[Acute Chagas' disease: transmission routes, clinical aspects and response to specific therapy in diagnosed cases in an urban center]

Serum proteomics reveals a tolerant immune phenotype across multiple pathogen taxa in wild vampire bats

Bats carry many zoonotic pathogens without showing pronounced pathology, with a few exceptions. The underlying immune tolerance mechanisms in bats remain poorly understood, although information-rich omics tools hold promise for identifying a wide range of immune markers and their relationship with infection. To evaluate the generality of immune responses to infection, we assessed the differences and similarities in serum proteomes of wild vampire bats (Desmodus rotundus) across infection status with five taxonomically distinct pathogens: bacteria (Bartonella spp., hemoplasmas), protozoa (Trypanosoma cruzi), and DNA (herpesviruses) and RNA (alphacoronaviruses) viruses. From 19 bats sampled in 2019 in Belize, we evaluated the up- and downregulated immune responses of infected versus uninfected individuals for each pathogen. Using a high-quality genome annotation for vampire bats, we identified 586 serum proteins but found no evidence for differential abundance nor differences in composition between infected and uninfected bats. However, using receiver operating characteristic curves, we identified four to 48 candidate biomarkers of infection depending on the pathogen, including seven overlapping biomarkers (DSG2, PCBP1, MGAM, APOA4, DPEP1, GOT1, and IGFALS). Enrichment analysis of these proteins revealed that our viral pathogens, but not the bacteria or protozoa studied, were associated with upregulation of extracellular and cytoplasmatic secretory vesicles (indicative of viral replication) and downregulation of complement activation and coagulation cascades. Additionally, herpesvirus infection elicited a downregulation of leukocyte-mediated immunity and defense response but an upregulation of an inflammatory and humoral immune response. In contrast to our two viral infections, we found downregulation of lipid and cholesterol homeostasis and metabolism with Bartonella spp. infection, of platelet-dense and secretory granules with hemoplasma infection, and of blood coagulation pathways with T. cruzi infection. Despite the small sample size, our results suggest that vampire bats have a similar suite of immune mechanisms for viruses distinct from responses to the other pathogen taxa, and we identify potential biomarkers that can expand our understanding of pathogenesis of these infections in bats. By applying a proteomic approach to a multi-pathogen system in wild animals, our study provides a distinct framework that could be expanded across bat species to increase our understanding of how bats tolerate pathogens.

Heterogeneity in network structure switches the dominant transmission mode of infectious diseases

Several recent emerging diseases have exhibited both sexual and nonsexual transmission modes (Ebola, Zika, and mpox). In the recent mpox outbreaks, transmission through sexual contacts appears to be the dominant mode of transmission. Motivated by this, we use an SIR-like model to argue that an initially dominant sexual transmission mode can be overtaken by casual transmission at later stages, even if the basic casual reproduction number is less than one. Our results highlight the risk of intervention designs which are informed only by the early dynamics of the disease.

Prospective study of ventricular function and myocardial deformation related to survival in acute Chagas disease: an experimental animal model

Chagas disease (CD) has been changing from an endemic Latino-American disease to a condition found outside endemic regions, due to migratory movements. Although often subclinical, its acute phase can be lethal. This study aimed to assess survival during the acute phase of CD and its relationship with ventricular function in an experimental model. To this end, 30 Syrian hamsters were inoculated with Trypanosoma cruzi (IG) and other 15 animals received saline solution (CG). Groups were monitored daily and submitted to echocardiography in two moments: before the challenge and 15 days post-infection. Left ventricular ejection fraction (LVEF) and global longitudinal myocardial strain (GLS) of the LV were measured. The IG was divided into groups of animals with and without clinical signs of disease. ANOVA for mixed models was used to compare ventricular function parameters. Survival analysis was studied using Kaplan-Meier curves and the log-rank test. The follow-up lasted 60 days. LVEF in IG was reduced through time (53.80 to 43.55%) compared to CG (57.86 to 59.73%) (p=0.002). There was also a reduction of GLS (-18.97% to -12.44%) in the IG compared to CG (p=0.012). Twelve animals from IG died compared to one animal from CG. Eleven out of the 12 animals from the IG group died before presenting with clinical signs of infection. Survival was reduced in the IG compared to CG over time (p=0.02). The reduced survival during the acute phase of this experimental model of Chagas disease was related to the significant reduction of LV function. The mortality rate in the IG was higher in the group presenting with clinical signs of infection.

