Trypanosoma cruzi: variability of stocks from Colombia determined by molecular karyotype and minicircle Southern blot analysis

A phased genome assembly of a Colombian Trypanosoma cruzi TcI strain and the evolution of gene families

Chagas is an endemic disease in tropical regions of Latin America, caused by the parasite Trypanosoma cruzi. High intraspecies variability and genome complexity have been challenges to assemble high quality genomes needed for studies in evolution, population genomics, diagnosis and drug development. Here we present a chromosome-level phased assembly of a TcI T. cruzi strain (Dm25). While 29 chromosomes show a large collinearity with the assembly of the Brazil A4 strain, three chromosomes show both large heterozygosity and large divergence, compared to previous assemblies of TcI T. cruzi strains. Nucleotide and protein evolution statistics indicate that T. cruzi Marinkellei separated before the diversification of T. cruzi in the known DTUs. Interchromosomal paralogs of dispersed gene families and histones appeared before but at the same time have a more strict purifying selection, compared to other repeat families. Previously unreported large tandem arrays of protein kinases and histones were identified in this assembly. Over one million variants obtained from Illumina reads aligned to the primary assembly clearly separate the main DTUs. We expect that this new assembly will be a valuable resource for further studies on evolution and functional genomics of Trypanosomatids.

Diversity and Epidemiology of Bat Trypanosomes: A One Health Perspective

Bats (order Chiroptera) have been increasingly recognised as important reservoir hosts for human and animal pathogens worldwide. In this context, molecular and microscopy-based investigations to date have revealed remarkably high diversity of Trypanosoma spp. harboured by bats, including species of recognised medical and veterinary importance such as Trypanosoma cruzi and Trypanosoma evansi (aetiological agents of Chagas disease and Surra, respectively). This review synthesises current knowledge on the diversity, taxonomy, evolution and epidemiology of bat trypanosomes based on both molecular studies and morphological records. In addition, we use a One Health approach to discuss the significance of bats as reservoirs (and putative vectors) of T. cruzi, with a focus on the complex associations between intra-specific genetic diversity and eco-epidemiology of T. cruzi in sylvatic and domestic ecosystems. This article also highlights current knowledge gaps on the biological implications of trypanosome co-infections in a single host, as well as the prevalence, vectors, life-cycle, host-range and clinical impact of most bat trypanosomes recorded to date. Continuous research efforts involving molecular surveillance of bat trypanosomes are required for improved disease prevention and control, mitigation of biosecurity risks and potential spill-over events, ultimately ensuring the health of humans, domestic animals and wildlife globally.

Strain-specific genome evolution in Trypanosoma cruzi, the agent of Chagas disease

The protozoan Trypanosoma cruzi almost invariably establishes life-long infections in humans and other mammals, despite the development of potent host immune responses that constrain parasite numbers. The consistent, decades-long persistence of T. cruzi in human hosts arises at least in part from the remarkable level of genetic diversity in multiple families of genes encoding the primary target antigens of anti-parasite immune responses. However, the highly repetitive nature of the genome-largely a result of these same extensive families of genes-have prevented a full understanding of the extent of gene diversity and its maintenance in T. cruzi. In this study, we have combined long-read sequencing and proximity ligation mapping to generate very high-quality assemblies of two T. cruzi strains representing the apparent ancestral lineages of the species. These assemblies reveal not only the full repertoire of the members of large gene families in the two strains, demonstrating extreme diversity within and between isolates, but also provide evidence of the processes that generate and maintain that diversity, including extensive gene amplification, dispersion of copies throughout the genome and diversification via recombination and in situ mutations. Gene amplification events also yield significant copy number variations in a substantial number of genes presumably not required for or involved in immune evasion, thus forming a second level of strain-dependent variation in this species. The extreme genome flexibility evident in T. cruzi also appears to create unique challenges with respect to preserving core genome functions and gene expression that sets this species apart from related kinetoplastids.

