Unusual frequency of Trypanosoma cruzi DTU TcI and predominance of hybrid lineages in Triatoma infestans before and after control interventions in the Argentinian Chaco

Abstract

Transmission of Trypanosoma cruzi involves diverse hosts, vectors and parasitic genotypes, in different environments.In recent decades, the distribution of T. cruzi has altered due to urbanization of affected people andvectors. We implemented a longitudinal intervention program between 2015 and 2022 which aimed to suppress(peri)domestic Triatoma infestans in the municipality of Avia Terai (Chaco Province, Argentina), and found amarginal risk of domestic vector-borne transmission across the rural-to-urban gradient after interventions. Here,we identified the parasite Discrete Typing Units (DTUs) in infected T. infestans collected throughout the interventionprogram (37 insects pre-intervention and 7 post-intervention). Identification of DTUs was conducted bytwo methodologies, using DNA extracted from T. infestans rectal ampoules. We also assessed the associationbetween blood-feeding sources and DTUs. Complete DTU identification was achieved in 48 % of samples. Thehybrid lineages TcV or TcVI and their combinations predominated (72 %), followed by TcI (16 %) and mixedinfections of TcI and hybrid lineages (14 %). Half (50 %) of the houses harbored TcI infected bugs either alone ormixed with TcII/TcV/TcVI. Humans predominated as the bloodmeal sources in all insects with identified DTU.All DTUs (TcI, TcV and TcII/TcV/TcVI) were recorded in both rural and peri-urban environments, with 62 % ofthe houses having more than one DTU. These results confirm the predominance of hybrid lineages in domestictransmission cycles of the Argentine Chaco. However, the finding of several triatomines infected with TcI bothpre- and post-intervention raises the question of which host(s) are involved in its transmission.