The molecular epidemiology and phylogeography of Trypanosoma cruzi and parallel research on Leishmania : looking back and to the future

Echocardiographic Documentation of Dilated Cardiomyopathy Development in Dogs Naturally Infected with Trypanosoma cruzi

We aimed to characterize the echocardiographic alterations in dogs from an endemic region that were naturally infected with T. cruzi. Dogs (n = 130) seropositive for antibodies against T. cruzi and/or with acute parasitemia were enrolled in the study. Indicators of changes in the structure and systolic and diastolic functions of the left ventricle (LV) and blood flow patterns were evaluated by echocardiography. The frequency and extent of alterations in these indicators were associated with the severity of the disease. Briefly, 15 (11.54%) dogs were diagnosed with dilated cardiomyopathy (DCM), and 115 (88.46%) dogs were diagnosed as being without DCM. Infected dogs with DCM exhibited structural features of LV dysfunction, e.g., a significant (p < 0.05) increase in the LV internal diameter at systole and diastole (LVID-s, LVID-d) and a decline in the LV posterior wall (LVPW-d) thickness at diastole. Despite an increase in stroke volume and cardiac output indicating contraction force, DCM resulted in a decreased ejection fraction, affecting systolic function. Dogs that were diagnosed as DCM-negative but were positive for T. cruzi by PCR exhibited a high frequency of an increase in the thickness of the interventricular septum in systole (IVS-s) and the LV posterior wall in diastole (LVPW-d), a decline in the LV inner diameter (LVID-d, LVID-s), and fractional shortening (FS). The thinning of the LVPW at systole was the most defining feature observed in chronically infected dogs. In summary, this is the first study reporting the echocardiographic changes occurring in dogs naturally infected with T. cruzi and developing DCM. Our data suggest that changes in LVID are a major indicator of risk of cardiac involvement, and the observation of changes in the IVS, LVPW, and FS have predictive value in determining the risk of DCM development in infected dogs.

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.

GSK-3 kinase a putative therapeutic target in trypanosomatid parasites

Trypanosomatids are an important group of parasites that predominate in tropical and subtropical areas of the planet, which cause diseases that are classified as forgotten and neglected by the world health organization. In this group of parasites, we find Trypanosoma cruzi, Trypanosoma brucei, Trypanosoma brucei rhodesiense and Leishmania spp, for which there is no vaccine available, and its control has focused mainly on pharmacological treatment. Due to the poverty situation where these diseases are found and the biological complexity of these parasites, there are multiple variables to control, including the diversity of species, the complexity of their life cycles, drug resistance, cytotoxicity, the limited use in pregnant women, the high costs of treatment and the little-known pharmacological mechanisms of action, among others. It is therefore necessary to find new strategies and approaches for the treatment of these parasitic diseases. Among these new approaches is the rational search for new targets based on the allosteric inhibition of protein kinases, which have been little studied in trypanosomatids. Among these kinases, we find Glycogen Synthase Kinase-3 (GSK-3), a kinase of great pharmacological interest, which is under intense basic and clinical research by pharmaceutical companies for the treatment of cancer. This kinase, highly studied in the PI3K/AKT/mTOR pathway signaling in humans, has an orthologous gene in these parasites (GSK-3 s), which has proven to be essential for them in response to different challenges; Therefore, it is notable to increase research in this kinase in order to achieve a broad structural and functional characterization in the different species of trypanosomatids.

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.

Visceral Leishmaniasis Caused by Leishmania Tropica

PURPOSE

In Turkey, the main causative agent of visceral leishmaniasis (VL) is Leishmania. infantum and the main causative agent of cutaneous leishmaniasis (CL) is Leishmania tropica. In this study, we aimed to discuss the possible mechanisms, clinical aspects, and threat of visceralizing L. tropica.

METHODS

This study includes seven cases of VL caused by L. tropica.Five patients were male (71%) and four were adults (57%).

RESULTS

All the VL patients complained of fever and splenomegaly. Fatigue, pancytopenia, and hepatomegaly were present in six patients each (86%), while weight loss and gastrointestinal system (GIS) symptoms were present in 5 patients (71%).

CONCLUSIONS

In this study, we have evaluated seven cases of visceralized L. tropica (VLT) in the context of the changing leishmaniasis epidemiology in Turkey. We have evaluated the possible mechanisms of visceralization; inter- and intraspecies genetic exchange with all the old world leishmaniasis agents present in the region, stress induced by inappropriate use of drugs, and possible ongoing adaptation mechanisms of Leishmania spp. The threat posed by VLT is significant as L. tropica is the most widespread and most common cause of leishmaniasis in Turkey. We do not know the vectorial capacity of the sand flies for the transmission of VLT strains or if these strains are in circulation in Turkey. Future studies should be carried out to investigate these issues as the transition of L. tropica from a mild disease-causing agent to a mortal one poses a significant public health concern for Turkey and Europe.

Accessing the Variability of Multicopy Genes in Complex Genomes using Unassembled Next-Generation Sequencing Reads: The Case of Trypanosoma cruzi Multigene Families

Repetitive elements cause assembly fragmentation in complex eukaryotic genomes, limiting the study of their variability. The genome of Trypanosoma cruzi, the parasite that causes Chagas disease, has a high repetitive content, including multigene families. Although many T. cruzi multigene families encode surface proteins that play pivotal roles in host-parasite interactions, their variability is currently underestimated, as their high repetitive content results in collapsed gene variants. To estimate sequence variability and copy number variation of multigene families, we developed a read-based approach that is independent of gene-specific read mapping and de novo assembly. This methodology was used to estimate the copy number and variability of MASP, TcMUC, and Trans-Sialidase (TS), the three largest T. cruzi multigene families, in 36 strains, including members of all six parasite discrete typing units (DTUs). We found that these three families present a specific pattern of variability and copy number among the distinct parasite DTUs. Inter-DTU hybrid strains presented a higher variability of these families, suggesting that maintaining a larger content of their members could be advantageous. In addition, in a chronic murine model and chronic Chagasic human patients, the immune response was focused on TS antigens, suggesting that targeting TS conserved sequences could be a potential avenue to improve diagnosis and vaccine design against Chagas disease. Finally, the proposed approach can be applied to study multicopy genes in any organism, opening new avenues to access sequence variability in complex genomes. IMPORTANCE Sequences that have several copies in a genome, such as multicopy-gene families, mobile elements, and microsatellites, are among the most challenging genomic segments to study. They are frequently underestimated in genome assemblies, hampering the correct assessment of these important players in genome evolution and adaptation. Here, we developed a new methodology to estimate variability and copy numbers of repetitive genomic regions and employed it to characterize the T. cruzi multigene families MASP, TcMUC, and transsialidase (TS), which are important virulence factors in this parasite. We showed that multigene families vary in sequence and content among the parasite's lineages, whereas hybrid strains have a higher sequence variability that could be advantageous to the parasite's survivability. By identifying conserved sequences within multigene families, we showed that the mammalian host immune response toward these multigene families is usually focused on the TS multigene family. These TS conserved and immunogenic peptides can be explored in future works as diagnostic targets or vaccine candidates for Chagas disease. Finally, this methodology can be easily applied to any organism of interest, which will aid in our understanding of complex genomic regions.

