Treatment and seroconversion in a cohort of children suffering from recent chronic Chagas infection in Yoro, Honduras

Review of pharmacological options for the treatment of Chagas disease

Chagas disease (CD) is a worldwide problem, with over 8 million people infected in both rural and urban areas. CD was first described over a century ago, but only two drugs are currently available for CD treatment: benznidazole (BZN) and nifurtimox (NF). Treating CD-infected patients, especially children and women of reproductive age, is vital in order to prevent long-term sequelae, such as heart and gastrointestinal dysfunction, but this aim is still far from being accomplished. Currently, the strongest data to support benefit-risk considerations come from trials in children. Treatment response biomarkers need further development as serology is being questioned as the best method to assess treatment response. This article is a narrative review on the pharmacology of drugs for CD, particularly BZN and NF. Data on drug biopharmaceutical characteristics, safety and efficacy of both drugs are summarized from a clinical perspective. Current data on alternative compounds under evaluation for CD treatment, and new possible treatment response biomarkers are also discussed. Early diagnosis and treatment of CD, especially in paediatric patients, is vital for an effective and safe use of the available drugs (i.e. BZN and NF). New biomarkers for CD are urgently needed for the diagnosis and evaluation of treatment efficacy, and to guide efforts from academia and pharmaceutical companies to accelerate the process of new drug development.

TcTASV Antigens of Trypanosoma cruzi: Utility for Diagnosis and High Accuracy as Biomarkers of Treatment Efficacy in Pediatric Patients

The discovery and characterization of novel parasite antigens to improve the diagnosis of Trypanosoma cruzi by serological methods and for accurate and rapid follow-up of treatment efficiency are still needed. TcTASV is a T. cruzi-specific multigene family, whose products are expressed on the parasite stages present in the vertebrate host. In a previous work, a mix of antigens from subfamilies TcTASV-A and TcTASV-C (Mix A + C) was sensitive and specific to identify dogs with active infection of high epidemiological relevance. Here, TcTASV-A and TcTASV-C were assayed separately as well as together (Mix A + C) in an ELISA format on human samples. The Mix A + C presented moderate sensitivity (78%) but high diagnostic accuracy with a 100% of specificity, evaluated on healthy, leishmaniasic, and Strongyloides stercoralis infected patients. Moreover, antibody levels of pediatric patients showed-2 years posttreatment-diminished reactivity against the Mix A + C (P < 0.0001), pointing TcTASV antigens as promising tools for treatment follow-up.

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.

Safety Profile of Benznidazole in the Treatment of Chronic Chagas Disease: Experience of a Referral Centre and Systematic Literature Review with Meta-Analysis

INTRODUCTION

Benznidazole is the preferred drug for treatment of Chagas disease. However, it is toxic and of limited value in chronic infection.

OBJECTIVE

We aimed to estimate the rates of and factors related to adverse reactions (ARs) to benznidazole and treatment discontinuations (TDs).

METHODS

A meta-analysis was performed using an electronic search of the published literature with no language restrictions until June 2017. Prospective studies were included of chronically infected patients in which at least one treatment arm included benznidazole. Data were added from a prospective cohort of patients with Chagas disease at our centre (January 2007-June 2017). Weighted rates of ARs and TDs were estimated, and potentially related factors were analysed.

RESULTS

Some 413 studies were found, from which we chose 42 (nine clinical trials and 33 observational studies, including ours), comprising data for 7822 patients. The weighted rate of ARs to benznidazole was 44.1% (95% confidence interval [CI] 37.2-51.2). ARs were more frequent in adults than in children (51.6 vs. 24.5%), with the most common being skin reactions (34%), gastrointestinal complaints (12.6%) and neurological symptoms (11.5%). Grade 4 ARs were recorded in 3% of cases. The weighted rate of TDs was 11.4% (95% CI 8.5-14.5); TDs were more frequent in adults than in children (14.2 vs. 3.8%). In our cohort, only female sex was related to an increased rate of ARs but not to TDs.

CONCLUSION

Benznidazole had a poor tolerability profile, with a high incidence of TDs, especially in adult patients and women. Optimised dosing schedules and/or new drugs are urgently needed.

Course of serological tests in treated subjects with chronic Trypanosoma cruzi infection: A systematic review and meta-analysis of individual participant data

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This is the first meta-analysis of individual data in chronic Trypanosoma cruzi infection after treatment.

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The probability of seroreversion is variable along the course of follow-up.