Clinical, Cardiological and Serologic Follow-Up of Chagas Disease in Children and Adolescents from the Amazon Region, Brazil: Longitudinal Study

BACKGROUND

Outbreaks of Chagas disease (CD) by foodborne transmission is a problem related to deforestation, exposing people to triatomines infected by T. cruzi, in the Amazon region. Once involving long-time follow-up, the treatment efficacy of the CD during its acute phase is still unknown. The authors aim to describe the clinical and epidemiologic profile of children and adolescents with CD, as well as treatment and cardiac involvement during the follow-up. Methods: A descriptive cohort study was conducted from 1998 to 2013 among children and adolescents up to 18 years-old with confirmed diagnosis of CD. All participants met the criteria of CD in the acute phase. Results: A total of 126 outpatients were included and received treatment and follow-up examinations during a medium period of 10.9 years/person. Most of them (68.3%) had their diagnosis established during oral transmission outbreaks. The diagnostic method with the most positive results rate (80.9%) was the IgM class anti-T. cruzi antibody test as an acute phase marker, followed by the thick blood smears (60.8%). Acute myopericarditis was demonstrated in 18.2% of the patients, most of them with favorable evolution, though 2.4% (3/126) persisted with cardiac injury observed at the end point of the follow-up. Conclusions: Antibodies against T. cruzi persisted in 54.8% of sera from the patients without prognostic correlation with cardiac involvement. Precocious treatment can decrease potential cardiac complications and assure good treatment response, especially for inhabitants living in areas with difficult accessibility.

An evaluation of benznidazole as a Chagas disease therapeutic

Introduction: As benznidazole is the first-line treatment for patients with Chagas disease, rational chemotherapy strategies are required based on the critical analysis of the evidence on the relevance and applicability of this drug at different disease stages. Areas covered: The authors discuss the current understanding of benznidazole-based chemotherapy for Chagas disease, focusing specifically on epidemiology, pharmacokinetics, mechanism of action, clinical recommendations, cure criteria, and therapeutic efficacy in different phases of the disease. Expert opinion: Benznidazole shows high bioavailability after oral administration. Benznidazole at 5-8 mg/kg/day and 5-10 mg/kg/day for 30-60 days are consistent clinical recommendations for children and adults, respectively. A high correlation between negative parasitological, serological, and polymerase chain reaction (PCR) assays in long-term post-therapeutic follow-up has been consistently used to evaluate therapeutic efficacy. These methods support the evidence that the success of benznidazole-based chemotherapy is closely correlated with the phase of infection in which the treatment is administered. The greater therapeutic efficacy is obtained in acute infections, gradually worsening as the infection becomes chronic. When therapeutic failure is confirmed by any diagnostic assay, benznidazole treatment does not always ensure better long-term prognosis, and Chagas cardiomyopathy may develop as well as in untreated patients.

Oral Route Driven Acute Trypanosoma cruzi Infection Unravels an IL-6 Dependent Hemostatic Derangement

Oral transmission of Trypanosoma cruzi, the etiologic agent of Chagas disease, is presently the most important route of infection in Brazilian Amazon. Other South American countries have also reported outbreaks of acute Chagas disease associated with food consumption. A conspicuous feature of this route of transmission is presenting symptoms such as facial and lower limbs edema, in some cases bleeding manifestations and risk of thromboembolism are evident. Notwithstanding, studies that address this route of infection are largely lacking regarding its pathogenesis and, more specifically, the crosstalk between immune and hemostatic systems. Here, BALB/c mice were orally infected with metacyclic trypomastigotes of T. cruzi Tulahuén strain and used to evaluate the cytokine response, primary and secondary hemostasis during acute T. cruzi infection. When compared with control uninfected animals, orally infected mice presented higher pro-inflammatory cytokine (TNF-α, IFN-γ, and IL-6) serum levels. The highest concentrations were obtained concomitantly to the increase of parasitemia, between 14 and 28 days post-infection (dpi). Blood counts in the oral infected group revealed concomitant leukocytosis and thrombocytopenia, the latter resulting in increased bleeding at 21 dpi. Hematological changes paralleled with prolonged activated partial thromboplastin time, Factor VIII consumption and increased D-dimer levels, suggest that oral T. cruzi infection relies on disseminated intravascular coagulation. Remarkably, blockade of the IL-6 receptor blunted hematological abnormalities, revealing a critical role of IL-6 in the course of oral infection. These results unravel that acute T. cruzi oral infection results in significant alterations in the hemostatic system and indicates the relevance of the crosstalk between inflammation and hemostasis in this parasitic disease.