Sex in protists: A new perspective on the reproduction mechanisms of trypanosomatids

The Protist kingdom individuals are the most ancestral representatives of eukaryotes. They have inhabited Earth since ancient times and are currently found in the most diverse environments presenting a great heterogeneity of life forms. The unicellular and multicellular algae, photosynthetic and heterotrophic organisms, as well as free-living and pathogenic protozoa represents the protist group. The evolution of sex is directly associated with the origin of eukaryotes being protists the earliest protagonists of sexual reproduction on earth. In eukaryotes, the recombination through genetic exchange is a ubiquitous mechanism that can be stimulated by DNA damage. Scientific evidences support the hypothesis that reactive oxygen species (ROS) induced DNA damage can promote sexual recombination in eukaryotes which might have been a decisive factor for the origin of sex. The fact that some recombination enzymes also participate in meiotic sex in modern eukaryotes reinforces the idea that sexual reproduction emerged as consequence of specific mechanisms to cope with mutations and alterations in genetic material. In this review we will discuss about origin of sex and different strategies of evolve sexual reproduction in some protists such that cause human diseases like malaria, toxoplasmosis, sleeping sickness, Chagas disease, and leishmaniasis.

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.

Comparative Study of the Effect of Snake Venoms on the Growth of Ciliates Tetrahymena pyriformis: Identification of Venoms with High Antiprotozoal Activity

To search for compounds with antiprotozoal activity, effects of snake venoms on the ciliates Tetrahymena pyriformis was studied. T. pyriformis from subkingdom of Protozoa, including the protozoal pathogens, was used as a model organism to select the venoms that are the most active against parasitic protozoans. Various concentrations of venoms were added to the cells, and the cells that survived after 24 h were counted. Among the six snake species from the Viperidae family, the venom of the viper Vipera berus, which completely killed the cells at 49 μg/mL, was the most active. Among four species from the Elapidae family, the previously studied cobra venoms containing cytotoxins with strong antiprotozoal activity as well as the venom of krait Bungarus multicinctus (10 μg/mL) were the most active. The venoms of the pit vipers and Nikolsky's viper did not show any activity at 12.5 mg/mL. Thus, the venoms of V. berus and B. multicinctus are promising for the isolation of new antiprotozoal compounds.

Worldwide Control and Management of Chagas Disease in a New Era of Globalization: a Close Look at Congenital Trypanosoma cruzi Infection

Population movements have turned Chagas disease (CD) into a global public health problem. Despite the successful implementation of subregional initiatives to control vectorial and transfusional Trypanosoma cruzi transmission in Latin American settings where the disease is endemic, congenital CD (cCD) remains a significant challenge. In countries where the disease is not endemic, vertical transmission plays a key role in CD expansion and is the main focus of its control. Although several health organizations provide general protocols for cCD control, its management in each geopolitical region depends on local authorities, which has resulted in a multitude of approaches. The aims of this review are to (i) describe the current global situation in CD management, with emphasis on congenital infection, and (ii) summarize the spectrum of available strategies, both official and unofficial, for cCD prevention and control in countries of endemicity and nonendemicity. From an economic point of view, the early detection and treatment of cCD are cost-effective. However, in countries where the disease is not endemic, national health policies for cCD control are nonexistent, and official regional protocols are scarce and restricted to Europe. Countries of endemicity have more protocols in place, but the implementation of diagnostic methods is hampered by economic constraints. Moreover, most protocols in both countries where the disease is endemic and those where it is not endemic have yet to incorporate recently developed technologies. The wide methodological diversity in cCD diagnostic algorithms reflects the lack of a consensus. This review may represent a first step toward the development of a common strategy, which will require the collaboration of health organizations, governments, and experts in the field.

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.

Phenotypic, functional and serological aspects of genotypic-specific immune response of experimental T. cruzi infection

The complexity and multifactorial characteristics of Chagas disease pathogenesis hampers the establishment of appropriate experimental/epidemiological sets, and therefore, still represents one of the most challenging fields for novel insights and discovery. In this context, we used a set of attributes including phenotypic, functional and serological markers of immune response as candidates to decode the genotype-specific immune response of experimental T. cruzi infection. In this investigation, we have characterized in C57BL/6 J mice, the early (parasitemia peak) and late (post-parasitemia peak) aspects of the immune response elicited by T. cruzi strains representative of TcI, TcII or TcVI. The results demonstrated earlier parasitemia peak for TcII/Y strain followed by TcVI/CL-Brener and TcI/Colombiana strains. A panoramic overview of phenotypic and functional features of the TCD4⁺, TCD8⁺ and B-cells from splenocytes demonstrated that mice infected with TcI/Colombiana strain exhibited at early stages of infection low levels of most cytokine⁺ cells with a slight increase at late stages of infection. Conversely, mice infected with TcII/Y strain presented an early massive increase of cytokine⁺ cells, which decreases at late stages. The TcVI/CL-Brener strain showed an intermediate profile at early stages of infection with a slight increase later on at post-peak of parasitemia. The panoramic analysis of immunological connectivity demonstrated that early after infection, the TcI/Colombiana strain trigger immunological network characterized by a small number of connectivity, selectively amongst cytokines that further shade towards the late stages of infection. In contrast, the TcII/Y strain elicited in more imbricate networks early after infection, comprising a robust number of interactions between pro-inflammatory mediators, regulatory cytokines and activation markers that also decrease at late infection. On the other hand, the infection with TcVI/CL-Brener strain demonstrated an intermediate profile with connectivity axes more stable at early and late stages of infection. The analysis of IgG2a reactivity to AMA, TRYPO and EPI antigens revealed that at early stages of infection, the genotype-specific reactivity to AMA, TRYPO and EPI to distinguish was higher for TcI/Colombiana as compared to TcII/Y and TcVI/CL while, at late stages of infection, higher reactivity to AMA was observed in mice infected with TcVI/CL and TcII/Y strains. The novel systems biology approaches and the use of a flow cytometry platform demonstrated that distinct T. cruzi genotypes influenced in the phenotypic and functional features of the host immune response and the genotype-specific serological reactivity during early and late stages of experimental T. cruzi infection.

Diversity and Epidemiology of Bat Trypanosomes: A One Health Perspective

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

Mechanisms Associated with Trypanosoma cruzi Host Target Cell Adhesion, Recognition and Internalization

Chagas disease is caused by the kinetoplastid parasite Trypanosoma cruzi, which is mainly transmitted by hematophagous insect bites. The parasite's lifecycle has an obligate intracellular phase (amastigotes), while metacyclic and bloodstream-trypomastigotes are its infective forms. Mammalian host cell recognition of the parasite involves the interaction of numerous parasite and host cell plasma membrane molecules and domains (known as lipid rafts), thereby ensuring internalization by activating endocytosis mechanisms triggered by various signaling cascades in both host cells and the parasite. This increases cytoplasmatic Ca2+ and cAMP levels; cytoskeleton remodeling and endosome and lysosome intracellular system association are triggered, leading to parasitophorous vacuole formation. Its membrane becomes modified by containing the parasite's infectious form within it. Once it has become internalized, the parasite seeks parasitophorous vacuole lysis for continuing its intracellular lifecycle, fragmenting such a vacuole's membrane. This review covers the cellular and molecular mechanisms involved in T. cruzi adhesion to, recognition of and internalization in host target cells.