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An interaction was found between age at treatment and country setting.

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The course of parasitological/molecular tests after treatment needs to be assessed.

Objective

To determine the course of serological tests in subjects with chronic Trypanosoma cruzi infection treated with anti-trypanosomal drugs.

Methods

A systematic review and meta-analysis was conducted using individual participant data. Survival analysis and the Cox proportional hazards regression model with random effects to adjust for covariates were applied. The protocol was registered in the PROSPERO database (http://www.crd.york.ac.uk/PROSPERO; CRD42012002162).

Results

A total of 27 studies (1296 subjects) conducted in eight countries were included. The risk of bias was low for all domains in 17 studies (63.0%). Nine hundred and thirteen subjects were assessed (149 seroreversion events, 83.7% censored data) for enzyme-linked immunosorbent assay (ELISA), 670 subjects (134 events, 80.0% censored) for indirect immunofluorescence assay (IIF), and 548 subjects (99 events, 82.0% censored) for indirect hemagglutination assay (IHA). A higher probability of seroreversion was observed within a shorter time span in subjects aged 1–19 years compared to adults. The chance of seroreversion also varied according to the country where the infection might have been acquired. For instance, the pooled adjusted hazard ratio between children/adolescents and adults for the IIF test was 1.54 (95% confidence interval 0.64–3.71) for certain countries of South America (Argentina, Bolivia, Chile, and Paraguay) and 9.37 (95% confidence interval 3.44–25.50) for Brazil.

Conclusions

The disappearance of anti-T. cruzi antibodies was demonstrated along the course of follow-up. An interaction between age at treatment and country setting was found.

IL18 Gene Variants Influence the Susceptibility to Chagas Disease

Chagas disease is a parasitic disorder caused by the infection with the flagellated protozoan Trypanosoma cruzi. According to the World Health Organization, more than six million people are currently infected in endemic regions. Genetic factors have been proposed to influence predisposition to infection and development of severe clinical phenotypes like chronic Chagas cardiomyopathy (CCC). Interleukin 18 (IL18) encodes a proinflammatory cytokine that has been proposed to be involved in controlling T. cruzi infection. In this study, we analyzed the possible role of six IL18 gene variants (rs5744258, rs360722, rs2043055, rs187238, rs1946518 and rs360719), which cover most of the variation within the locus, in the susceptibility to infection by T. cruzi and/or CCC. In total, 1,171 individuals from a Colombian region endemic for Chagas disease, classified as seronegative (n = 595), seropositive asymptomatic (n = 175) and CCC (n = 401), were genotyped using TaqMan probes. Significant associations with T. cruzi infection were observed when comparing seronegative and seropositive individuals for rs187238 (P = 2.18E-03, OR = 0.77), rs360719 (P = 1.49E-03, OR = 0.76), rs2043055 (P = 2.52E-03, OR = 1.29), and rs1946518 (P = 0.0162, OR = 1.22). However, dependence analyses suggested that the association was mainly driven by the polymorphism rs360719. This variant is located within the promoter region of the IL18 gene, and it has been described that it creates a binding site for the transcription factor OCT-1 affecting IL-18 expression levels. In addition, no evidence of association was observed between any of the analyzed IL18 gene polymorphisms and the development of CCC. In summary, our data suggest that genetic variation within the promoter region of IL18 is directly involved in the susceptibility to infection by T. cruzi, which provides novel insight into disease pathophysiology and adds new perspectives to achieve a more effective disease control.

Course of Chronic Trypanosoma cruzi Infection after Treatment Based on Parasitological and Serological Tests: A Systematic Review of Follow-Up Studies

Background

Chagas disease is caused by the flagellate protozoan Trypanosoma cruzi (T. cruzi). It is endemic in Latin American countries outside the Caribbean. The current criterion for cure in the chronic phase of the disease is the negativization of at least two serological tests such as enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IIF) and indirect hemagglutination assay (IHA). The serological evolution of treated subjects with chronic T. cruzi infection is variable. Treatment failure is indicated by a positive parasitological and/or molecular test (persistence of parasitemia).

Objectives

To summarize the pattern of response to treatment of parasitological, molecular and serological tests performed during the follow-up of subjects with chronic T. cruzi infection.

Methods

Electronic searches in relevant databases and screening of citations of potentially eligible articles were accomplished. Organizations focusing on neglected infectious diseases were asked for help in identifying relevant studies.

