Over Six Thousand Trypanosoma cruzi Strains Classified into Discrete Typing Units (DTUs): Attempt at an Inventory

Unusual frequency of Trypanosoma cruzi DTU TcI and predominance of hybrid lineages in Triatoma infestans before and after control interventions in the Argentinian Chaco

Transmission of Trypanosoma cruzi involves diverse hosts, vectors and parasitic genotypes, in different environments. In recent decades, the distribution of T. cruzi has altered due to urbanization of affected people and vectors. We implemented a longitudinal intervention program between 2015 and 2022 which aimed to suppress (peri)domestic Triatoma infestans in the municipality of Avia Terai (Chaco Province, Argentina), and found a marginal risk of domestic vector-borne transmission across the rural-to-urban gradient after interventions. Here, we identified the parasite Discrete Typing Units (DTUs) in infected T. infestans collected throughout the intervention program (37 insects pre-intervention and 7 post-intervention). Identification of DTUs was conducted by two methodologies, using DNA extracted from T. infestans rectal ampoules. We also assessed the association between blood-feeding sources and DTUs. Complete DTU identification was achieved in 48 % of samples. The hybrid lineages TcV or TcVI and their combinations predominated (72 %), followed by TcI (16 %) and mixed infections of TcI and hybrid lineages (14 %). Half (50 %) of the houses harbored TcI infected bugs either alone or mixed with TcII/TcV/TcVI. Humans predominated as the bloodmeal sources in all insects with identified DTU. All DTUs (TcI, TcV and TcII/TcV/TcVI) were recorded in both rural and peri-urban environments, with 62 % of the houses having more than one DTU. These results confirm the predominance of hybrid lineages in domestic transmission cycles of the Argentine Chaco. However, the finding of several triatomines infected with TcI both pre- and post-intervention raises the question of which host(s) are involved in its transmission.

Ninoa T. cruzi Strain Modifies the Expression of microRNAs in Cardiac Tissue and Plasma During Chagas Disease Infection

Background: Chronic chagasic cardiomyopathy is the most severe clinical manifestation of Chagas disease, which affects approximately seven million people worldwide. Latin American countries bear the highest burden, with the greatest morbidity and mortality rates. Currently, diagnostic methods do not provide information on the risk of progression to severe stages of the disease. Recently, microRNAs (miRNAs) have been proposed as promising tools for monitoring the progression of Chagas disease. This study aimed to analyze the expression profiles of the miRNAs miR-1, miR-16, miR-208, and miR-208b in cardiac tissue, plasma, and plasma extracellular vesicles from Ninoa TcI-infected mice during the acute and indeterminate phases of Chagas disease. Methods: The cardiac-specific miRNAs and miR-16 levels were examined in all samples using RT-qPCR. Additionally, pathway analysis was performed to investigate the impact of potential miRNA target genes across various databases. Results: Elevated miR-208b expression was observed in cardiac tissue and plasma during the acute phase. Bioinformatic analysis identified three pathways implicated in disease progression: phosphatidylinositol 3-kinase signaling, Fc gamma receptor-mediated phagocytosis, and leukocyte transendothelial migration, as well as cholinergic synapse pathways. Conclusions: MiR-208b was upregulated during the acute phase and downregulated in the indeterminate phase, suggesting it may play a crucial role in disease progression.

Presence of Trypanosoma cruzi (TcI) in different tissues of Didelphis virginiana from the metropolitan area of Merida, southeastern Mexico: Epidemiological relevance and implications for non-vector transmission routes

BACKGROUND

Trypanosoma cruzi is mainly transmitted to mammals by vectors, but other transmission routes exist. For example, opossums can harbor the infectious form of the parasite in their anal glands, underscoring their potential role in non-vectorial transmission. T. cruzi has been detected in the anal gland secretions of various opossum species, and their infectivity has been confirmed in Didelphis marsupialis and D. albiventris. Vertical transmission has also been proposed in D. virginiana. However, if this occurs in opossums, it remains unclear whether it happens during pregnancy or lactation. In Mexico, Didelphis virginiana and D. marsupialis are the main opossum species. Our objective was to investigate the possible contribution of urban opossums to non-vectorial transmission of T. cruzi in the metropolitan area of Merida, Yucatan, in southeastern Mexico.

METHODOLOGY/PRINCIPAL FINDINGS

Blood, anal gland secretions, and milk were collected from opossums captured in Merida, Mexico, all identified as D. virginiana using taxonomic keys and Cytb sequencing. By PCR, T. cruzi was detected in 16/102 opossums (15.69%) in at least one type of sample. The prevalence was 14.71% (15/102) in blood and 0.98% (1/102) in anal gland secretions. 1/22 milk samples (4.55%) tested positive. Blood of 37 offspring from T. cruzi-positive mothers was collected and tested negative. qPCR revealed that females with offspring tended to have lower parasite load in blood compared to females without offspring and males. Genotyping of the parasite through multiplex PCR revealed only the DTU TcI.

CONCLUSIONS/SIGNIFICANCE

This study agrees with previous works where D. virginiana was the most abundant opossum species in urban areas in southeastern Mexico and confirms that it is associated with TcI. Detection of T. cruzi in a sample of anal gland secretions underscores the potential risk represented by D. virginiana in non-vectorial transmission in urban areas of southeastern Mexico. Detection in the milk of a lactating female, along with the observed tendency towards a lower parasite load in females with offspring, highlight the importance of further investigating vertical transmission in D. virginiana.

Immunopeptidomic MHC-I profiling and immunogenicity testing identifies Tcj2 as a new Chagas disease mRNA vaccine candidate

Trypanosoma cruzi is a protozoan parasite that causes Chagas disease. Globally 6 to 7 million people are infected by this parasite of which 20-30% will progress to develop Chronic Chagasic Cardiomyopathy (CCC). Despite its high disease burden, no clinically approved vaccine exists for the prevention or treatment of CCC. Developing vaccines that can stimulate T. cruzi-specific CD8+ cytotoxic T cells and eliminate infected cells requires targeting parasitic antigens presented on major histocompatibility complex-I (MHC-I) molecules. We utilized mass spectrometry-based immunopeptidomics to investigate which parasitic peptides are displayed on MHC-I of T. cruzi infected cells. Through duplicate experiments, we identified an array of unique peptides that could be traced back to 17 distinct T. cruzi proteins. Notably, six peptides were derived from Tcj2, a trypanosome chaperone protein and member of the DnaJ (heat shock protein 40) family, showcasing its potential as a viable candidate vaccine antigen with cytotoxic T cell inducing capacity. Upon testing Tcj2 as an mRNA vaccine candidate in mice, we observed a strong memory cytotoxic CD8+ T cell response along with a Th1-skewed humoral antibody response. In vitro co-cultures of T. cruzi infected cells with splenocytes of Tcj2-immunized mice restricted the replication of T. cruzi, demonstrating the protective potential of Tcj2 as a vaccine target. Moreover, antisera from Tcj2-vaccinated mice displayed no cross-reactivity with DnaJ in lysates from mouse and human indicating a decreased likelihood of triggering autoimmune reactions. Our findings highlight how immunopeptidomics can identify new vaccine targets for Chagas disease, with Tcj2 emerging as a promising new mRNA vaccine candidate.

Network Analysis of Pathogenesis Markers in Murine Chagas Disease Under Antimicrobial Treatment

Chagas disease (CD), a disease affecting millions globally, remains shrouded in scientific uncertainty, particularly regarding the role of the intestinal microbiota in disease progression. This study investigates the effects of antibiotic-induced microbiota depletion on parasite burden, immune responses, and clinical outcomes in BALB/c mice infected with either the Trypanosoma cruzi Colombiana or CL Brener strains. Mice were treated with a broad-spectrum antibiotic cocktail before infection, and parasite burden was quantified via qPCR at 30 and 100 days post-infection (dpi). Immune responses were analyzed using flow cytometry and ELISA, while histopathology was conducted on cardiac and intestinal tissues. Antibiotic treatment uncovered strain-specific correlations, with Colombiana infections affecting Bifidobacterium populations and CL Brener infections linked to Lactobacillus. Microbiota depletion initially reduced parasite burden in the heart and intestine, but an increase was observed in the chronic phase, except in the CL Brener-infected gut, where an early burden spike was followed by a decline. Antibiotic-induced bacterial shifts, such as reductions in Bacteroides and Bifidobacterium, promoted a more pro-inflammatory immune profile. These findings highlight the importance of microbiota and strain-specific factors in CD and suggest further research into microbiota manipulation as a potential therapeutic strategy.