Chagas Cardiomyopathy: From Romaña Sign to Heart Failure and Sudden Cardiac Death

Despite nearly a century of research and accounting for the highest disease burden of any parasitic disease in the Western Hemisphere, Chagas disease (CD) is still a challenging diagnosis, primarily due to its poor recognition outside of Latin America. Although initially considered endemic to Central and South America, globalization, urbanization, and increased migration have spread the disease worldwide in the last few years, making it a significant public health threat. The international medical community's apparent lack of interest in this disease that was previously thought to be geographically restricted has delayed research on the complex host-parasite relationship that determines myocardial involvement and its differential behavior from other forms of cardiomyopathy, particularly regarding treatment strategies. Multiple cellular and molecular mechanisms that contribute to degenerative, inflammatory, and fibrotic myocardial responses have been identified and warrant further research to expand the therapeutic arsenal and impact the high burden attributed to CD. Altogether, cardiac dysautonomia, microvascular disturbances, parasite-mediated myocardial damage, and chronic immune-mediated injury are responsible for the disease's clinical manifestations, ranging from asymptomatic disease to severe cardiac and gastrointestinal involvement. It is crucial for healthcare workers to better understand CD transmission and disease dynamics, including its behavior on both its acute and chronic phases, to make adequate and evidence-based decisions regarding the disease. This review aims to summarize the most recent information on the epidemiology, pathogenesis, clinical presentation, diagnosis, screening, and treatment of CD, emphasizing on Chagasic cardiomyopathy's (Ch-CMP) clinical presentation and pathobiological mechanisms leading to sudden cardiac death.

The sexual side of parasitic protists

Much of the vast evolutionary landscape occupied by Eukaryotes is dominated by protists. Though parasitism has arisen in many lineages, there are three main groups of parasitic protists of relevance to human and livestock health: the Apicomplexa, including the malaria parasite Plasmodium and coccidian pathogens of livestock such as Eimeria; the excavate flagellates, encompassing a diverse range of protist pathogens including trypanosomes, Leishmania, Giardia and Trichomonas; and the Amoebozoa, including pathogenic amoebae such as Entamoeba. These three groups represent separate, deep branches of the eukaryote tree, underlining their divergent evolutionary histories. Here, I explore what is known about sex in these three main groups of parasitic protists.

Surveillance of Trypanosoma cruzi infection in Triatomine vectors, feral dogs and cats, and wild animals in and around El Paso county, Texas, and New Mexico

The causative agent of Chagas disease, Trypanosoma cruzi, is transmitted by triatomine vectors. The insect is endemic in the Americas, including the United States, where epidemiological studies are limited, particularly in the Southwestern region. Here, we have determined the prevalence of T. cruzi in triatomines, feral cats and dogs, and wild animals, the infecting parasite genotypes and the mammalian host bloodmeal sources of the triatomines at four different geographical sites in the U.S.-Mexico border, including El Paso County, Texas, and nearby cities in New Mexico. Using qualitative polymerase chain reaction to detect T. cruzi infections, we found 66.4% (n = 225) of triatomines, 45.3% (n = 95) of feral dogs, 39.2% (n = 24) of feral cats, and 71.4% (n = 7) of wild animals positive for T. cruzi. Over 95% of T. cruzi genotypes or discrete typing units (DTUs) identified were TcI and some TcIV. Furthermore, Triatoma rubida was the triatomine species most frequently (98.2%) collected in all samples analyzed. These findings suggest a high prevalence of T. cruzi infections among triatomines, and feral and wild animals in the studied sites. Therefore, our results underscore the urgent need for implementation of a systematic epidemiological surveillance program for T. cruzi infections in insect vectors, and feral and wild animals, and Chagas disease in the human population in the southwestern region of the United States.

Chagas disease is caused by the parasite Trypanosoma cruzi and one of the major transmission routes is the contaminated feces of blood-feeding triatomine insect vectors, popularly known as kissing bugs. In recent years, this disease has become an important public health concern to the United States and other nonendemic regions of the world. Despite many studies about the prevalence of T. cruzi in triatomines, and domestic, feral and wild animals in central and southern Texas, there have been no studies in west Texas and New Mexico. In this study, we report the presence of triatomines in residences in El Paso County, TX, and surrounding communities in New Mexico (cities of Anthony and Las Cruces), as well as T. cruzi infections in feral and wild animals. Using two molecular techniques to analyze the bloodmeal source in triatomines, we detected 12 different mammalian bloodmeal sources, including human and canine. Finally, parasite genotyping showed that most (95%) of the samples belonged to the genotype TcI, which is prevalent in North America. Our findings indicate that the El Paso County and surrounding communities (>950,000 people) are high risk areas for T. cruzi transmission to humans, feral cats and dogs, and wild animals. Thus, there is an urgent necessity for a public health epidemiological surveillance program for T. cruzi infections in kissing bugs, feral and wild animals, and in the human population in the U.S.-Mexico border region.

Human Chagas-Flow ATE-IgG1 for advanced universal and Trypanosoma cruzi Discrete Typing Units-specific serodiagnosis of Chagas disease

The molecular and serological methods available for Discrete Typing Units (DTU)-specific diagnosis of Trypanosoma cruzi in chronic Chagas disease present limitations. The study evaluated the performance of Human Chagas-Flow ATE-IgG1 for universal and DTU-specific diagnosis of Chagas disease. A total of 102 sera from Chagas disease patients (CH) chronically infected with TcI, TcVI or TcII DTUs were tested for IgG1 reactivity to amastigote/(A), trypomastigote/(T) and epimastigote/(E) antigens along the titration curve (1:250-1:32,000). The results demonstrated that "AI 250/40%", "EVI 250/30%", "AII 250/40%", "TII 250/40%" and "EII 250/30%" have outstanding accuracy (100%) to segregate CH from non-infected controls. The attributes "TI 4,000/50%", "EI 2,000/50%", "AVI 8,000/60%" and "TVI 4,000/50%" were selected for DTU-specific serotyping of Chagas disease. The isolated use of "EI 2,000/50%" provided the highest co-positivity for TcI patients (91%). The combined decision tree algorithms using the pre-defined sets of attributes showed outstanding full accuracy (92% and 97%) to discriminate "TcI vs TcVI vs TcII" and "TcI vs TcII" prototypes, respectively. The elevated performance of Human Chagas-Flow ATE-IgG1 qualifies its use for universal and TcI/TcVI/TcII-specific diagnosis of Chagas disease. These findings further support the application of this method in epidemiological surveys, post-therapeutic monitoring and clinical outcome follow-ups for Chagas disease.

Quantification of parasite burden of Trypanosoma cruzi and identification of Discrete Typing Units (DTUs) in blood samples of Latin American immigrants residing in Barcelona, Spain

BACKGROUND

Trypanosoma cruzi has a high genetic and biological diversity and has been subdivided into seven genetic lineages, named TcI-TcVI and TcBat. DTUs TcI-TcII-TcV and TcVI are agents of ChD in different regions of Latin America. Due to population movements, the disease is an emergent global public health problem. Thus, the aim of this study was to quantify the parasitic load and identify the presence of T. cruzi DTUs in 101 Latin American immigrants with chronic ChD, residing in Barcelona, Spain.

