Amplicon Sequencing Reveals Complex Infection in Infants Congenitally Infected With Trypanosoma Cruzi and Informs the Dynamics of Parasite Transmission

Congenital transmission of Trypanosoma cruzi is an important source of new Chagas infections worldwide. The mechanisms of congenital transmission remain poorly understood, but there is evidence that parasite factors are involved. Investigating changes in parasite strain diversity during transmission could provide insight into the parasite factors that influence the process. Here we use amplicon sequencing of a single copy T. cruzi gene to evaluate the diversity of infection in clinical samples from Chagas positive mothers and their infected infants. Several infants and mothers were infected with multiple parasite strains, mostly of the same TcV lineage, and parasite strain diversity was higher in infants than mothers. Two parasite haplotypes were detected exclusively in infant samples, while one haplotype was never found in infants. Together, these data suggest multiple parasites initiate a congenital infection and that parasite factors influence the probability of vertical transmission.

Prospective multicenter evaluation of real time PCR Kit prototype for early diagnosis of congenital Chagas disease

BACKGROUND

Current algorithm for Congenital Chagas Disease (cCD) diagnosis is unsatisfactory due to low sensitivity of the parasitological methods. Moreover, loss to follow-up precludes final serodiagnosis after nine months of life in many cases. A duplex TaqMan qPCR kit for Trypanosoma cruzi DNA amplification was prospectively evaluated in umbilical cord (UCB) and peripheral venous blood (PVB) of infants born to CD mothers at endemic and non-endemic sites of Argentina.

METHODS

We enrolled and followed-up 370 infants; qPCR was compared to gold-standard cCD diagnosis following studies of diagnostic accuracy guidelines.

FINDINGS

Fourteen infants (3·78%) had cCD. The qPCR sensitivity and specificity were higher in PVB (72·73%, 99·15% respectively) than in UCB (66·67%, 96·3%). Positive and negative predictive values were 80 and 98·73% and 50 and 98·11% for PVB and UCB, respectively. The Areas under the Curve (AUC) of ROC analysis for qPCR and micromethod (MM) were 0·81 and 0·67 in UCB and 0·86 and 0·68 in PVB, respectively. Parasitic loads ranged from 37·5 to 23,709 parasite equivalents/mL. Discrete typing Unit Tc V was identified in five cCD patients and in six other cCD cases no distinction among Tc II, Tc V or Tc VI was achieved.

INTERPRETATION

This first prospective field study demonstrated that qPCR was more sensitive than MM for early cCD detection and more accurate in PVB than in UCB. Its use, as an auxiliary diagnostic tool to MM will provide more accurate records on cCD incidence.

FUNDING

FITS SALUD 001-CHAGAS (FONARSEC, MINCyT, Argentina) to the Public-Private Consortium (INGEBI-CONICET, INP-ANLIS MALBRAN and Wiener Laboratories); ERANET-LAC-HD 328 to AGS and PICT 2015-0074 (FONCYT, MinCyT) to AGS and FA.

Congenital chagas disease: Development and assessment of a specific IgM capture-based assay for diagnosis of transmission