Included studies were randomized controlled trials (RCTs), quasi-RCTs, and cohort studies involving adults and children with chronic infection who received trypanocidal treatment (benznidazole or nifurtimox) and were followed over time. The assessment of risk of bias was performed separately for each study design. The Cochrane Collaboration’s tool and the guidelines developed by Hayden et al. were used. Two reviewers extracted all data independently. A third review author was consulted in case of discordant opinion.

Additional analyses were defined in ad-hoc basis. Scatter plots for percentage of positive parasitological and molecular tests and for negative serological tests were developed by using the lowess curve technique. Heterogeneity was measured by I².

The protocol was registered in PROSPERO, an international prospective register of systematic review protocols (Registration Number CRD42012002162).

Results

Out of 2,136 citations screened, 54 studies (six RCTs and 48 cohort studies) were included. The smoothed curves for positive xenodiagnosis and positive polymerase chain reaction (PCR) were characterized by a sharp decrease at twelve month posttreatment. Afterwards, they reached 10–20% and 40% for xenodiagnosis and PCR, respectively. The smoothed curves for negative conventional serological tests increased up to 10% after 48 months of treatment. In the long-term, the rate of negativization was between 20% and 45%.

The main sources of bias identified across cohort studies were the lack of control for confounding and attrition bias. In general, RCTs were judged as low risk of bias in all domains. The level of heterogeneity across included studies was moderate to high.

Additional analysis were incomplete because of the limited availability of data. In this regard, the country of origin of study participants might affect the results of parasitological and molecular tests, while the level of risk of bias might affect serological outcomes. Subgroup analysis suggested that seronegativization occurs earlier in children compared to adults.

Conclusions

We acknowledge that there is a dynamic pattern of response based on parasitological, molecular and serological tests in subjects chronically infected with T. cruzi after treatment. Our findings suggest a trypanocidal effect in the long-term follow-up.

Further research is needed to explore potential sources of heterogeneity and to conduct reliable subgroup analysis.

Trypanocidal drugs for chronic asymptomatic Trypanosoma cruzi infection

BACKGROUND

Prevention of chronic chagasic cardiomyopathy (CCC) by treating infected populations with trypanocidal therapy (TT) remains a challenge. Despite a renewed enthusiasm for TT, uncertainty regarding its efficacy, concerns about its safety and limited availability remain barriers for a wider use of conventional drugs. We have updated a previous version of this review.

OBJECTIVES

To systematically search, appraise, identify and extract data from eligible studies comparing the outcome of cohorts of seropositive individuals to Trypanosoma cruzi exposed to TT versus placebo or no treatment.

SEARCH METHODS

We sought eligible studies in electronic databases (Cochrane Central Register of Controlled Trials (CENTRAL), Issue 1, 2014); MEDLINE (Ovid, 1946 to January week 5 2014); EMBASE (Ovid, 1980 to 2014 week 6) and LILACS (up to 6 May 2010)) by combining terms related with the disease and the treatment. The search also included a Google search, handsearch for references in review or selected articles, and search of expert files. We applied no language restrictions.

SELECTION CRITERIA

Review authors screened the retrieved references for eligibility (those dealing with human participants treated with TT) and then assessed the pre-selected studies in full for inclusion. We included randomised controlled trials (RCTs) and observational studies that provided data on either mortality or clinical progression of CCC after at least four years of follow-up.

DATA COLLECTION AND ANALYSIS

Teams of two review authors independently carried out the study selection, data extraction and risk of bias assessment, with a referee resolving disagreement within the pairs. Data collection included study design, characteristics of the population and interventions or exposures and outcome measures. We defined categories of outcome data as parasite-related (positive serology, xenodiagnosis or polymerase chain reaction (PCR) after TT) and participant-related (including efficacy outcomes such as progression towards CCC, all-cause mortality and side effects of TT). We reported pooled outcome data as Mantel-Haenszel odds ratios (OR) or standardised mean differences (SMD) along with 95% confidence intervals (CI), using a random-effects model. I(2) statistics provided an estimate of heterogeneity across studies. We conducted an exploratory meta-regression analysis of the relationship between positive-serology and progression of CCC or mortality.

