Trypanosoma cruzi IV causing outbreaks of acute Chagas disease and infections by different haplotypes in the Western Brazilian Amazonia

Comparative analysis of metacyclogenesis and infection curves in different discrete typing units of Trypanosoma cruzi

Chagas disease (CD), caused by the complex life cycle parasite Trypanosoma cruzi, is a global health concern and impacts millions globally. T. cruzi's genetic variability is categorized into discrete typing units (DTUs). Despite their widespread presence in the Americas, a comprehensive understanding of their impact on CD is lacking. This study aims to analyze life cycle traits across life cycle stages, unraveling DTU dynamics. Metacyclogenesis curves were generated, inducing nutritional stress in epimastigotes of five DTUs (TcI (MG), TcI (DA), TcII(Y), TcIII, TcIV, and TcVI), resulting in metacyclic trypomastigotes. Infection dynamics in Vero cells from various DTUs were evaluated, exploring factors like amastigotes per cell, cell-derived trypomastigotes, and infection percentage. Statistical analyses, including ANOVA tests, identified significant differences. Varying onset times for metacyclogenesis converged on the 7th day. TcI (MG) exhibited the highest metacyclogenesis potential. TcI (DA) stood out, infecting 80% of cells within 24 h. TcI demonstrated the highest potential in both metacyclogenesis and infection among the strains assessed. Intra-DTU diversity was evident among TcI strains, contributing to a comprehensive understanding of Trypanosoma cruzi dynamics and genetic diversity.

New insights into Trypanosoma cruzi genetic diversity, and its influence on parasite biology and clinical outcomes

Chagas disease, caused by Trypanosoma cruzi, remains a serious public health problem worldwide. The parasite was subdivided into six distinct genetic groups, called "discrete typing units" (DTUs), from TcI to TcVI. Several studies have indicated that the heterogeneity of T. cruzi species directly affects the diversity of clinical manifestations of Chagas disease, control, diagnosis performance, and susceptibility to treatment. Thus, this review aims to describe how T. cruzi genetic diversity influences the biology of the parasite and/or clinical parameters in humans. Regarding the geographic dispersion of T. cruzi, evident differences were observed in the distribution of DTUs in distinct areas. For example, TcII is the main DTU detected in Brazilian patients from the central and southeastern regions, where there are also registers of TcVI as a secondary T. cruzi DTU. An important aspect observed in previous studies is that the genetic variability of T. cruzi can impact parasite infectivity, reproduction, and differentiation in the vectors. It has been proposed that T. cruzi DTU influences the host immune response and affects disease progression. Genetic aspects of the parasite play an important role in determining which host tissues will be infected, thus heavily influencing Chagas disease's pathogenesis. Several teams have investigated the correlation between T. cruzi DTU and the reactivation of Chagas disease. In agreement with these data, it is reasonable to suppose that the immunological condition of the patient, whether or not associated with the reactivation of the T. cruzi infection and the parasite strain, may have an important role in the pathogenesis of Chagas disease. In this context, understanding the genetics of T. cruzi and its biological and clinical implications will provide new knowledge that may contribute to additional strategies in the diagnosis and clinical outcome follow-up of patients with Chagas disease, in addition to the reactivation of immunocompromised patients infected with T. cruzi.

Detection and Genotyping of Trypanosoma cruzi Samples in Species of Genus Rhodnius from Different Environments in the Brazilian Amazon

Background: In the Amazon region, several species of triatomines occur in the natural environments. Among them, species of the genus Rhodnius are a risk to human populations due to their high rates of infection with Trypanosoma cruzi. The aim of this study was to identify the T. cruzi genotypes in Rhodnius specimens and their relationship with sylvatic hosts from different environments in the Brazilian Amazon. Methods: A total of 492 triatomines were collected from the municipalities of Monte Negro, Rondônia state, and Humaitá, Amazonas state, 382 of them being nymphs and 110 adults. Genotyping of T. cruzi in six discrete typing units (DTUs) was performed using conventional multilocus PCR. The triatomines that were positive for T. cruzi and engorged with blood were also targeted for amplification of the cytochrome B (cytB) gene to identify bloodmeal sources. Results: Of the 162 positive samples, the identified DTUs were TcI (87.65%) and TcIV (12.35%). It was observed that 102 specimens were engorged with a variety of bloodmeals. Triatomines infected with TcI were associated with DNA of all identified vertebrates, except Plecturocebus brunneus. TcIV was detected in triatomines that fed on Coendou prehensilis, Didelphis marsupialis, Mabuya nigropunctata, P. brunneus, Pithecia irrorata, Sapajus apella, and Tamandua tetradactyla. Conclusion: Results highlight the need to understand the patterns of T. cruzi genotypes in Rhodnius spp. and their association with sylvatic hosts to better elucidate their role in the transmission of Chagas disease in the Amazon region.

Fifteen Years after the Definition of Trypanosoma cruzi DTUs: What Have We Learned?

Trypanosoma cruzi, the protozoan causative of Chagas disease (ChD), exhibits striking genetic and phenotypic intraspecific diversity, along with ecoepidemiological complexity. Human-pathogen interactions lead to distinct clinical presentations of ChD. In 2009, an international consensus classified T. cruzi strains into six discrete typing units (DTUs), TcI to TcVI, later including TcBat, and proposed reproducible genotyping schemes for DTU identification. This article aims to review the impact of classifying T. cruzi strains into DTUs on our understanding of biological, ecoepidemiological, and pathogenic aspects of T. cruzi. We will explore the likely origin of DTUs and the intrinsic characteristics of each group of strains concerning genome organization, genomics, and susceptibility to drugs used in ChD treatment. We will also provide an overview of the association of DTUs with mammalian reservoirs, and summarize the geographic distribution, and the clinical implications, of prevalent specific DTUs in ChD patients. Throughout this review, we will emphasize the crucial roles of both parasite and human genetics in defining ChD pathogenesis and chemotherapy outcome.

Chronic Chagas Cardiomyopathy in the Brazilian Amazon region: clinical characteristics and regional distinctiveness

Objectives

This study aims to provide a comprehensive analysis of clinical and epidemiological data related to Chronic Chagas Cardiomyopathy (CCC) in the Amazon region of Brazil.

Methods

A review of observational, retrospective, and cross-sectional studies related to Chagas Disease in the Amazon region of Brazil was conducted, and a case series addressing CCC in patients treated at the FMT-HVD outpatient clinic, a reference center for Chagas disease in Brazil, was carried out.

Results

Clinical characteristics of 55 patients from the Amazon region with CCC were described. The most common electrocardiographic alteration observed was abnormal ventricular repolarization (AVR), present in 40% of cases. The most common echocardiographic finding was left ventricular systolic dysfunction (49%), followed by akinesia or hypokinesia of the inferior and/or inferolateral walls (38.1%) and the presence of an apical aneurysm (32.7%).

Conclusions

Overall, this study demonstrates that CCC in the Amazon region presents clinical characteristics and severity that are similar to those observed in other regions. However, certain peculiarities, such as the frequency of right bundle branch block (RBBB) and anterior and septal involvement during the acute phase, require additional investigation to better comprehend the disease in the region. Overall, the study provides crucial clinical insights for the diagnosis and treatment of CCC in the Amazon region.

Detection of Trypanosoma cruzi DTUs TcI and TcIV in two outbreaks of orally-transmitted Chagas disease in the Northern region of Brazil

This study describes the laboratory investigation of two acute Chagas disease outbreaks that occurred in the riverside communities of Marimarituba and Cachoeira do Arua, in the Santarem municipality, Para State, located in the Northern region of Brazil, and occurred in March 2016 and August 2017, respectively. The generation of data regarding the diversity of Trypanosoma cruzi parasites circulating in the Amazon region is key for understanding the emergence and expansion of Chagas disease. This study aimed to identify T. cruzi Discrete Typing Units (DTUs) involved in two outbreaks of acute Chagas disease (ACD) directly from the patient's biological sample. Nested and multiplex PCR targeting the 24Sα (rRNA) and mini-exon genes, respectively, were used to identify T. cruzi DTU in blood samples from patients diagnosed with ACD. The samples with positive cPCR were submitted for analysis for T. cruzi DTUs, which included 13 samples from the patients with ACD by oral transmission and two samples collected from two newborns of two women with ACD, from Marimarituba and Cachoeira do Arua. The samples were classified as T. cruzi TcIV, from Marimarituba's outbreak, and T. cruzi TcI, from Cachoeira do Arua's outbreak. The molecular identification of T. cruzi may increase understanding of the role of this parasite in Chagas disease's emergence within the Amazon region, contributing to the improvement of the management of this important, but also neglected, disease.