The effect of nutritional and oxidative stress on the metabolome of Trypanosoma cruzi

Trypanosoma cruzi, a flagellated protozoan, is the causative agent of Chagas disease. The parasite has developed various mechanisms to get through its intricate life cycle and adapt to different evolutionary phases. T. cruzi proliferates in the insect vector's digestive tract as an epimastigote form, encountering fluctuating nutrient availability and oxidative stress caused by the digestion of red blood cells from the mammalian host blood meal. To unravel how the parasite's metabolism adapts to these changing conditions, we conducted an analysis of the chemical species present in epimastigote forms. This involved comparing cultured parasites with those subjected to nutritional deficiency or oxidative stress using untargeted metabolomics. We looked at 21 samples: seven biological copies of parasites that were actively growing, seven samples that were put in a medium without nutrients for 3 h, and seven samples that were treated with glucose oxidase for 30 min to make H2O2 continuously. Importantly, in all conditions, parasite viability was maintained when the samples were collected. Upon nutrient removal, we observed a substantial decrease in amino acids and carbohydrate metabolites, accompanied by the accumulation of fatty acids and steroids, with the predominance of inositol and sphingolipid metabolism, along with a simultaneous decrease in the levels of H2O2. In the presence of H2O2, a significant rise in components of the pentose pathway and specific amino acids such as methionine and serine occurred, along with pathways related to an increase in antioxidant species metabolism such as ribulose 5-phosphate and glyceric acid. Conversely, fatty acid and steroid levels decrease. We found no common increase in metabolites or lipids. In contrast, eight species (succinic acid, glutamic acid, valine, 2-hydroxyisocaproic acid, alanine, indolelactic acid, proline, and lanosterol) were consumed under both stresses. These findings underscore the rapid and distinct enrichment responses in amino acids, lipids, and carbohydrates required to cope with each different environmental condition. We concluded that T. cruzi presents a flexible metabolism that rapidly adapts to variable changes in the environment.

Triatomine (Hemiptera: Reduviidae) populations and Trypanosoma cruzi genotyping in peridomestic and sylvatic environments in the semiarid region of Sergipe, Northeastern, Brazil

We assessed the diversity of triatomines, the rates of natural infection, and the discrete typing units (DTUs) of Trypanosoma cruzi isolated from them in two municipalities in the state of Sergipe, Brazil. Active searches for triatomines were conducted in the peridomicily and wild enviroments of 10 villages within the two municipalities. Triatomines were taxonomically identified and their feces were extracted using the abdominal compression method. Parasite detection was performed using optical microscopy. For Trypanosoma cruzi genotyping via PCR-FFLB, 151 samples of the subspecies Triatoma brasiliensis macromelasoma and Triatoma brasiliensis were isolated from both municipalities. In total, 505 triatomines were collected, with Triatoma brasiliensis macromelasoma being the most frequent species (58.81 %). Triatoma b. brasiliensis was the only species in both peridomestic and wild environments. Regarding the other species, T. pseudomaculata was found only in the peridomestic environment; and T. b. macromelasoma and Psammolestes tertius were found in the wild environment. Three Discrete Typing Units were identified: TcI (87.51 %) detected in T. b. brasiliensis and T. b. macromelasoma, TcI+TcIII (10.41 %) in T. b. macromelasoma, and TcI+Trypanosoma rangeli (2.08 %) in T. b. macromelasoma. It is concluded that T. b. macromelasoma is the species collected most frequently in the studied region and the one that presents the highest rates of natural infection, highlighting its epidemiological importance for the vectorial transmission of Chagas disease in Sergipe.

Trypanosoma cruzi infection in American black bears (Ursus americanus): A case report in a cub from California and serologic survey for exposure in wild black bears from several states

Trypanosoma cruzi is an important cause of disease and death in humans and dogs, and although wildlife infections are common, less is known about disease manifestations. A 12-week-old male American black bear (Ursus americanus) cub with mild lethargy and anorexia presented to a wildlife rehabilitation center in Lake Tahoe, California. The cub continued to become increasingly weak and showed decreasing interest in play and other activities. The cub was anemic and had increased γ-glutamyltransferase (GGT) liver enzymes. A large number of trypanosomes were noted on a thin blood smear. Trypanosoma cruzi was isolated in culture from a subsequent blood collection. Proliferative bony lesions were noted on radiographs, but this finding was considered unrelated to the T. cruzi infection. The number of parasites observed in thin blood smears dramatically dropped over time, but it remained PCR positive until at least nine months. The cub continued to gain weight and became increasingly active. Serum samples from the cub were positive with three different serologic assays (IFA, ELISA, and ICT). The bear was not treated because of the decreasing parasitemia and the improvement in activity and appetite. Although the bear could not be released due to issues unrelated to T. cruzi, it remains healthy in a captive facility. Sequence analysis of the DHFR-TS and COII-ND1 gene sequences confirmed the bear was infected with DTC TcIV. Following the detection of this clinical case, a serologic survey was conducted to determine the prevalence of T. cruzi exposure of black bears in California, North Carolina, and Pennsylvania. Because no serologic assay has been validated for use in bears, three different assays were used. Marked differences in apparent seroprevalence range from 1% (requiring all three assays to be positive) to ∼20.7% (requiring only one assay to be positive). Black bears are naturally exposed to T. cruzi across the United States. Future studies using PCR testing of tissues or blood would be needed to better understand the prevalence of T. cruzi in wild black bears, lineages most commonly associated with infection, and if T. cruzi represents a health threat to bears.

Presence of Trypanosoma cruzi TcI and Trypanosoma dionisii in sylvatic bats from Yucatan, Mexico

BACKGROUND

Chagas disease is caused by Trypanosoma cruzi, whose genetic structure is divided into six discrete typing units (DTUs) known as TcI-TcVI. In the Yucatan Peninsula, Mexico, information regarding the DTUs circulating in wild mammals is scarce, while this is important knowledge for our understanding of T. cruzi transmission dynamics.

METHODS

In the current study, we sampled wild mammals in a sylvatic site of the Yucatan Peninsula and assessed their infection with T. cruzi by PCR. Then, for infected mammals, we amplified and sequenced nuclear and mitochondrial T. cruzi genetic markers for DTU identification.

RESULTS

In total, we captured 99 mammals belonging to the orders Chiroptera, Rodentia and Didelphimorphia. The prevalence of infection with T. cruzi was 9% (9/99; 95% CI [5, 16]), and we identified TcI in a Jamaican fruit bat, Artibeus jamaicensis. Moreover, we fortuitously identified Trypanosoma dionisii in another Jamaican fruit bat and detected an unidentified Trypanosoma species in a third specimen. While the latter discoveries were not expected because we used primers designed for T. cruzi, this study is the first to report the identification of T. dionisii in a bat from Yucatan, Mexico, adding to a recent first report of T. dionisii in bats from Veracruz, and first report of this Trypanosoma species in Mexico.

CONCLUSION

Further research is needed to enhance our knowledge of T. cruzi DTUs and Trypanosoma diversity circulating in wildlife in Southeastern Mexico.

Diversity of Chagas disease diagnostic antigens: Successes and limitations

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, remains a public health issue in endemic regions of the Americas, and is becoming globalised due to migration. In the chronic phase, 2 accordant serological tests are required for diagnosis. In addition to "in-house" assays, commercial tests are available (principally ELISA and rapid diagnostic tests). Herein, we discuss the discovery era of defined T. cruzi serological antigens and their utilisation in commercialised tests. A striking feature is the re-discovery of the same antigens from independent studies, and their overlapping use among commonly reported commercial serological tests. We also consider reports of geographical variation in assay sensitivity and areas for refinement including applications to congenital diagnosis, treatment monitoring, and lineage-specific antigens.

Novel 3D human trophoblast culture to explore T. cruzi infection in the placenta

Introduction

Human trophoblastic cell lines, such as BeWo, are commonly used in 2D models to study placental Trypanosoma cruzi infections. However, these models do not accurately represent natural infections. Three-dimensional (3D) microtissue cultures offer a more physiologically relevant in vitro model, mimicking tissue microarchitecture and providing an environment closer to natural infections. These 3D cultures exhibit functions such as cell proliferation, differentiation, morphogenesis, and gene expression that resemble in vivo conditions.

Methods

We developed a 3D culture model using the human trophoblastic cell line BeWo and nonadherent agarose molds from the MicroTissues® 3D Petri Dish® system. Both small (12-256) and large (12-81) models were tested with varying initial cell numbers. We measured the diameter of the 3D cultures and evaluated cell viability using Trypan Blue dye. Trophoblast functionality was assessed by measuring β-hCG production via ELISA. Cell fusion was evaluated using confocal microscopy, with Phalloidin or ZO-1 marking cell edges and DAPI staining nuclei. T. cruzi infection was assessed by microscopy and quantitative PCR, targeting the EF1-α gene for T. cruzi and GAPDH for BeWo cells, using three parasite strains: VD (isolated from a congenital Chagas disease infant and classified as Tc VI), and K98 and Pan4 (unrelated to congenital infection and classified as Tc I).