Evolution of anti-Trypanosoma cruzi antibody production in patients with chronic Chagas disease: Correlation between antibody titers and development of cardiac disease severity

Chagas disease is one of the most important endemic infections in Latin America affecting around 6–7 million people. About 30–50% of patients develop the cardiac form of the disease, which can lead to severe cardiac dysfunction and death. In this scenario, the identification of immunological markers of disease progression would be a valuable tool for early treatment and reduction of death rates. In this observational study, the production of anti-Trypanosoma cruzi antibodies through a retrospective longitudinal follow-up in chronic Chagas disease patients´ cohort and its correlation with disease progression and heart commitment was evaluated. Strong inverse correlation (ρ = -0.6375, p = 0.0005) between anti-T. cruzi IgG₁ titers and left ventricular ejection fraction (LVEF) in chronic Chagas cardiomyopathy (CCC) patients were observed after disease progression. Elevated levels of anti-T. cruzi IgG₃ titers were detected in all T. cruzi-infected patients, indicating a lack of correlation of this IgG isotype with disease progression. Furthermore, low levels of anti-T. cruzi IgG₂, IgG₄, and IgA were detected in all patients through the follow-up. Although without statistical significance anti-T. cruzi IgE tends to be more reactive in patients with the indeterminate form (IND) of the disease (p = 0.0637). As this study was conducted in patients with many years of chronic disease no anti-T. cruzi IgM was detected. Taken together, these results indicate that the levels of anti-T. cruzi IgG₁ could be considered to seek for promising biomarkers to predict the severity of chronic Chagas disease cardiomyopathy.

Trypanosoma cruzi is the etiological agent of Chagas disease that affects about 7 million people in Latin America, being considered one of the most important neglected diseases of developing countries. Chronic Chagas disease might be present in different forms as an asymptomatic indeterminate form or even with severe cardiac commitment, known as chronic Chagas cardiomyopathy. In fact, the cardiac form can lead to death due to disease progression. Seeking for biomarkers of cardiomyopathy progression has become important to understand the cardiac progression and to predict or even prevent the disease worsening and to improve the quality of life of affected individuals. In this work, we followed the anti-T. cruzi antibody profile in a retrospective longitudinal study in a cohort of chronic Chagas disease patients, and further correlate with heart commitment and cardiac disease progression. We found an inverse correlation between anti-T. cruzi IgG₁ titers and cardiac disease severity in patients with progressive disease. These data suggest that anti-T. cruzi IgG₁ levels could be considered a suitable candidate tool for early identification of cardiac disease progression.

The TcI and TcII Trypanosoma cruzi experimental infections induce distinct immune responses and cardiac fibrosis in dogs

Trypanosoma cruzi infection may be caused by different strains with distinct discrete typing units (DTUs) that can result in variable clinical forms of chronic Chagas disease. The present study evaluates the immune response and cardiac lesions in dogs experimentally infected with different T. cruzi strains with distinct DTUs, namely, the Colombian (Col) and Y strains of TcI and TcII DTU, respectively. During infection with the Col strain, increased levels of alanine aminotransferase, erythrocytes, haematocrit and haemoglobin were observed. In addition, CD8⁺ T-lymphocytes isolated from the peripheral blood produced higher levels of interleukin (IL)-4. The latter suggests that during the acute phase, infection with the Col strain may remain unnoticed by circulating mononuclear cells. In the chronic phase, a significant increase in the number of inflammatory cells was detected in the right atrium. Conversely, infection with the Y strain led to leucopoenia, thrombopoenia, inversion of the ratio of CD4⁺/CD8⁺ T-lymphocytes and alterations in monocyte number. The Y strain stimulated the production of interferon-γ by CD4⁺ and CD8⁺ T-lymphocytes and IL-4 by CD8⁺ T-cells. In the chronic phase, significant heart inflammation and fibrosis were observed, demonstrating that strains of different DTUs interact differently with the host.