Mixed infections by different Trypanosoma cruzi discrete typing units among Chagas disease patients in an endemic community in Panama

Background

Trypanosoma cruzi, the hemoparasite that causes Chagas disease, is divided into six Discrete Typing Units or DTUs: TcI-TcVI plus Tcbat. This genetic diversity is based on ecobiological and clinical characteristics associated with particular populations of the parasite. The main objective of this study was the identification of DTUs in patients with chronic chagasic infections from a mountainous rural community in the eastern region of Panama.

Methods

A total of 106 patients were tested for Chagas disease with three serological tests (ELISA, rapid test, and Western blot). Molecular diagnosis and DTU typing were carried out by conventional PCRs and qPCR targeting different genomic markers, respectively. As a control sample for the typing, 28 patients suspected to be chagasic from the metropolitan area of Panama City were included.

Results

Results showed a positivity in the evaluated patients of 42.3% (33/78); high compared to other endemic regions in the country. In the control group, 20/28 (71.43%) patients presented positive serology. The typing of samples from rural patients showed that 78.78% (26/33) corresponded to TcI, while 9.09% (3/33) were mixed infections (TcI plus TcII/V/VI). Seventy-five percent (15/20) of the patients in the control group presented TcI, and in five samples it was not possible to typify the T. cruzi genotype involved.

Conclusions

These results confirm that TcI is the main DTU of T. cruzi present in chronic chagasic patients from Panama. However, the circulation of other genotypes (TcII/V/VI) in this country is described for the first time. The eco-epidemiological characteristics that condition the circulation of TcII/V/VI, as well as the immune and clinical impact of mixed infections in this remote mountainous region should be investigated, which will help local action programs in the surveillance, prevention, and management of Chagas disease.

Understanding the oral transmission of Trypanosoma cruzi as a veterinary and medical foodborne zoonosis

Chagas disease is a neglected tropical disease transmitted by the protozoan Trypanosoma cruzi that lately has been highlighted because several outbreaks attributed to oral transmission of the parasite have occurred. These outbreaks are characterized by high mortality rates and massive infections that cannot be related to other types of transmission such as the vectorial route. Oral transmission of Chagas disease has been reported in Brazil, Colombia, Venezuela, Bolivia, Ecuador, Argentina and French Guiana, most of them are massive oral outbreaks caused by the ingestion of beverages and food contaminated with triatomine feces or parasites' reservoirs secretions and considered since 2012 as a foodborne disease. In this review, we present the current status and all available data regarding oral transmission of Chagas disease, highlighting its relevance as a veterinary and medical foodborne zoonosis.

Whole genome sequencing of Trypanosoma cruzi field isolates reveals extensive genomic variability and complex aneuploidy patterns within TcII DTU

BACKGROUND

Trypanosoma cruzi, the etiologic agent of Chagas disease, is currently divided into six discrete typing units (DTUs), named TcI-TcVI. TcII is among the major DTUs enrolled in human infections in South America southern cone, where it is associated with severe cardiac and digestive symptoms. Despite the importance of TcII in Chagas disease epidemiology and pathology, so far, no genome-wide comparisons of the mitochondrial and nuclear genomes of TcII field isolates have been performed to track the variability and evolution of this DTU in endemic regions.

RESULTS

In the present work, we have sequenced and compared the whole nuclear and mitochondrial genomes of seven TcII strains isolated from chagasic patients from the central and northeastern regions of Minas Gerais, Brazil, revealing an extensive genetic variability within this DTU. A comparison of the phylogeny based on the nuclear or mitochondrial genomes revealed that the majority of branches were shared by both sequences. The subtle divergences in the branches are probably consequence of mitochondrial introgression events between TcII strains. Two T. cruzi strains isolated from patients living in the central region of Minas Gerais, S15 and S162a, were clustered in the nuclear and mitochondrial phylogeny analysis. These two strains were isolated from the other five by the Espinhaço Mountains, a geographic barrier that could have restricted the traffic of insect vectors during T. cruzi evolution in the Minas Gerais state. Finally, the presence of aneuploidies was evaluated, revealing that all seven TcII strains have a different pattern of chromosomal duplication/loss.