METHODOLOGY / PRINCIPAL FINDINGS

5ml of peripheral blood were collected in guanidine/EDTA from each patient for DNA extraction, quantification of the parasitic load and genotyping. A great variation of the parasitic load of the patients was verified: from 0.001 to 22.2 T. cruzi DNA (fg) / Blood DNA (ng). In patients from Bolivia the parasitic load was 3.76±4.43 T. cruzi DNA (fg) / Blood DNA (ng) (mean ± SD), in patients of other countries was 0.95±1.38 T. cruzi DNA (fg) / Blood DNA (ng). No statistically significant difference was observed in the parasitic load between patients with the indeterminate and cardiac forms of ChD (p = 0,57). Parasite genotyping was performed by multilocus conventional PCR. In patients from Bolivia there was a nearly equal prevalence of DTUs TcV (27/77), TcII/TcV/TcVI (26/77), and TcII/TcVI (22/77). TcVI was detected in only 2 samples (2/77). A higher prevalence of TcII/TcVI (19/24) was verified in patients of other countries, with low prevalence of TcII/TcV/TcVI (4/24) and TcV (1/24).

CONCLUSIONS/SIGNIFICANCE

In this study, low/medium parasitic load was found in all patients evaluated. Our data corroborate previous conclusions indicating that patients from the Bolivia, living in Spain, are predominantly infected by TcV, and TcVI DTUs. On the other hand, in Non-Bolivians patients TcII/TcVI predominated. Surprisingly, in our cohort of 101 patients no infection by TcI DTU was observed.

Genomics and High-Resolution Typing Confirm Predominant Clonal Evolution Down to a Microevolutionary Scale in Trypanosoma cruzi

Trypanosoma cruzi, the agent of Chagas disease, is a paradigmatic case of the predominant clonal evolution (PCE) model, which states that the impact of genetic recombination in pathogens' natural populations is not sufficient to suppress a persistent phylogenetic signal at all evolutionary scales. In spite of indications for occasional recombination and meiosis, recent genomics and high-resolution typing data in T. cruzi reject the counterproposal that PCE does not operate at lower evolutionary scales, within the evolutionary units (=near-clades) that subdivide the species. Evolutionary patterns in the agent of Chagas disease at micro- and macroevolutionary scales are strikingly similar ("Russian doll pattern"), suggesting gradual, rather than saltatory evolution.

Potential association of Trypanosoma cruzi DTUs TcV and TcVI with the digestive form of Chagas disease

The relationship among genetic diversity of Trypanosoma cruzi and clinical forms of Chagas disease remain elusive. In order to assess the possible association between different T. cruzi Discrete Typing Units (DTUs) and the clinical pictures of the disease, 205 chronic patients from Salta province, Argentina, were analysed. One hundred and twenty-two of these patients were clinically categorized as: cardiac 38.5% (47/122), digestive 15% (18/122), cardio-digestive 16% (20/122) and asymptomatic 30% (37/122). From each patient, blood samples were taken for both, Polymerase Chain Reaction (PCR) targeting kDNA and blood culture analyses. The presence of T. cruzi kDNA was detected in 43% (88/205) of the patients. T. cruzi DTUs were identified in 74% (65/88) of the kDNA positive patients by PCR-hybridization using specific probes. We detected the presence of DTUs TcI, TcII, TcV and TcVI. Single infections (i.e. presence of only one DTU in the sample) were detected in 38.64% of the samples (34/88), while mixed infections were 35.23% (31/88). TcV was the most prevalent DTU (60.3%- 53/88). The association analyses showed, for the first time to the best of our knowledge, that TcV and TcVI were associated with the digestive form of Chagas Disease (Fisher p = .0001).

Knocking Down TcNTPDase-1 Gene Reduces in vitro Infectivity of Trypanosoma cruzi

Ecto-Nucleoside Triphosphate Diphosphohydrolases are enzymes that hydrolyze tri- and/or diphosphate nucleosides. Evidences pointed out to their participation in Trypanosoma cruzi virulence, infectivity, and purine acquisition. In this study, recombinant T. cruzi knocking out or overexpressing the TcNTPDase-1 gene were built, and the role of TcNTPDase-1 in the in vitro interaction with VERO cells was investigated. Results show that epimastigote forms of hemi-knockout parasites showed about 50% lower level of TcNTPDase-1 gene expression when compared to the wild type, while the T. cruzi overexpressing this gene reach 20 times higher gene expression. In trypomastigote forms, the same decreasing in TcNTPDase-1 gene expression was observed to the hemi-knockout parasites. The in vitro infection assays showed a reduction to 51.6 and 59.9% at the adhesion and to 25.2 and 26.4% at the endocytic indexes to the parasites knockout to one or other allele (Hygro and Neo hemi-knockouts), respectively. In contrast, the infection assays with T. cruzi overexpressing TcNTPDase-1 from the WT or Neo hemi-knockout parasites showed an opposite result, with the increasing to 287.7 and 271.1% at the adhesion and to 220.4 and 186.7% at the endocytic indexes, respectively. The parasitic load estimated in infected VERO cells by quantitative real time PCR corroborated these findings. Taken together, the partial silencing and overexpression of the TcNTPDase-1 gene generated viable parasites with low and high infectivity rates, respectively, corroborating that the enzyme encoded for this gene plays an important role to the T. cruzi infectivity.

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.

Development and evaluation of a duplex TaqMan qPCR assay for detection and quantification of Trypanosoma cruzi infection in domestic and sylvatic reservoir hosts

Background

A question of epidemiological relevance in Chagas disease studies is to understand Trypanosoma cruzi transmission cycles and trace the origins of (re)emerging cases in areas under vector or disease surveillance. Conventional parasitological methods lack sensitivity whereas molecular approaches can fill in this gap, provided that an adequate sample can be collected and processed and a nucleic acid amplification method can be developed and standardized. We developed a duplex qPCR assay for accurate detection and quantification of T. cruzi satellite DNA (satDNA) sequence in samples from domestic and sylvatic mammalian reservoirs. The method incorporates amplification of the gene encoding for the interphotoreceptor retinoid-binding protein (IRBP), highly conserved among mammalian species, as endogenous internal amplification control (eIAC), allowing distinction of false negative PCR findings due to inadequate sample conditions, DNA degradation and/or PCR interfering substances.

Results

The novel TaqMan probe and corresponding primers employed in this study improved the analytical sensitivity of the assay to 0.01 par.eq/ml, greater than that attained by previous assays for Tc I and Tc IV strains. The assay was tested in 152 specimens, 35 from 15 different wild reservoir species and 117 from 7 domestic reservoir species, captured in endemic regions of Argentina, Colombia and Mexico and thus potentially infected with different parasite discrete typing units. The eIACs amplified in all samples from domestic reservoirs from Argentina and Mexico, such as Canis familiaris, Felis catus, Sus scrofa, Ovis aries, Equus caballus, Bos taurus and Capra hircus with quantification cycles (Cq’s) between 23 and 25. Additionally, the eIACs amplified from samples obtained from wild mammals, such as small rodents Akodon toba, Galea leucoblephara, Rattus rattus, the opossums Didelphis virginiana, D. marsupialis and Marmosa murina, the bats Tadarida brasiliensis, Promops nasutus and Desmodus rotundus, as well as in Conepatus chinga, Lagostomus maximus, Leopardus geoffroyi, Lepus europaeus, Mazama gouazoubira and Lycalopex gymnocercus, rendering Cq’s between 24 and 33.

Conclusions

This duplex qPCR assay provides an accurate laboratory tool for screening and quantification of T. cruzi infection in a vast repertoire of domestic and wild mammalian reservoir species, contributing to improve molecular epidemiology studies of T. cruzi transmission cycles.