Infection susceptibility and vector competence of Rhodnius robustus Larrousse, 1927 and R. pictipes Stal, 1872 (Hemiptera, Reduviidae, Triatominae) for strains of Trypanosoma cruzi (Chagas, 1909) (Kinetoplastida, Trypanosomatidae) I, II and IV

Background

Rhodnius robustus and Rhodnius pictipes are vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease (CD), that are found in the Brazilian Amazon region. Susceptibility to infection and vector competence depend on the parasite-vector relationship. Our objective was to evaluate the interaction between T. cruzi and these two triatomine vectors in pure and mixed experimental infections of T. cruzi strains from the same or different geographic regions.

Methods

Fifth-instar nymphs of R. robustus and R. pictipes were fed on mice infected with four T. cruzi strains, namely genotypes TcIAM, TcIMG, TcIIPR, and TcIVAM, respectively, from the Brazilian states of Amazonas, Minas Gerais and Paraná. Over a period of 120 days, excreta were examined every 20 days to assess vector competence, and intestinal contents (IC) were examined every 30 days to determine susceptibility to infection.

Results

The highest positive rate in the fresh examination (%+FE, 30.0%), the highest number of parasitic forms (PF, n = 1969) and the highest metacyclogenesis rate (%MC, 53.8%) in the excreta were recorded for R. robustus/TcIVAM. Examination of the IC of R. pictipes revealed a higher number of PF in infections with TcIAM (22,680 PF) and TcIIPR (19,845 PF) alone or in association (17,145 PF), as well as a %+FE of 75.0% with TcII, in comparison with the other genotypes. The highest %MC (100%) was recorded for the mixed infections of TcIAM with TcIIPR or TcIVAM in the IC of R. pictipes.

Conclusions

Overall, both species were found to be susceptible to the T. cruzi strains studied. Rhodnius robustus showed vector competence for genotypes TcIVAM and TcIAM+TcIVAM and R. pictipes for TcIAM+TcIVAM and TcIAM+TcIIPR; there was elimination of infective forms as early as at 20 days. Our results suggest that both the genetics of the parasite and its geographic origin influence the susceptibility to infection and vector competence, alone or in association.

Graphical Abstract

Triatoma williami in intradomiciliary environments of urban areas in Mato Grosso State, Brazil: domiciliation process of a wild species?

Background

Triatomines in Latin America are natural Chagas disease (ChD) vectors. Triatomine domiciliation is one of the main factors increasing the occurrence risk of this disease in humans. There are 66 triatomine species in Brazil, with three genera of significant epidemiological importance—Panstrongylus, Rhodnius, and Triatoma. Among the Triatoma species, Triatoma williami, a wild species, has been reported in Goiás, Mato Grosso, and Mato Grosso do Sul. In the Barra do Garças, Mato Grosso, the invasion by triatomines has been reported, with T. williami being the most common species. This study aimed to survey triatomine fauna and determine the Trypanosoma cruzi natural infection rates in triatomines in the urban area of Barra do Garças, Mato Grosso, Brazil.

Methods

Triatomine specimens were sampled by passive surveillance or active search by agents combating endemic diseases from 2019 to 2020. A parasitological feces diagnosis was performed to detect the presence of T. cruzi after the specimens were identified. Concerning T. cruzi identification, molecular diagnosis and genetic sequencing were performed to determine the strain, also called discrete typing units (DTUs).

Results

The 211 triatomines were collected, distributed in specimens of T. williami (84.4%), P. geniculatus (3.3%), P. diasi (1.4%), and R. neglectus (10.9%). Two colonies of T. williami were found through morphological analyses. These insects were sampled inside domiciles in an urban area neighboring Jardim Pitaluga (15° 51′57.7″ N, 052° 16′ 04.5 E). The records were sampled in September 2019 and January 2021. The rate of natural infection by T. cruzi was 39.4%. Two T. williami specimens from the sampled colonies were positive for the T. cruzi strain DTU IV.

Conclusions

This is the first time that T. williami has been confirmed in an urban area of Barra do Garças, Mato Grosso, Brazil. Further studies are needed for a clearer understanding of the ecology of this species for prevention and control mechanisms since its sampled specimens had a high rate of natural infection by T. cruzi.

Graphical Abstract

Experimental infection of Rhodnius robustus Larrousse, 1927 (Hemiptera, Reduviidae, Triatominae) with Trypanosoma cruzi (Chagas, 1909) (Kinetoplastida, Trypanosomatidae) IV

Vector competence of triatomines (kissing bugs) for Trypanosoma cruzi transmission depends on the parasite-vector interaction and the genetic constitution of both. This study evaluates the susceptibility and vector competence of Rhodnius robustus experimentally infected with T. cruzi IV (TcIV). Nymphs were fed on infected mice or an artificial feeder with blood containing culture-derived metacyclic trypomastigotes (CMT) or blood trypomastigotes (BT). The intestinal contents (IC) and excreta of the insects were examined by fresh examination and kDNA-PCR. The rate of metacyclogenesis was also determined by differential counts. Fifth instar nymphs fed with CMT ingested a greater blood volume (mean of 74.5 μL) and a greater amount of parasites (mean of 149,000 CMT/μL), and had higher positivity in the fresh examination of the IC. Third instar nymphs fed with CMT had higher positivity (33.3%) in the fresh examination of the excreta. On the 20th day after infection (dai), infective metacyclic trypomastigote (MT) forms were predominant in the excreta of 3/4 experimental groups, and on the 30th dai, the different parasitic forms were observed in the IC of all the groups. Higher percentages of MT were observed in the excreta of the 5th instar nymphs group (84.1%) and in the IC of the 3rd instar nymphs group (80.0%). Rhodnius robustus presented high susceptibility to infection since all nymphs were infected, regardless of the method used for blood meal, in addition these insects demonstrated vector competence for TcIV with high rates of metacyclogenesis being evident.

Bioecological aspects of triatomines and marsupials as wild Trypanosoma cruzi reservoirs in urban, peri-urban and rural areas in the Western Brazilian Amazon

In the Amazon region, Trypanosoma cruzi transmission cycles involve a great diversity of Triatominae vectors and mammal reservoirs. Some Rhodnius spp. mainly inhabit palm trees that act as microhabitats for hosts and vectors. The current study aimed to describe aspects of the bio-ecology of the vectors and reservoirs of T. cruzi in relation to human populations resident near areas with large quantities of palm trees, in rural, peri-urban and urban collection environments, located in the Western Brazilian Amazon. Rhodnius pictipes and Didelphis marsupialis were respectively the most predominant vector and reservoir, with rates of 71% for R. pictipes and 96.5% for D. marsupialis. The vast majority of T. cruzi isolates clustered with TcI. The most prevalent haplotype was TcI COII1 (69.7%). Mauritia flexuosa and Attalea phalerata were the main ecological indicators of infestation by triatomines. Birds were the most common food source (27,71%). T. cruzi isolated from R. robustus has the haplotype HUM-13, previously detected in a chronic Chagas patient living in the same area. Our results demonstrate the relevance of this study, with the occurrence of elevated infection rates in animals, and suggest the importance of the Amazon zones where there is a risk of infection in humans.