MAIN RESULTS

We included 13 studies involving 4229 participants (six RCTs, n = 1096, five RCTs of intermediate risk of bias, one RCT of high risk of bias; four non-randomised experiments, n = 1639 and three observational studies, n = 1494). Ten studies tested nitroderivative drugs nifurtimox or benznidazole (three exposed participants to allopurinol, one to itraconazole). Five studies were conducted in Brazil, five in Argentina, one in Bolivia, one in Chile and one in Venezuela.TT was associated with substantial, but heterogeneous reductions on parasite-related outcomes such as positive serology (9 studies, OR 0.21, 95% CI 0.10 to 0.44, I(2) = 76%), positive PCR (2 studies, OR 0.50, 95% CI 0.27 to 0.92, I(2) = 0%), positive xenodiagnosis after treatment (6 studies, OR 0.35, 95% CI 0.14 to 0.86, I(2) = 79%), or reduction on antibody titres (3 studies, SMD -0.56, 95% CI -0.89 to -0.23, I(2) = 28%). Efficacy data on patient-related outcomes was largely from non-RCTs. TT with nitroderivatives was associated with potentially important, but imprecise and inconsistent reductions in progression of CCC (4 studies, 106 events, OR 0.74, 95% CI 0.32 to 1.73, I(2) = 66%) and mortality after TT (6 studies, 99 events, OR 0.55, 95% CI 0.26 to 1.14, I(2) = 48%). The overall median incidence of any severe side effects among 1475 individuals from five studies exposed to TT was 2.7%, and the overall discontinuation of this two-month therapy in RCTs (5 studies, 134 events) was 20.5% (versus 4.3% among controls) and 10.4% in other five studies (125 events).

AUTHORS' CONCLUSIONS

Despite the evidence that TT reduced parasite-related outcomes, the low quality and inconsistency of the data for patient-important outcomes must be treated with caution. More geographically diverse RCTs testing newer forms of TT are warranted in order to 1. estimate efficacy more precisely, 2. explore factors potentially responsible for the heterogeneity of results and 3. increase knowledge on the efficacy/tolerance balance of conventional TT.

Benznidazole treatment in chronic children infected with Trypanosoma cruzi: serological and molecular follow-up of patients and identification of Discrete Typing Units

A total of 221 children from two rural settlements in Northeast Argentina were examined for T. cruzi infection. Blood samples were taken for serology tests and PCR assays. In addition, T. cruzi Discrete Typing Units (DTUs) were determined by hybridization with specific DNA probes of the minicircle hypervariable regions (mHVR). Serological results indicated that 26% (57/215) were reactive against T. cruzi antigens. PCR analyses were performed on seropositive samples showing presence of parasite DNA in 31 out of 53 samples (58.5%). All seropositive children underwent specific chemotherapy with Benznidazole (5mg/kg/day) for a period of two months and were monitored two and five years after treatment. Overall the treatment was well tolerated and low side effects were observed. Serological conversion was observed at two years post -treatment in one child form Pampa Ávila and at five years in two children from Tres Estacas. However, at the end of the follow-up period, T. cruzi DNA could not be detected by PCR in samples from treated children, except in two cases. In addition, the results of hybridizations with specific DNA probes showed that DTU TcV was detected in 68% (21/31), TcVI in 7% (2/31) and TcV/VI in 3% (1/31) of the samples. Altogether, results of the follow-up of treated children showed a low rate of seroconversion; however trend toward seroconversion was evident at five years post-treatment. On the other hand, detection of T. cruzi DNA by PCR significantly decreased after Benznidazole treatment. The existence of data regarding serological and molecular follow-ups from controlled studies in the Chaco Region will be important for future treatment efforts against T. cruzi infection in this region. The results obtained in the present study represent a contribution in this regard.

Dried blood as an alternative to plasma or serum for Trypanosoma cruzi IgG detection in screening programs

Trypanosoma cruzi serological screening is recommended for people potentially exposed to this parasite in countries where Trypanosoma cruzi is endemic and those where it is not endemic. Blood samples on filter paper may be a practical alternative to plasma/serum for antibody detection. Using the Architect Chagas assay, we detected the presence of IgG against T. cruzi in matched serum and dried blood spots (DBS) collected from 147 patients residing in Madrid, Spain, who had potential previous exposure to T. cruzi. The κ statistic for the DBS/serum proportion of agreement for the detection of antibodies against T. cruzi was 0.803, considering an S/CO (assay result unit; chemiluminescent signal from the sample [S] divided by the mean chemiluminescent signal for the three calibrators used in the test [CO]) cutoff value of ≥1.00. The relative sensitivity of the Architect test using DBS increased from 95.2% to 98.8% when the cutoff was lowered from ≥1.00 to ≥0.88, while the relative specificity decreased from 84.1% to 71.6%. Overall, the median S/CO values for DBS were significantly lower than those for serum (2.6 versus 6.5; P < 0.001). Discrepancies that occurred with the use of DBS included 10 false positives (with low S/CO values in 9 cases [median, 2.13]) and 4 false negatives, with mean S/CO values of 0.905 (gray zone). Using DBS plus a highly sensitive and specific enzyme-linked immunosorbent assay (ELISA) may be a simple and reliable method for detecting IgG against T. cruzi when blood sampling by venipuncture is not feasible. This method may also reduce the false-negative rates observed with some rapid diagnostic tests. The lower relative sensitivity compared to the reference method may be increased by lowering the optical density threshold.

