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. 2015 Feb 24:8:123.
doi: 10.1186/s13071-015-0730-8.

Genotype diversity of Trypanosoma cruzi in small rodents and Triatoma sanguisuga from a rural area in New Orleans, Louisiana

Affiliations

Genotype diversity of Trypanosoma cruzi in small rodents and Triatoma sanguisuga from a rural area in New Orleans, Louisiana

Claudia P Herrera et al. Parasit Vectors. .

Abstract

Background: Chagas disease is an anthropozoonosis caused by the protozoan parasite Trypanosoma cruzi that represents a major public health problem in Latin America. Although the United States is defined as non-endemic for Chagas disease due to the rarity of human cases, the presence of T. cruzi has now been amply demonstrated as enzootic in different regions of the south of the country from Georgia to California. In southeastern Louisiana, a high T. cruzi infection rate has been demonstrated in Triatoma sanguisuga, the local vector in this area. However, little is known about the role of small mammals in the wild and peridomestic transmission cycles.

Methods: This study focused on the molecular identification and genotyping of T. cruzi in both small rodents and T. sanguisuga from a rural area of New Orleans, Louisiana. DNA extractions were prepared from rodent heart, liver, spleen and skeletal muscle tissues and from cultures established from vector feces. T. cruzi infection was determined by standard PCR using primers specific for the minicircle variable region of the kinetoplastid DNA (kDNA) and the highly repetitive genomic satellite DNA (satDNA). Genotyping of discrete typing units (DTUs) was performed by amplification of mini-exon and 18S and 24Sα rRNA genes and subsequent sequence analysis.

Results: The DTUs TcI, TcIV and, for the first time, TcII, were identified in tissues of mice and rats naturally infected with T. cruzi captured in an area of New Orleans, close to the house where the first human case of Chagas disease was reported in Louisiana. The T. cruzi infection rate in 59 captured rodents was 76%. The frequencies of the detected DTUs in such mammals were TcI 82%, TcII 22% and TcIV 9%; 13% of all infections contained more than one DTU.

Conclusions: Our results indicate a probable presence of a considerably greater diversity in T. cruzi DTUs circulating in the southeastern United States than previously reported. Understanding T. cruzi transmission dynamics in sylvatic and peridomestic cycles in mammals and insect vectors will be crucial to estimating the risk of local, vector-borne transmission of T. cruzi to humans in the United States.

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Figures

Figure 1
Figure 1
Molecular characterization of the flagellate forms from T. sanguisuga feces and T. cruzi strain isolates by amplification of the mini-exon intergenic region. (1–3) DNA from flagellate forms in feces: WB1F, WB2F, WB3F (4–6) DNA from T. cruzi strain isolates from feces of samples 1–3 respectively, (7–9) DNA from T. cruzi strain isolates WB4, WB758, WB759. DNA from references strains: TcI (Sylvio 10X), TcII (Esmeraldo). Agarose 2.5% gel.
Figure 2
Figure 2
Molecular phylogenetic analysis by Maximum Likelihood method. The phylogram depicting the phylogenetic relationships among the 27 T. cruzi DNA sequences corresponding to eight rodents, based on Miniexon intergenic gene sequencing. The un-rooted tree with the highest -lnL = 890.6637 is shown, allowing identification of the three different clusters corresponding to three different DTUs in the rodent tissue samples analyzed. Bootstrap values appear on each clustering branch. The last letter in the sample name refers to H: heart, M: skeletal muscle, L: liver, S: spleen. *indicates mice with mixed infections.

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