Maxicircle architecture and evolutionary insights into Trypanosoma cruzi complex

We sequenced maxicircles from T. cruzi strains representative of the species evolutionary diversity by using long-read sequencing, which allowed us to uncollapse their repetitive regions, finding that their real lengths range from 35 to 50 kb. T. cruzi maxicircles have a common architecture composed of four regions: coding region (CR), AT-rich region, short (SR) and long repeats (LR). Distribution of genes, both in order and in strand orientation are conserved, being the main differences the presence of deletions affecting genes coding for NADH dehydrogenase subunits, reinforcing biochemical findings that indicate that complex I is not functional in T. cruzi. Moreover, the presence of complete minicircles into maxicircles of some strains lead us to think about the origin of minicircles. Finally, a careful phylogenetic analysis was conducted using coding regions of maxicircles from up to 29 strains, and 1108 single copy nuclear genes from all of the DTUs, clearly establishing that taxonomically T. cruzi is a complex of species composed by group 1 that contains clades A (TcI), B (TcIII) and D (TcIV), and group 2 (1 and 2 do not coincide with groups I and II described decades ago) containing clade C (TcII), being all hybrid strains of the BC type. Three variants of maxicircles exist in T. cruzi: a, b and c, in correspondence with clades A, B, and C from mitochondrial phylogenies. While A and C carry maxicircles a and c respectively, both clades B and D carry b maxicircle variant; hybrid strains also carry the b- variant. We then propose a new nomenclature that is self-descriptive and makes use of both the phylogenetic relationships and the maxicircle variants present in T. cruzi.

Therapeutic effects of benznidazole in Swiss mice that are orally inoculated with Trypanosoma cruzi IV strains from the Western Brazilian Amazon

Strains of Trypanosoma cruzi, etiological agent of Chagas disease, are classified into different discrete typing units that may present distinct dynamics of infection and susceptibility to benznidazole (BZ) treatment. Mice that were orally inoculated with T. cruzi IV strains exhibited a more intense course of infection compared with intraperitoneally inoculated mice, reflected by higher parasite loads. We evaluated the efficacy of BZ treatment in Swiss mice that were inoculated with T. cruzi IV strains from the Western Brazilian Amazon. The mice were orally (OR) or intraperitoneally (IP) inoculated with 2 × 10⁶ culture-derived metacyclic trypomastigotes of the AM14, AM16, AM64, and AM69 strains of T. cruzi that were obtained from two outbreaks of orally acquired acute Chagas disease in the state of Amazonas, Brazil. The animals were treated with BZ (100 mg/kg/day for 20 days). Fresh blood examination, hemoculture, conventional and quantitative real-time polymerase chain reaction were performed to monitor the therapeutic effects of BZ. Significant reductions in five of 24 parameters of parasitemia and parasite load were found in different tissues in the OR group, indicating worse response to BZ treatment compared with the IP group, in which significant reductions in nine of those 24 parameters were observed. The cure rates in the OR groups ranged from 18.2% (1/11) to 75.0% (9/12) and in the IP groups from 58.3% (7/12) to 91.7% (11/12), for the AM14 and AM69 strains, respectively. These findings indicate that treatment with BZ had fewer beneficial effects with regard to reducing parasitemia and parasite load in different tissues of mice that were OR inoculated with four TcIV strains compared with IP inoculation. Therefore, the route of infection with T. cruzi should be considered when evaluating the therapeutic efficacy of BZ in patients with Chagas disease.

Suspected vertical transmission of Chagas disease caused by DTU TcIV in an infection probably transmitted orally, during anoutbreak in the Brazilian Amazon

This study describes difficulties in the monitoring of a child born during an oral outbreak of Chagas disease, in which there are several indications that the transmission occurred through the congenital route: 1. the mother was in the third trimester of pregnancy when she was infected; 2. She presented high parasitemia at the time of delivery; 3. In both, the mother and her daughter, T. cruzi was classified as DTU TcIV. The parasites were not found in the blood at birth and the infection was detected only three months later in an asymptomatic infant. As the mother and her child live in a highly endemic area, vector transmission could not be excluded during this period.

The Selvester QRS score as an estimative of myocardial injury in acute chagasic patients from the Brazilian Amazon

BACKGROUND

In the Brazilian Amazon, a new epidemiological profile of Chagas disease transmission, the oral route, has been detected and cited as being responsible for the increase in acute cases in Brazil. The clinical evaluation of acute Chagas disease (ACD) has been a challenge since it can progress to a chronic phase with cardiac alterations, and the follow-up by modern diagnostic methods is very difficult due to the socio-geographical characteristics of the Brazilian Amazon. Thus, alternatives should be sought to alleviate this problem. We conducted a study to evaluate subjects with ACD using the 12-lead ECG QRS score (Selvester score) as an estimative of myocardial injury progression before and after ACD treatment.

METHODS

The study included indigenous subjects from the Amazon region with ACD in clinical follow-up at the Fundação de Medicina Tropical Dr. Heitor Vieira Dourado (FMT-HVD) Chagas Disease outpatient clinic in the state of Amazonas, Brazil. The control group consisted of 31 healthy volunteers with no history of heart disease and no reactive serology for Chagas disease. Baseline ECG was performed in all subjects. The Selvester scoring method was performed according to the standardized guide (< 3 points: no myocardial injury,> 3: points × 3% = % of the predicted LV infarction).

RESULTS

A total of 62 subjects were included, 31 as cases and 31 as controls. The mean follow-up of the case group was 17 months. The control group presented normal ECG. The case group presented 13 alterations before treatment and 11 after. Nineteen individuals presented scores > 3 points, 6 before and 13 after. In 19.36% of subjects, myocardial injury was found before treatment and in 41.94% after treatment.

CONCLUSION

This is the first study that uses the Selvester score (SS) to predict myocardial injury in subjects with ACD. The results of this study suggest the significant presence of myocardial injury from the beginning of treatment to the period post treatment of ACD, which demonstrates that the SS can be applied for stratification and follow-up of Chagas disease in the Amazon region.

Culture-free genome-wide locus sequence typing (GLST) provides new perspectives on Trypanosoma cruzi dispersal and infection complexity

Analysis of genetic polymorphism is a powerful tool for epidemiological surveillance and research. Powerful inference from pathogen genetic variation, however, is often restrained by limited access to representative target DNA, especially in the study of obligate parasitic species for which ex vivo culture is resource-intensive or bias-prone. Modern sequence capture methods enable pathogen genetic variation to be analyzed directly from host/vector material but are often too complex and expensive for resource-poor settings where infectious diseases prevail. This study proposes a simple, cost-effective 'genome-wide locus sequence typing' (GLST) tool based on massive parallel amplification of information hotspots throughout the target pathogen genome. The multiplexed polymerase chain reaction amplifies hundreds of different, user-defined genetic targets in a single reaction tube, and subsequent agarose gel-based clean-up and barcoding completes library preparation at under 4 USD per sample. Our study generates a flexible GLST primer panel design workflow for Trypanosoma cruzi, the parasitic agent of Chagas disease. We successfully apply our 203-target GLST panel to direct, culture-free metagenomic extracts from triatomine vectors containing a minimum of 3.69 pg/μl T. cruzi DNA and further elaborate on method performance by sequencing GLST libraries from T. cruzi reference clones representing discrete typing units (DTUs) TcI, TcIII, TcIV, TcV and TcVI. The 780 SNP sites we identify in the sample set repeatably distinguish parasites infecting sympatric vectors and detect correlations between genetic and geographic distances at regional (< 150 km) as well as continental scales. The markers also clearly separate TcI, TcIII, TcIV and TcV + TcVI and appear to distinguish multiclonal infections within TcI. We discuss the advantages, limitations and prospects of our method across a spectrum of epidemiological research.

Host Genetics Background Influence in the Intragastric Trypanosoma cruzi Infection

Background

Considering the complexity of the factors involved in the immunopathology of Chagas disease, which influence the Chagas' disease pathogenesis, anti-T. cruzi immune response, and chemotherapy outcome, further studies are needed to improve our understanding about these relationships. On this way, in this article we analyzed the host genetic influence on hematological, histopathological and immunological aspects after T. cruzi infection.

