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. 2012 Oct;139(12):1570-9.
doi: 10.1017/S0031182012000856. Epub 2012 Jul 19.

Direct molecular identification of Trypanosoma cruzi discrete typing units in domestic and peridomestic Triatoma infestans and Triatoma sordida from the Argentine Chaco

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Direct molecular identification of Trypanosoma cruzi discrete typing units in domestic and peridomestic Triatoma infestans and Triatoma sordida from the Argentine Chaco

L Maffey et al. Parasitology. 2012 Oct.

Abstract

We assessed the distribution of Trypanosoma cruzi Discrete Typing Units (DTUs) in domestic and peridomestic Triatoma infestans and Triatoma sordida specimens collected in a well-defined rural area in Pampa del Indio, northeastern Argentina. Microscopically-positive bugs were randomly selected with a multi-level sampling design, and DTUs were identified using direct PCR strategies. TcVI predominated in 61% of 69 T. infestans and in 56% of 9 T. sordida. TcV was the secondary DTU in T. infestans (16%) and was found in 1 T. sordida specimen (11%). Three T. sordida (33%) were found infected with TcI, a DTU also identified in local Didelphis albiventris opossums. Mixed DTU infections occurred rarely (5%) and were detected both directly from the bugs' rectal ampoule and parasite cultures. The identified DTUs and bug collection sites of T. infestans were significantly associated. Bugs infected with TcV were almost exclusively captured in domiciles whereas those with TcVI were found similarly in domiciles and peridomiciles. All mixed infections occurred in domiciles. TcV-infected bugs fed more often on humans than on dogs, whereas TcVI-infected bugs showed the reverse pattern. T. sordida is a probable sylvatic vector of TcI linked to D. albiventris, and could represent a secondary vector of TcVI and TcV in the domestic/peridomestic cycle.

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Figures

Figure 1
Figure 1
Map of the study area in Pampa del Indio showing villages (polygons) and houses positive for T. cruzi-infected triatomine bugs (dots). Dots identify positive houses sampled for DTU identification in T. infestans (red dots) and T. sordida specimens (green dots).
Figure 2
Figure 2
Example of the heminested 24Sα rDNA PCR using primers D71-D76 product size polymorphism in DNA samples from parasites cultures and bugs’ rectal ampoules. Bands a-e show the two patterns that individuals infected with TcV display: a single band of 125 bp or two bands of 125 + 140 bp, (bands a and d are samples obtained from bugs’ rectal ampoules; bands b and e from parasite cultures; band c: TcV reference stock, PAH 265). Central lane: 100 bp ladder. Bands f-h show the unique pattern for TcVI, a single band of 140 bp (band f: parasite culture sample, band g: rectal ampoule sample, band h: TcVI reference stock CL-Brener). Finally, bands i (parasite culture sample) and j (rectal ampoule sample) show the pattern observed for mixed infections TcV+TcVI that correspond also to a double band of 125 + 140 bp.
Figure 3
Figure 3
Geographical variation of T. cruzi DTU distribution in T. infestans from three study areas in the Argentine Chaco. Numbers on top of the bars represent the total number of bugs with identified DTUs.

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