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. 2016 Aug 29;10(8):e0004792.
doi: 10.1371/journal.pntd.0004792. eCollection 2016 Aug.

Over Six Thousand Trypanosoma cruzi Strains Classified into Discrete Typing Units (DTUs): Attempt at an Inventory

Simone Frédérique Brenière  1   2 , Etienne Waleckx  3 , Christian Barnabé  1
Affiliations

Over Six Thousand Trypanosoma cruzi Strains Classified into Discrete Typing Units (DTUs): Attempt at an Inventory

Simone Frédérique Brenière et al. PLoS Negl Trop Dis. .

Abstract

Trypanosoma cruzi, the causative agent of Chagas disease, presents wide genetic diversity. Currently, six discrete typing units (DTUs), named TcI to TcVI, and a seventh one called TcBat are used for strain typing. Beyond the debate concerning this classification, this systematic review has attempted to provide an inventory by compiling the results of 137 articles that have used it. A total of 6,343 DTU identifications were analyzed according to the geographical and host origins. Ninety-one percent of the data available is linked to South America. This sample, although not free of potential bias, nevertheless provides today's picture of T. cruzi genetic diversity that is closest to reality. DTUs were genotyped from 158 species, including 42 vector species. Remarkably, TcI predominated in the overall sample (around 60%), in both sylvatic and domestic cycles. This DTU known to present a high genetic diversity, is very widely distributed geographically, compatible with a long-term evolution. The marsupial is thought to be its most ancestral host and the Gran Chaco region the place of its putative origin. TcII was rarely sampled (9.6%), absent, or extremely rare in North and Central America, and more frequently identified in domestic cycles than in sylvatic cycles. It has a low genetic diversity and has probably found refuge in some mammal species. It is thought to originate in the south-Amazon area. TcIII and TcIV were also rarely sampled. They showed substantial genetic diversity and are thought to be composed of possible polyphyletic subgroups. Even if they are mostly associated with sylvatic transmission cycles, a total of 150 human infections with these DTUs have been reported. TcV and TcVI are clearly associated with domestic transmission cycles. Less than 10% of these DTUs were identified together in sylvatic hosts. They are thought to originate in the Gran Chaco region, where they are predominant and where putative parents exist (TcII and TcIII). Trends in host-DTU specificities exist, but generally it seems that the complexity of the cycles and the participation of numerous vectors and mammal hosts in a shared area, maintains DTU diversity.

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Conflict of interest statement

The authors have declared that no completing interest exist.

Figures

Fig 1
Fig 1. T. cruzi DTUs distribution (TcI-TcVI and Tcbat) over 6234 determinations in vector and mammalian hosts from 19 endemic countries in the overall endemic area: In North America (n = 459), Central America (n = 120) and South America (n = 5655).
The ambiguous determinations of DTUs were deleted from the samples.
Fig 2
Fig 2. T. cruzi DTU distribution per country in South America out of a total of 5655 identifications.
The ambiguous determinations of DTUs were deleted from the samples.
Fig 3
Fig 3. Differential T. cruzi DTUs distributions in wild and domestic cycles.
The ambiguous determinations of DTUs were deleted from the samples.
Fig 4
Fig 4. Comparative distribution of the T. cruzi DTUs in humans and dogs.
See this image and copyright information in PMC

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