Methods

BALB/c and A mice were intragastrically infected with T. cruzi SC2005 strain, isolated from a patient of an outbreak of Chagas disease. Parameters such as parasite load, survival rates, cytokines production, macrophages, T and B cell frequencies, and histopathology analysis were carried out.

Results

BALB/c mice presented higher parasitemia and mortality rates than A mice. Both mouse lineages exhibited hematological alterations suggestive of microcytic hypochromic anemia and histopathological alterations in stomach, heart and liver. The increase of CD8+ T cells, in heart, liver and blood, and the increase of CD19+ B cells, in liver, associated with a high level of proinflammatory cytokines (IL-6, TNF-α, IFN-γ), confer a resistance profile to the host. Although BALB/c animals exhibited the same findings observed in A mice, the response to infection occurred later, after a considerable parasitemia increase. By developing an early response to the infection, A mice were found to be less susceptible to T. cruzi SC2005 infection.

Conclusions

Host genetics background shaping the response to infection. The early development of a cytotoxic cellular response profile with the production of proinflammatory cytokines is important to lead a less severe manifestation of Chagas disease.

Landmarks of the Knowledge and Trypanosoma cruzi Biology in the Wild Environment

Trypanosomatids are ancient parasitic eukaryotes that still maintain prokaryotic characteristics. Trypanosoma cruzi, a primarily wild mammal parasite, infected humans already long before European colonization of the Americas. T. cruzi heterogeneity remains an unsolved question, and until now, it has still not been possible to associate T. cruzi genotypes with any biological or epidemiological feature. One of the first biochemical attempts to cluster the T. cruzi subpopulations recognized three main subpopulations (zymodemes) that have been associated with the transmission cycles in the wild (Z1; Z3) and in the domestic environment (Z2). The description of wild mammal species harboring Z2 two decades later challenged this assemblage attempt. Currently, the genotypes of T. cruzi are assembled in seven discrete typing units (DTUs). The biology of T. cruzi still shows novelties such as the description of epimastigotes multiplying and differentiating to metacyclic trypomastigotes in the lumen of the scent glands of Didelphis spp. and the capacity of the true meiosis in parallel to clonal reproduction. The study of the transmission cycle among wild animals has broken paradigms and raised new questions: (i) the interaction of the T. cruzi DTUs with each of its mammalian host species displays peculiarities; (ii) the impact of mixed genotypes and species on the transmissibility of one or another species or on pathogenesis is still unknown; (iii) independent T. cruzi transmission cycles may occur in the same forest fragment; (iv) the capacity to act as a reservoir depends on the peculiarities of the host species and the parasite genotype; and (v) faunistic composition is a defining trait of the T. cruzi transmission cycle profile. The development of models of environmental variables that determine the spatial distribution of the elements that make up T. cruzi transmission by spatial analysis, followed by map algebra and networking, are the next steps toward interpreting and dealing with the new profile of Chagas disease with its many peculiarities. There is no way to solve this neglected disease once and for all if not through a multidisciplinary look that takes into account all kinds of human and animal activities in parallel to environmental variations.

Chagas Disease in the United States: a Public Health Approach

Trypanosoma cruzi is the etiological agent of Chagas disease, usually transmitted by triatomine vectors. An estimated 20 to 30% of infected individuals develop potentially lethal cardiac or gastrointestinal disease. Sylvatic transmission cycles exist in the southern United States, involving 11 triatomine vector species and infected mammals such as rodents, opossums, and dogs. Nevertheless, imported chronic T. cruzi infections in migrants from Latin America vastly outnumber locally acquired human cases. Benznidazole is now FDA approved, and clinical and public health efforts are under way by researchers and health departments in a number of states. Making progress will require efforts to improve awareness among providers and patients, data on diagnostic test performance and expanded availability of confirmatory testing, and evidence-based strategies to improve access to appropriate management of Chagas disease in the United States.

Co-infection with distinct Trypanosoma cruzi strains induces an activated immune response in human monocytes

AIMS

The aim of the study was to evaluate the immune response triggered by the first contact of human monocytes with two T cruzi strains from distinct discrete typing units (DTUs) IV and V, and whether co-infection with these strains leads to changes in monocyte immune profiles, which could in turn influence the subsequent infection outcome.

METHODS AND RESULTS

We evaluated the influence of in vitro single- and co-infection with AM64 and 3253 strains on immunological characteristics of human monocytes. Single infection of monocytes with AM64 or 3253 induced opposing anti-inflammatory and inflammatory responses, respectively. Co-infection was observed in over 50% of monocytes after 15 hours of culture, but this percentage dropped ten-fold after 72 hours. Co-infection led to high monocyte activation and an increased percentage of both IL-10 and TNF. The decreased percentage of co-infected cells observed after 72 hours was associated with a decreased frequency of TNF-expressing cells.

CONCLUSION

Our results show that the exacerbated response observed in co-infection with immune-polarizing strains is associated with a decreased frequency of co-infected cells, suggesting that the activated response favours parasite control. These findings may have implications for designing new Chagas disease preventive strategies.

Oral Transmission of Trypanosoma cruzi, Brazilian Amazon

In the Brazilian Amazon, the suspected source of infection in an outbreak of acute Chagas disease involving 10 patients was Euterpe oleracea (açaí berry) juice. Patient blood and juice samples contained Trypanosoma cruzi TcIV, indicating oral transmission of the Chagas disease agent.

Cardiac Evaluation in the Acute Phase of Chagas' Disease with Post-Treatment Evolution in Patients Attended in the State of Amazonas, Brazil

Background

In the past two decades, a new epidemiological profile of Chagas' disease (CD) has been registered in the Brazilian Amazon where oral transmission has been indicated as responsible for the increase of acute cases. In the Amazonas state, five outbreaks of acute CD have been registered since 2004. The cardiac manifestations in these cases may be characterized by diffuse myocarditis, with alteration in the electrocardiogram (ECG) and transthoracic echocardiogram (TTE).

Objective

To perform a cardiac evaluation in autochthonous patients in the acute phase and at least one year after submitted to treatment for acute CD and evaluate the demographic variables associated with the presence of cardiac alterations.

Methods

We evaluated patients diagnosed with acute CD through direct parasitological or serological (IgM) methods from 2007 to 2015. These patients were treated with benznidazole and underwent ECG and TTE before and after treatment. We assumed a confidence interval of 95% (CI 95%, p < 0.05) for all variables analyzed.

Results

We observed 63 cases of an acute CD in which oral transmission corresponded to 75%. Cardiac alterations were found in 33% of the cases, with a greater frequency of ventricular repolarization alteration (13%), followed by pericardial effusion (10%) and right bundle branch block and left anterior fascicular block (2%). The follow-up occurred in 48 patients with ECG and 25 with TTE for a mean period of 15.5 ± 4.1 months after treatment. Of these, 8% presented normalization of the cardiac alterations in ECG, 62.5% remained with the normal exams. All of the patients presented normal results in TTE in the post-treatment period. As for the demographic variables, isolated cases presented more cardiac alterations than outbreaks (p = 0.044) as well as cases from Central Amazonas mesoregion (p = 0.020).

Conclusions

Although cardiac alterations have not been frequent in most of the studied population, a continuous evaluation of the clinical-epidemiological dynamics of the disease in the region is necessary in order to establish preventive measures.