CONCLUSIONS

Analysis of genomic variability and aneuploidies suggests that there is significant genomic variability within Minas Gerais TcII strains, which could be exploited by the parasite to allow rapid selection of favorable phenotypes. Also, the aneuploidy patterns vary among T. cruzi strains and does not correlate with the nuclear phylogeny, suggesting that chromosomal duplication/loss are recent and frequent events in the parasite evolution.

Geographical, landscape and host associations of Trypanosoma cruzi DTUs and lineages

Background

The evolutionary history and ecological associations of Trypanosoma cruzi, the need to identify genetic markers that can distinguish parasite subpopulations, and understanding the parasite’s evolutionary and selective processes have been the subject of a significant number of publications since 1998, the year when the first DNA sequence analysis for the species was published.

Methods

The current analysis systematizes and re-analyzes this original research, focusing on critical methodological and analytical variables and results that have given rise to interpretations of putative patterns of genetic diversity and diversification of T. cruzi lineages, discrete typing units (DTUs), and populations, and their associations with hosts, vectors, and geographical distribution that have been interpreted as evidence for parasite subpopulation specificities.

Results

Few studies use hypothesis-driven or quantitative analysis for T. cruzi phylogeny (16/58 studies) or phylogeography (10/13). Among these, only one phylogenetic and five phylogeographic studies analyzed molecular markers directly from tissues (i.e. not from isolates). Analysis of T. cruzi DTU or lineage niche and its geographical projection demonstrate extensive sympatry among all clades across the continent and no significant niche differences among DTUs. DTU beta-diversity was high, indicating diverse host assemblages across regions, while host dissimilarity was principally due to host species turnover and to a much lesser degree to nestedness. DTU-host order specificities appear related to trophic or microenvironmental interactions.

Conclusions

More rigorous study designs and analyses will be required to discern evolutionary processes and the impact of landscape modification on population dynamics and risk for T. cruzi transmission to humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1918-2) contains supplementary material, which is available to authorized users.

Multilocus analysis indicates that Trypanosoma cruzi I genetic substructure associated with sylvatic and domestic cycles is not an attribute conserved throughout Colombia

Trypanosoma cruzi, the causative agent of Chagas disease, has been classified into six discrete typing units (DTUs) named TcI to TcVI. Furthermore, subcontinental scale studies based on analysis of the splice leader intergenic region (SL-IR) of the mini-exon gene have subdivided TcI in five genetic groups (Ia-Ie) related to the domestic and non-domestic cycles. However, a current review of this marker among all the sequences deposited in the GenBank demonstrates no correlation between the genetic structure and the eco-epidemiological features of parasite transmission. In this study, we performed a multilocus analysis of TcI isolates from a diverse array of hosts and vectors in a wide eco-geographical area of Colombia. Sequences from SL-IR and mitochondrial cyt b genes as well as PCR-RFLP profiles for four nuclear genes were analyzed. Multilocus analysis indicates that genetic structuration associated with sylvatic and domestic cycles in Colombia is not an attribute conserved across the entire eco-geography where TcI can be found.

Chromosomal copy number variation reveals differential levels of genomic plasticity in distinct Trypanosoma cruzi strains

BACKGROUND

Trypanosoma cruzi, the etiologic agent of Chagas disease, is currently divided into six discrete typing units (DTUs), named TcI-TcVI. CL Brener, the reference strain of the T. cruzi genome project, is a hybrid with a genome assembled into 41 putative chromosomes. Gene copy number variation (CNV) is well documented as an important mechanism to enhance gene expression and variability in T. cruzi. Chromosomal CNV (CCNV) is another level of gene CNV in which whole blocks of genes are expanded simultaneously. Although the T. cruzi karyotype is not well defined, several studies have demonstrated a significant variation in the size and content of chromosomes between different T. cruzi strains. Despite these studies, the extent of diversity in CCNV among T. cruzi strains based on a read depth coverage analysis has not been determined.