Geographic distribution of Trypanosoma cruzi genotypes detected in chronic infected people from Argentina. Association with climatic variables and clinical manifestations of Chagas disease

Chronic Chagas disease affects large number of people in Latin America where it remains one of the biggest public health problems. Trypanosoma cruzi is genetically divided into seven discrete typing units (DTUs), TcI-TcVI and Tcbat, and exhibits differential distribution across vectors, host and transmission cycles. Clinical manifestations (cardiac, digestive and / or neurological) vary according to the geographical region; and the DTUs more frequently found in any of the chronic form of the disease, indeterminate or clinical, are TcI, TcII, TcV and TcVI. However, why they have a particular geographical distribution and how they affect the development of Chagas disease is still unknown. In this study, we assessed the geographic distribution of T. cruzi genotypes detected in chronic infected people from 57 localities of endemic regions of Argentina and analyzed their association with climatic variables. The prevalent DTUs detected in the whole population were TcV (47.4%) and TcVI (66.0%). TcI and TcII were identified in 5.2% each. All DTUs were detected in single and mixed infections (78.4% and 21.6%, respectively). TcV was found in infected people from localities with significantly higher average annual temperature, seasonal temperature and annual temperature range than those infected with TcVI. When we evaluated the association of DTUs with clinical manifestations of Chagas disease, the probability of finding TcVI in subjects with chronic Chagas cardiomyopathy (CCC) was higher than other DTUs, but without reaching statistical significance. Moreover, the probability of finding TcV in those who have not developed the disease after 20 years of infection was significantly higher than in CCC, either if it was present as unique DTU (reciprocal OR=4.95 95%CI: 1.42 to 17.27) (p=0.0117) or if it was also part of mixed infections (reciprocal OR=3.375; 95%CI: 1.227 to 9.276) (p=0.0264). There was no difference in the distribution of TcI between asymptomatic people and those with clinical manifestations, while TcII appeared more frequently in CCC cases, but without statiscal significance.

Trypanosomatids in Small Mammals of an Agroecosystem in Central Brazil: Another Piece in the Puzzle of Parasite Transmission in an Anthropogenic Landscape

We surveyed infection by Trypanosoma spp. and Leishmania spp. in small wild mammals from Cumari, Goiás State aiming to investigate the diversity of trypanosomatid in a modified landscape of the Brazilian Cerrado (and possible infection overlapping with canids from the same area). Blood, skin, spleen, and liver samples were collected for parasitological, serological, and molecular assays. Gracilinanus agilis was the most abundant species (N = 70; 48.6%) and it was the only one with patent parasitemia. Characterization by mini-exon and 18SrDNA targets were achieved in 7/10 hemocultures with positive fresh blood examination, which confirmed the T. cruzi infection by Discrete Typing Units (DTU) TcI in single (N = 2) and mixed infections with other DTUs (N = 5). T. rangeli and T. dionisii were detected in skin fragments from Didelphis albiventris and Oecomys cleberi, respectively. G. agilis were found to be infected by L. braziliensis and L. guyanensis, while Leishmania sp. DNA was detected in the liver of Oligoryzomys nigripes and Calomys expulsus. Subpatent infection by T. cruzi and Leishmania sp. was serologically detected in 15% and 9% of the small mammal fauna, respectively. Small mammals from Cumari are included in T. cruzi and Leshmania spp. transmission cycles, showing a higher diversity of trypanosomatid species and/or genotypes than that observed in canids of the same agroecosystem.

Congenital Chagas disease: current diagnostics, limitations and future perspectives

PURPOSE OF REVIEW

Congenital transmission is an important route of Trypanosoma cruzi infection, both in Latin America and internationally, with considerable populations of infected women of child-bearing age residing in the United States and Europe. This review examines recent literature on congenital Chagas disease, with a focus on the changing clinical spectrum and potential new diagnostic tools.

RECENT FINDINGS

Vertical transmission occurs in approximately 5-10% of births from T. cruzi-infected mothers. Historically, congenital Chagas disease was associated with high levels of neonatal morbidity and mortality. Bolivian birth cohort data from the early 1990s to the present indicate that the incidence of symptomatic neonatal disease has declined. Treatment with trypanocides is greater than 90% effective and well tolerated in infants. Current programs face challenges from the multistep screening algorithm, low sensitivity of microscopy and high loss to follow-up.

SUMMARY

Congenital Chagas disease remains an important contributor to the global disease burden because of T. cruzi. PCR and related molecular techniques represent the most sensitive diagnostic modalities for early detection but require further optimization for resource-limited settings. Several novel diagnostic tests show promise for the future but further validation and adaptation to field settings are needed.

A novel multilocus sequence typing scheme identifying genetic diversity amongst Leishmania donovani isolates from a genetically homogeneous population in the Indian subcontinent

In the Indian subcontinent, infection with Leishmania donovani can cause fatal visceral leishmaniasis. Genetic variation in L. donovani is believed to occur rapidly from environmental changes and through selective drug pressures, thereby allowing continued disease occurrence in this region. All previous molecular markers that are commonly in use multilocus microsatellite typing and multilocus sequence typing, were monomorphic in L. donovani originating from the Indian subcontinent (with only a few exceptions) and hence are not suitable for this region. An multilocus sequence typing scheme consisting of a new set of seven housekeeping genes was developed in this study, based on recent findings from whole genome sequencing data. This new scheme was used to assess the genetic diversity amongst 22 autochthonous L. donovani isolates from Bangladesh. Nineteen additional isolates of the L. donovani complex (including sequences of L. donovani reference strain BPK282A1) from other countries were included for comparison. By using restriction fragment length polymorphism of the internal transcribed spacer 1 region (ITS1-RFLP) and ITS1 sequencing, all Bangladeshi isolates were confirmed to be L. donovani. Population genetic analyses of 41 isolates using the seven new MLST loci clearly separated L. donovani from Leishmania infantum. With this multilocus sequence typing scheme, seven genotypes were identified amongst Bangladeshi L. donovani isolates, and these isolates were found to be phylogenetically different compared with those from India, Nepal, Iraq and Africa. This novel multilocus sequence typing approach can detect intra- and inter-species variations within the L. donovani complex, but most importantly these molecular markers can be applied to resolve the phylogenetically very homogeneous L. donovani strains from the Indian subcontinent. Four of these markers were found suitable to differentiate strains originating from Bangladesh, with marker A2P being the most discriminative one.

Trypanosoma dionisii in insectivorous bats from northern China

Although bats were considered as a major host of trypanosomatid flagellates, information of trypanosomes in bats is unknown in China. We collected bats in 2015 from Shandong Province of China and used PCR to amplify the Trypanosoma glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) gene and 18S rRNA gene from the bat blood samples and heart tissues. The results showed that 10.3% (13/126) of bats (Eptesicus serotinus and Myotis pequinius) were positive for trypanosomatid DNA and DNA sequencing showed that all PCR amplified Trypanosoma DNA belonged to T. dionisii. We concluded that T. dionisii had a infection rate in bats from China. For the first time, Trypanosoma infections were detected in bats from China, providing valuable information on the prevalence of these parasites in Asia. This is also the first report of Trypanosoma dionisii in Myotis pequinius, suggesting that Trypanosoma dionisii has a broad host species.

