratory conditions. First instar R. prolixus ingested plant tissue from S. lycopersicum fruits, and this increased the amount of blood ingested and urine excreted. Decreased mortality was also observed after blood feeding. Exposure to S. lycopersicum increased longevity and reduced weight loss caused by desiccation., Conclusions: We describe here the first report of sugar feeding and phytophagy in a species that was considered to be a strict blood-feeder for over a century. We suggest that local plants might be not merely shelters for insects and vertebrate hosts as previously described, but may have a nutritional role for the maintenance of the triatomine vectors. The description of sugar and plant meals in triatomines opens new perspectives for the study and control of Chagas Disease.

Background: Phlebotomine sand flies transmit the haemoflagellate Leishmania, the causative agent of human leishmaniasis. The Leishmania promastigotes are confined to the gut lumen and are exposed to the gut microbiota within female sand flies. Here we study the colonisation resistance of yeast and bacteria in preventing the establishment of a Leishmania population in sand flies and the ability of Leishmania to provide colonisation resistance towards the insect bacterial pathogen Serratia marcescens that is also pathogenic towards Leishmania., Methods: We isolated microorganisms from wild-caught and laboratory-reared female Lutzomyia longipalpis, identified as Pseudozyma sp. Asaia sp. and Ochrobactrum intermedium. We fed the females with a sugar meal containing the microorganisms and then subsequently fed them with a bloodmeal containing Leishmania mexicana and recorded the development of the Leishmania population. Further experiments examined the effect of first colonising the sand fly gut with L. mexicana followed by feeding with, Serratia marcescens, an insect bacterial pathogen. The mortality of the flies due to S. marcescens was recorded in the presence and absence of Leishmania., Results: There was a reduction in the number of flies harbouring a Leishmania population that had been pre-fed with Pseudozyma sp. and Asaia sp. or O. intermedium. Experiments in which L. mexicana colonised the sand fly gut prior to being fed an insect bacterial pathogen, Serratia marcescens, showed that the survival of flies with a Leishmania infection was significantly higher compared to flies without Leishmania infection., Conclusions: The yeast and bacterial colonisation experiments show that the presence of sand fly gut microorganisms reduce the potential for Leishmania to establish within the sand fly vector. Sand flies infected with Leishmania were able to survive an attack by the bacterial pathogen that would have killed the insect and we concluded that Leishmania may benefit its insect host whilst increasing the potential to establish itself in the sand fly vector. We suggest that the increased ability of the sand fly to withstand a bacterial entomopathogen, due to the presence of the Leishmania, may provide an evolutionary pressure for the maintenance of the Leishmania-vector association.