RESULTS

We identify the CCNV in T. cruzi strains from the TcI, TcII and TcIII DTUs, by analyzing the depth coverage of short reads from these strains using the 41 CL Brener chromosomes as reference. This study led to the identification of a broader extent of CCNV in T. cruzi than was previously speculated. The TcI DTU strains have very few aneuploidies, while the strains from TcII and TcIII DTUs present a high degree of chromosomal expansions. Chromosome 31, which is the only chromosome that is supernumerary in all six T. cruzi samples evaluated in this study, is enriched with genes related to glycosylation pathways, highlighting the importance of glycosylation to parasite survival.

CONCLUSIONS

Increased gene copy number due to chromosome amplification may contribute to alterations in gene expression, which represents a strategy that may be crucial for parasites that mainly depend on post-transcriptional mechanisms to control gene expression.

Eco-epidemiology of Chagas disease in an endemic area of Colombia: risk factor estimation, Trypanosoma cruzi characterization and identification of blood-meal sources in bugs

The Sierra Nevada de Santa Marta (SNSM) is a mountainous area in Colombia that is highly endemic to Chagas disease. We explored some eco-epidemiological attributes involved in the Chagas disease transmission scenario in three Indigenous communities. An epidemiological survey was done, where parasite infection in reservoirs and insects, Trypanosoma cruzi genotyping, identification of blood-meal sources in intradomiciliary insects using the high-resolution melting technique, and some risk factors were evaluated. The results suggest that several dwelling conditions such as thatched palm roofs and mud walls carried the highest risk of finding intradomiciliary Rhodnius prolixus, which 56.41% were infected with T. cruzi and fed with human blood. Moreover, T. cruzi Ia was the most frequent haplotype found in insects. These results indicate the existence of a domestic T. cruzi transmission cycle that does not overlap with the sylvatic cycle, and highlight the need for efficient entomological control focused to this area.

Anti-Trypanosoma cruzi antibody detection in eastern Andalusia (Spain)

BACKGROUND

Chagas disease caused by the protozoan haemoflagellate Trypanosoma cruzi is no longer found exclusively in Latin America; the disease is occurring in Europe, and Spain is the country with the highest prevalence.

METHODS

Our aim was to detect anti-T. cruzi antibodies in blood donors from southeast Spain, and we performed eight serological diagnostic assays on each of 550 blood samples collected in March-June 2010. Two in-house ELISA methods were used to test against a parasite lysate (ELISA-H) and the semi-purified superoxide dismutase excreted by T. cruzi (ELISA-SODe); we also used the Western blot technique against the same antigen (WB-SODe), indirect immunofluorescence (IFA) and four commercial tests.

RESULTS

The serological test results showed a range of seroprevalence values, the lowest being 1.1%, determined by IFA and two commercial tests (Ab rapid and Chagascreen); other values were: 1.3% (commercial ELISA [Chagas ELISA IgG+IgM]); 2.1% (immunochromatographic test [Stick Chagas]); 2.7% (ELISA-H); 4.0% (WB-SODe); and 4.2%, the highest value (ELISA-SODe).

CONCLUSIONS

The excellent specificity of SODe antigen for the detection of antibodies to T. cruzi in donors lead us to affirm that the serological test performed with this biomarker could provide a useful screening and confirmatory test method for cases of Chagas disease.