Opportunity cost for early treatment of Chagas disease in Mexico

Background

Given current neglect for Chagas disease in public health programs in Mexico, future healthcare and economic development policies will need a more robust model to analyze costs and impacts of timely clinical attention of infected populations.

Methodology/Principal Findings

A Markov decision model was constructed to simulate the natural history of a Chagas disease cohort in Mexico and to project the associated short and long-term clinical outcomes and corresponding costs. The lifetime cost for a timely diagnosed and treated Chagas disease patient is US$ 10,160, while the cost for an undiagnosed individual is US$ 11,877. The cost of a diagnosed and treated case increases 24-fold from early acute to indeterminate stage. The major cost component for lifetime cost was working days lost, between 44% and 75%, depending on the program scenario for timely diagnosis and treatment.

Conclusions/Significance

In the long term, it is cheaper to diagnose and treat chagasic patients early, instead of doing nothing. This finding by itself argues for the need to shift current policy, in order to prioritize and attend this neglected disease for the benefit of social and economic development, which implies including treatment drugs in the national formularies. Present results are even more relevant, if one considers that timely diagnosis and treatment can arrest clinical progression and enhance a chronic patient's quality of life.

Chagas disease is caused by the flagellated protozoan parasite Trypanosoma cruzi, vectored in Mexico in both rural and urban areas via one of 18 triatomine bug species. Despite ample morbidity and mortality evidence, however, health policy managers in Mexico have continued to neglect prevention, control and clinical attention for the disease. A computer simulation Markov model was programmed and fed with information from published evidence and an expert panel. The lifetime cost for a timely diagnosed and treated Chagas disease patient is US$ 10,160, while the cost for an undiagnosed individual is US$ 11,877. The cost of a diagnosed and treated case increases 24-fold from early acute to indeterminate stage. The major cost component for lifetime cost was working days lost, between 44% and 75%, depending on the program scenario for timely diagnosis and treatment. Timely medical attention for infected individuals is cheaper than doing nothing, especially if life and labor costs are included. The evidence provided, essential for decision-making, should be used to develop disease-specific prevention, control and patient clinical diagnosis and treatment policies for Chagas disease in Mexico.

Chagas disease and breast-feeding

Mothers with this disease should continue breast-feeding unless they are experiencing the acute phase, reactivated disease, or bleeding nipples.

Chagas disease (infection by the protozoan Trypanosoma cruzi) is a major parasitic disease of the Americas and one of the main neglected tropical diseases. Although various routes of transmission sre recognized, the risk for transmission of the infection through breast-feeding has not clearly been established. We reviewed the literature on transmission of T. cruzi through breast-feeding to provide breast-feeding mothers with Chagas disease with medical guidance. Although data from animal studies and human studies are scarce, we do not recommend that mothers with Chagas disease discontinue breast-feeding, unless they are experiencing the acute phase of the disease, reactivated disease resulting from immunosuppression, or bleeding nipples. In these cases, thermal treatment of milk before feeding the infant may be considered.

Antiparasitical chemotherapy in Chagas' disease cardiomyopathy: current evidence

Chronic chagasic cardiomyopathy affects 20% of Chagas' disease patients. At present, Chagas' disease chemotherapy uses nitrofurans, benznidazole (Rochagan®, Rodanil®, Roche) or nifurtimox (Lampit®, Bayer). Treatment during acute and recent chronic phases in childhood effects 71.5% and 57.6%, respectively, of parasitological cure. However, in clinical trials during the late chronic phase, only 5.9% of parasitological cure were achieved. This review focuses on the benefit from aetiological treatment to avoid, stop or revert myocarditis. Divergent data gathered from clinical practice are not convincing to support prescription of aetiological treatment as routine for indeterminate and cardiac chronic patients.

Hematological alterations during experimental canine infection by Trypanosoma cruzi

To confirm that Beagle dogs are a good experimental model for Chagas disease, we evaluated hematological alterations during the acute and chronic phases in Beagle dogs infected with the Y, Berenice-78 (Be-78) and ABC strains of Trypanosomacruzi, correlating clinical signs with the parasitemia curve. We demonstrate that the acute phase of infection was marked by lethargy and loss of appetite. Simultaneously, we observed anemia, leukocytosis and lymphocytosis. Also,we describe hematological alterations and clinical signs that were positively correlated with the parasitemia during the experimental infection with the three strains of T.cruzi, and demonstrate that experimental infection of Beagle is a trustworthy model for Chagas disease.