Results

Seeding 1000 BeWo cells per microwell in the large model resulted in comparable cellular viability to 2D cultures, with a theoretical diameter of 408.68 ± 12.65 μm observed at 5 days. Functionality, assessed through β-hCG production, exceeded levels in 2D cultures at both 3 and 5 days. T. cruzi infection was confirmed by qPCR and microscopy, showing parasite presence inside the cells for all three tested strains. The distribution and progression of the infection varied with each strain.

Discussion

This innovative 3D model offers a simple yet effective approach for generating viable and functional cultures susceptible to T. cruzi infection, presenting significant potential for studying the placental microenvironment.

Domestic Dog Infection with Trypanosoma cruzi from Northern and Southern Regions of Mexico

Background: Chagas disease or American trypanosomiasis, caused by Trypanosoma cruzi and vectored by triatomines, affects millions of people worldwide. In endemic countries including Mexico, infections in domestic animals, such as dogs, may affect the risk of human disease when they serve as a source of infection to vectors that subsequently infect humans. Materials and Methods: We conducted a cross-sectional study of 296 dogs from two cities near the northern and southern borders of Mexico: Reynosa, Tamaulipas, and Tuxtla Gutierrez, Chiapas. Infection was measured based on testing of blood using T. cruzi quantitative PCR (qPCR) and up to three antibody detection assays. The StatPak immunochromatographic assay was used to screen samples and the indirect fluorescent antibody (IFA) and multiplex microsphere immunoassay (MIA) tests were used as secondary tests on all samples that screened positive and a subset of negatives. Serologic positivity was defined based on reactivity on at least two independent tests. Results: Of the 280 samples tested for parasite DNA, two (0.7%) were positive, one of which (0.4%) was confirmed as T. cruzi discrete typing unit TcIV. Overall, 72 (24.3%) samples were reactive for T. cruzi antibodies via StatPak of which 8 were also positive using MIA and 2 were also positive using IFA (including one of the PCR-positive dogs). Overall, nine dogs (3.4%) met study criteria of positivity based on either/both serology or PCR tests. Positive dogs were found in both regions of Mexico; five (2.7%) from Reynosa and four (3.6%) from Tuxtla Gutierrez. We found no association between infection status and state of origin, sex, age group, breed group, neighborhood, and whether other pets lived in the home. Conclusion: Our results re-emphasize dogs' utility as sentinels for T. cruzi in Mexico and underscore the need for improved veterinary diagnostic tests and parasite surveillance at the household level in endemic countries.

Circulation of Trypanosoma cruzi in triatomines and Didelphis sp. in urban areas: Transmission risk assessment in the Metropolitan Region

The presence of Trypanosoma cruzi vectors in urban areas has been frequent, with colonization of homes and associated with reservoir animals that increase risk to humans, with simultaneous circulation of vectors and T. cruzi. The study aimed to describe the circulation of triatomines and T. cruzi in the Metropolitan Region of São Paulo, as well as evaluate risk situations. For analysis purposes, the triatomine notification information from January 2016 to July 2023 was used. While for Didelphis sp. collection with the aid of traps, notification information used was from 2019 to 2023. Information about triatomines came from spontaneous demand by the population and notification services were carried out by state field teams following defined protocols. 202 notifications were received with the capture of 448 triatomines. The positivity for T. cruzi observed was 60.5%. Regarding Didelphis sp., 416 animals were collected, 5.3% of which were positive for T. cruzi. There was overlapping areas of presence of infected triatomines and Didelphis sp., whose Discrete Typing Unit (DTU) was T. cruzi I. This work indicates the presence of infected vectors in urban areas, and the presence of a wild cycle of T. cruzi in didelphiids, reaffirming the need for and importance of vector surveillance work, through actions that can prevent the transmission of Chagas disease.

Development of a Colorimetric Loop-Mediated Isothermal Amplification Assay for the Detection of Trypanosoma cruzi in Low-Resource Settings

Chagas disease is an inflammatory parasitic infection caused by Trypanosoma cruzi (T. cruzi). Early diagnosis is crucial in guiding treatment and slowing disease progression; however, current diagnostic methods have insufficient detection limits and often require skilled technicians. Molecular tests, especially isothermal nucleic acid assays, are advantageous due to their excellent sensitivity, specificity, speed, and simplicity. Here, we optimized a colorimetric loop-mediated isothermal amplification (LAMP) assay for T. cruzi. We can detect as few as 2 genomic copies/reaction using three different T. cruzi strains. We examined selectivity using other parasitic protozoans and successfully detected T. cruzi DNA extracted from parasites in human whole blood down to 1.2 parasite equivalents/reaction. We also performed a blinded study using canine blood samples and established a 100% sensitivity, specificity, and accuracy for the colorimetric LAMP assay. Finally, we used a heated 3D printer bed and an insulated thermos cup to demonstrate that the LAMP incubation step could be performed with accessible, low-cost materials. Altogether, we have developed a high-performing assay for T. cruzi with a simple colorimetric output that would be ideal for rapid, low-cost screening at the point of use.

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.

Ecoepidemiology of Chagas Disease in a Biological Corridor in Southeastern Mexico: A Promising Approach to Understand the Risk of Chagas Disease

Ecoepidemiology is an emerging field that attempts to explain how biotic, environmental, and even social factors influence the dynamics of infectious diseases. Particularly in vector-borne diseases, the study under this approach offers us an overview of the pathogens, vectors, and hosts that coexist in a given region and their ecological determinants. As a result of this, risk predictions can be established in a changing environment and how it may impact human populations. This paper is aimed at evaluating some ecoepidemiological characteristics of Chagas disease in a natural reserve in southeastern Mexico that borders human settlements. We carry out a cross-sectional study in 2022 where we search insects manually and with light traps. We set traps for small mammals and bats and conducted interviews with the inhabitants living around the study site. We identified the presence of Triatoma dimidiata and T. huehuetenanguensis species with a percentage of TcI T. cruzi infection of 68.4% (95% CI: 66.9-69.9). Temperature and humidity were not determining factors for the probability of insect capture. Of the 108 wild mammals (Chiroptera, Rodentia, and Didelphimorphia), none was infected with T. cruzi. Knowledge about Chagas disease in nearby inhabitants is poor, and some characteristics were found on the periphery of dwellings that could offer a refuge for insect vectors. With this information, surveillance strategies can be generated in the study area that reduce the risk of transmission of T. cruzi parasite to humans, and it is expected to motivate the use of this field in future research.

Comparative evaluation of lateral flow assays to diagnose chronic Trypanosoma cruzi infection in Bolivia

Bolivia has the highest incidence of Chagas disease (CD) worldwide. Caused by the parasite Trypanasoma cruzi, CD is generally a chronic condition. Diagnosis is logistically and financially challenging, requiring at least two different laboratory-based serological tests. Many CD cases are missed; in Bolivia it is estimated just 6% of individuals chronically infected with T. cruzi get diagnosed. Achieving control on the way to elimination of CD requires a radical simplification of the current CD testing pathways, to overcome the barriers to accessing CD treatment. We aimed to generate unbiased performance data of lateral flow assays (LFAs) for T. cruzi infection in Bolivia, to evaluate their usefulness for improving T. cruzi diagnosis rates in a precise and efficient manner. This retrospective, laboratory-based, diagnostic evaluation study sought to estimate the sensitivity/specificity of 10 commercially available LFAs for T. cruzi, using the current CD diagnostic algorithm employed in Bolivia as the reference test method. All tests were blinded at the study site and performed by three operators. In total, 470 serum samples were tested, including 221 and 249 characterized as CD-positive/-negative, respectively. The LFAs were scored according to their relative importance using a decision-tree-based algorithm, with the mean decrease in Gini index as the scoring metric. The estimates of sensitivities ranged from 62.2-97.7% (95% confidence interval (CI) lower bound 55.0-94.7%); for specificities the range was 78.6-100% (95% CI lower bound 72.0-97.5%); 5/10 and 6/10 tests had sensitivity >90% and specificity >95%, respectively. Four LFAs showed high values of both sensitivity (93-95%) and specificity (97-99%). The agreement between 6 LFAs and the reference tests was almost perfect (Kappa 0.83-0.94). Most LFAs evaluated thus showed performances comparable with current laboratory-based diagnostic methods.

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.

