Piassaba palm extractivism as an associated factor with Chagas disease: seroprevalence and immunological profile in native inhabitants of the Central Amazonia, Brazil

Abstract

In the Brazilian Amazon, Chagas disease is considered a zoonosis with low virulence and pathogenicity that primarily appears in chronic latent infections. To examine the seroprevalence, epidemiological and immunological profiles of Chagas disease in the microregion of the Negro river (Central Amazonia), an observational and cross-sectional study was conducted on native people from the Municipality of Barcelos, the most important piassaba (Leopoldinia piassaba) fibre extractivism site in the Amazonas State. Serology tests were performed using both ELISA and indirect immunofluorescence tests. Immunophenotyping and profiles of Th1, Th2 and Th17 cytokines were determined. The seroprevalence in native inhabitants ranged from 2.6 to 6.5%. The low level of circulating INF-γ was associated to the low percentage of T-helper CD3+ CD4+ lymphocytes. As INF-γ is an important factor associated with the development of severe cardiomyopathy, the low levels INF-γ in seropositive individuals from the Central Amazonia suggests the downregulation of the Th1 immune response, which might explain the long and latent asymptomatic phase of Trypanosoma cruzi infections.