Bat Flies and Their Microparasites: Current Knowledge and Distribution

Bats are the second most diverse mammalian group, playing keystone roles in ecosystems but also act as reservoir hosts for numerous pathogens. Due to their colonial habits which implies close contacts between individuals, bats are often parasitized by multiple species of micro- and macroparasites. The particular ecology, behavior, and environment of bat species may shape patterns of intra- and interspecific pathogen transmission, as well as the presence of specific vectorial organisms. This review synthetizes information on a multi-level parasitic system: bats, bat flies and their microparasites. Bat flies (Diptera: Nycteribiidae and Streblidae) are obligate, hematophagous ectoparasites of bats consisting of ~500 described species. Diverse parasitic organisms have been detected in bat flies including bacteria, blood parasites, fungi, and viruses, which suggest their vectorial potential. We discuss the ecological epidemiology of microparasites, their potential physiological effects on both bats and bat flies, and potential research perspectives in the domain of bat pathogens. For simplicity, we use the term microparasite throughout this review, yet it remains unclear whether some bacteria are parasites or symbionts of their bat fly hosts.

Oral infection of mice and host cell invasion by Trypanosoma cruzi strains from Mexico

Oral infection by Trypanosoma cruzi has been responsible for frequent outbreaks of acute Chagas disease in the north of South America and in the Amazon region, where T. cruzi genetic group TcI predominates. TcI strains from different geographical regions have been used in oral infection in mice, but there is no information about strains from Mexico where TcI is prevalent. Here, we analyzed four Mexican strains as concerns the course of oral infection, the ability to invade host cells in vitro, and the profile of metacyclic trypomastigote surface molecules gp82 and gp90 that are implicated in parasite internalization. Oral infection of mice with metacyclic forms of all strains resulted in reduced blood and tissue parasitism, and mild to moderate inflammatory process in the heart/skeletal muscle. They expressed pepsin-resistant gp82 and gp90 molecules at high levels and invaded host cells poorly in full nutrient medium and efficiently under nutrient-deprived condition. The properties exhibited by Mexican strains were similar to those displayed by TcI strains from other geographical regions, reinforcing the notion that these features are common to the genetic group TcI as a whole.

Usefulness of Serial Blood Sampling and PCR Replicates for Treatment Monitoring of Patients with Chronic Chagas Disease

This work evaluated a serial blood sampling procedure to enhance the sensitivity of duplex real-time quantitative PCR (qPCR) for baseline detection and quantification of parasitic loads and posttreatment identification of failure in the context of clinical trials for treatment of chronic Chagas disease, namely, DNDi-CH-E1224-001 (ClinicalTrials.gov registration no. NCT01489228) and the MSF-DNDi PCR Sampling Optimization Study (NCT01678599).

This work evaluated a serial blood sampling procedure to enhance the sensitivity of duplex real-time quantitative PCR (qPCR) for baseline detection and quantification of parasitic loads and posttreatment identification of failure in the context of clinical trials for treatment of chronic Chagas disease, namely, DNDi-CH-E1224-001 (ClinicalTrials.gov registration no. NCT01489228) and the MSF-DNDi PCR Sampling Optimization Study (NCT01678599). Patients from Cochabamba (n = 294), Tarija (n = 257), and Aiquile (n = 220) were enrolled. Three serial blood samples were collected at each time point, and qPCR triplicates were tested for each sample. The first two samples were collected during the same day and the third one 7 days later. A patient was considered PCR positive if at least one qPCR replicate was detectable. Cumulative results of multiple samples and qPCR replicates enhanced the proportion of pretreatment sample positivity from 54.8% to 76.2%, 59.5% to 77.8%, and 73.5% to 90.2% in Cochabamba, Tarija, and Aiquile cohorts, respectively. This strategy increased the detection of treatment failure from 72.9% to 91.7%, 77.8% to 88.9%, and 42.9% to 69.1% for E1224 low-, short-, and high-dosage regimens, respectively, and from 4.6% to 15.9% and 9.5% to 32.1% for the benznidazole arm in the DNDi-CH-E1224-001 and MSF-DNDi studies, respectively. The addition of the third blood sample and third qPCR replicate in patients with nondetectable PCR results in the first two samples gave a small, non-statistically significant improvement in qPCR positivity. No change in clinical sensitivity was seen with a blood volume increase from 5 to 10 ml. The monitoring of patients treated with placebo in the DNDi-CH-E1224-001 trial revealed fluctuations in parasitic loads and occasionally nondetectable results. In conclusion, a serial sampling strategy enhanced PCR sensitivity to detecting treatment failure during follow-up and has the potential for improving recruitment capacity in Chagas disease trials, which require an initial positive qPCR result for patient admission.

Genotyping of Trypanosoma cruzi from Clinical Samples by Multilocus Conventional PCR

By the most recent nomenclature, Trypanosoma cruzi isolates are classified into six discrete typing units (DTUs)-T. cruzi I to T. cruzi VI and TcBat. One of the major challenges in the Chagas disease study is to find an association between DTUs and clinical manifestations of the disease or response to treatment. Herein, a protocol based on the amplification of T. cruzi SL-IRac, SL-IR I and II, 24Sα rDNA, and A10 targets by multilocus conventional PCRs is described. Following this methodology, it is possible to perform the genotyping directly from the blood and other clinical samples, without the need to isolate the parasite prior to the DNA extraction, even in a lower parasite concentration. Furthermore, this methodology increases the probability to detect mixed infections, avoiding a possible selection of strains during the parasite isolation.

Phylogenetic Studies

Phylogenetics is an important component of the systems biology approach. Knowledge about evolution of the genus Leishmania is essential to understand various aspects of basic biology of these parasites, such as parasite-host or parasite-vector relationships, biogeography, or epidemiology. Here, we present a comprehensive guideline for performing phylogenetic studies based on DNA sequence data, but with principles that can be adapted to protein sequences or other molecular markers. It is presented as a compilation of the most commonly used genetic targets for phylogenetic studies of Leishmania, including their respective primers for amplification and references, as well as details of PCR assays. Guidelines are, then, presented to choose the best targets in relation to the types of samples under study. Finally, and importantly, instructions are given to obtain optimal sequences, alignments, and datasets for the subsequent data analysis and phylogenetic inference. Different bioinformatics methods and software for phylogenetic inference are presented and explained. This chapter aims to provide a compilation of methods and generic guidelines to conduct phylogenetics of Leishmania for nonspecialists.

Triatoma brasiliensis Neiva, 1911: food sources and diversity of Trypanosoma cruzi in wild and artificial environments of the semiarid region of Ceará, northeastern Brazil

Background

Knowledge of triatomine food sources in different ecotopes enables the estimation of T. cruzi transmission risk in diverse environments, as well as its dynamics of dispersion and ecological niche. For Triatoma brasiliensis in the Caatinga, in the northeast of Brazil, seasonal differences influence feeding eclecticism and rates of T. cruzi infection. The objective of the present study was to monitor food sources and to characterize the populations of T. cruzi associated with T. brasiliensis in wild and domestic environments in the Caatinga of northeast Brazil.

Methods

A cross-sectional study based on a search for triatomines in wild and domestic environments, was undertaken at five different time periods from 2009 to 2015. Insects from 2015 were used for identification of food sources. Two universal primers, based on the conserved regions of the 12S rRNA locus, were used to amplify fragments of 215 bp. The content of the intestinal tract of triatomines was identified by a comparison between the sequences obtained and those deposited in the GenBank database, using BLAST. In triatomines with parasitological diagnosis of infection by trypanosomatids, xenoculture was performed for the isolation and characterization of strains, using cox2, the amplification of the SL-IL mini-exon intergenic spacer and the polymorphism of the D7 divergent domain of the gene 24αrDNA-LSU.