Parasite Burden of Trypanosoma cruzi in Whole Blood and Buffy Coat Determined by Real-Time PCR in Individuals with Chronic Chagas Disease

The objective of this study was to compare, by qPCR, the circulating blood parasite load of Trypanosoma cruzi in the buffy coat, and in whole blood mixed with boiled and unboiled guanidine hydrochloride-EDTA buffer, of individuals with chronic ChD. The concentration and purity of DNA were evaluated in a Nanodrop Denovix DS-11FX Series Spectrophotometer (DeNovix Inc., Wilmington, NC, USA). The parasite load was determined with the Taqman® qPCR system using a Stratagene Mx3000P thermocycler (Agilent Technologies, Santa Clara, CA, USA) with Cruzi 1 and Cruzi 2 satellite primers. Student's t-test with Bonferroni correction, Chi-squared (χ2) tests and Spearman's correlation coefficient were applied. The concentration and purity of DNA were higher in the buffy coat. Parasite DNA was detected and quantifiable in the three types of samples in seven patients, without statistically significant differences in the parasite load obtained. Higher correlations were found between the total DNA concentrations and the parasite loads obtained in the samples of the buffy coat.

Outcomes of patients in Chagas disease of the central nervous system: a systematic review

Chagas disease is a parasitic infection caused by the protozoan Trypanosoma cruzi. One of the complications of the disease is the infection of the central nervous system (CNS), as it can result from either the acute phase or by reactivation during the chronic phase, exhibiting high mortality in immunocompromised patients. This systematic review aimed to determine clinical and paraclinical characteristics of patients with Chagas disease in the CNS. Articles were searched from PubMed, Scopus and LILACS until January 2023. From 2325 articles, 59 case reports and 13 case series of patients with Chagas in the CNS were retrieved from which 138 patients were identified. In this population, 77% of the patients were male, with a median age of 35 years old, from which most of them came from Argentina and Brazil. Most of the individuals were immunocompromised from which 89% were HIV-positive, and 54 patients had an average of 48 cells per mm3 CD4+ T cells. Motor deficits and seizures were the most common manifestation of CNS compromise. Furthermore, 90 patients had a documented CNS lesion by imaging from which 89% were supratentorial and 86% were in the anterior/middle cranial fossa. The overall mortality was of 74%. Among patients who were empirically treated with anti-toxoplasma drugs, 70% died. This review shows how Chagas disease in the CNS is a devastating complication requiring prompt diagnosis and treatment to improve patients’ outcomes.

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.

Trypanosoma cruzi infection in dogs along the US-Mexico border: R0 changes with vector species composition

Infection with Trypanosoma cruzi, etiological agent of Chagas disease, is common in US government working dogs along the US-Mexico border. This 3145 km long border comprises four states: Texas (TX), New Mexico (NM), Arizona (AZ) and California (CA) with diverse ecosystems and several triatomine (a.k.a., kissing bug) species, primary vectors of T. cruzi in this region. The kissing bug (Heteroptera: Reduviidae) community ranging from CA to TX includes Triatoma protracta (Uhler), Triatoma recurva (Stål) and Triatoma rubida (Uhler) and becomes dominated by Triatoma gerstaeckeri Stål in TX. Here, we ask if T. cruzi infection dynamics in dogs varies along this border region, potentially reflecting changes in vector species and their vectorial capacity. Using reversible catalytic models of infection, where seropositivity can be lost, we estimated an R0 (Estimate ± S.E.) of 1.192 ± 0.084 for TX and NM. In contrast, seropositivity decayed to zero as dogs aged in AZ and CA. These results suggest that dogs are likely infected by T. cruzi during their training in western TX, with a force of infection large enough for keeping R0 above 1, i.e., the disease endemically established, in TX and NM. In AZ and CA, a lower force of infection, probably associated with different vector species communities and associated vectorial capacity and/or different lineages of T. cruzi, results in dogs decreasing their seropositivity with age.

Revisiting gene typing and phylogeny of Trypanosoma cruzi reference strains: Comparison of the relevance of mitochondrial DNA, single-copy nuclear DNA, and the intergenic region of mini-exon gene

Chagas disease is a widespread neglected disease in Latin America. Trypanosoma cruzi, the causative agent of the disease, is currently subdivided into six DTUs (discrete typing units) named TcI-TcVI, and although no clear association has been found between parasite genetics and different clinical outcomes of the disease or different transmission cycles, genetic characterization of T. cruzi strains remains crucial for integrated epidemiological studies. Numerous markers have been used for this purpose, although without consensus. These include mitochondrial genes, single or multiple-copy nuclear genes, ribosomal RNA genes, and the intergenic region of the repeated mini-exon gene. To increase our knowledge of these gene sequences and their usefulness for strain typing, we sequenced fragments of three mitochondrial genes, nine single-copy nuclear genes, and the repeated intergenic part of the mini-exon gene by Next Generation Sequencing (NGS) on a sample constituted of 16 strains representative of T. cruzi genetic diversity, to which we added the corresponding genetic data of the 38 T. cruzi genomes fully sequenced until 2022. Our results show that single-copy nuclear genes remain the gold standard for characterizing T. cruzi strains; the phylogenetic tree from concatenated genes (3959 bp) confirms the six DTUs previously recognized and provides additional information about the alleles present in the hybrid strains. In the tree built from the three mitochondrial concatenated genes (1274 bp), three main clusters are identified, including one with TcIII, TcIV, TcV, and TcVI DTUs which are not separated. Nevertheless, mitochondrial markers remain necessary for detecting introgression and heteroplasmy. The phylogenetic tree built from the sequence alignment of the repeated mini-exon gene fragment (327 bp) displayed six clusters, but only TcI was associated with a single cluster. The sequences obtained from strains belonging to the other DTUs were scattered into different clusters. Therefore, while the mini-exon marker may bring, for some biological samples, some advantages in terms of sensibility due to its repeated nature, mini-exon sequences must be used with caution and, when possible, avoided for T. cruzi typing and phylogenetic studies.

Deep serological profiling of the Trypanosoma cruzi TSSA antigen reveals different epitopes and modes of recognition by Chagas disease patients

BACKGROUND

Trypanosoma cruzi, the agent of Chagas disease, displays a highly structured population, with multiple strains that can be grouped into 6-7 evolutionary lineages showing variable eco-epidemiological traits and likely also distinct disease-associated features. Previous works have shown that antibody responses to 'isoforms' of the polymorphic parasite antigen TSSA enable robust and sensitive identification of the infecting strain with near lineage-level resolution. To optimize the serotyping performance of this molecule, we herein used a combination of immunosignaturing approaches based on peptide microarrays and serum samples from Chagas disease patients to establish a deep linear B-cell epitope profiling of TSSA.

METHODS/PRINCIPLE FINDINGS

Our assays revealed variations in the seroprevalence of TSSA isoforms among Chagas disease populations from different settings, hence strongly supporting the differential distribution of parasite lineages in domestic cycles across the Americas. Alanine scanning mutagenesis and the use of peptides of different lengths allowed us to identify key residues involved in antibody pairing and the presence of three discrete B-cell linear epitopes in TSSAII, the isoform with highest seroprevalence in human infections. Comprehensive screening of parasite genomic repositories led to the discovery of 9 novel T. cruzi TSSA variants and one TSSA sequence from the phylogenetically related bat parasite T. cruzi marinkellei. Further residue permutation analyses enabled the identification of diagnostically relevant or non-relevant substitutions among TSSA natural polymorphisms. Interestingly, T. cruzi marinkellei TSSA displayed specific serorecognition by one chronic Chagas disease patient from Colombia, which warrant further investigations on the diagnostic impact of such atypical TSSA.

CONCLUSIONS/SIGNIFICANCE

Overall, our findings shed new light into TSSA evolution, epitope landscape and modes of recognition by Chagas disease patients; and have practical implications for the design and/or evaluation of T. cruzi serotyping strategies.

Validation of the NAT Chagas IVD Kit for the Detection and Quantification of Trypanosoma cruzi in Blood Samples of Patients with Chagas Disease

In the absence of validated biomarkers to control the cure of Chagas disease, PCR-based diagnosis is being used as the main tool for an early indication of therapeutic failure. However, since it is considered a technique of complex reproducibility, mainly due to difficulties in establishing accurate controls to guarantee the quality of the reaction, the use of PCR for Chagas disease diagnosis is restricted to specialized centers. In an effort to disseminate the molecular diagnosis of Chagas disease and its applications, new diagnostic kits based on qPCR have been made available in the market in recent years. Here, we show the results of the validation of the NAT Chagas kit (Nucleic Acid Test for Chagas Disease) for the detection and quantification of T. cruzi in blood samples of patients suspected of Chagas disease infection. The kit, composed of a TaqMan duplex reaction targeting the T. cruzi satellite nuclear DNA and an exogenous internal amplification control, presented a reportable range from 10⁴ to 0.5 parasite equivalents/mL and a limit of detection (LOD) of 0.16 parasite equivalents/mL of blood. In addition, the NAT Chagas kit detected T. cruzi belonging to all six discrete typing units (DTUs-TcI to TcVI), similarly to the in-house real-time PCR performed with commercial reagents, which has been selected as the best performance assay in the international consensus for the validation of qPCR for Chagas disease. In the clinical validation presented here, the kit showed 100% sensitivity and 100% specificity when compared to the consensus in-house real-time PCR assay. Thus, the NAT Chagas kit, which is produced entirely in Brazil under the international standards of good manufacturing practices (GMP), appears as an excellent alternative to enable the molecular diagnosis of Chagas disease in public and private diagnostic centers, as well as to facilitate the monitoring of patients under etiological treatment participating in clinical trials.

