Comprehensive study of Trypanosoma cruzi genetic diversity from Triatominae vectors in the Southern United States: Geographic structuring, mitochondrial introgression, and multiclonality
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Background
Trypanosoma cruzi , the causative agent of Chagas disease, is subdivided into distinct genetic groups known as Discrete Typing Units (DTUs), each with distinct genetic traits that influence epidemiology and transmission dynamics. Several triatomine species serve as potential vectors of T. cruzi in the United States. However, despite the growing number of Chagas disease cases in the country, little is known about the genetic diversity and population structure of T. cruzi in natural vector populations.
Methodology/Principal Findings
We applied a multilocus metabarcoding approach to improve DTU resolution and characterize the genetic diversity and structure of T. cruzi in triatomines collected across five states of the southern United States. Five single-copy nuclear markers and one mitochondrial marker were amplified and processed by high- throughput sequencing to assess genetic diversity. We recovered 35 nuclear and 15 mitochondrial haplotypes from 70 infected specimens. Overall, genetic diversity was low (π < 0.01 at all nuclear loci), with DTUs TcI and the North American lineage of TcIV detected, TcI being the most prevalent. Geographic structuring was particularly evident in TcI strains, which exhibited a distinctive haplotype profile in Florida populations, potentially linked to the recently revalidated vector species Triatoma ambigua . Mitochondrial introgression from TcIV into TcI suggests inter-DTU genetic exchange in these populations. Multiple haplotypes within individual insects detected across single-copy nuclear markers, support multiclonal infection as common feature of T. cruzi in natural vectors.
Conclusions/Significance
These findings provide new insights into the genetic landscape and evolution of T. cruzi in the United States. Evolutionary connectivity through mitochondrial introgression and frequent multiclonality highlights the importance of deep sequencing approaches for resolving T. cruzi genetic diversity, with direct implications for understanding for transmission dynamics, disease monitoring and control.
Author summary
Kissing bugs are blood-feeding insects best known for transmitting Trypanosoma cruzi , the parasite that causes Chagas disease. The disease is usually associated with Latin America, and the United States is not recognized as an endemic country. Nonetheless, the insects live across the southern states, and people there have become infected without traveling abroad. Surprisingly little is known about the parasites themselves in this region. We collected kissing bugs from five southern states and sequenced six genetic markers using high-throughput sequencing to study the parasite variants present in those populations. We found parasites from Florida formed a genetically distinct group, and this separation aligns with a kissing bug species recently recognized as distinct. We also found that individual insects often carried several different parasite variants at once, and that some parasites combined genetic material from separate parasite groups. Characterizing T. cruzi infections improves our understanding of the ecological and epidemiological dynamics within hosts in the United States.