Molecular characterization of Trypanosoma cruzi samples derived from Triatoma vitticeps and Panstrongylus geniculatus of the Atlantic rainforest, southeast Brazil

Background: In rural areas of Espírito Santo state, southeast Brazil, triatomine species attracted by light frequently invade residences. The aim of this study was to investigate the Trypanosoma cruzi discrete typing units (DTUs) harbored by these triatomines. Methods: Triatomine’s intestinal contents were examined, inoculated in mice, and the positive samples were cultivated. Flagellates obtained from infected mice hemoculture were submitted to DNA extraction using a salting-out method and to TcSC5D gene amplification. The amplified samples were sequenced, and polymorphism was analyzed for DTU identification. Results: Three hundred and ninety-four triatomines were identified: Triatoma vitticeps (90.03%), Panstrongylus geniculatus (8.89%), Panstrongylus megistus (0.54%), Panstrongylus diasi (0.27%), and Triatoma tibiamaculata (0.27%). Among the specimens, 251/394 (67.65%) presented flagellated forms similar to T. cruzi. After triatomine intestinal content inoculation into mice, 134 mice presented T. cruzi-like trypomastigotes from Tr. vitticeps and P. geniculatus and 89 samples were positive in hemoculture. Sixty-two samples were analyzed for the TcSC5D gene and TcI, TcII, TcIII, and TcIV DTUs were identified. Conclusions: We observed T. cruzi DTU diversity in Tr. vitticeps and P. geniculatus, which showed the predominance of TcII and occurrence of TcI, TcIII and TcIV. Triatomines presented high T. cruzi infection rates. Since little is known regarding the possible mammalian hosts that maintain the T. cruzi cycle, further studies are necessary to obtain a better understanding of the parasite transmission cycle in this region.

Trypanosoma cruzi genetic diversity: Something new for something known about Chagas disease manifestations, serodiagnosis and drug sensitivity

The genetic diversity of Trypanosoma cruzi, the protozoan agent of Chagas disease, is widely recognized. At present, T. cruzi is partitioned into seven discrete typing units (DTUs), TcI-TcVI and Tcbat. This article reviews the present knowledge on the parasite population structure, the evolutionary relationships among DTUs and their distinct, but not exclusive ecological and epidemiological associations. Different models for the origin of hybrid DTUs are examined, which agree that genetic exchange among T. cruzi populations is frequent and has contributed to the present parasite population structure. The geographic distribution of the prevalent DTUs in humans from the southern United States to Argentina is here presented and the circumstantial evidence of a possible association between T. cruzi genotype and Chagas disease manifestations is discussed. The available information suggests that parasite strains detected in patients, regardless of the clinical presentation, reflect the principal DTU circulating in the domestic transmission cycles of a particular region. In contrast, in several orally transmitted outbreaks, sylvatic strains are implicated. As a consequence of the genotypic and phenotypic differences of T. cruzi strains and the differential geographic distribution of DTUs in humans, regional variations in the sensitivity of the serological tests are verified. The natural resistance to benznidazole and nifurtimox, verified in vivo and in vitro for some parasite stocks, is not associated with any particular DTU, and does not explain the marked difference in the anti-parasitic efficacy of both drugs in the acute and chronic phases of Chagas disease. Throughout this review, it is emphasized that the interplay between parasite and host genetics should have an important role in the definition of Chagas disease pathogenesis, anti-T. cruzi immune response and chemotherapy outcome and should be considered in future investigations.

Imaging the development of chronic Chagas disease after oral transmission

Chagas disease is a zoonosis caused by the protozoan parasite Trypanosoma cruzi. Transmission cycles are maintained by haematophagous triatomine bug vectors that carry infective T. cruzi in their faeces. Most human infections are acquired by contamination of mucosal membranes with triatomine faeces after being bitten, however, T. cruzi can be transmitted by several other routes. Oral transmission is an increasingly important aspect of Chagas disease epidemiology, typically involving food or drink products contaminated with triatomines. This has recently caused numerous outbreaks and been linked to unusually severe acute infections. The long-term impact of oral transmission on infection dynamics and disease pathogenesis is unclear. We used highly sensitive bioluminescence imaging and quantitative histopathology to study orally transmitted T. cruzi infections in mice. Both metacyclic and bloodform trypomastigotes were infectious via the oral cavity, but only metacyclics led to established infections by intra-gastric gavage. Mice displayed only mild acute symptoms but later developed significantly increased myocardial collagen content (p = 0.017), indicative of fibrosis. Gastrointestinal tissues and skin were the principal chronic infection reservoirs. Chronic phase parasite load profiles, tissue distribution and myocardial fibrosis severity were comparable to needle-injected controls. Thus, the oral route neither exacerbates nor ameliorates experimental Chagas disease.

Trypanosoma cruzi discrete typing unit TcIV implicated in a case of acute disseminated canine Chagas disease

In 2006, Nabity et al. reported on an atypical presentation of Trypanosoma cruzi (T. cruzi) infection in an 8-month old English Mastiff from central Texas. Clinical signs and laboratory findings included lymphadenopathy, weight loss, amastigotes in lymph node aspirates, and initial serological results suggestive of either T. cruzi or Leishmania infection. Given the poor prognosis, the dog was euthanized and subsequent testing and culture of parasites from a lymph node revealed T. cruzi infection. Because different parasite discrete typing units (DTUs) are potentially associated with different disease outcomes in a variety of mammalian hosts, an understanding of these relationships in naturally infected dogs may be useful for informing canine prognosis and may also have human health implications. Here, we compared strains using culture versus culture-independent methods. We subjected archived cultured parasites harvested from the lymph node in the infected Mastiff to two independent approaches for determining parasite DTU, including sequencing of the TcSC5D gene and use of DTU-specific qPCR probes to hybridize the nuclear spliced leader intergenic region (SL-IR). Both approaches revealed T. cruzi discrete typing unit TcIV. Testing of multiple other tissues directly without culturing, including heart/tongue, intestine, trachea/lymph nodes, and uterus/ovary, provided further evidence of disseminated TcIV infection in this dog. We report T. cruzi DTU TcIV as the cause of a severe disseminated infection in a dog from an area with triatomine vectors in central Texas, adding to the limited body of clinicopathologic data that links specific parasite strains to disease outcomes in dogs in the US. Future studies to type parasites from asymptomatic dogs and those with diverse disease manifestations will be useful in informing the degree to which parasite genetics is associated with disease presentation and severity. If applied to antemortem samples, diagnostic typing of parasites from infected dogs may assist in determining prognosis.

Efficacy of essential oil of Syzygium aromaticum alone and in combination with benznidazole on murine oral infection with Trypanosoma cruzi IV

Chagas disease (CD), caused by Trypanosoma cruzi, remains a serious public health problem. One of the causes of the high morbidity and mortality in patients is the lack of an effective drug therapy. Thus, the aim of this study was to evaluate the efficacy of the essential oil of Syzygium aromaticum alone and in combination with benznidazole (BZ) in mice orally inoculated with strain of T. cruzi IV obtained from oral CD outbreak occurred in Western Brazilian Amazonia. All the animals inoculated with metacyclic trypomastigote forms (AM14 strain, BZ resistant), derived from the insect Rhodnius robustus, became infected and there was no difference in the mortality rate between the experimental groups. When compared with untreated control animals (UTC), the treatment with essential oil of S. aromaticum (EOSA) alone promoted reduction in 1/5 parameters derived from the parasitemia curve, whereas the treatments with BZ alone or in combination (BZ + EOSA) promoted reduction in 4/5 of those parameters, presenting similar profiles of parasitemia curve. The animals treated with BZ and with the combination BZ + EOSA presented lower patency periods in comparison with the animals in EOSA group, and lower positivity of blood cultures when compared with the UTC group. The results of molecular analysis by qPCR in both blood and cardiac tissue did not show differences between the groups. The cure rates obtained with the different treatments presented the following ascending order: EOSA = 12.5% (1/8), BZ = 25.0% (2/8) and BZ + EOSA = 37.5% (3/8). Although there are no significant differences between them, these results claims that the use of this essential oil could be of interest for treatment of Chagas disease.

Sympatry influence in the interaction of Trypanosoma cruzi with triatomine

INTRODUCTION

Trypanosoma cruzi, the etiologic agent of Chagas disease, is widely distributed in nature, circulating between triatomine bugs and sylvatic mammals, and has large genetic diversity. Both the vector species and the genetic lineages of T. cruzi present a varied geographical distribution. This study aimed to verify the influence of sympatry in the interaction of T. cruzi with triatomines. Methods: The behavior of the strains PR2256 (T. cruzi II) and AM14 (T. cruzi IV) was studied in Triatoma sordida (TS) and Rhodnius robustus (RR). Eleven fifth-stage nymphs were fed by artificial xenodiagnosis with 5.6 × 103 blood trypomastigotes/0.1mL of each T. cruzi strain. Every 20 days, their excreta were examined for up to 100 days, and every 30 days, the intestinal content was examined for up to 120 days, by parasitological (fresh examination and differential count with Giemsa-stained smears) and molecular (PCR) methods. Rates of infectivity, metacyclogenesis and mortality, and mean number of parasites per insect and of excreted parasites were determined.