Risk Factors for Progression to Chronic Chagas Cardiomyopathy: A Systematic Review and Meta-Analysis

Approximately one-third of people with chronic Trypanosoma cruzi infection develop Chagas cardiomyopathy, which carries a poor prognosis. Accurate prediction of which individuals will go on to develop Chagas cardiomyopathy remains elusive. We performed a systematic review of literature comparing characteristics of individuals with chronic Chagas disease with or without evidence of cardiomyopathy. Studies were not excluded on the basis of language or publication date. Our review yielded a total of 311 relevant publications. We further examined the subset of 170 studies with data regarding individual age, sex, or parasite load. A meta-analysis of 106 eligible studies indicated that male sex was associated with having Chagas cardiomyopathy (Hedge's g: 1.56, 95% CI: 1.07-2.04), and a meta-analysis of 91 eligible studies indicated that older age was associated with having Chagas cardiomyopathy (Hedge's g: 0.66, 95% CI: 0.41-0.91). A meta-analysis of four eligible studies did not find an association between parasite load and disease state. This study provides the first systematic review to assess whether age, sex, and parasite load are associated with Chagas cardiomyopathy. Our findings suggest that older and male patients with Chagas disease are more likely to have cardiomyopathy, although we are unable to identify causal relationships due to the high heterogeneity and predominantly retrospective study designs in the current literature. Prospective, multidecade studies are needed to better characterize the clinical course of Chagas disease and identify risk factors for progression to Chagas cardiomyopathy.

The Trypanosoma cruzi Antigen and Epitope Atlas: antibody specificities in Chagas disease patients across the Americas

During an infection the immune system produces pathogen-specific antibodies. These antibody repertoires become specific to the history of infections and represent a rich source of diagnostic markers. However, the specificities of these antibodies are mostly unknown. Here, using high-density peptide arrays we examined the human antibody repertoires of Chagas disease patients. Chagas disease is a neglected disease caused by Trypanosoma cruzi, a protozoan parasite that evades immune mediated elimination and mounts long-lasting chronic infections. We describe a proteome-wide search for antigens, characterised their linear epitopes, and show their reactivity on 71 individuals from diverse human populations. Using single-residue mutagenesis we revealed the core functional residues for 232 of these epitopes. Finally, we show the diagnostic performance of identified antigens on challenging samples. These datasets enable the study of the Chagas antibody repertoire at an unprecedented depth and granularity, while also providing a rich source of serological biomarkers.

Protozoal meningoencephalitis and myelitis in 4 dogs associated with Trypanosoma cruzi infection

American trypanosomiasis is caused by the zoonotic protozoa Trypanosoma cruzi and primarily results in heart disease. Organisms also infect the central nervous system (CNS). The Texas A&M University veterinary teaching hospital archive was searched for dogs with CNS disease with intralesional protozoal amastigotes. This study summarizes 4 cases of dogs with disseminated trypanosomiasis and CNS involvement confirmed by quantitative polymerase chain reaction (qPCR) with T. cruzi primers. Clinical signs included lethargy, respiratory distress, tetraparesis, and seizures. Central nervous system lesions included meningeal congestion (1/4), necrosis with hemorrhage in the spinal cord gray and white matter (2/4), and histiocytic meningoencephalitis (4/4), and meningomyelitis (2/4) with intralesional and intracellular protozoal. Genotyping identified 1 case of T. cruzi discrete typing unit (DTU) TcI and 2 cases as TcIV, both are common variants in the United States. Trypanosomiasis should be considered a differential diagnosis for dogs with CNS signs in T. cruzi-endemic areas.

Effects of Acute and Chronic Trypanosoma cruzi Infection on Pregnancy Outcomes in Mice: Parasite Transmission, Mortality, Delayed Growth, and Organ Damage in Pups

Chagas disease is caused by Trypanosoma cruzi. This study aimed to determine the effects of T. cruzi infection on fertility rate and health of the newborn pups in pregnant mice. Female mice were challenged with T. cruzi and mated at 21 days (acute parasitemic phase) or 90 days (chronic parasite persistence phase) after infection. Pups were examined for growth up to 20 days after birth; and parasite burden in brain, heart, skeletal muscle, and intestine was measured by real-time quantitative PCR. The inflammatory infiltrate, necrosis, and fibrosis in pups' heart and brain tissues were evaluated by histology. T. cruzi infection in dams delayed the onset of pregnancy, decreased the fertility rate, and led to vertical transmission of parasite to the pups. Furthermore, infected dams delivered pups that exhibited decreased survival rate, decreased birth weight, and decreased growth rate. Significantly increased inflammation, necrosis, and fibrosis of cardiac and brain tissues were noted in pups born to infected dams. Initial challenge with higher parasite dose had more detrimental effects on fertility rate and pups' health in both acutely and chronically infected dams. In conclusion, mice offer a promising model to evaluate the efficacy of new vaccines and therapeutic drugs in controlling the acute and chronic maternal T. cruzi infection and congenital transmission to newborns, and in improving the fertility rate and pups' health outcomes.

The Low Variability of Tc24 in Trypanosoma cruzi TcI as an Advantage for Chagas Disease Prophylaxis and Diagnosis in Mexico

(1) Background: Chagas disease is the main neglected tropical disease in America. It is estimated that around 6 million people are currently infected with the parasite in Latin America, and 25 million live in endemic areas with active transmission. The disease causes an estimated economic loss of USD 24 billion dollars annually, with a loss of 75,200 working years per year of life; it is responsible for around ~12,000 deaths annually. Although Mexico is an endemic country that recorded 10,186 new cases of Chagas disease during the period of 1990–2017, few studies have evaluated the genetic diversity of genes that could be involved in the prophylaxis and/or diagnosis of the parasite. One of the possible candidates proposed as a vaccine target is the 24 kDa trypomastigote excretory–secretory protein, Tc24, whose protection is linked to the stimulation of T. cruzi-specific CD8+ immune responses. (2) Methods: The aim of the present study was to evaluate the fine-scale genetic diversity and structure of Tc24 in T. cruzi isolates from Mexico, and to compare them with other populations reported in the Americas with the aim to reconsider the potential role of Tc24 as a key candidate for the prophylaxis and improvement of the diagnosis of Chagas disease in Mexico. (3) Results: Of the 25 Mexican isolates analysed, 48% (12) were recovered from humans and 24% (6) recovered from Triatoma barberi and Triatoma dimidiata. Phylogenetic inferences revealed a polytomy in the T. cruzi clade with two defined subgroups, one formed by all sequences of the DTU I and the other formed by DTU II–VI; both subgroups had high branch support. Genetic population analysis detected a single (monomorphic) haplotype of TcI throughout the entire distribution across both Mexico and South America. This information was supported by Nei’s pairwise distances, where the sequences of TcI showed no genetic differences. (4) Conclusions: Given that both previous studies and the findings of the present work confirmed that TcI is the only genotype detected from human isolates obtained from various states of Mexico, and that there is no significant genetic variability in any of them, it is possible to propose the development of in silico strategies for the production of antigens that optimise the diagnosis of Chagas disease, such as quantitative ELISA methods that use this region of Tc24.

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.

