Trypanosoma cruzi III causing the indeterminate form of Chagas disease in a semi-arid region of Brazil

• Trypanosoma cruzi TcI, TcII, and TcIII were identified in patients with different clinical forms of Chagas disease.
• TcIII in humans is reported for the first time from the semi-arid region of Rio Grande do Norte.
• Euphractus sexcinctus and Galea spixii may be involved in the overlap between the sylvatic and domestic transmission cycles in this region.

SummaryObjectiveTrypanosoma cruzi is subdivided into six discrete typing units (DTUs), TcI–TcVI. The precise identification of each can contribute to tracking wild DTUs that invade the domiciliary environment.MethodsTwenty T. cruzi stocks isolated from 16 chagasic patients, two Panstrongylus lutzi, one Galea spixii, and one Euphractus sexcinctus, from different localities in the State of Rio Grande do Norte, Brazil, were characterized by genotyping the 3′ region of the 24Sα rRNA gene, the mitochondrial cytochrome oxidase subunit 2 gene, and the spliced leader intergenic region.ResultsTcIII was identified in 18.7% (3/16) of patients from different municipalities, as well as in P. lutzi, G. spixii, and E. sexcinctus, indicating the connection between the sylvatic and domestic cycles in this Brazilian semi-arid region. TcI and TcII were also detected, in 37.5% (6/16) and 43.8% (7/16) of patients, respectively. These DTUs were associated with cardiac, digestive, and indeterminate clinical forms, while TcIII was identified only in patients with the indeterminate form.ConclusionsThe occurrence of these DTUs reveals important phylogenetic diversity in T. cruzi isolates from humans. TcIII is reported for the first time in northeastern Brazil. These findings appear to indicate an overlap between the sylvatic and domestic transmission cycles of the parasite in this region.