Chagas disease in non-endemic countries: epidemiology, clinical presentation and treatment

Imported Chagas disease (Trypanosoma cruzi infection) is increasingly recognized as an emerging problem in the USA and Europe due to immigration from Latin America. Most migrants from endemic countries will have been infected during childhood. Based on the natural history of the disease, up to 35 % of those infected may develop cardiac and/or gastrointestinal manifestations during the third or fourth decade of life. This disease was described more than 100 years ago, yet many challenges still remain such as the identification of risk factors for visceral involvement, effective treatment for chronic cases, and reliable markers of cure following treatment. Transmission of the infection may occur even in non-endemic areas through non-vectorial routes and many countries are therefore currently facing the challenge of this emerging public health problem.

Preponderance of inhibitory versus excitatory intramuscular nerve fibres in human chagasic megacolon

INTRODUCTION

Megacolon, chronic dilation of a colonic segment, is a frequent sign of Chagas disease. It is accompanied by an extensive neuron loss which, as shown recently, results in a partial, selective survival of nitrergic myenteric neurons. Here, we focused on the balance of intramuscular excitatory (choline acetyltransferase [ChAT]-immunoreactive) and inhibitory (neuronal nitric oxide synthase [NOS]- as well as vasoactive intestinal peptide [VIP]-immunoreactive) nerve fibres.

MATERIALS AND METHODS

From surgically removed megacolonic segments of seven patients, three sets of cryosections (from non-dilated oral, megacolonic and non-dilated anal parts) were immunhistochemically triple-stained for ChAT, NOS and VIP. Separate area measurements of nerve profiles within the circular and longitudinal muscle layers, respectively, were compared with those of seven non-chagasic control patients. Additionally, wholemounts from the same regions were stained for NOS, VIP and neurofilaments (NF).

RESULTS

The intramuscular nerve fibre density was significantly reduced in all three chagasic segments. The proportions of inhibitory (NOS only, VIP only, or NOS/VIP-coimmunoreactive) intramuscular nerves were 68 %/58 % (circular/longitudinal muscle, respectively) in the controls and increased to 75 %/69 % (oral parts), 84 %/76 % (megacolonic) and 87 %/94 % (anal) in chagasic specimens. In the myenteric plexus, NF-positive neurons co-staining for NOS and VIP also increased proportionally. The almost complete lack of dendritic structures in ganglia of chagasic specimens hampered morphological identification.

DISCUSSION AND CONCLUSION

We suggest that preponderance of inhibitory, intramuscular nerve fibres may be one factor explaining the chronic dilation. Since the nerve fibre imbalance is most pronounced in the anal, non-dilated segment, other components of the motor apparatus (musculature, interstitial cells, submucosal neurons) have to be considered.

Posttherapeutic cure criteria in Chagas' disease: conventional serology followed by supplementary serological, parasitological, and molecular tests

We performed a critical study of conventional serology, followed by supplementary serological, parasitological, and molecular tests, to assess the response to etiologic treatment of Chagas' disease. A group of 94 Chagas' disease patients treated with benznidazole at least 10 years earlier were evaluated from the laboratory and clinical points of view. When conventional serology (enzyme-linked immunosorbent assay [ELISA], indirect immunofluorescence [IIF], and indirect hemagglutination [IHA]) and classic criteria (consistent results with any two of the three tests) or more rigorous criteria (consistent results from the three tests) were used, 10.6% and 8.5% of patients were considered treated and cured (TC) by classic and rigorous criteria, respectively. Patients were then evaluated using supplementary (recombinant ELISA and Trypanosoma cruzi excreted-secreted antigen blotting [TESA-blot]), parasitological (hemoculture), and molecular (PCR) tests. The results of recombinant ELISA were similar to those with the rigorous criterion (three consistent test results). The TESA-blot group showed a higher percentage (21.3%) of negative results than the groups defined by either cure criterion. Hemoculture and PCR gave negative results for all treated and cured (TC) patients, regardless of the criterion used. Recombinant ELISA and TESA-blot tests showed negative results for 70% and 87.5% of the patients categorized as TC by the classic and three-test criteria, respectively. For patients with discordant conventional serology, the supplementary serological and molecular tests were the decisive factor in determining therapeutic failure. Clinical evaluation showed that 62.5% of TC patients presented with the indeterminate form of the disease. Additionally, treated patients with negative TESA-blot results should be reevaluated later with all methodologies used here to verify whether TESA-blot is a reliable way to determine early parasitological cure of Chagas' disease.