Results

Food sources were identified in 76.3% (213/279) T. brasiliensis specimens sampled in 2015. The most frequent sources in a total of 20 vertebrate species were: rodents (58%, 123/213), ruminants (30%, 64/213) and cats (6%, 12/213). A total of 49% (44/89) of the samples of T. cruzi isolated in the period from 2009 to 2015 were characterized: TcII (43%, 19/44), TcI (41%, 18/44) and TcIII (16%, 7/44).

Conclusions

The feeding eclecticism of T. brasiliensis shows its importance in maintaining the transmission dynamics of T. cruzi, with evidence of intense circulation between anthropic and wild environments. Attention should be placed on the association among T. brasiliensis, rodents and ruminants, in addition to the presence of TcIII in the study region.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3235-4) contains supplementary material, which is available to authorized users.

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.

Triatoma costalimai Naturally Infected by Trypanosoma cruzi: A Public Health Concern

The rupestrian Triatoma costalimai species has been found infected by Trypanosoma cruzi in wild, peridomicile, and intradomicile environments in the municipality of Aurora do Tocantins, Tocantins, Brazil. Proximity between rock outcrops increases the risk of vector transmission of Chagas disease via this species. This work describes a focus of colonization by T. costalimai specimens infected by T. cruzi in rock outcrops located in an urban area in this municipality. Parasitological examination of feces from the collected specimens, axenic cultivation of T. cruzi-positive samples, and genetic characterization of the isolates were performed. Nymph and adult specimens were collected with a high infection prevalence (64.5%) for T. cruzi discrete type unit (DTU I). Participation of the T. costalimai species in the wild cycle of T. cruzi in rock outcrops located in an urban area demonstrates the need for entomological surveillance and control of vector transmission of Chagas disease in the municipality of Aurora do Tocantins, Tocantins.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

Exploring the parasite load and molecular diversity of Trypanosoma cruzi in patients with chronic Chagas disease from different regions of Brazil

Chagas disease is still a major public health issue in many Latin American countries. One of the current major challenges is to find an association between Trypanosoma cruzi discrete typing units (DTUs) and clinical manifestations of the disease. In this study, we used a multilocus conventional PCR and quantitative real time PCR (qPCR) approaches to perform the molecular typing and parasite load quantification directly from blood specimens of 65 chronic Chagas disease patients. All patients were recruited at the same health center, but their place of birth were widely distributed in different geographic regions of Brazil. Of the 65 patients, 35 (53.8%) presented positive amplification by real time qPCR, being 20 (30.7%) with the clinical indeterminate form and 15 (23.1%) with the cardiac form of the disease. The parasite load median for all positive patients was 2.54 [1.43-11.14] parasite equivalents/mL (par. Eq./mL), with the load ranging from 0.12 to 153.66 par. Eq./mL. Noteworthy, the parasite load was significantly higher in patients over 70 years old (median 20.05 [18.29-86.86] par. Eq./mL). Using guanidine-EDTA blood samples spiked with reference T. cruzi strains, belonging to the six DTUs, it was possible to genotype the parasite up to 0.5 par. Eq./mL, with high specificity. Of the patients with positive qPCR, it was possible to identify the T. cruzi DTU in 28 patients (80%). For the remaining patients (20%), at least a partial result was obtained. Analysis of specimens showed prevalences of TcVI, TcII and mixed infection TcVI+TcII equal to 40%, 17.1% and 14.3%, respectively. In addition, two patients were infected by TcV, and one patient was coinfected by TcIII+TcVI, These last three patients were in stage A of chronic chagasic cardiomyopathy (CCC), and they were born at the Bahia State (northeast region of Brazil). When T. cruzi genotypes were compared with the parasite load, more elevated parasite loads were observed in patients infected by TcII in general (parasite load median of 7.56 par. Eq./mL) in comparison to patients infected by TcVI (median of 2.35 par. Eq./mL). However, while the frequency of CCC was 50% in patients infected by TcVI and TcV, only 16.7% of patients infected by TcII evolved to CCC. Taking together, our results contribute to update the epidemiological knowledge of T. cruzi DTUs in Brazil, and highlight the age of patient and infection by TcII as important features that lead to the observation of higher parasitemia levels.

Uncovering vector, parasite, blood meal and microbiome patterns from mixed-DNA specimens of the Chagas disease vector Triatoma dimidiata

Chagas disease, considered a neglected disease by the World Health Organization, is caused by the protozoan parasite Trypanosoma cruzi, and transmitted by >140 triatomine species across the Americas. In Central America, the main vector is Triatoma dimidiata, an opportunistic blood meal feeder inhabiting both domestic and sylvatic ecotopes. Given the diversity of interacting biological agents involved in the epidemiology of Chagas disease, having simultaneous information on the dynamics of the parasite, vector, the gut microbiome of the vector, and the blood meal source would facilitate identifying key biotic factors associated with the risk of T. cruzi transmission. In this study, we developed a RADseq-based analysis pipeline to study mixed-species DNA extracted from T. dimidiata abdomens. To evaluate the efficacy of the method across spatial scales, we used a nested spatial sampling design that spanned from individual villages within Guatemala to major biogeographic regions of Central America. Information from each biotic source was distinguished with bioinformatics tools and used to evaluate the prevalence of T. cruzi infection and predominant Discrete Typing Units (DTUs) in the region, the population genetic structure of T. dimidiata, gut microbial diversity, and the blood meal history. An average of 3.25 million reads per specimen were obtained, with approximately 1% assigned to the parasite, 20% to the vector, 11% to bacteria, and 4% to putative blood meals. Using a total of 6,405 T. cruzi SNPs, we detected nine infected vectors harboring two distinct DTUs: TcI and a second unidentified strain, possibly TcIV. Vector specimens were sufficiently variable for population genomic analyses, with a total of 25,710 T. dimidiata SNPs across all samples that were sufficient to detect geographic genetic structure at both local and regional scales. We observed a diverse microbiotic community, with significantly higher bacterial species richness in infected T. dimidiata abdomens than those that were not infected. Unifrac analysis suggests a common assemblage of bacteria associated with infection, which co-occurs with the typical gut microbial community derived from the local environment. We identified vertebrate blood meals from five T. dimidiata abdomens, including chicken, dog, duck and human; however, additional detection methods would be necessary to confidently identify blood meal sources from most specimens. Overall, our study shows this method is effective for simultaneously generating genetic data on vectors and their associated parasites, along with ecological information on feeding patterns and microbial interactions that may be followed up with complementary approaches such as PCR-based parasite detection, 18S eukaryotic and 16S bacterial barcoding.

Using the health belief model to identify communication opportunities to prevent Chagas disease in Southern Ecuador

Background

Chagas disease (CD) is a life-threatening illness caused by the protozoan parasite Trypanosoma cruzi, which is transmitted by triatomine bugs. Triatomine bugs inhabit poorly constructed homes that create multiple hiding spots for the bugs. Modifying the actual structure of a home, along with the homeowners’ practices, can reduce triatomine infestation. This research was designed to collect culturally-relevant information to develop a health campaign to decrease risk of CD transmission by promoting home maintenance and better hygiene in rural communities of southern Ecuador.

