# Trypanosoma cruzi DTU parasite diversity and clinical outcomes in mesoregions of the Northeast Brazilian State of Pernambuco

## TL;DR

This study examines how different genetic types of the Chagas disease parasite vary in patients from Pernambuco, Brazil, but finds no clear link between parasite type and disease form.

## Contribution

The study reveals a predominance of TcV and TcIII DTUs in Pernambuco, suggesting underreporting of their geographic distribution in Brazil.

## Key findings

- TcV and TcIII DTUs were most commonly found in chronic Chagas disease patients from Pernambuco.
- No significant association was found between T. cruzi DTUs and specific clinical forms of Chagas disease.
- Mixed infections with multiple DTUs were observed, indicating complex parasite dynamics in the region.

## Abstract

Chagas disease (CD), caused by infection with the protozoan parasite Trypanosoma cruzi, is a neglected tropical illness that affects 6–7 million individuals worldwide. CD may progress to chronic cardiac (CARD), digestive (DIG), or cardio-digestive (CARD/DIG) forms. Parasite genetic diversity, defined in discrete typing units (DTUs) TcI-TcVI and TcBat, may contribute to clinical forms. Here, we challenged this idea by studying a population born in the State of Pernambuco, Northeast of Brazil.

Patients born in eco-geographically distinct mesoregions (Sertão, Agreste, Zona da Mata, and Metropolitan Region) attending the referral PROCAPE hospital were serologically diagnosed for CD and characterized as non-CARD (16.5%), CARD (67%), DIG (12.1%), and CARD/DIG (4.3%). Out of 346 CD patients not subjected to etiological treatment, 128 (37%) were positive for conventional PCR targeting T. cruzi kDNA. DTU genotyping using pre-established primers and algorithms revealed 85/128 (66%) samples amplified for at least one target, and of these, 49 (58%) were classified into DTUs, showing a higher distribution of DTUs TcV (16) and TcIII (13) but also TcIV (7), TcI (3), TcVI (3), and TcII (1). Mixed infections by TcI + TcV (2), TcIII + TcIV (3), and TcIII + TcV (1) were also found. Out of the 49 classified samples, 36 were CARD patients (73.5%), infected mainly by TcV (13) and TcIII (10). Considering patients’ birthplace, in the Agreste, all DTUs were detected, with prevailing TcV and TcIII; in Zona da Mata, DTU characterization reflected the input of samples (21/49, 43%), again mainly TcV and TcIII.

DTUs TcI-TcVI were only detected in the blood of patients born in the Agreste, area of ecological transition. Although not frequently found in human infections in Brazil, the prevailing TcV, TcIII, and TcIV were detected in patients born in Pernambuco. These data could not disclose an identifiable association of T. cruzi DTU circulating in the blood of patients with clinical forms of CD.

Chagas disease (CD), a neglected disease that affects 6-7 million individuals worldwide, may have different clinical manifestations such as CARD, CARD/DIG, and DIG forms. The etiological agent of CD, the flagellate protozoan parasite Trypanosoma cruzi shows a significant biological and genetic diversity. T. cruzi, isolates are classified and grouped by genetic similarity and common molecular markers into seven discrete typing units (DTUs) – TcI to TcVI, and TcBat. To date, there is insufficient evidence to associate the use of T. cruzi genotypes as biomarkers for clinical stage outcome and/or disease progression. However, TcI has been associated with the CARD form in some populations. Here, in a group of clinically classified Brazilian chronic CD patients, we genotyped the T. cruzi parasite in DTUs and explored its possible association with the different clinical forms. These data support the lack of association between T. cruzi genotype and clinical forms of CD. However, we bring new evidence showing a predominance of TcV and TcIII DTUs in chronic CD patients born in Pernambuco, Northeastern Brazil, indicating an underreporting of the geographic distribution of T. cruzi DTUs circulating in Brazil.