Transcriptomic analysis of the adaptation to prolonged starvation of the insect-dwelling Trypanosoma cruzi epimastigotes

Trypanosoma cruzi is a digenetic unicellular parasite that alternates between a blood-sucking insect and a mammalian, host causing Chagas disease or American trypanosomiasis. In the insect gut, the parasite differentiates from the non-replicative trypomastigote forms that arrive upon blood ingestion to the non-infective replicative epimastigote forms. Epimastigotes develop into infective non-replicative metacyclic trypomastigotes in the rectum and are delivered via the feces. In addition to these parasite stages, transitional forms have been reported. The insect-feeding behavior, characterized by few meals of large blood amounts followed by long periods of starvation, impacts the parasite population density and differentiation, increasing the transitional forms while diminishing both epimastigotes and metacyclic trypomastigotes. To understand the molecular changes caused by nutritional restrictions in the insect host, mid-exponentially growing axenic epimastigotes were cultured for more than 30 days without nutrient supplementation (prolonged starvation). We found that the parasite population in the stationary phase maintains a long period characterized by a total RNA content three times smaller than that of exponentially growing epimastigotes and a distinctive transcriptomic profile. Among the transcriptomic changes induced by nutrient restriction, we found differentially expressed genes related to managing protein quality or content, the reported switch from glucose to amino acid consumption, redox challenge, and surface proteins. The contractile vacuole and reservosomes appeared as cellular components enriched when ontology term overrepresentation analysis was carried out, highlighting the roles of these organelles in starving conditions possibly related to their functions in regulating cell volume and osmoregulation as well as metabolic homeostasis. Consistent with the quiescent status derived from nutrient restriction, genes related to DNA metabolism are regulated during the stationary phase. In addition, we observed differentially expressed genes related to the unique parasite mitochondria. Finally, our study identifies gene expression changes that characterize transitional parasite forms enriched by nutrient restriction. The analysis of the here-disclosed regulated genes and metabolic pathways aims to contribute to the understanding of the molecular changes that this unicellular parasite undergoes in the insect vector.

High Parasitic Loads Quantified in Sylvatic Triatoma melanica, a Chagas Disease Vector

Triatoma melanica is a sylvatic vector species in Brazil. In We aimed to characterize the Trypanosoma cruzi discrete typing units (DTUs), the parasitic loads, and the blood meal sources of insects collected in rocky outcrops in rural areas in the state of Minas Gerais. An optical microscope (OM) and kDNA-PCR were used to examine natural infection by T. cruzi, and positive samples were genotyped by conventional multilocus PCR. Quantification of the T. cruzi load was performed using qPCR, and the blood meal sources were identified by Sanger sequencing the 12S rRNA gene. A total of 141 T. melanica were captured. Of these, ~55% (61/111) and ~91% (63/69) were positive by OM and KDNA-PCR, respectively. We genotyped ~89% (56/63) of the T. cruzi-positive triatomines, with TcI (~55%, 31/56) being the most prevalent DTU, followed by TcIII (~20%, 11/56) and TcII (~7%, 4/56). Only TcI+TcIII mixed infections were detected in 10 (~18%) specimens. A wide range of variation in the parasitic loads of T. melanica was observed, with an overall median value of 104 parasites/intestine, with females having higher T. cruzi loads than N2, N4, and N5. TcII showed lower parasitic loads compared to TcI and TcIII. The OM positive diagnosis odds ratio between T. cruzi infection when the parasite load is 107 compared to 103 was approximately 29.1. The most frequent blood meal source was Kerodon rupestris (~58%), followed by Thrichomys apereoides (~18%), Wiedomys cerradensis (~8%), Galactis cuja (~8%) and Gallus gallus (~8%). Our findings characterize biological and epidemiological aspects of the sylvatic population of T. melanica in the study area, highlighting the need to extend surveillance and control to this vector.

Parasitemia Levels in Trypanosoma cruzi Infection in Spain, an Area Where the Disease Is Not Endemic: Trends by Different Molecular Approaches

Trypanosoma cruzi infection has expanded globally through human migration. In Spain, the mother-to-child route is the mode of transmission contributing to autochthonous Chagas disease (CD); however, most people acquired the infection in their country of origin and were diagnosed in the chronic phase (imported chronic CD). In this context, we assessed the quantitative potential of the Loopamp Trypanosoma cruzi detection kit (Sat-TcLAMP) based on satellite DNA (Sat-DNA) to determine parasitemia levels compared to those detected by real-time quantitative PCRs (qPCRs) targeting Sat-DNA (Sat-qPCR) and kinetoplast DNA minicircles (kDNA-qPCR). This study included 173 specimens from 39 autochthonous congenital and 116 imported chronic CD cases diagnosed in Spain. kDNA-qPCR showed higher sensitivity than Sat-qPCR and Sat-TcLAMP. According to all quantitative approaches, parasitemia levels were significantly higher in congenital infection than in chronic CD (1 × 10-1 to 5 × 105 versus >1 × 10-1 to 6 × 103 parasite equivalents/mL, respectively [P < 0.001]). Sat-TcLAMP, Sat-qPCR, and kDNA-qPCR results were equivalent at high levels of parasitemia (P = 0.381). Discrepancies were significant for low levels of parasitemia and older individuals. Differences between Sat-TcLAMP and Sat-qPCR were not qualitatively significant, but estimations of parasitemia using Sat-TcLAMP were closer to those by kDNA-qPCR. Parasitemia changes were assessed in 6 individual cases in follow-up, in which trends showed similar patterns by all quantitative approaches. At high levels of parasitemia, Sat-TcLAMP, Sat-qPCR, and kDNA-qPCR worked similarly, but significant differences were found for the low levels characteristic of late chronic CD. A suitable harmonization strategy needs to be developed for low-level parasitemia detection using Sat-DNA- and kDNA-based tests. IMPORTANCE Currently, molecular equipment has been introduced into many health care centers, even in low-income countries. PCR, qPCR, and loop-mediated isothermal amplification (LAMP) are becoming more accessible for the diagnosis of neglected infectious diseases. Chagas disease (CD) is spreading worldwide, and in countries where the disease is not endemic, such as Spain, the parasite Trypanosoma cruzi is transmitted from mother to child (congenital CD). Here, we explore why LAMP, aimed at detecting T. cruzi parasite DNA, is a reliable option for the diagnosis of congenital CD and the early detection of reactivation in chronic infection. When the parasite load is high, LAMP is equivalent to any qPCR. In addition, the estimations of T. cruzi parasitemia in patients living in Spain, a country where the disease is not endemic, resemble natural evolution in areas of endemicity. If molecular tests are introduced into the diagnostic algorithm for congenital infection, early diagnosis and timely treatment would be accomplished, so the interruption of vertical transmission can be an achievable goal.

Microevolution and subspecific taxonomy of Trypanosoma cruzi

Trypanosoma cruzi, the agent of Chagas disease, is a highly polymorphic species, subdivided into 6 main evolutionary lineages or near-clades (formerly discrete typing units or DTUs). An additional near-clade (TC-bat) has recently been evidenced. This pattern is considered to be the result of predominant clonal evolution (PCE). PCE is compatible with occasional mating/hybridization, which do not break the prevalent pattern of clonal evolution, the main trait of it being the presence of Multigene Bifurcating Trees (MGBTs) at all evolutionary levels ("clonal frame"). The development of highly resolutive genetic (microsatellites*) and genomic (sequencing and multi-single nucleotide polymorphism {SNP}* typing) markers shows that PCE also operates at a microevolutionary* level within each of the near-clades ("Russian doll pattern"), in spite of occasional meiosis and hybridization events. Within each near-clade, one can evidence widespread clonal multilocus genotypes*, linkage disequilibrium*, Multigene Bifurcating Trees and lesser near-clades. The within near-clade population structure is like a miniature picture of that of the whole species, suggesting gradual rather than saltatory evolution. Additional data are required to evaluate the stability of these lesser near-clades in the long run and to evaluate the need for an adequate nomenclature for this microevolutionary level.

The History of the ABC Proteins in Human Trypanosomiasis Pathogens

Human trypanosomiasis affects nearly eight million people worldwide, causing great economic and social impact, mainly in endemic areas. T. cruzi and T. brucei are protozoan parasites that present efficient mechanisms of immune system evasion, leading to disease chronification. Currently, there is no vaccine, and chemotherapy is effective only in the absence of severe clinical manifestations. Nevertheless, resistant phenotypes to chemotherapy have been described in protozoan parasites, associated with cross-resistance to other chemically unrelated drugs. Multidrug resistance is multifactorial, involving: (i) drug entry, (ii) activation, (iii) metabolism and (iv) efflux pathways. In this context, ABC transporters, initially discovered in resistant tumor cells, have drawn attention in protozoan parasites, owing to their ability to decrease drug accumulation, thus mitigating their toxic effects. The discovery of these transporters in the Trypanosomatidae family started in the 1990s; however, few members were described and functionally characterized. This review contains a brief history of the main ABC transporters involved in resistance that propelled their investigation in Trypanosoma species, the main efflux modulators, as well as ABC genes described in T. cruzi and T. brucei according to the nomenclature HUGO. We hope to convey the importance that ABC transporters play in parasite physiology and chemotherapy resistance.