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.

Mechanisms of Trypanosoma cruzi persistence in Chagas disease

Trypanosoma cruzi infection leads to development of chronic Chagas disease. In this article, we provide an update on the current knowledge of the mechanisms employed by the parasite to gain entry into the host cells and establish persistent infection despite activation of a potent immune response by the host. Recent studies point to a number of T. cruzi molecules that interact with host cell receptors to promote parasite invasion of the diverse host cells. T. cruzi expresses an antioxidant system and thromboxane A(2) to evade phagosomal oxidative assault and suppress the host's ability to clear parasites. Additional studies suggest that besides cardiac and smooth muscle cells that are the major target of T. cruzi infection, adipocytes and adipose tissue serve as reservoirs from where T. cruzi can recrudesce and cause disease decades later. Further, T. cruzi employs at least four strategies to maintain a symbiotic-like relationship with the host, and ensure consistent supply of nutrients for its own survival and long-term persistence. Ongoing and future research will continue to help refining the models of T. cruzi invasion and persistence in diverse tissues and organs in the host.

Partial, selective survival of nitrergic neurons in chagasic megacolon

One frequent chronic syndrome of Chagas’ disease is megacolon, an irreversible dilation of a colonic segment. Extensive enteric neuron loss in the affected segment is regarded as key factor for deficient motility. Here, we assessed the quantitative balance between cholinergic and nitrergic neurons representing the main limbs of excitatory and inhibitory colonic motor innervation, respectively. From surgically removed megacolonic segments of four patients, each three myenteric wholemounts (from non-dilated oral, megacolonic and non-dilated anal parts) was immunohistochemically triple-stained for choline acetyltransferase, neuronal nitric oxide synthase (NOS) and the panneuronal human neuronal protein Hu C/D. Degenerative changes were most pronounced in the megacolonic and anal regions, e.g. bulked, honeycomb-like ganglia with few neurons which were partly enlarged or atrophic or vacuolated. Neuron counts from each 15 ganglia of 12 megacolonic wholemounts were compared with those of 12 age- and region-matched controls. Extensive neuron loss, mainly in megacolonic and anal wholemounts, was obvious. In all three regions derived from megacolonic samples, the proportion of NOS-positive neurons (control: 55%) was significantly increased: in non-dilated oral parts to 61% (p = 0.003), in megacolonic regions to 72% (p < 0.001) and in non-dilated anal regions to 78% (p < 0.001). We suggest the chronic dilation of megacolonic specimens to be due to the preponderance of the nitrergic, inhibitory input to the intestinal muscle. However, the observed neuronal imbalance was not restricted to the dilated regions: the non-dilated anal parts may be innervated by ascending, cholinergic axons emerging from less affected, more anally located regions.

Chagas disease: changes in knowledge and management

More than 100 years after the discovery of human American trypanosomiasis by Carlos Chagas, our knowledge and management of the disease are profoundly changing. Substantial progress made by disease control programmes in most endemic areas contrasts with persisting difficulties in the Gran Chaco region in South America and the recent emergence of the disease in non-endemic areas because of population movements. In terms of pathogenesis, major discoveries have been made about the life cycle and genomics of Trypanosoma cruzi, and the role of the parasite itself in the chronic phase of the disease. From a clinical perspective, a growing number of arguments have challenged the notion of an indeterminate phase, and suggest new approaches to manage patients. New methods such as standardised PCR will be necessary to ensure follow-up of this chronic infection. Although drugs for treatment of Chagas disease are limited, poorly tolerated, and not very effective, treatment indications are expanding. The results of the Benznidazole Evaluation For Interrupting Trypanosomiasis (BENEFIT) trial in 2012 will also help to inform treatment. Mobilisation of financial resources to fund research on diagnosis and randomised controlled trials of treatment are international health priorities.