Nationwide molecular epidemiology of Trypanosoma cruzi TcI in El Salvador using multi-locus sequence typing

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, remains a major public health problem in Latin America. In endemic countries, transmission to humans is primarily mediated by infected triatomine bugs. In this study, we investigated the molecular epidemiology of T. cruzi in Triatoma dimidiata, the principal vector in El Salvador. A total of 145 T. cruzi DNA samples were obtained from T. dimidiata collected from anthropic (domestic and peri-domestic) environments nationwide. Discrete typing unit analysis followed by multi-locus sequence typing (MLST) using thirteen housekeeping genes (5121 bp) was performed to characterize genetic diversity. The predominant lineage found in the country was T. cruzi lineage I (TcI) (144/145, 99.3%). Complete MLST profiles were obtained for 40 of the 145 samples, revealing additional TcI lineage diversity. The Salvadoran samples formed a well-supported monophyletic TcI subclade, genetically distinct from South American TcI strains. Bayesian molecular clock analysis estimated that the Central and South American TcI clades diverged approximately 131,000-162,000 years ago, depending on calibration used. Furthermore, twelve diploid sequence types (DSTs) were identified among 40 Salvadoran samples. Some DSTs were distributed across multiple regions of the country, whereas others showed more restricted geographical distributions. Our results suggest that Central American TcI represents a genetically differentiated subclade within TcI that diverged from South American TcI. This study provides the first MLST-based characterization of T. cruzi circulating in T. dimidiata in El Salvador and establishes a valuable molecular baseline for future epidemiological surveillance and geographically targeted control efforts in this region.