Transplacental transmission by Trypanosoma cruzi (T. cruzi) infection can be effectively treated if parasiticide drugs are administered as early as possible during childhood. Furthermore, an ideal situation would be to diagnose the infection near birth in order to avoid the loss of patients during the subsequent follow-up. These situation are desirable due to the maximum benefit of drugs in early stages which, consequently, implies a relevant contribution to eliminate mother-to-child transmission. However, available techniques for that purpose have limitations as being operator-dependent (microhematocrit), require several months follow-up (IgG detection) or specialized laboratories (PCR). In this study we propose to detect specific IgM antibodies (Ab) by developing a capture-based ELISA employing an improved antigen (Ag) to diagnose the transplacental transmission of T. cruzi, and in consequence, to enhance access to effective treatment. Firstly, a new chimera Ag (CP4) was obtained from the fusion of CP1 and CP3 protein, carrying FRA, SAPA, MAP, TSSAII/V/VI and TcD Ag from T. cruzi. Then, we optimized the assay by capturing IgM Ab with a polyclonal anti-IgM Ab and evaluating three Ag formulations to detect specific IgM bound. The formulations were formed as follows: i) F1: CP1 and CP3; ii) F2: CP1, CP3, B13 and P2β; iii) F3: by CP4. Detection of Ab-binding Ag was carried out using an anti-His Ab since all Ag were expressed with a His-tag. The evaluation panel consisted of sera from vertically infected children under 1-year-old (6 younger than 15 days, 7 older) and samples from non-infected children of women with chronic Chagas Disease. The ELISA assay employing CP4 showed better performance with notable high sensitivity and specificity (92.3% and 93.9%, respectively). Positive and negative likelihood ratios of the test (15.2 and 0.082) suggest its potential clinical relevance in term of post-test probability of infection. In conclution, we developed a standardized and non-operator dependent test to detect specific anti-T. cruzi IgM Ab. Although increased sample size is needed for its validation, our results indicate that this capture-based technique employing CP4 Ag can certainly improve the diagnosis of connatal infection.

Trypanosoma cruzi loop-mediated isothermal amplification (Trypanosoma cruzi Loopamp) kit for detection of congenital, acute and Chagas disease reactivation

A Trypanosoma cruzi Loopamp kit was recently developed as a ready-to-use diagnostic method requiring minimal laboratory facilities. We evaluated its diagnostic accuracy for detection of acute Chagas disease (CD) in different epidemiological and clinical scenarios. In this retrospective study, a convenience series of clinical samples (venous blood treated with EDTA or different stabilizer agents, heel-prick blood in filter paper or cerebrospinal fluid samples (CSF)) from 30 infants born to seropositive mothers (13 with congenital CD and 17 noninfected), four recipients of organs from CD donors, six orally-infected cases after consumption of contaminated guava juice and six CD patients coinfected with HIV at risk of CD reactivation (N = 46 patients, 46 blood samples and 1 CSF sample) were tested by T. cruzi Loopamp kit (Tc LAMP) and standardized quantitative real-time PCR (qPCR). T. cruzi Loopamp accuracy was estimated using the case definition in the different groups as a reference. Cohen's kappa coefficient (κ) was applied to measure the agreement between Tc LAMP (index test) and qPCR (reference test). Sensitivity and specificity of T. cruzi Loopamp kit in blood samples from the pooled clinical groups was 93% (95% CI: 77-99) and 100% (95% CI: 80-100) respectively. The agreement between Tc LAMP and qPCR was almost perfect (κ = 0.92, 95% CI: 0.62-1.00). The T. cruzi Loopamp kit was sensitive and specific for detection of T. cruzi infection. It was carried out from DNA extracted from peripheral blood samples (via frozen EDTA blood, guanidine hydrochloride-EDTA blood, DNAgard blood and dried blood spots), as well as in CSF specimens infected with TcI or TcII/V/VI parasite populations. The T. cruzi Loopamp kit appears potentially useful for rapid detection of T. cruzi infection in congenital, acute and CD reactivation due to HIV infection.

[Congenital transmission of Trypanosoma cruzi. Argentina 2002-2014]