RESULTS

Sympatric groups RR+AM14 and TS+PR2256 showed higher values of the four parameters, except for mortality rate, which was higher (27.3%) in the TS+AM14 group. General infectivity was 72.7%, which was mainly proven by PCR, showing the following decreasing order: RR+AM14 (100%), TS+PR2256 (81.8%), RR+PR2256 (72.7%) and TS+AM14 (36.4%).

CONCLUSIONS

Our working hypothesis was confirmed once higher infectivity and vector capacity (flagellate production and elimination of infective metacyclic forms) were recorded in the groups that contained sympatric T. cruzi lineages and triatomine species.

Identification of novel mammalian hosts and Brazilian biome geographic distribution of Trypanosoma cruzi TcIII and TcIV

Trypanosoma cruzi is a parasitic protozoan responsible for Chagas disease. Seven different Discrete Typing Units (DTUs) of T. cruzi are currently identified in nature: TcI-TcVI, and TcBat whose distribution patterns in nature, hosts/reservoirs and eco-epidemiological importance are still little known. Here, we present novel data on the geographic distribution and diversity of mammalian hosts and vectors of T. cruzi DTUs TcIII and TcIV. In this study, we analyzed 61 T. cruzi isolates obtained from 18 species of mammals (five orders) and two Hemiptera genera. Samples were collected from five Brazilian biomes (Pantanal, Caatinga, Cerrado, Atlantic Rainforest, and Amazon) previously characterized as Z3 or mixed infection (TcI-Z3) by mini-exon gene PCR. To identify TcIII and TcIV genotypes, we applied restriction fragment length polymorphism analysis to the PCR-amplified histone 3 gene. DTUs TcIII and TcIV were identified in single and mixed infections from wide dispersion throughout five Brazilian biomes studied, with TcIV being the most common. Pantanal was the biome that displayed the largest number of samples characterized as TcIII and TcIV in single and mixed infections, followed by Atlantic Rainforest and Amazon. Species from the Didelphimorphia order displayed the highest frequency of infection and were found in all five biomes. We report, for the first time, the infection of a species of the Artiodactyla order by DTU TcIII. In addition, we describe new host species: five mammals (marsupials and rodents) and two genera of Hemiptera. Our data indicate that DTUs TcIII and TcIV are more widespread and infect a larger number of mammalian species than previously thought. In addition, they are transmitted in restricted foci and cycles, but in different microhabitats and areas with distinct ecological profiles. Finally, we show that DTUs TcIII and TcIV do not present any specific association with biomes or host species.

Unraveling Chagas disease transmission through the oral route: Gateways to Trypanosoma cruzi infection and target tissues

Oral transmission of Trypanosoma cruzi, the causative agent of Chagas disease, is the most important route of infection in Brazilian Amazon and Venezuela. Other South American countries have also reported outbreaks associated with food consumption. A recent study showed the importance of parasite contact with oral cavity to induce a highly severe acute disease in mice. However, it remains uncertain the primary site of parasite entry and multiplication due to an oral infection. Here, we evaluated the presence of T. cruzi Dm28c luciferase (Dm28c-luc) parasites in orally infected mice, by bioluminescence and quantitative real-time PCR. In vivo bioluminescent images indicated the nasomaxillary region as the site of parasite invasion in the host, becoming consistently infected throughout the acute phase. At later moments, 7 and 21 days post-infection (dpi), luminescent signal is denser in the thorax, abdomen and genital region, because of parasite dissemination in different tissues. Ex vivo analysis demonstrated that the nasomaxillary region, heart, mandibular lymph nodes, liver, spleen, brain, epididymal fat associated to male sex organs, salivary glands, cheek muscle, mesenteric fat and lymph nodes, stomach, esophagus, small and large intestine are target tissues at latter moments of infection. In the same line, amastigote nests of Dm28c GFP T. cruzi were detected in the nasal cavity of 6 dpi mice. Parasite quantification by real-time qPCR at 7 and 21 dpi showed predominant T. cruzi detection and expansion in mouse nasal cavity. Moreover, T. cruzi DNA was also observed in the mandibular lymph nodes, pituitary gland, heart, liver, small intestine and spleen at 7 dpi, and further, disseminated to other tissues, such as the brain, stomach, esophagus and large intestine at 21 dpi. Our results clearly demonstrated that oral cavity and adjacent compartments is the main target region in oral T. cruzi infection leading to parasite multiplication at the nasal cavity.

Oral transmission of Trypanosoma cruzi associated with food/beverage consumption is presently an important route of infection in Brazil and Venezuela. Colombia, Bolivia, Argentina and Ecuador have also reported to have acute cases of Chagas disease transmission through the oral route. Significant studies about this form of T. cruzi infection are largely lacking. In addition to the classic cardiac involvement, orally-infected patient progress to a highly symptomatic disease and increased mortality rate (8–35%), surpassing the calculated mortality produced by the disease resulting from the biting of infected insect vectors (5–10%). Here, we explored by in vivo bioluminescent images, qPCR and fluorescence microscopy the primary site of parasite entry and multiplication in oral infection (OI). Our results clearly demonstrated that the oral cavity is the main T. cruzi target region in OI, leading to parasite multiplication at the nasal cavity and parasite dissemination to the brain and peripheral tissues. Interestingly, facial edema, paraesthesia of the tongue, gingivitis and dry cough were already described in affected patients. These findings might be associated to our present data, which describe for the first time the nasomaxillary region as the main target tissue following oral T. cruzi infection.

Polymorphisms of blood forms and in vitro metacyclogenesis of Trypanosoma cruzi I, II, and IV

Trypanosoma cruzi is the etiologic agent of American trypanosomiasis has broad biological and genetic diversity. Remaining to be studied are polymorphisms of the blood forms and metacyclogenesis of different T. cruzi discrete typing units (DTUs). Our goal was to evaluate the relationship between T. cruzi DTUs, the morphology of blood trypomastigotes, and in vitro metacyclogenesis. T. cruzi strains that pertained to DTUs TcI, TcII, and TcIV from different Brazilian states were used. Parameters that were related to the morphology of eight strains were assessed in thin blood smears that were obtained from mice that were inoculated with blood or culture forms, depending on strain. The metacyclogenesis of 12 strains was measured using smears with Liver Infusion Tryptose culture medium and M16 culture medium (which is poor in nutrients and has a low pH) at the exponential phase of growth, both stained with Giemsa. The morphological pattern of TcII strains was consistent with broad forms of the parasite. In TcIV strains, slender forms predominated. The Y strain (TcII) was morphologically more similar to TcIV. Significant differences in polymorphisms were observed between DTUs. Metacyclogenesis parameters, although displaying large standard deviations, differed between the DTUs, with the following descending rank order: TcII > TcI > TcIV. The mean numbers of metacyclic trypomastigotes for TcII were significantly higher than the other DTUs. Although the DTUs presented overlapping characteristics, the general pattern was that different DTUs exhibited significantly different morphologies and metacyclogenesis, suggesting that the genetic diversity of T. cruzi could be related to parameters that are associated with the evolution of infection in mammalian hosts and its ability to disperse in nature.

