The protozoan Trypanosoma cruzi, its mammalian reservoirs, and vectors have existed in nature for millions of years. The human infection, named Chagas disease, is a major public health problem for Latin America. T. cruzi is genetically highly diverse and the understanding of the population structure of this parasite is critical because of the links to transmission cycles and disease. At present, T. cruzi is partitioned into six discrete typing units (DTUs), TcI-TcVI. Here we focus on the current status of taxonomy-related areas such as population structure, phylogeographical and eco-epidemiological features, and the correlation of DTU with natural and experimental infection. We also summarize methods for DTU genotyping, available for widespread use in endemic areas. For the immediate future multilocus sequence typing is likely to be the gold standard for population studies. We conclude that greater advances in our knowledge on pathogenic and epidemiological features of these parasites are expected in the coming decade through the comparative analysis of the genomes from isolates of various DTUs.
In an effort to unify the nomenclature of Trypanosoma cruzi, the causative agent of Chagas disease, an updated system was agreed upon at the Second Satellite Meeting. A consensus was reached that T. cruzi strains should be referred to by six discrete typing units (T. cruzi I-VI). The goal of a unified nomenclature is to improve communication within the scientific community involved in T. cruzi research. The justification and implications will be presented in a subsequent detailed report.
An international study was performed by 26 experienced PCR laboratories from 14 countries to assess the performance of duplex quantitative real-time PCR (qPCR) strategies on the basis of TaqMan probes for detection and quantification of parasitic loads in peripheral blood samples from Chagas disease patients. Two methods were studied: Satellite DNA (SatDNA) qPCR and kinetoplastid DNA (kDNA) qPCR. Both methods included an internal amplification control. Reportable range, analytical sensitivity, limits of detection and quantification, and precision were estimated according to international guidelines. In addition, inclusivity and exclusivity were estimated with DNA from stocks representing the different Trypanosoma cruzi discrete typing units and Trypanosoma rangeli and Leishmania spp. Both methods were challenged against 156 blood samples provided by the participant laboratories, including samples from acute and chronic patients with varied clinical findings, infected by oral route or vectorial transmission. kDNA qPCR showed better analytical sensitivity than SatDNA qPCR with limits of detection of 0.23 and 0.70 parasite equivalents/mL, respectively. Analyses of clinical samples revealed a high concordance in terms of sensitivity and parasitic loads determined by both SatDNA and kDNA qPCRs. This effort is a major step toward international validation of qPCR methods for the quantification of T. cruzi DNA in human blood samples, aiming to provide an accurate surrogate biomarker for diagnosis and treatment monitoring for patients with Chagas disease.
The objectives of this study were to establish the prevalence of Chagas' disease among HIV seropositive patients and to define the clinical profile of co-infected cases. Cross-sectional study: the prevalence of co-infected subjects was 1.3% and there was no significant difference between co-infected and non co-infected patients relative to race, birthplace, home address and CD4 T cells. The co-infected group comprised predominantly women and mean age and median viral load were higher. Longitudinal study: included 20 patients (12 women) and described the clinical presentation and natural history of concomitant infections. The mean follow-up time was 35.8 months, mean age was 43+/-8.7 years and 60% of patients were white. During the follow-up, a total of 113 serological tests for Chagas' disease were performed: 89 (78.8%) were reactive/positive, 21 (18.6%) were doubtful and three (2.6%) were non-reactive/negative. Positive results for xenodiagnosis were high (81%). At the baseline evaluation, thirteen patients had the indeterminate form of Chagas' disease and seven cardiopathy. One patient developed from indeterminate to digestive form, three had a reactivation of Chagas' disease in the central nervous system, all had parasitological confirmation and received specific treatment. There were 11 deaths. Thus, HIV-infected patients should be tested for Chagas' disease when epidemiologically relevant.
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