In Argentina, around 1500 children are born each year with Trypanosoma cruzi infection. Mother-to-child transmission is the main source of new cases of Chagas disease and of its occurrence in non-endemic areas. Our objective was to survey the information available on congenital T. cruzi infection, to analyze its evolution and its relation with the index of maternal infection and the risk for vector-borne infection by province of Argentina. Data concerning the public health sector for the period 1997-2014 were retrieved from national and local records. An increase in the number and proportion of pregnant women examined for Chagas was observed, reaching 60.3% coverage in 2014. The prevalence of maternal infection dropped from 9.0% to 2.6%. The control of newborns from infected women was highly variable (23.3%-93.6%), and data quality was deficient, varying amply by province and year. The rate of congenital infection had an irregular evolution and its national average fluctuated between 1.9 and 8.2%. An association was observed between the risk for vector-borne infection and the prevalence of maternal infection by province (Wilcoxon test p = 0.017). The rate of congenital transmission by province was neither associated with the rate of maternal infection (linear regression p = 0.686) nor with the risk for vectorial infection (Kruskal-Wallis test p = 0.3154). The available data show insufficient control of children born from infected mothers, as well as deficient recording of these procedures. Both aspects must be improved to achieve better epidemiological information and to enable timely access of infected children to treatment.

Differential infectivity of two Trypanosoma cruzi strains in placental cells and tissue

Congenital Chagas disease, caused by Trypanosoma cruzi (T. cruzi), has become epidemiologically relevant. The probability of congenital transmission depends on the maternal and developing fetal/newborn immune responses, placental factors and importantly, the virulence of the parasite. It has been proposed, that different genotypes of T. cruzi and their associated pathogenicity, virulence and tissue tropism may play an important role in congenital infection. Since there is no laboratory or animal model that recapitulates the complexities of vertical transmission in humans, here we studied parasite infectivity in human placental explants (HPE) as well as in the human trophoblast-derived cell line BeWo of the Y(DTU II) and the VD (TcVI) T. cruzi strains; the latter was isolated from a human case of congenital infection. Our results show that the VD strain is more infective and pathogenic than the Y strain, as demonstrated by qPCR and cell counting as well as by histopathological analysis. The present study constitutes the first approach to study the relationship between parasite two parasite strains from different genotypes and the infection efficiency in human placenta.

Towards Chagas disease elimination: Neonatal screening for congenital transmission in rural communities

Chagas disease is a neglected tropical disease that continues to affect populations living in extreme poverty in Latin America. After successful vector control programs, congenital transmission remains as a challenge to disease elimination. We used the PRECEDE-PROCEED planning model to develop strategies for neonatal screening of congenital Chagas disease in rural communities of Guatemala. These communities have persistent high triatomine infestations and low access to healthcare. We used mixed methods with multiple stakeholders to identify and address maternal-infant health behaviors through semi-structured interviews, participatory group meetings, archival reviews and a cross-sectional survey in high risk communities. From December 2015 to April 2016, we jointly developed a strategy to illustratively advertise newborn screening at the Health Center. The strategy included socioculturally appropriate promotional and educational material, in collaboration with midwives, nurses and nongovernmental organizations. By March 2016, eight of 228 (3.9%) pregnant women had been diagnosed with T. cruzi at the Health Center. Up to this date, no neonatal screening had been performed. By August 2016, seven of eight newborns born to Chagas seropositive women had been parasitologically screened at the Health Center, according to international standards. Thus, we implemented a successful community-based neonatal screening strategy to promote congenital Chagas disease healthcare in a rural setting. The success of the health promotion strategies developed will depend on local access to maternal-infant services, integration with detection of other congenital diseases and reliance on community participation in problem and solution definition.

Chagas disease is caused by a parasite transmitted by insects that infest households living in extreme poverty conditions. The parasite can also be transmitted from mother to child during pregnancy. If detected at birth, the infection can be treated effectively with available drugs. However, access to professional neonatal healthcare is limited in rural communities such as those affected by Chagas disease. We developed a strategy to promote access to a simple neonatal diagnostic test in a rural region of Guatemala considered at risk for Chagas disease. The strategy included collaboration between Health Center personnel, midwives and non-governmental organizations that play a local role in maternal-infant care. During the implementation of a health promotion campaign, screening revealed previous infection in almost one of every 25 pregnant women. Most babies born to positive women were tested at the Health Center for parasites in blood. The implementation of similar strategies to prevent congenital Chagas in other rural areas should consider local maternal-infant care practices. This strategy of collaboration between Ministry of Health, community health workers, non-government organizations, academia and external governmental support could be expanded to screen for other diseases, such as Zika, that require early detection to improve overall infant health.