[Chagas disease in the Americas: an ecohealth perspective]

The historical processes involved in Chagas disease transmission relate to the patterns and conditions of human settlements, especially in rural areas, due to proximity to forest areas, where both vectors and Trypanosoma cruzi can occur, combined with precarious housing conditions and underlying poverty. However, seasonal and permanent rural-urban migration has played a major role in re-mobilizing vectors, T. cruzi, and Chagas-infected individuals. A new agricultural frontier in the Amazon has led to a new transmission pattern, especially with palm trees located close to houses. Improved blood bank surveillance has decreased transmission by blood transfusions. International migration also plays a role in Chagas disease epidemiology. The United States and Spain, where specific health services for Chagas disease diagnosis and treatment are largely absent, harbor an unknown number of individuals with Chagas, probably infected decades ago. The article discusses major strides in Chagas disease knowledge and control, besides identifying persistent gaps, such as the need for housing improvements, especially in poor rural areas in the Americas.

Chagasic encephalitis in HIV patients: common presentation of an evolving epidemiological and clinical association

We present a case of chagasic meningoencephalitis reactivation in an HIV-infected woman with advanced immunosuppression. Prolonged survival was attained with antiparasitic therapy and secondary prophylaxis, in conjunction with the use of highly-active antiretroviral therapy. The geographic expansion of the HIV epidemic around the world coupled with global migration and international travel have created a favourable situation for Trypanosoma cruzi and HIV coinfection. The clinical manifestations of Chagas disease in HIV-positive people usually represent reactivation and not acute infection with T cruzi (coinfection). Symptomatic reactivation of chronic latent T cruzi infection can be triggered by severe immunosuppression associated with HIV infection. In this setting, Chagas disease reactivation often presents as meningoencephalitis resembling toxoplasma encephalitis. We review, in this Grand Round, the clinical manifestations, diagnostic approach, pathogenesis, natural history, treatment, prognosis, and prevention of Chagas disease reactivation among HIV-infected people with an emphasis on CNS manifestations.

Chagas disease

Chagas disease is the clinical condition triggered by infection with the protozoan Trypanosoma cruzi. The infection is transmitted by triatomine insects while blood feeding on a human host. Field studies predict that one third of an estimated 18 million T cruzi-infected humans in Latin America will die of Chagas disease. Acute infections are usually asymptomatic, but the ensuing chronic T cruzi infections have been associated with high ratios of morbidity and mortality: Chagas heart disease leads to unexpected death in 37.5% of patients, 58% develop heart failure and die and megacolon or megaoesophagus has been associated with death in 4.5%. The pathogenesis of Chagas disease appears to be related to a parasite-induced mutation of the vertebrate genome. Currently, treatment is unsatisfactory.

The dog as model for chemotherapy of the Chagas' disease

In the present study, we investigated the role of dogs as experimental models for acute and chronic phases of Chagas' disease, before and after therapeutic treatments. Dogs were infected with Trypanosoma cruzi strains of different susceptibilities to benznidazole (Bz) and treated with the same therapeutic scheme as used for human chagasic. The treatment with Bz was able to prevent death and induced parasitological cure in 62.5% (acute phase) and 38.7% (chronic recent phase) of the tested animals. These results were similar to those reported in clinical trials for treated human patients (cured and uncured) in both phases of the disease. We also showed that parasitologic and serologic tests for monitoring the cure were similar to those obtained for human trials. In addition, Polymerase chain reaction showed the highest sensitivity when compared with hemoculture as an indicator of parasite clearance. In conclusion, the proposed experimental model should be relevant for chemotherapy studies for the control of Chagas' disease.