Trypanosoma cruzi genotyping supports a common source of infection in a school-related oral outbreak of acute Chagas disease in Venezuela

Trypanosoma cruzi I, a discrete typing unit (DTU) found in human infections in Venezuela and other countries of the northern region of South America and in Central America, has been recently classified into five intra-DTU genotypes (Ia, Ib, Ic, Id, Ie) based on sequence polymorphisms found in the spliced leader intergenic region. In this paper we report the genotype identification of T. cruzi human isolates from one outbreak of acute orally acquired Chagas disease that occurred in a non-endemic region of Venezuela and from T. cruzi triatomine and rat isolates captured at a guava juice preparation site which was identified as the presumptive source of infection. The genotyping of all these isolates as TcId supports the view of a common source of infection in this oral Chagas disease outbreak through the ingestion of guava juice. Implications for clinical manifestations and dynamics of transmission cycles are discussed.

Molecular epidemiology of human oral Chagas disease outbreaks in Colombia

Background

Trypanosoma cruzi, the causative agent of Chagas disease, displays significant genetic variability revealed by six Discrete Typing Units (TcI-TcVI). In this pathology, oral transmission represents an emerging epidemiological scenario where different outbreaks associated to food/beverages consumption have been reported in Argentina, Bolivia, Brazil, Ecuador and Venezuela. In Colombia, six human oral outbreaks have been reported corroborating the importance of this transmission route. Molecular epidemiology of oral outbreaks is barely known observing the incrimination of TcI, TcII, TcIV and TcV genotypes.

Methodology and Principal Findings

High-throughput molecular characterization was conducted performing MLMT (Multilocus Microsatellite Typing) and mtMLST (mitochondrial Multilocus Sequence Typing) strategies on 50 clones from ten isolates. Results allowed observing the occurrence of TcI, TcIV and mixed infection of distinct TcI genotypes. Thus, a majority of specific mitochondrial haplotypes and allelic multilocus genotypes associated to the sylvatic cycle of transmission were detected in the dataset with the foreseen presence of mitochondrial haplotypes and allelic multilocus genotypes associated to the domestic cycle of transmission.

Conclusions

These findings suggest the incrimination of sylvatic genotypes in the oral outbreaks occurred in Colombia. We observed patterns of super-infection and/or co-infection with a tailored association with the severe forms of myocarditis in the acute phase of the disease. The transmission dynamics of this infection route based on molecular epidemiology evidence was unraveled and the clinical and biological implications are discussed.

Chagas disease represents a serious health problem affecting more than 10 million people in the Americas. The oral transmission route has emerged as a new epidemiological scenario that needs to be considered in prevention and control strategies. Herein was developed a high-resolution molecular characterization using mtMLST and MLMT tools in order to unravel the molecular epidemiology and transmission dynamics drivers in six well-characterized human oral outbreaks in Colombia. We observed the majority of clones typed as TcI and one clone as TcIV. The analysis of mitochondrial haplotypes allowed us to observe a high frequency of sylvatic haplotypes and a low proportion of domestic haplotypes. Likewise, a tailored allelic profile by each outbreak was observed. Our results suggest that sylvatic populations of T. cruzi are the causative agents of Chagas disease oral outbreaks and these findings should help to pursue new initiatives of control and prevention in those areas where domiciliated vectorial transmission has been interrupted.

Multilocus PCR-RFLP profiling in Trypanosoma cruzi I highlights an intraspecific genetic variation pattern

Chagas disease represents a serious problem in public health. This zoonotic pathology is caused by the kinetoplastid Trypanosoma cruzi which displays a high genetic diversity falling into six Discrete Typing Units (TcI-TcVI). In Colombia, the prevalent DTU is TcI with findings of TcII, TcIII and TcIV in low proportions. The aim of this work was to observe the genetic variability within TcI using a multilocus PCR-RFLP strategy. We analyzed 70 single-celled clones from triatomines, reservoirs and humans that were amplified and restricted via ten PCR-RFLPs targets across TcI genome, the restriction fragments were used to construct phylograms according to calculated genetic distances. We obtained five polymorphic targets (1f8, HSP60, HSP70, SAPA and H1) and the consensus tree constructed according to these regions allowed us to observe two well-defined groups with close association to the transmission cycles (domestic/peridomestic and sylvatic) of Chagas disease in Colombia. Our findings allowed us to corroborate the previous reported genotypes based on the intergenic region of mini-exon gene. More studies examining the genetic diversity among T. cruzi I populations must be conducted in order to obtain a better understanding in regions where this DTU is endemic.