[TORCH syndrome: Rational approach of pre and post natal diagnosis and treatment. Recommendations of the Advisory Committee on Neonatal Infections Sociedad Chilena de Infectología, 2016]

There is a lot of bacterial, viral or parasite infections who are able to be transmitted vertically from the mother to the fetus or newborn which implicates an enormous risk for it. The TORCH acronym is used universally to refer to a fetus or newborn which presents clinical features compatible with a vertically acquired infection and allows a rational diagnostic and therapeutic approach. The traditional "TORCH test" is nowadays considered not appropriate and it has been replaced for specific test for specific pathogens under well defined circumstances. The present document reviews the general characteristics, epidemiology, pathogenesis, diagnostic and therapeutic options for the most frequently involved pathogens in the fetus or newborn with TORCH suspicion.

Congenital Chagas disease as an ecological model of interactions between Trypanosoma cruzi parasites, pregnant women, placenta and fetuses

The aim of this paper is to discuss the main ecological interactions between the parasite Trypanosoma cruzi and its hosts, the mother and the fetus, leading to the transmission and development of congenital Chagas disease. One or several infecting strains of T. cruzi (with specific features) interact with: (i) the immune system of a pregnant woman whom responses depend on genetic and environmental factors, (ii) the placenta harboring its own defenses, and, finally, (iii) the fetal immune system displaying responses also susceptible to be modulated by maternal and environmental factors, as well as his own genetic background which is different from her mother. The severity of congenital Chagas disease depends on the magnitude of such final responses. The paper is mainly based on human data, but integrates also complementary observations obtained in experimental infections. It also focuses on important gaps in our knowledge of this congenital infection, such as the role of parasite diversity vs host genetic factors, as well as that of the maternal and placental microbiomes and the microbiome acquisition by infant in the control of infection. Investigations on these topics are needed in order to improve the programs aiming to diagnose, manage and control congenital Chagas disease.

Deep sequencing of the Trypanosoma cruzi GP63 surface proteases reveals diversity and diversifying selection among chronic and congenital Chagas disease patients

Background

Chagas disease results from infection with the diploid protozoan parasite Trypanosoma cruzi. T. cruzi is highly genetically diverse, and multiclonal infections in individual hosts are common, but little studied. In this study, we explore T. cruzi infection multiclonality in the context of age, sex and clinical profile among a cohort of chronic patients, as well as paired congenital cases from Cochabamba, Bolivia and Goias, Brazil using amplicon deep sequencing technology.

Methodology/ Principal Findings

A 450bp fragment of the trypomastigote TcGP63I surface protease gene was amplified and sequenced across 70 chronic and 22 congenital cases on the Illumina MiSeq platform. In addition, a second, mitochondrial target—ND5—was sequenced across the same cohort of cases. Several million reads were generated, and sequencing read depths were normalized within patient cohorts (Goias chronic, n = 43, Goias congenital n = 2, Bolivia chronic, n = 27; Bolivia congenital, n = 20), Among chronic cases, analyses of variance indicated no clear correlation between intra-host sequence diversity and age, sex or symptoms, while principal coordinate analyses showed no clustering by symptoms between patients. Between congenital pairs, we found evidence for the transmission of multiple sequence types from mother to infant, as well as widespread instances of novel genotypes in infants. Finally, non-synonymous to synonymous (dn:ds) nucleotide substitution ratios among sequences of TcGP63Ia and TcGP63Ib subfamilies within each cohort provided powerful evidence of strong diversifying selection at this locus.

