Lineage-specific rapid diagnostic tests efficiently resolve Trypanosoma cruzi TcII/V/VI ecological and epidemiological associations in the Argentine Gran Chaco
Trypanosoma cruzi, the protozoan agent of Chagas disease, is comprised by at least 6 genetic lineages (TcI-TcVI). Their geographical distribution, clinical associations, and reservoir hosts are not fully elucidated, as genotyping is hampered due the difficulty in isolation and culture. Lineage-specific serological techniques may address these issues.
Synthetic peptides representing lineage specific epitopes of the T. cruzi trypomastigote small surface antigen (TSSA) were used in ELISA and a TcII/V/VI peptide was used in a novel rapid diagnostic test (RDT) to identify specific IgG. These assays were performed on human, canine, feline and armadillo sera from the Gran Chaco in Northern Argentina, a region of ongoing transmission cycles.
The novel RDT, using Protein G to detect human and canine IgG, was at least as sensitive as ELISA for TSSApep-II/V/VI. The epitope common to lineages TcII/V/VI was recognised in humans by RDT (242/396), in dogs by RDT (48/73), in cats by specific ELISA (5/19) and in armadillos by RDT (1/7). In humans TSSA-II/V/VI recognition was associated with being in households with another TSSA-II/V/VI reactive householder (p ≤ 0.0428). For dogs TSSA-II/V/VI recognition was associated with being born before the mass spraying (p ≤ 0.0462) and Toba household (p ≤ 0.0462).
This study has shown that this Protein G- based RDT can replace ELISA for TcII/V/VI recognition in humans and dogs, and that this can be detected in cats and armadillos, and revealed statistically significant associations. Furthermore, elsewhere we have reported a significant association between level of TcII/V/VI response and severity of chagasic cardiomyopathy. These results form the basis for more detailed studies, enabling rapid in-the-field surveillance of the distribution and clustering of these lineages among humans and mammalian reservoirs of T. cruzi infection.