The revised Trypanosoma cruzi subspecific nomenclature: rationale, epidemiological relevance and research applications

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.

Trypanosoma cruzi I diversity: towards the need of genetic subdivision?

Trypanosoma cruzi the aethiological agent of Chagas disease, a complex zoonoses that affects the American continent is a genetically variable parasite subdivided into six Discrete Typing Units (DTUs). T. cruzi I is the most prevalent DTU affecting the northern countries of America with sporadical cases in the southern countries. T. cruzi I has shown great genetic diversity showing plausible subdivisions needed for this group. Recently, TcI has gained novel importance because of the lately discovered relation with cardiomyopathy manifestations that raises the importance of establishing subdivisions within this DTU.

Phylogenetic reconstruction based on Cytochrome b (Cytb) gene sequences reveals distinct genotypes within Colombian Trypanosoma cruzi I populations

Chagas disease caused by Trypanosoma cruzi comprises an important problem of public health in the Americas. This parasite has been recently divided into six Discrete Typing Units (DTUs) due to its high genetic diversity. We sequenced the Cytochorme b (Cytb) gene of 70 T. cruzi I Colombian clones finding four genotypes related to transmission cycles of Chagas disease in Colombia and also to specific hosts of T. cruzi. The genotypes herein described based on Cytb gene sequences are in accordance with those found using the mini-exon gene and reveals once again the enormous genetic diversity at sub-DTU level evidenced in T. cruzi I.

Immunological identification of Trypanosoma cruzi lineages in human infection along the endemic area

Genotyping studies show a polarized geographic distribution of Trypanosoma cruzi lineages in humans. Here, we assessed their distribution along Latin America through an immunological approach we designated Western blot (WB) assay with Trypomastigote small-surface antigen (TSSA) I and TSSA II (TSSA-WB). These antigens are expressed by T. cruzi I (TCI; now TcI) and T. cruzi II (TCII; reclassified as TcII to TcVI) parasites. TSSA-WB showed good concordance with genotyping tests. An unexpected frequency of TSSA II recognition was observed in Colombia, Venezuela, and Mexico (northern region of Latin America). In Argentina and Paraguay (southern region), immunophenotyping confirmed the already reported TCII (TcII to TcVI) dominance. The lineage distribution between these regions showed significant difference but not among countries within them (except for Colombia and Venezuela). TSSA-WB shows TCII emergence in the northern region where TCI was reported as dominant or even as the unique T. cruzi lineage infecting humans.

Trypanosoma cruzi I genotypes in different geographical regions and transmission cycles based on a microsatellite motif of the intergenic spacer of spliced-leader genes

The intergenic region of spliced-leader (SL-IR) genes from 105 Trypanosoma cruzi I (Tc I) infected biological samples, culture isolates and stocks from 11 endemic countries, from Argentina to the USA were characterised, allowing identification of 76 genotypes with 54 polymorphic sites from 123 aligned sequences. On the basis of the microsatellite motif proposed by Herrera et al. (2007) to define four haplotypes in Colombia, we could classify these genotypes into four distinct Tc I SL-IR groups, three corresponding to the former haplotypes Ia (11 genotypes), Ib (11 genotypes) and Id (35 genotypes); and one novel group, Ie (19 genotypes). Genotypes harbouring the Tc Ic motif were not detected in our study. Tc Ia was associated with domestic cycles in southern and northern South America and sylvatic cycles in Central and North America. Tc Ib was found in all transmission cycles from Colombia. Tc Id was identified in all transmission cycles from Argentina and Colombia, including Chagas cardiomyopathy patients, sylvatic Brazilian samples and human cases from French Guiana, Panama and Venezuela. Tc Ie gathered five samples from domestic Triatoma infestans from northern Argentina, nine samples from wild Mepraia spinolai and Mepraia gajardoi and two chagasic patients from Chile and one from a Bolivian patient with chagasic reactivation. Mixed infections by Tc Ia+Tc Id, Tc Ia+Tc Ie and Tc Id+Tc Ie were detected in vector faeces and isolates from human and vector samples. In addition, Tc Ia and Tc Id were identified in different tissues from a heart transplanted Chagas cardiomyopathy patient with reactivation, denoting histotropism. Trypanosoma cruzi I SL-IR genotypes from parasites infecting Triatoma gerstaeckeri and Didelphis virginiana from USA, T. infestans from Paraguay, Rhodnius nasutus and Rhodnius neglectus from Brazil and M. spinolai and M. gajardoi from Chile are to our knowledge described for the first time.