Discrete Typing Units of Trypanosoma cruzi Identified by Real-Time PCR in Peripheral Blood and Dejections of Triatoma infestans Used in Xenodiagnosis Descriptive Study

Chagas disease (ChD) is a vector zoonosis native to the American continent caused by the protozoan parasite Trypanosoma cruzi; the biological vectors are multiple species of hematophagous insects of the family Triatominae. A relevant aspect in the host–parasite relationship is the identification of the various genotypes of T. cruzi called discrete typing units (DTU) that circulate in mammals and vectors. In Chile, it has been described that the DTUs TcI, TcII, TcV, and TcVI circulate in infected humans, vectors, and wild animals. Identifying DTUs has acquired clinical importance, since it has been suggested that different genotypes could cause distinct pathologies, circulate in different geographical areas, and present different sensitivities to trypanocidal drugs. In this study, circulating T. cruzi DTUs in peripheral blood and Triatoma infestans dejections used in xenodiagnosis (XD) were amplified by qPCR in 14 Chilean patients with chronic ChD from highly endemic areas. More positive samples were detected by XD compared to peripheral blood samples, and 64.28% of the cases were simple infections and 35.72% mixed, with a statistically significant difference in the frequency of TcV DTU. This study would suggest that T. infestans from Chile is more competent to amplify one DTU over others, probably due to a process of co-evolution.

Trypanosoma cruzi strain and starvation-driven mitochondrial RNA editing and transcriptome variability

Trypanosoma cruzi is a unicellular protistan parasitic species that is comprised of strains and isolates exhibiting high levels of genetic and metabolic variability. In the insect vector, it is known to be highly responsive to starvation, a signal for progression to a life stage in which it can infect mammalian cells. Most mRNAs encoded in its mitochondrion require the targeted insertion and deletion of uridines to become translatable transcripts. This study defined differences in uridine-insertion/deletion RNA editing among three strains and established the mechanism whereby abundances of edited (and, thus, translatable) mitochondrial gene products increase during starvation. Our approach utilized our custom T-Aligner toolkit to describe transcriptome-wide editing events and reconstruct editing products from high-throughput sequencing data. We found that the relative abundance of mitochondrial transcripts and the proportion of mRNAs that are edited varies greatly between analyzed strains, a characteristic that could potentially impact metabolic capacity. Starvation typically led to an increase in overall editing activity rather than affecting a specific step in the process. We also determined that transcripts CR3, CR4, and ND3 produce multiple open reading frames that, if translated, would generate different proteins. Finally, we quantitated the inherent flexibility of editing in T. cruzi and found it to be higher relative to that in a related trypanosomatid lineage. Over time, new editing domains or patterns could prove advantageous to the organism and become more widespread within individual transcriptomes or among strains.

Trypanosomatid Richness Among Rats, Opossums, and Dogs in the Caatinga Biome, Northeast Brazil, a Former Endemic Area of Chagas Disease

Parasites are important components of the immense n-dimensional trophic network that connects all living beings because they, among others, forge biodiversity and deeply influence ecological evolution and host behavior. In this sense, the influence of Trypanosomatidae remains unknown. The aim of this study was to determine trypanosomatid infection and richness in rats, opossums, and dogs in the semiarid Caatinga biome. We submitted DNA samples from trypanosomatids obtained through axenic cultures of the blood of these mammals to mini exon multiplex-PCR, Sanger, and next-generation sequencing targeting the 18S rDNA gene. Phylogenetic analyses were performed to identify genetic diversity in the Trypanosomatidae family. Shannon, Simpson, equability, and beta-diversity indices were calculated per location and per mammalian host. Dogs were surveyed for trypanosomatid infection through hemocultures and serological assays. The examined mammal species of this area of the Caatinga biome exhibited an enormous trypanosomatid species/genotypes richness. Ten denoised Operational Taxonomic Units (ZOTUs), including three species (Trypanosoma cruzi, Trypanosoma rangeli and Crithidia mellificae) and one Trypanosoma sp. five genotypes/lineages (T. cruzi DTU TcI, TcII, and TcIV; T. rangeli A and B) and four DTU TcI haplotypes (ZOTU1, ZOTU2, ZOTU5, and ZOTU10 merged), as well as 13 Amplicon Sequence Variants (ASVs), including five species (T. cruzi, T. rangeli, C. mellificae, Trypanosoma dionisii, and Trypanosoma lainsoni), five genotypes/lineages (same as the ZOTUs) and six DTU TcI haplotypes (ASV, ASV1, ASV2, ASV3, ASV5 and ASV13), were identified in single and mixed infections. We observed that trypanosomatids present a broad host spectrum given that species related to a single host are found in other mammals from different taxa. Concomitant infections between trypanosomatids and new host-parasite relationships have been reported, and this immense diversity in mammals raised questions, such as how this can influence the course of the infection in these animals and its transmissibility. Dogs demonstrated a high infection rate by T. cruzi as observed by positive serological results (92% in 2005 and 76% in 2007). The absence of positive parasitological tests confirmed their poor infectivity potential but their importance as sentinel hosts of T. cruzi transmission.

Exhausted PD-1+ TOX+ CD8+ T Cells Arise Only in Long-Term Experimental Trypanosoma cruzi Infection

Infection with Trypanosoma cruzi remains the most important neglected zoonosis in Latin America. This infection does not lead to specific symptoms in the acute phase, but chronic infection can result in Chagas disease (CD) with cardiac and/or gastrointestinal manifestations that can lead to death. CD8+ T cells are highly effective and essential to control this infection, but fail to eliminate all parasites. In this study, we show that the CD8+ T cells are modulated by the transient induction of co-inhibitory receptors during acute infection of C57BL/6 mice. Therapeutic intervention strategies with blocking antibodies only had a marginal effect on the elimination of parasite reservoirs. Only long-term chronic infection gave rise to dysfunctional CD8+ T cells, which were characterized by high expression of the inhibitory receptor PD-1 and the co-expression of the transcription factor TOX, which plays a crucial role in the maintenance of the exhausted phenotype. PD-1+ TOX+ CD8+ T cells isolated from the site of infection produced significantly less IFN-γ, TNF-α and Granzyme B than their PD-1- TOX- CD8+ T cell counterparts after T. cruzi-specific stimulation ex vivo. Taken together, we provide evidence that, in the context of experimental infection of mice, the magnitude of the CD8+ T cell response in the acute phase is sufficient for parasite control and cannot be further increased by targeting co-inhibitory receptors. In contrast, persistent long-term chronic infection leads to an increase of exhausted T cells within the tissues of persistence. To our knowledge, this is the first description of infection-induced CD8+ T cells with an exhausted phenotype and reduced cytokine production in muscles of T. cruzi-infected mice.

Parasitological, serological and molecular diagnosis of acute and chronic Chagas disease: from field to laboratory

There is no consensus on the diagnostic algorithms for many scenarios of Trypanosoma cruzi infection, which hinders the establishment of governmental guidelines in endemic and non-endemic countries. In the acute phase, parasitological methods are currently employed, and standardised surrogate molecular tests are being introduced to provide higher sensitivity and less operator-dependence. In the chronic phase, IgG-based serological assays are currently used, but if a single assay does not reach the required accuracy, PAHO/WHO recommends at least two immunological tests with different technical principles. Specific algorithms are applied to diagnose congenital infection, screen blood and organ donors or conduct epidemiological surveys. Detecting Chagas disease reactivation in immunosuppressed individuals is an area of increasing interest. Due to its neglect, enhancing access to diagnosis of patients at risk of suffering T. cruzi infection should be a priority at national and regional levels.

Trypanosoma cruzi infection in the wild Chagas disease vector, Mepraia spinolai: Parasitic load, discrete typing units, and blood meal sources

BACKGROUND

Mepraia spinolai, a wild vector of Trypanosoma cruzi in Chile, is an abundant triatomine species that is frequently infected by the parasite that causes Chagas disease. The aim of this study was to determine if the parasitic load of T. cruzi in M. spinolai is related to its blood meal source and the infecting DTUs of T. cruzi.

METHODS

The vector was captured in rural areas. In the laboratory, DNA was extracted from its abdomen and T. cruzi was quantified using qPCR. Real time PCR assays for four T. cruzi DTUs were performed. Blood meal sources were identified by real-time PCR amplification of vertebrate cytochrome b gene sequences coupled with high resolution melting (HRM).

RESULTS

Trypanosoma cruzi was detected in 735 M. spinolai; in 484 we identified one blood meal source, corresponding to human, sylvatic, and domestic species. From these, in 224 we were able to discriminate the infecting DTU. When comparing the parasitic loads between the unique blood meal sources, no significant differences were found, but infections with more than one DTU showed higher parasitic loads than single infections. DTU TcI was detected in a high proportion of the samples.

CONCLUSIONS

Higher parasitic loads are related to a greater number of T. cruzi DTUs infecting M. spinolai, and this triatomine seems to have a wide span of vertebrate species in its diet.

