Guhl, F. | Search bioRxiv

bioRxiv2019

Is vectorial transmission of Trypanosoma cruzi an efficient route to support high infection rates in sylvatic hosts?"

Chagas disease is caused by the parasite Trypanosoma cruzi and it is transmitted to humans by the triatomine bug Rhodnius prolixus. The main insect vector in the Andean countries presents sylvatic and domestic cycles involving humans, insects and reservoirs (e.g small mammals). It is commonly assumed that vectorial transmission is the main route for parasite spread between hosts. Recent studies have reported high percentages (21-80%) of infected opossums (Didelphis marsupialis) in the sylvatic cycle, raising the question of whether such a high proportion of infected could be only maintained by vectorial transmission, a seemingly inefficient pathway. To address this question, we formulated a mathematical model that describes the sylvatic transmission dynamics considering vectors and hosts and parametrized with field data. Our results show that vectorial transmission it is not sufficient to explain such high percentages of infected host-mammals reported in the literature. Here we propose oral transmission as an alternate route of transmission that may increase the number of infected individuals found in field studies.

ecology↗

bioRxiv2018

Repeat-driven generation of antigenic diversity in a major human pathogen, Trypanosoma cruzi

Trypanosoma cruzi, a zoonotic kinetoplastid protozoan with a complex genome, is the causative agent of American trypanosomiasis (Chagas disease). The parasite uses a highly diverse repertoire of surface molecules, with roles in cell invasion, immune evasion and pathogenesis. Thus far, the genomic regions containing these genes have been impossible to resolve and it has been impossible to study the structure and function of the several thousand repetitive genes encoding the surface molecules of the parasite. We here present an improved genome assembly of a T. cruzi clade I (TcI) strain using high coverage PacBio single molecule sequencing, together with Illumina sequencing of 34 T. cruzi TcI isolates and clones from different geographic locations, sample sources and clinical outcomes. Resolution of the surface molecule gene structure reveals an unusual duality in the organisation of the parasite genome, a core genomic region syntenous with related protozoa flanked by unique and highly plastic subtelomeric regions encoding surface antigens. The presence of abundant interspersed retrotransposons in the subtelomeres suggests that these elements are involved in a recombination mechanism for the generation of antigenic variation and evasion of the host immune response. The comparative genomic analysis of the cohort of TcI strains revealed multiple cases of such recombination events involving surface molecule genes and has provided new insights into T. cruzi population structure.

genomics↗