Genotyping of Trypanosoma cruzi sublineage in human samples from a North-East Argentina area by hybridization with DNA probes and specific polymerase chain reaction (PCR)

We have evaluated blood samples of chronic and congenital Trypanosoma cruzi-infected patients from the city of Reconquista located in the northeast of Argentina where no information was previously obtained about the genotype of infecting parasites. Fourteen samples of congenital and 19 chronical patients were analyzed by hybridization with DNA probes of minicircle hypervariable regions (mHVR). In congenital patients, 50% had single infections with TcIId, 7% single infections with TcIIe, 29% mixed infections with TcIId/e, and 7% had mixed infections with TcIId/b and 7% TcIId/b, respectively. In Chronical patients, 52% had single infections with TcIId, 11% single infections with TcIIe, 26% had mixed infections with TcIId/e, and 11% had non-identified genotypes. With these samples, we evaluated the minicircle lineage-specific polymerase chain reaction assay (MLS-PCR), which involves a nested PCR to HVR minicircle sequences and we found a correlation with hybridization probes of 96.4% for TcIId and 54.8% for TcIIe.

Haplotype identification within Trypanosoma cruzi I in Colombian isolates from several reservoirs, vectors and humans

Genetic variability in the Trypanosoma cruzi I group has recently been revealed in Colombian isolates from humans, reservoirs and vectors. Genomic rearrangements and the polymorphic regions in taxonomic markers, such as the miniexon gene, have led to the development of molecular tools to identify phylogenetic haplotypes in T. cruzi isolates. From genetic polymorphisms found in T. cruzi I isolates, they have been classified into four haplotypes according to their epidemiologic transmission cycles. Haplotype Ia is associated with domestic isolates, from Rhodnius prolixus; haplotype Ib, with the domestic and peridomestic cycle, mainly associated with Triatoma dimidiata; haplotype Ic is a poorly characterized group, which has been associated with the peridomestic cycle; and haplotype Id has been related to the sylvatic cycle. In order to demonstrate that the circulating T. cruzi I isolates in Colombia can be classified in the four proposed haplotypes, specific primers were designed on polymorphic regions of the miniexon gene's intergenic sequences. This set of primers allowed the molecular characterization of 33 Colombian isolates, classifying them into three of the four proposed haplotypes (Ia, Ib and Id). Results obtained from maximum parsimony and maximum-likelihood-based phylogenetic analyses correlated with the molecular classification of the isolates and their transmission cycles. This study brings insights into the Chagas disease epidemiology and the parasite's transmission dynamics.

Geographical clustering of Trypanosoma cruzi I groups from Colombia revealed by low-stringency single specific primer-PCR of the intergenic regions of spliced-leader genes