Involvement of CD4(+) Th1 cells in systemic immunity protective against primary and secondary challenges with Trypanosoma cruzi

In general, gamma interferon (IFN-gamma)-producing CD4(+) Th1 cells are important for the immunological control of intracellular pathogens. We previously demonstrated an association between parasite-specific induction of IFN-gamma responses and resistance to the intracellular protozoan Trypanosoma cruzi. To investigate a potential causal relationship between Th1 responses and T. cruzi resistance, we studied the ability of Th1 cells to protect susceptible BALB/c mice against virulent parasite challenges. We developed immunization protocols capable of inducing polarized Th1 and Th2 responses in vivo. Induction of parasite-specific Th1 responses, but not Th2 responses, protected BALB/c mice against virulent T. cruzi challenges. We generated T. cruzi-specific CD4(+) Th1 and Th2 cell lines from BALB/c mice that were activated by infected macrophages to produce their corresponding cytokine response profiles. Th1 cells, but not Th2 cells, induced nitric oxide production and inhibited intracellular parasite replication in T. cruzi-infected macrophages. Despite the ability to inhibit parasite replication in vitro, Th1 cells alone could not adoptively transfer protection against T. cruzi to SCID mice. In addition, despite the fact that the adoptive transfer of CD4(+) T lymphocytes was shown to be necessary for the development of immunity protective against primary T. cruzi infection in our SCID mouse model, protective secondary effector functions could be transferred to SCID mice from memory-immune BALB/c mice in the absence of CD4(+) T lymphocytes. These results indicate that, although CD4(+) Th1 cells can directly inhibit intracellular parasite replication, a more important role for these cells in T. cruzi systemic immunity may be to provide helper activity for the development of other effector functions protective in vivo.

Autochthonous acute Chagas' disease in São Paulo State, Brazil: epidemiological aspects

Since the beginning of the seventies the natural transmission of Chagas' infection has been considered to be under control in the State of São Paulo and not even a case of American Trypanosomiasis, transmitted by triatomine bugs, has been detected by the epidemiological surveillance system. This situation justifies the report of a case of acute Chagas' disease that occurred in a forest area considered free of domiciliary triatomines along the Southern seacoast of São Paulo State. In May, 1995 the presence of trypomastigote forms of Trypanosoma cruzi had been diagnosed in a retired 57 year-old male patient, born and living in Santos (São Paulo State), complaining of fever, fatigue and malaise. The patient reported that 40 days before he had participated with 17 friends in a 7-day excursion in a forest area of the municipalities of Itanhaém and Peruíbe. During this period the group had been lodged in three houses located within the forest. Eight days after the end of the excursion the patient began to have fever, malaise and fatigue. During the next 31 days he had received medical care both as an inpatient and an outpatient, without any significant improvement. After the detection of T. cruzi trypomastigotes in his blood stream the patient began to be treated with benzonidazole in a hospital but died 8 days after the beginning of treatment. The epidemiological investigation carried out showed no signs of the presence of triatomine bugs in the three houses where the group had been lodged, or any indication of Chagas' infection in other excursionists.

American trypanosomiasis (Chagas' disease)

Gastrointestinal dysfunction is a major problem for many patients with chronic Chagas' disease, as are cardiac dysrhythmias and cardiomyopathy. The underlying anatomic abnormality in these patients is a denervation of the gastrointestinal tract. This process of nerve destruction usually develops insidiously over many years, and it is highly variable in terms of its extent in individual patients as well as in the segments of the gastrointestinal tract that are most affected. Megaesophagus is the most common manifestation of gastrointestinal Chagas disease, and mechanical dilation of the esophageal sphincter or surgery in advanced cases usually give satisfactory relief of symptoms. Megacolon, particularly of the sigmoid segment, is also common in patients with chronic T. cruzi infections, and its presence can be complicated by fecal impaction or sigmoid volvulus. Patients with advanced megacolon who have resections of the sigmoid colon and most of the rectum generally do well postoperatively.

