Natural Reservoir of Trypanosoma cruzi Found in Triatomines Targeting Humans: Results from Nation-wide Vector Surveillance in El Salvador

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Introduction: Chagas disease is one of the most critical of the neglected tropical diseases in Latin America where it poses a serious public health issue. However, the current burden of vectorial transmission from natural reservoirs to humans is unclear. This study aimed to clarify the active mode of transmission to humans disentangled from the feeding pattern of Triatoma dimidiata (T. dimidiata) infected by Trypanosoma cruzi (T. cruzi).

Methods: A total of 1,376 T. dimidiata specimens were collected across the 14 departments of El Salvador. From these specimens, 135 midgut samples from 37 households in eight departments were positive for T. cruzi (n = 135/1,376; 9.8% [95% confidential interval (CI): 8.35%-11.5%]). Using a universal vertebrate primer, vertebrate blood sources were positively identified by next-generation sequence analysis of deoxyribonucleic acid (DNA) extracted from the midgut contents of T. dimidiata.

Results: A total of 13 vertebrates were detected as blood sources; humans, and five domestic, three synanthropic, and four sylvatic species. Triatomines identified as having fed on human blood accounted for approximately 67% (n = 90/135 [95% CI: 58.3%-74.1%]) of the samples analyzed.

Conclusions: In this study, a holistic understanding of the feeding patterns of T. cruzi-positive T. dimidiata in El Salvador is dated. The detection of human DNA in the midgut contents of T. dimidiata indicated the possibility of active vectorial transmission to humans.