Conclusions/Significance

Our results shed light on the diversity of parasite DTUs within each patient, as well as the extent to which parasite strains pass between mother and foetus in congenital cases. Although we were unable to find any evidence that parasite diversity accumulates with age in our study cohorts, putative diversifying selection within members of the TcGP63I gene family suggests a link between genetic diversity within this gene family and survival in the mammalian host.

Trypanosoma cruzi, the causal agent of Chagas disease in Latin America, infects several million people in some of the most economically deprived regions of Latin America. T. cruzi infection is lifelong and has a variable prognosis: some patients never exhibit symptoms while others experience debilitating and fatal complications. Available data suggest that parasite genetic diversity within and among disease foci can be exceedingly high. However, little is know about the frequency of multiple genotype infections in humans, as well as their distribution among different age classes and possible impact on disease outcome. In this study we develop a next generation amplicon deep sequencing approach to profile parasite diversity within chronic Chagas Disease patients from Bolivia and Brazil. We were also able to compare parasite genetic diversity present in eleven congenitally infants with parasite genetic diversity present in their mothers. We did not detect any specific association between the number and diversity of parasite genotypes in each patient with their age, sex or disease status. We were, however, able to detect the transmission of multiple parasite genotypes between mother and foetus. Furthermore, we also detected powerful evidence for natural selection at the antigenic locus we targeted, suggesting a possible interaction with the host immune system.

Congenital co-infection with different Trypanosoma cruzi lineages

Variability of mixed Trypanosoma cruzi congenital infection in Chile in twenty one congenital samples of Chagas disease is reported. Recognition of infecting strains was performed by minicircle hybridization tests. Seven newborns with double infection were found. Trypanosoma cruzi TcII and TcV lineages were the most frequent in single and mixed infections. With these results we pretend to understand the epidemiological significance of the T. cruzi lineages for which the placenta does not seem to represent an actual barrier in congenital infections.

How to improve the early diagnosis of Trypanosoma cruzi infection: relationship between validated conventional diagnosis and quantitative DNA amplification in congenitally infected children

Background

According to the Chagas congenital transmission guides, the diagnosis of infants, born to Trypanosoma cruzi infected mothers, relies on the detection of parasites by INP micromethod, and/or the persistence of T. cruzi specific antibody titers at 10–12 months of age.

Methodology and Principal Findings

Parasitemia levels were quantified by PCR in T. cruzi-infected children, grouped according to the results of one-year follow-up diagnosis: A) Neonates that were diagnosed in the first month after delivery by microscopic blood examination (INP micromethod) (n = 19) had a median parasitemia of 1,700 Pe/mL (equivalent amounts of parasite DNA per mL); B) Infants that required a second parasitological diagnosis at six months of age (n = 10) showed a median parasitemia of around 20 Pe/mL and 500 Pe/mL at 1 and 6 months old, respectively, and C) babies with undetectable parasitemia by three blood microscopic observations but diagnosed by specific anti - T. cruzi serology at around 1 year old, (n = 22), exhibited a parasitemia of around 5 Pe/mL, 800 Pe/mL and 20 Pe/mL 1, 6 and 12 month after delivery, respectively. T. cruzi parasites were isolated by hemoculture from 19 congenitally infected children, 18 of which were genotypified as DTU TcV, (former lineage TcIId) and only one as TcI.

Significance

This report is the first to quantify parasitemia levels in more than 50 children congenitally infected with T. cruzi, at three different diagnostic controls during one-year follow-up after delivery. Our results show that the parasite burden in some children (22 out of 51) is below the detection limit of the INP micromethod. As the current trypanocidal treatment proved to be very effective to cure T. cruzi - infected children, more sensitive parasitological methods should be developed to assure an early T. cruzi congenital diagnosis.