Strategies for prevention of transfusion-associated Chagas' disease

Available epidemiological data indicate that Chagas' disease, a zoonosis caused by the flagellate protozoan parasite T cruzi, is a very important medical and social problem in Latin America. More than 60% of T cruzi-infected individuals have migrated to urban areas, in both endemic and nonendemic countries. Thus, with the implementation and maintenance of regular vector control programs in some countries, allogeneic blood transfusions have been the main mechanism for the continuation of this endemy. The risk of infection after transfusion of a unit of T cruzi-infected blood product depends mainly on the amount of blood transfused, parasite concentration in the infected transfused blood unit, and the recipient's immunological status. Current strategies to prevent transfusion-associated Chagas' disease include the identification of T cruzi-infected blood donors by predonation questionnaire, serological tests for T cruzi antibodies, and the treatment of the blood collected with gentian violet. Because T cruzi infection is lifelong, and most infected persons are asymptomatic, the identification of high-risk blood donors by a predonation questionnaire is relevant in nonendemic countries but this strategy seems to be of limited usefulness for donor deferral in endemic areas. Because T cruzi antigens are shared by other parasites, the serological diagnosis of T cruzi infection is complex yielding both false-positive and false-negative results. Although sensitive, the tests currently available for the serodiagnosis of T cruzi infection lack specificity and a more specific, confirmatory test is still needed for the routine confirmation of T cruzi chronic infection. In areas of high endemicity or where serological screening is not available, the risk of T cruzi transmission by blood transfusion may be reduced by the addition of gentian violet to the collected blood. The use of gentian violet, alone or combined with ascorbic acid and light, effectively inactivate T cruzi present in donor blood; however, the long-term toxicity of this agent for blood recipients is still an open issue. In conclusion, the prevention of TA-CD is based on various strategies that are not mutually exclusive. Blood donor education, identification of putatively infectious blood donors by questionnaire or serological screening tests, and methods of parasite inactivation may significantly reduce the transmission of T cruzi by allogeneic blood transfusions.

High resolution of Trypanosoma cruzi amastigote antigen in serodiagnosis of different clinical forms of Chagas' disease

The serodiagnosis of Chagas' disease, a highly prevalent disorder in South American countries, is usually made by the detection of antibodies to Trypanosoma cruzi epimastigote antigen. In this study, we assess the diagnostic performance of the immunofluorescence test with T. cruzi (Y strain) amastigote antigen from an LLC-MK2-infected cell supernatant in comparison with a test with the conventional epimastigote antigen. A total of 238 serum samples from patients in the acute and chronic phases of the disease, with the chronic indeterminate, cardiac, and digestive forms, and from nonchagasic individuals were tested for the presence of immunoglobulin G (IgG), IgM, and IgA antibodies. The reactivity of the amastigote antigen in terms of geometric mean titers was 2 to 4 times higher than that of the epimastigote antigen. Clear-cut results were obtained with the amastigote antigen, with no overlapping of true and false positives. IgG antibodies to amastigotes were found in all patients with Chagas' disease, whereas all sera from nonchagasic patients were negative, except for those from patients with visceral leishmaniasis, in which 63% cross-reactivity was observed. IgM antibodies to amastigotes were detected in 100% of sera from patients with acute Chagas' disease and in 7.5% of sera from patients with chronic Chagas' disease, whereas IgA antibodies were found in 60% of sera from patients in the acute phase and in 33% of sera from patients in the chronic phase. Despite the cross-reactivity observed with sera from visceral leishmaniasis patients, the IgG immunofluorescence test with the amastigote antigen had the highest sensitivity, specificity, and efficiency. No relationship was observed between the class-specific antibodies or their titers and the clinical forms of patients in the chronic phase. Amastigotes from the cell culture supernatant proved to be useful as an alternative antigen to epimastigotes because of their high resolution in the serodiagnosis of Chagas' disease.

Chagas' disease

Chagas' disease, caused by Trypanosoma cruzi, is an important cause of morbidity in many countries in Latin America. The important modes of transmission are by the bite of the reduviid bug and blood transfusion. The organism exists in three morphological forms: trypomastigotes, amastigotes, and epimastigotes. The mechanism of transformation and differentiation is currently being explored, and signal transduction pathways of the parasites may be involved in this process. Parasite adherence to and invasion of host cells is a complex process involving complement, phospholipase, penetrin, neuraminidase, and hemolysin. Two clinical forms of the disease are recognized, acute and chronic. During the acute stage pathological damage is related to the presence of the parasite, whereas in the chronic stage few parasites are found. In recent years the roles of tumor necrosis factor, gamma interferon, and the interleukins in the pathogenesis of this infection have been reported. The common manifestations of chronic cardiomyopathy are arrhythmias and thromboembolic events. Autoimmune, neurogenic, and microvascular factors may be important in the pathogenesis of the cardiomyopathy. The gastrointestinal tract is another important target, and "mega syndromes" are common manifestations. The diagnosis and treatment of this infection are active areas of investigation. New serological and molecular biological techniques have improved the diagnosis of chronic infection. Exacerbations of T. cruzi infection have been reported for patients receiving immuno-suppressive therapy and for those with AIDS.