Phylogenetic diversity of two common Trypanosoma cruzi lineages in the Southwestern United States

Trypanosoma cruzi is the causative agent of Chagas disease, a devastating parasitic disease endemic to Central and South America, Mexico, and the USA. We characterized the genetic diversity of Trypanosoma cruzi circulating in five triatomine species (Triatoma gerstaeckeri, T. lecticularia, T.indictiva, T. sanguisuga and T. recurva) collected in Texas and Southern Arizona using multilocus sequence typing (MLST) with four single-copy loci (cytochrome oxidase subunit II- NADH dehydrogensase subunit 1 region (COII-ND1), mismatch-repair class 2 (MSH2), dihydrofolate reductase-thymidylate synthase (DHFR-TS) and a nuclear gene with ID TcCLB.506529.310). All T. cruzi variants fall in two main genetic lineages: 75% of the samples corresponded to T. cruzi Discrete Typing Unit (DTU) I (TcI), and 25% to a North American specific lineage previously labelled TcIV-USA. Phylogenetic and sequence divergence analyses of our new data plus all previously published sequence data from those four loci collected in the USA, show that TcIV-USA is significantly different from any other previously defined T. cruzi DTUs. The significant level of genetic divergence between TcIV-USA and other T. cruzi DTUs should lead to an increased focus on understanding the epidemiological importance of this DTU, as well as its geographical range and pathogenicity in humans and domestic animals. Our findings further corroborate the fact that there is a high genetic diversity of the parasite in North America and emphasize the need for appropriate surveillance and vector control programs for Chagas disease in southern USA and Mexico.

Molecular characterization of Trypanosoma cruzi DTUs of the triatomine species in a Chagas disease endemic area

Trypanosoma cruzi is the etiological agent of Chagas disease, a neglected tropical infection with great public health importance. This protozoan has triatomine insects as vector but may also be transmitted through blood transfusion, organ transplants, ingestion of contaminated food, or congenitally. It has a heterogeneous population classified into Discrete Typing Units (DTUs), TcI-TcVI and TcBat. The aim of this study was to molecularly characterize the DTUs of T. cruzi in triatomines from a Chagas disease endemic area in Northeastern Brazil. Triatomines were collected and the gut content was microscopically analyzed to investigate the presence of trypanosomatid flagellates. In addition, digestive tracts of some specimens were dissected and molecularly analyzed through PCR for Trypanosoma spp. and sequencing. PCR positive samples were further submitted to a multiplex PCR for DTUs of T. cruzi. A total of 117 triatomines were collected, 93.16% being in intradomicile and 6.84% in peridomicile environments. Insects were identified as Panstrongylus lutzi (37.60%), Triatoma pseudomaculata (26.50%), Triatoma brasiliensis (23.08%) and Panstrongylus megistus (12.82%). The specimens herein analyzed presented infection rates by T. cruzi of 5.49% and 12.09% in parasitological and molecular examinations, respectively. Multiplex PCR screening revealed 70.59% of the TcI genotype, detected in all triatomine species identified in this study and 29.41% of the DTU TcIII/TcIV detected in P. megistus and P. lutzi. T. cruzi infect triatomines in intradomicile and peridomicile environments, which brings attention to the risk of human infections and to the importance of the implementation of surveillance and entomological control actions.

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

Biological characterization of Trypanosoma cruzi epimastigotes derived from trypomastigotes isolated from Brazilian chagasic patients

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T. cruzi TcII isolates from chagasic patients have distinct biological parameters.

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Isolates were more glucose-dependent than long-term cultivated Y strain parasites.

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Significant differences were observed on complex II and IV-supported respiration.

Chagas disease (CD), caused by Trypanosoma cruzi, occurs in several countries in Latin America and non-endemic countries. Heterogeneity among T. cruzi population has been the Achilles’ heel to find a better treatment for CD. In this study, we characterized the biochemical parameters and mitochondrial bioenergetics of epimastigotes differentiated from eight T. cruzi isolates (I1-I8) obtained from Brazilian CD patients. Molecular analysis of parasites DTUs grouped all of them as TcII. The profile of the growth curves in axenic cultures was distinct among them, except for I1 and I3 and I2 and I4. Doubling times, growth rates, cell body length, and resistance to benznidazole were also significantly different among them. All the isolates were more glucose-dependent than other T. cruzi strains adapted to grow in axenic culture. Mitochondrial bioenergetics analysis showed that each isolate behaved differently regarding oxygen consumption rates in non-permeabilized and in digitonin-permeabilized cells in the presence of a complex II-linked substrate. When complex IV-linked respiratory chain substrate was used to provide electrons to the mitochondrial respiratory chain (MRC), similarity among the isolates was higher. Our findings show that TcII epimastigotes derived from patients’ trypomastigotes displayed their own characteristics in vitro, highlighting the intra-TcII diversity, especially regarding the functionality of mitochondrial respiratory complexes II and IV. Understanding T. cruzi intraspecific biological features help us to move a step further on our comprehension regarding parasite's survival and adaptability offering clues to improve the development of new therapies for CD.

Genetic Diversity of Trypanosoma cruzi in Panama Inferred by Multi-locus Sequence Typing of Mitochondrial Genes

The objective of this study was to provide information on Trypanosoma cruzi genetic diversity among isolates obtained from different biological sources circulating in endemic areas of Panama. Initial discrete typing units (DTUs) assignment was performed evaluating three single locus molecular markers (mini-exon, heat shock protein 60 and glucose-6-phosphate isomerase genes). Further diversity within TcI lineages was explored using a multi-locus sequence typing approach with six maxicircle genes. Haplotype network analysis and evolutionary divergency estimations were conducted to investigate the genetic relatedness between Panamanian TcI isolates and isolates from different endemic regions in the Americas. Our molecular approach validated that TcI is the predominant DTU circulating in Panama across different hosts and vector species, but also confirmed the presence of TcIII and TcVI circulating in the country. The phylogenetic tree topography for most Panamanian TcI isolates displayed a high level of genetic homogeneity between them. The haplotype network analysis inferred a higher genetic diversity within Panamanian TcI isolates, displaying eight different haplotypes circulating in endemic regions of the country, and revealed geographical structuring among TcI from different endemic regions in the Americas. This study adds novelty on the genetic diversity of T. cruzi circulating in Panama and complements regional phylogeographic studies regarding intra-TcI variations.

Trypanosoma cruzi genetic diversity: impact on transmission cycles and Chagas disease

Trypanosoma cruzi, the agent of Chagas disease (ChD), exhibits remarkable biological and genetic diversity, along with eco-epidemiological complexity. In order to facilitate communication among researchers aiming at the characterisation of biological and epidemiological aspects of T. cruzi, parasite isolates and strains were partitioned into seven discrete typing units (DTUs), TcI-TcVI and TcBat, identifiable by reproducible genotyping protocols. Here we present the potential origin of the genetic diversity of T. cruzi and summarise knowledge about eco-epidemiological associations of DTUs with mammalian reservoirs and vectors. Circumstantial evidence of a connection between T. cruzi genotype and ChD manifestations is also discussed emphasising the role of the host’s immune response in clinical ChD progression. We describe genomic aspects of DTUs focusing on polymorphisms in multigene families encoding surface antigens that play essential functions for parasite survival both in the insect vector and the mammalian host. Such antigens most probably contributed to the parasite success in establishing infections in different hosts and exploring several niches. Gaps in the current knowledge and challenges for future research are pointed out.

Genetic diversity of Trypanosoma cruzi strains isolated from chronic chagasic patients and non-human hosts in the state of São Paulo, Brazil

BACKGROUND

Trypanosoma cruzi shows an exuberant genetic diversity. Currently, seven phylogenetic lineages, called discrete typing units (DTUs), are recognised: TcI-TcVI and Tcbat. Despite advances in studies on T. cruzi and its populations, there is no consensus regarding its heterogeneity.

OBJECTIVES

This study aimed to perform molecular characterisation of T. cruzi strains, isolated in the state of São Paulo, to identify the DTUs involved and evaluate their genetic diversity.

METHODS

T. cruzi strains were isolated from biological samples of chronic chagasic patients, marsupials and triatomines through culture techniques and subjected to molecular characterisation using the fluorescent fragment length barcoding (FFLB) technique. Subsequently, the results were correlated with complementary information to enable better discrimination between the identified DTUs.

FINDINGS

It was possible to identify TcI in two humans and two triatomines; TcII/VI in 19 humans, two marsupials and one triatomine; and TcIII in one human host, an individual that also presented a result for TcI, which indicated the possibility of a mixed infection. Regarding the strains characterised by the TcII/VI profile, the correlation with complementary information allowed to suggest that, in general, these parasite populations indeed correspond to the TcII genotype.

MAIN CONCLUSIONS

The TcII/VI profile, associated with domestic cycles and patients with chronic Chagas disease, was the most prevalent among the identified DTUs. Furthermore, the correlation of the study results with complementary information made it possible to suggest that TcII is the predominant lineage of this work.