Methods and main findings

The Health Belief Model (HBM) guided focus group discussions and the interpretation of the results. Four focus groups ranging from 4 to 10 participants were conducted between May and June 2014 in three communities of Loja province in Southern Ecuador. A thematic analysis was used to identify within the data related to perceptions of susceptibility, severity, benefits, barriers and self-efficacy related to CD and its prevention. The results provide clear guidance for the development of Chagas-prevention messages.

Conclusion

Data obtained emphasize the importance of standardizing messages presented to the communities for CD prevention. Messages should provide more information on the protective nature of the behaviors promoted for CD prevention; overcoming barriers such as cost and convenience, and build on facilitating factors, including community members’ interest on quality of life, protection of their families, and relationship with the land.

This study focuses on Chagas disease (CD) prevention in southern Ecuador. This region has a high rate of triatomine infestation. We used the Health Belief Model (HBM) to understand why people do or do not engage in CD preventive behaviors, particularly those related to home improvement. Additionally, we wanted to learn how to communicate most effectively about CD prevention. We gathered information about community member’s perceptions of CD in four focus groups, with a total of 26 participants. Our results indicate that communities do not see triatomines and CD as a threat. Lack of structures, cost, and convenience were the three key barriers mentioned by research participants for implementing CD preventive behaviors. However, participants were open to work with prevention programs since they saw it as an opportunity for community members to work together under the motivation of improving their living conditions. Capitalizing on motivators and removing barriers will be important for subsequent communication campaigns. Messages evoking fear of triatomine bugs and CD will contradict participants’ personal experience; instead, messages focusing how these behaviors will improve communities’ quality of life, protect their families, and strengthen their relationship with the land, will be more acceptable and appealing.

Molecular diagnosis of Trypanosoma cruzi

Chagas disease, caused by the kinetoplastid protozoan Trypanosoma cruzi, affects millions of people, most of them neglected populations. The different phases of the disease, the transmission mode and the high genetic variability of the parasite determine that molecular detection methods display different degree of success. Molecular diagnostic tests may be employed during epidemiological surveys of transmission, for early diagnosis of congenital transmission and acute infections due to oral transmission, transfusion or transplantation routes, reactivation due to immunosuppression and monitoring of treatment response in chronically infected patients receiving trypanocidal chemotherapy. This manuscript summarizes the most widely used molecular tools to detect T. cruzi infection in different epidemiological and clinical scenarios.

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.

Trypanosoma cruzi load in synanthropic rodents from rural areas in Chile

BACKGROUND

Trypanosoma cruzi is the agent of Chagas disease, a major public health problem in Latin America. Many wild and domestic animals are naturally infected with T. cruzi; rodents are one of the groups which have been consistently detected infected in different countries. The aim of this work was to characterize blood T. cruzi load in naturally infected rodents from a Chagas disease endemic region in Chile.

METHODS

Baited traps were set in domestic and peridomestic areas of rural dwellings. The rodents were anesthetized and blood sampled; DNA was extracted and the parasite load was quantified by T. cruzi satellite DNA real-time PCR assays.

RESULTS

Seventy-one rodents of four species, Rattus rattus, Mus musculus, Phyllotis darwini and Octodon degus, were captured; R. rattus was the most abundant species. Fifty-nine samples (83.1%) were T. cruzi-positive and the median value of the parasite load was 2.99 parasite equivalents (par-eq)/ml. The comparison of frequency of infection or parasite load by species showed no differences. However, one R. rattus presented very elevated parasitemia (1644 par-eq/ml).

CONCLUSIONS

The overall levels of parasitemia were similar to those found in humans in Chile. The high infection levels in exotic and endemic rodents very near to rural settlements increases their relevance as T. cruzi hosts.

Accomplishing the genotype-specific serodiagnosis of single and dual Trypanosoma cruzi infections by flow cytometry Chagas-Flow ATE-IgG2a

The methods currently available for genotype-specific diagnosis of T. cruzi infection still present relevant limitations, especially to identify mixed infection. In the present investigation, we have evaluated the performance of Chagas-Flow ATE-IgG2a test for early and late differential diagnosis of single and dual genotype-specific T. cruzi infections. Serum samples from Swiss mice at early and late stages of T. cruzi infection were assayed in parallel batches for genotype-specific diagnosis of single (TcI, TcVI or TcII) and dual (TcI+TcVI, TcVI+TcII or TcII+TcI) infections. The intrinsic reactivity to TcI, TcVI and TcII target antigens, including amastigote (AI/AVI/AII), trypomastigote-(TI/TVI/TII) and epimastigote (EI/EVI/EII), at specific reverse of serum dilutions (500 to 64,000), was employed to provide reliable decision-trees for "early" vs "late", "single vs "dual" and "genotype-specific" serology. The results demonstrated that selective set of attributes "EII 500/EI 2,000/AII 500" were able to provide high-quality accuracy (81%) to segregate early and late stages of T. cruzi infection. The sets "TI 2,000/AI 1,000/EII 1,000" and "TI 8,000/AII 32,000" presented expressive scores to discriminate single from dual T. cruzi infections at early (85%) and late stages (84%), respectively. Moreover, the attributes "TI 4,000/TVI 500/TII 1,000", "TI 16,000/EI 2,000/EII 2,000/AI 500/TVI 500" showed good performance for genotype-specific diagnosis at early stage of single (72%) and dual (80%) T. cruzi infections, respectively. In addition, the attributes "TI 4,000/AII 1,000/EVI 1,000", "TI 64,000/AVI 500/AI 2,000/AII 1,000/EII 4,000" showed moderate performance for genotype-specific diagnosis at late stage of single (69%) and dual (76%) T. cruzi infections, respectively. The sets of decision-trees were assembled to construct a sequential algorithm with expressive accuracy (81%) for serological diagnosis of T. cruzi infection. These findings engender new perspectives for the application of Chagas-Flow ATE-IgG2a method for genotype-specific diagnosis in humans, with relevant contributions for epidemiological surveys as well as clinical and post-therapeutic monitoring of Chagas disease.

Assembly of highly repetitive genomes using short reads: the genome of discrete typing unit III Trypanosoma cruzi strain 231

Next-generation sequencing (NGS) methods are low-cost high-throughput technologies that produce thousands to millions of sequence reads. Despite the high number of raw sequence reads, their short length, relative to Sanger, PacBio or Nanopore reads, complicates the assembly of genomic repeats. Many genome tools are available, but the assembly of highly repetitive genome sequences using only NGS short reads remains challenging. Genome assembly of organisms responsible for important neglected diseases such as Trypanosoma cruzi, the aetiological agent of Chagas disease, is known to be challenging because of their repetitive nature. Only three of six recognized discrete typing units (DTUs) of the parasite have their draft genomes published and therefore genome evolution analyses in the taxon are limited. In this study, we developed a computational workflow to assemble highly repetitive genomes via a combination of de novo and reference-based assembly strategies to better overcome the intrinsic limitations of each, based on Illumina reads. The highly repetitive genome of the human-infecting parasite T. cruzi 231 strain was used as a test subject. The combined-assembly approach shown in this study benefits from the reference-based assembly ability to resolve highly repetitive sequences and from the de novo capacity to assemble genome-specific regions, improving the quality of the assembly. The acceptable confidence obtained by analyzing our results showed that our combined approach is an attractive option to assemble highly repetitive genomes with NGS short reads. Phylogenomic analysis including the 231 strain, the first representative of DTU III whose genome was sequenced, was also performed and provides new insights into T. cruzi genome evolution.