What is the ‘true’ effect ofTrypanosoma rangelion its triatomine bug vector?

Abstract

The phrase, "T. rangeli is pathogenic to its insect vector, " is commonly found in peer-reviewed publications on the matter, such that it has become the orthodox view of this interaction. In a literature survey, we identified over 20 papers with almost the exact phrase and several others alluding to it. The idea is of particular importance in triatomine population dynamics and the study of vector-borne T. cruzi transmission, as it could mean that triatomines infected with T. rangeli have lower fitness than uninfected insects. Trypanosoma rangeli pathogenicity was first observed in a series of studies carried out over fifty years ago using the triatomine species Rhodnius prolixus. However, there are few studies of the effect of T. rangeli on its other vector species, and several of the studies were carried out with R. prolixus under non-physiological conditions. Here, we re-evaluate the published studies that led to the conclusion that T. rangeli is pathogenic to its vector, to determine whether or not this indeed is the "true" effect of T. rangeli on its triatomine vector.

A darker chromatic variation of Rhodnius pallescens infected by specific genetic groups of Trypanosoma rangeli and Trypanosoma cruzi from Panama

“…On the other hand, Gottdenker et al [ 28 ] postulated that T. rangeli / T. cruzi co-infection may confer a survival advantage for R. pallescens throughout adulthood. The same conclusion was reached by Peterson & Graham [ 27 ] who observed that R. prolixus experimentally co-infected with T. cruzi and T. rangeli have higher survival than bugs infected with just one of the species. In any case, a better evaluation of the occurrences and consequences of the infection with T. cruzi and/or T. rangeli in the dark variant of R. pallescens is necessary.…”

“…These high infection frequencies with T. rangeli seem to be inconsistent with the described pathological effects of T. rangeli for its vectors [ 26 ]. Recently, Peterson & Graham [ 27 ] also called attention to the lack of sufficient evidence to support the assumption that T. rangeli is pathogenic to all Rhodnius species. On the other hand, Gottdenker et al [ 28 ] postulated that T. rangeli / T. cruzi co-infection may confer a survival advantage for R. pallescens throughout adulthood.…”

Trypanosoma cruzi and Trypanosoma rangeli co-infection patterns in insect vectors vary across habitat types in a fragmented forest landscape

“…Prior studies in Panama have shown that T. cruzi infection in R. pallescens increases in response to anthropogenic disturbance (Gottdenker et al 2012). Furthermore, R. pallescens is frequently co-infected by T. cruzi congeneric T. rangeli , a trypanosome species that is entomopathogenic in experimentally infected Rhodnius prolixus , but is not believed to cause disease in mammals (Groot and Hernandez Mora, 1947; Groot et al 1951; Herbig-Sandreuter, 1957; Añez, 1981; Añez et al 1985; Nieves and Añez, 1992; Peterson and Graham, 2016). Trypanosoma rangeli is epidemiologically important, as it shares 60% of its antigens with T. cruzi , and the two parasites can cross-react in serological tests (Guhl and Marinkelle, 1982; Saldana & Sousa, 1996 a , b ; Guhl and Vallejo, 2003).…”

Remarkable genetic diversity of Trypanosoma cruzi and Trypanosoma rangeli in two localities of southern Ecuador identified via deep sequencing of mini-exon gene amplicons

“…Co-infection with T. cruzi and T. rangeli occurred in 73.5% of analyzed triatomines. Despite earlier reports suggesting T. rangeli infection is pathogenic to triatomines, more recent studies point to the need of more solid evidence before generalizing this claim [72]. Indeed, recent reports suggest co-infection increases R. prolixus survival, reproduction and fitness, which in turn would favor transmission of both parasite species [73].…”