Applying Next-Generation Sequencing to the Genetics and Ecology of Rhodnius Pallescens, A Vector of Chagas Disease

Abstract

Chagas disease is a neglected tropical disease that affects an estimated eight million people, predominantly in impoverished areas throughout Latin America (WHO 2017). It is caused by the protozoan Trypanosoma cruzi, which is transmitted to humans and other mammals through the feces of domestic and sylvatic triatomine bugs (Feliciangeli et al. 2004). Past studies and control efforts have mainly targeted well-known domestic triatomine species (Fitzpatrick et al. 2015; Gürtler et al. 2007); however, there are several primarily sylvatic species, like Rhodnius pallescens, that also continue to transmit the parasite to humans (Pineda et al. 2008). R. pallescens poses a significant threat to reducing vector-borne Chagas disease transmission in Panama, yet it remains underinvestigated. Now, with Next-Generation Sequencing (NGS) and the genome sequencing of Rhodnius prolixus, we have powerful new approaches to study the biology and genetics of triatomine bugs. For this project, we applied the R. prolixus genome and highly sensitive NGS techniques to detect and quantify parasites, to measure genetic diversity within and across species, and to identify blood meal sources among R. pallescens samples. Our results detected the presence of both T. cruzi and T. rangeli within R. pallescens samples, estimated a within-R. pallescens genetic diversity of 0.463% and a divergence from R. prolixus of 4.53%, and confirmed multiple mammalian blood meal sources within each sample. These findings highlight several aspects related to the vector-parasite-host interactions of R. pallescens that could influence vector population dynamics, the frequency and spread of infected triatomine species, as well as T. cruzi transmission to humans. They also set the stage for the use of NGS to study other domestic and sylvatic triatomine bug species. Looking ahead, a comprehensive understanding of the genetics and ecology of all relevant domestic and sylvatic triatomine species will allow us to better characterize T. cruzi parasite transmission and the risk for human infection, which will ultimately lead to better vector control and Chagas disease prevention strategies.