Outcome of oral infection in mice inoculated with Trypanosoma cruzi IV of the Western Brazilian Amazon

A new epidemiological view of American trypanosomiasis or Chagas disease has been formulated in recent decades. Oral transmission of the etiological agent of Chagas disease, Trypanosoma cruzi, has been the most common form of transmission. The T. cruzi discrete typing units TcI and TcIV have been involved in tens outbreaks of acute cases of Chagas disease in the Brazilian Amazon region. We investigated the intensity of infection in mice that were orally inoculated (OR group) with four strains of TcIV that were isolated from two outbreaks of acute Chagas disease that was orally acquired in the state of Amazonas, Brazil. We compared the OR group with mice that were intraperitoneally inoculated (IP group). Blood samples were analyzed by fresh blood examination, hemoculture, and conventional and qualitative real-time polymerase chain reaction (PCR). Samples of different tissues were analyzed by quantitative real-time PCR. The OR group exhibited a higher maximum peak of parasitemia, greater rates of positivity, and higher parasite loads in different tissues during acute infection compared with the IP group, indicating a greater intensity of orally acquired infection. Mice that were orally inoculated with TcIV strains that were obtained from two outbreaks of orally acquired Chagas disease in Amazonas, Brazil, exhibited a more intense course of infection compared with intraperitoneally inoculated mice, reflected by higher levels of parasitemia and parasite loads.

Ecological scenario and Trypanosoma cruzi DTU characterization of a fatal acute Chagas disease case transmitted orally (Espírito Santo state, Brazil)

BACKGROUND

Trypanosoma cruzi infection via oral route results in outbreaks or cases of acute Chagas disease (ACD) in different Brazilian regions and poses a novel epidemiological scenario. In the Espírito Santo state (southeastern Brazil), a fatal case of a patient with ACD led us to investigate the enzootic scenario to avoid the development of new cases. At the studied locality, Triatoma vitticeps exhibited high T. cruzi infection rates and frequently invaded residences.

METHODS

Sylvatic and domestic mammals in the Rio da Prata locality, where the ACD case occurred, and in four surrounding areas (Baia Nova, Buenos Aires, Santa Rita and Todos os Santos) were examined and underwent parasitological and serological tests. Triatomines were collected for a fecal material exam, culturing and mini-exon gene molecular characterization, followed by RFLP-PCR of H3/Alul. Paraffin-embedded cardiac tissue of a patient was washed with xylene to remove paraffin and DNA was extracted using the phenol-chloroform method. For genotype characterization, PCR was performed to amplify the 1f8, GPI and 18S rRNA genes. In the case of V7V8 SSU rRNA, the PCR products were molecularly cloned. PCR products were sequenced and compared to sequences in GenBank. Phylogenetic analysis using maximum likelihood method with 1000 bootstrap replicates was performed.

RESULTS

None of the animals showed positive hemocultures. Three rodents and two dogs showed signs of infection, as inferred from borderline serological titers. T. vitticeps was the only triatomine species identified and showed T. cruzi infection by DTUs TcI and TcIV. The analysis of cardiac tissue DNA showed mixed infection by T. cruzi (DTUs I, II, III and IV) and Trypanosoma dionisii.

CONCLUSIONS

Each case or outbreak of ACD should be analyzed as a particular epidemiological occurrence. The results indicated that mixed infections in humans may play a role in pathogenicity and may be more common than is currently recognized. Direct molecular characterization from biological samples is essential because this procedure avoids parasite selection. T. dionisii may under certain and unknown circumstances infect humans. The distribution of T. cruzi DTUS TcIII and TcIV in Brazilian biomes is broader than has been assumed to date.

Prevalence of Trypanosoma cruzi's Discrete Typing Units in a cohort of Latin American migrants in Spain

Chagas disease is caused by the protozoan Trypanosoma cruzi. This is an endemic disease in the Americas, but increased migration to Europe has made it emerge in countries where it was previously unknown, being Spain the second non endemic country in number of patients. T. cruzi is a parasite with a wide genetic diversity, which has been grouped by consensus into 6 Discrete Typing Units (DTUs) affecting humans. Some authors have linked these DTUs either to a specific epidemiological context or to the different clinical presentations. Our main objective was to describe the T. cruzi DTUs identified from a population of chronically infected Latin American migrants attending a reference clinic in Madrid. 149 patients meeting this condition were selected for the study. Molecular characterization was performed by an algorithm that combines PCR of the intergenic region of the mini exon-gene, the 24Sα and 18S regions of rDNA and the variable region of the satellite DNA. A descriptive analysis was performed and associations between geographical/clinical data and the different DTUs were tested. DTUs could be determined in 105 out of 149 patients, 93.3% were from Bolivia, 67.7% were women and median age was 35 years (IQR 29-44). The most common DTU found was TcV (58; 55.2%), followed by TcIV (17; 16.2%), TcII (10; 9.5%) and TcI (4; 3.8%). TcIII and TcVI were not identified from any patient, and 15.2% patients presented mixed infections. In addition, we determined DTUs after treatment in a subset of patients. In 57% patients had different DTUs before and after treatment. DTUs distribution from this study indicates active transmission of T. cruzi is occurring in Bolivia, in both domestic and sylvatic cycles. TcIV was confirmed as a cause of chronic human disease. The current results indicate no correlation between DTU and any specific clinical presentation associated with Chagas disease, nor with geographical origin. Treatment with benznidazole does not always clear T. cruzi's genetic material from blood, and DTUs detected in the same patient may vary over time indicating that polyparasitism is frequent.

Genotyping of Trypanosoma cruzi DTUs and Trypanosoma rangeli genetic groups in experimentally infected Rhodnius prolixus by PCR-RFLP

The specific detection and genetic typing of trypanosomes that infect humans, mammalian reservoirs, and vectors is crucial for diagnosis and epidemiology. We utilized a PCR-RFLP assay that targeted subunit II of cytochrome oxidase and 24Sα-rDNA to simultaneously detect and discriminate six Trypanosoma cruzi discrete typing units (DTUs) and two genetic groups of Trypanosoma rangeli (KP1+/KP1-) in intestinal contents of experimentally infected Rhodnius prolixus. The PCR assays showed that in 23 of 29 (79.4%) mixed infections with the six T. cruzi DTUs and mixed infections with individual DTUs and/or groups KP1+ and KP1-, both parasites were successfully detected. In six mixed infections that involved TcIII, the TcI, TcII, TcV, and TcVI DTUs predominated to the detriment of TcIII, indicating the selection of genetic groups. Interactions between different genetic groups and vectors may lead to genetic selection over TcIII. The elimination of this DTU by the immune system of the vector appears unlikely because TcIII was present in other mixed infections (TcIII/TcIV and TcIII/KP1+). Both molecular markers used in this study were sensitive and specific, demonstrating their usefulness in a wide geographical area where distinct genotypes of these two species are sympatric. Although the cellular and molecular mechanisms that are involved in parasite-vector interactions are still poorly understood, our results indicate a dynamic selection toward specific T. cruzi DTUs in R. prolixus during mixed genotype infections.

Differential parasitological, molecular, and serological detection of Trypanosoma cruzi I, II, and IV in blood of experimentally infected mice

Trypanosoma cruzi is the etiological agent of American trypanosomiasis (Chagas' disease), which affects 6-7 million people worldwide, mainly in Latin America. It presents great genetic and biological variability that plays an important role in the clinical and epidemiological features of the disease. Our working hypothesis is that the genetic diversity of T. cruzi has an important impact on detection of the parasite using diagnostic techniques. The present study evaluated the diagnostic performance of parasitological, molecular, and serological techniques for detecting 27 strains of T. cruzi that belonged to discrete typing units (DTUs) TcI (11 strains), TcII (four strains), and TcIV (12 strains) that were obtained from different hosts in the states of Amazonas and Paraná, Brazil. Blood samples were taken from experimentally infected mice and analyzed by fresh blood examination, hemoculture in Liver Infusion Tryptose (LIT) medium, polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay (ELISA). Polymerase chain reaction presented the best detection of TcI, with 80.4% positivity. For all of the detection methods, the animals that were inoculated with TcII presented the highest positivity rates (94.1-100%). ELISA that was performed 7 months after inoculation presented a higher detection ability (95.4%) for TcIV. Intra-DTU comparisons showed that the reproducibility of the majority of the results that were obtained with the different methods was weak for TcI and good for TcII and TcIV. Our data indicate that the detection capability of different techniques varies with the DTUs of the parasites in mammalian blood. The implications of these findings with regard to the diagnosis of human T. cruzi infection are discussed.