A low-stringency single-primer polymerase chain reaction (LSSP-PCR) typing procedure targeted to the intergenic regions of spliced-leader genes (SL) was designed to profile Trypanosoma cruzi I stocks from endemic regions of Colombia. Comparison between SL-LSSP-PCR profiles of parasite DNA from vector faeces and cultures isolated from those faeces showed more conservative signatures than profiles using LSSP-PCR targeted to the minicircle variable regions (kDNA). This was also observed by analysing 15 parasite clones from one stock as well as serial samples of a same stock after in vitro culturing or inoculation into mice. Thus, SL-LSSP-PCR appears more appropriate than kDNA-LSSP-PCR for reliable typing of major T. cruzi I groups from in vitro cultured stocks and triatomine faeces. SL-LSSP-PCR grouped 46 of 47 T. cruzi I Colombian stocks according to their geographical procedences in four clusters: Cluster Cas from Casanare Department, Cluster Mg from Northern Magdalena department, Cluster Mom from Momposina Depression in Southern Magdalena and finally Cluster NW from northwestern Colombia, including Sucre, Chocó, Córdoba and Antioquia departments. Sequence analysis identified punctual mutations among amplicons from each cluster. Within Cluster Mg, sequence polymorphism allowed association with different sylvatic vector species. Novel SL sequences and LSSP-PCR profiles are reported from T. cruzi I infecting Eratyrus cuspidatus, Panstrongylus geniculatus and Rhodnius pallescens vectors.

Biological characterization of Trypanosoma cruzi stocks from domestic and sylvatic vectors in Sierra Nevada of Santa Marta, Colombia

Sierra Nevada of Santa Marta is one of the most endemic regions of Chagas disease in Colombia. In this study, we compared the biological behavior and genetic features of Trypanosoma cruzi stocks that were isolated from domestic and sylvatic insects in this area. Rhodnius prolixus (from domestic environments) and Triatoma dimidiata (from sylvatic, peridomestic and domestic environments) are the most important vectors in this region. Genetic characterization showed that all stocks corresponded to T. cruzi I, but LSSP-PCR analyses indicated that some genotypes were present in both environments. Biological characterization in vitro showed a low growth rate in sylvatic T. cruzi stocks and in some domestic T. cruzi stocks, possibly indicating the presence of stocks with similar behavior in both transmission cycles. In parallel, in vivo behavioral analysis also indicated that T. cruzi stocks are variable and this species did not show a correlation between the environments where they were isolated. In addition, all stocks demonstrated a low mortality rate and histopathological lesions in heart, skeletal muscle and colon tissue. Moreover, our data indicated that experimentally infected chagasic mice displayed a relation between their myocardial inflammation intensity, parasitism tissue and parasite load using the qPCR. In conclusion, our results indicate that the T. cruzi stocks present in SNSM have similar biological behavior and do not show a correlation with the different transmission cycles. This could be explained by the complex transmission dynamics of T. cruzi in Sierra Nevada of Santa Marta, where hosts, vectors (e.g., T. dimidiata) and reservoirs circulate in both environments due to the close contact between the two transmission cycles, favoring environment overlapping. This knowledge is an important key to understanding the epidemiology and pathology of Chagas disease in this Colombian region. Furthermore, our findings could be of significant use in the design of control strategies restricted to a specified endemic region.

Trypanosoma cruzi: exploring the nuclear genome of zymodeme 3 stocks by chromosome size polymorphism

Chagas disease is emerging in the Brazilian Amazon. We evaluated the position of eight zymodeme 3 isolates from Amazonian sylvatic vectors and one human case in relation to Trypanosoma cruzi I and II major groups and hybrid strains by chromosome size polymorphism. Nineteen isolates were analyzed by mapping nine coding sequences on chromosomal bands (0.6-3.3Mbp). Numerical analysis was based on the absolute chromosomal size difference index (aCSDI). A dendrogram was obtained applying the minimum evolution criterion and considering the aCSDI values to estimate the branch lengths. The isolates were distributed in four groups. Group A clustered hybrid isolates; Groups B and C, T. cruzi II and T. cruzi I isolates, respectively. Seven Z3 stocks were clustered in Group D, which showed low intra-group diversity and was the most divergent. The proportion of two different-sized homologous chromosomes was determined. Wild vectors harboring Z3 stocks constitute a potential reservoir of human infection in the Amazon.