Acute Chagas outbreaks: molecular and biological features of Trypanosoma cruzi isolates, and clinical aspects of acute cases in Santander, Colombia

BACKGROUND

Outbreaks of acute Chagas disease associated with oral transmission are easily detected nowadays with trained health personnel in areas of low endemicity, or in which the vector transmission has been interrupted. Given the biological and genetic diversity of Trypanosoma cruzi, the high morbidity, mortality, and the observed therapeutic failure, new characteristics of these outbreaks need to be addressed at different levels, both in Trypanosoma cruzi as in patient response. The aim of this work was to evaluate the patient's features involved in six outbreaks of acute Chagas disease which occurred in Santander, Colombia, and the characteristics of Trypanosoma cruzi clones isolated from these patients, to establish the potential relationship between the etiologic agent features with host behavior.

METHODS

The clinical, pathological and epidemiological aspects of outbreaks were analyzed. In addition, Trypanosoma cruzi clones were biologically characterized both in vitro and in vivo, and the susceptibility to the classical trypanocidal drugs nifurtimox and benznidazole was evaluated. Trypanosoma cruzi clones were genotyped by means of mini-exon intergenic spacer and cytochrome b genes sequencing.

RESULTS

All clones were DTU I, and based on the mini-exon intergenic spacer, belong to two genotypes: G2 related with sub-urban, and G11 with rural outbreaks. Girón outbreak clones with higher susceptibility to drugs presented G2 genotype and C/T transition in Cyt b. The outbreaks affected mainly young population (±25.9 years), and the mortality rate was 10 %. The cardiac tissue showed intense inflammatory infiltrate, myocardial necrosis and abundant amastigote nests. However, although the gastrointestinal tissue was congestive, no inflammation or parasites were observed.

CONCLUSIONS

Although all clones belong to DTU I, two intra-DTU genotypes were found with the sequencing of the mini-exon intergenic spacer, however there is no strict correlation between genetic groups, the cycles of the parasite or the clinical forms of the disease. Trypanosoma cruzi clones from Girón with higher sensitivity to nifurtimox presented a particular G2 genotype and C/T transition in Cyt b. When the diagnosis was early, the patients responded well to antichagasic treatment, which highlights the importance of diagnosis and treatment early to prevent fatal outcomes associated with these acute episodes.

Between a bug and a hard place: Trypanosoma cruzi genetic diversity and the clinical outcomes of Chagas disease

Over the last 30 years, concomitant with successful transnational disease control programs across Latin America, Chagas disease has expanded from a neglected, endemic parasitic infection of the rural poor to an urbanized chronic disease, and now a potentially emergent global health problem. Trypanosoma cruzi infection has a highly variable clinical course, ranging from complete absence of symptoms to severe and often fatal cardiovascular and/or gastrointestinal manifestations. To date, few correlates of clinical disease progression have been identified. Elucidating a putative role for T. cruzi strain diversity in Chagas disease pathogenesis is complicated by the scarcity of parasites in clinical specimens and the limitations of our contemporary genotyping techniques. This article systematically reviews the historical literature, given our current understanding of parasite genetic diversity, to evaluate the evidence for any association between T. cruzi genotype and chronic clinical outcome, risk of congenital transmission or reactivation and orally transmitted outbreaks.

Impact of benznidazole on infection course in mice experimentally infected with Trypanosoma cruzi I, II, and IV

American trypanosomiasis is an emerging zoonosis in the Brazilian Amazon. Studies on benznidazole (BZ) chemotherapy with Trypanosoma cruzi from this region have great relevance, given the different discrete typing units (DTUs) that infect humans in the Amazon and other regions of Brazil. We performed a parasitological, histopathological, and molecular analysis of mice inoculated with strains of T. cruzi I, II, and IV that were BZ-treated during the acute phase of infection. Groups of Swiss mice were inoculated; 13 received oral BZ, whereas the other 13 comprised the untreated controls. Unlike parasitemia, the infectivity and mortality did not vary among the DTUs. Trypanosoma cruzi DNA was detected in all tissues analyzed and the proportion of organs parasitized varied with the parasite DTU. The BZ treatment reduced the most parasitological parameters, tissue parasitism and the inflammatory processes at all infection stages and for all DTUs. However, the number of significant reductions varied according to the DTU and infection phase.

Expanding the knowledge of the geographic distribution of Trypanosoma cruzi TcII and TcV/TcVI genotypes in the Brazilian Amazon

Trypanosoma cruzi infection is a complex sylvatic enzooty involving a wide range of animal species. Six discrete typing units (DTUs) of T. cruzi, named TcI to TcVI, are currently recognized. One unanswered question concerning the epidemiology of T. cruzi is the distribution pattern of TcII and hybrid DTUs in nature, including their virtual absence in the Brazilian Amazon, the current endemic area of Chagas disease in Brazil. Herein, we characterized biological samples that were collected in previous epizootiological studies carried out in the Amazon Basin in Brazil. We performed T. cruzi genotyping using four polymorphic genes to identify T. cruzi DTUs: mini-exon, 1f8, histone 3 and gp72. This analysis was conducted in the following biological samples: (i) two T. cruzi isolates obtained by culturing of stools from the triatomine species Rhodnius picttipes and (ii) five serum samples from dogs in which trypomastigotes were observed during fresh blood examination. We report for the first time the presence of TcII and hybrid DTUs (TcV/TcVI) in the Amazon region in mixed infections with TcI. Furthermore, sequencing of the constitutive gene, gp72, demonstrated diversity in TcII even within the same forest fragment. These data show that TcII is distributed in the five main Brazilian biomes and is likely more prevalent than currently described. It is very probable that there is no biological or ecological barrier to the transmission and establishment of any DTU in any biome in Brazil.

Comparative pathogenicity in Swiss mice of Trypanosoma cruzi IV from northern Brazil and Trypanosoma cruzi II from southern Brazil

The geographical heterogeneity of Chagas disease (ChD) is mainly caused by genetic variability of the etiological agent Trypanosoma cruzi. Our hypothesis was that the pathogenicity for mice may vary with the genetic lineage (or Discrete Typing Unit - DTU) of the parasite. To test this hypothesis, parasitological and histopathological evaluations were performed in mice inoculated with strains belonging to the DTU T. cruzi IV (TcIV) from the State of Amazonas (northern Brazil), or the DTU T. cruzi II (TcII) from the State of Paraná (southern Brazil). Groups of 10 Swiss mice were inoculated with eight strains of TcIV obtained from acute cases (7) from two outbreaks of orally acquired ChD, and from the triatomine Rhodnius robustus (1) from Amazonas; and three strains of TcII obtained from chronic patients in Paraná. We evaluated the pre-patent period, patent period, maximum peak of parasitemia, day of maximum peak of parasitemia, area under the parasitemia curve, inflammatory process, and tissue parasitism in the acute phase. TcIV was less virulent than TcII, and showed significantly (p < 0.005) lower parasitemia levels. Although the levels of tissue parasitism did not differ statistically, mice infected with TcIV displayed significantly (p < 0.001) fewer inflammatory processes than mice infected with TcII. This supported the working hypothesis, since TcIV from Amazonas was less pathogenic than TcII from Paraná; and agreed with the lower severity of human cases of ChD in the Amazon region.

The history of Chagas disease

The ancestor of Trypanosome cruzi was probably introduced to South American via bats approximately 7-10 million years ago. When the first humans arrived in the New World, a sylvatic cycle of Chagas disease was then already well established. Paleoparasitological data suggests that human American trypanosomiasis originated in the Andean area when people founded the first settlements in the coastal region of the Atacama Desert. Identification of T. cruzi as the etiological agent and triatome bugs as the transmission vector of Chagas disease occurred within a few years at the beginning of the 20th century. History also teaches us that human activity leading to environmental changes, in particular deforestation, is the main cause for the spread of Chagas disease. Recently, migration of T. cruzi-infected patients has led to a distribution of Chagas disease from Latin America to non-endemic countries in Europe, North America and western Pacific region.