Chagas or American Trypanosomiasis is a disease that affects around 8–10 million people in Latin America, and can be transmitted by congenital infection. In areas where the vector insect and blood transfusions are controlled, this mode of transmission is epidemiologically important, as 15,000 Trypanosoma cruzi-infected children are born each year. Parasitological methods are available to detect T. cruzi but our results suggest that more sensitive diagnostic methods should be developed, as not all newborns have high parasite burdens to be detected by microscopy. If congenital infected babies are promptly diagnosed after delivery they can be cured, as the trypanocidal treatment is very effective in children and with no significant side effects.

A model for Chagas disease with oral and congenital transmission

This work presents a new mathematical model for the domestic transmission of Chagas disease, a parasitic disease affecting humans and other mammals throughout Central and South America. The model takes into account congenital transmission in both humans and domestic mammals as well as oral transmission in domestic mammals. The model has time-dependent coefficients to account for seasonality and consists of four nonlinear differential equations, one of which has a delay, for the populations of vectors, infected vectors, infected humans, and infected mammals in the domestic setting. Computer simulations show that congenital transmission has a modest effect on infection while oral transmission in domestic mammals substantially contributes to the spread of the disease. In particular, oral transmission provides an alternative to vector biting as an infection route for the domestic mammals, who are key to the infection cycle. This may lead to high infection rates in domestic mammals even when the vectors have a low preference for biting them, and ultimately results in high infection levels in humans.

Fertility, gestation outcome and parasite congenital transmissibility in mice infected with TcI, TcII and TcVI genotypes of Trypanosoma cruzi

This work aims to compare the effects of acute or chronic infections with the T. cruzi genotypes TcI (X10 strain), TcII (Y strain) and TcVI (Tulahuen strain) on fertility, gestation, pup growth and the possible vertical transmission of parasites in BALB/c mice. The occurrence of congenital infection was evaluated by microscopic examination of blood and/or qPCR on blood and heart in newborn pups and/or older offspring submitted to cyclophosphamide-induced immunosuppression in order to detect possible cryptic congenital infection. Altogether, the results show that: i) for the three strains tested, acute infection occurring after the embryo implantation in the uterus (parasite inoculation 4 days before mating), or close to delivery (parasite inoculation on day 13 of gestation), prevents or severely jeopardizes gestation outcome (inducing pup mortality and intra-uterine growth retardation); ii) for the three strains tested, gestation during chronic infection results in intra-uterine growth retardation, whereas re-inoculation of TcVI parasites during gestation in such chronically infected mice, in addition, strongly increases pup mortality; iii) congenital infection remains a rare consequence of infection (occurring in approximately 4% of living pups born to acutely infected dams); iv) PCR, detecting parasitic DNA and not living parasites, is not convenient to detect congenial infection close to delivery; v) transmission of parasites by breast milk is unlikely. This study should encourage further investigations using other parasite strains and genotypes to explore the role of virulence and other factors, as well as the mechanisms of such effects on gestation and on the establishment of congenital infection.

Centers for Disease Control and Prevention (CDC). Congenital transmission of Chagas disease - Virginia, 2010

Chagas disease, caused by infection with the parasite Trypanosoma cruzi, affects 8-11 million persons globally. In the endemic areas of Mexico, Central America, and South America, most infections are transmitted by triatomine insect (kissing bug) vectors. However, infection also can be acquired congenitally or through blood transfusion, organ transplantation, consumption of triatomine-contaminated food or drink, or laboratory accident. Early detection and treatment are highly effective; however, acute infection often is subclinical, and most persons are unaware of their infection. If left untreated, the infection is lifelong. The majority of persons with chronic infection remain without signs or symptoms, but 20%-30% eventually develop disease manifestations, most commonly, cardiomyopathy. Migration from endemic areas has led to an estimated 300,000 persons in the United States with chronic Chagas disease, including women of reproductive age who risk transmitting the infection to their children. This report describes the first case of congenital Chagas disease in the United States confirmed by CDC and highlights the importance of raising awareness of Chagas disease among health-care providers.

[Effect of congenital infection by Trypanosoma cruzi on intrauterine development and the fetal-neonatal immune response]

In congenital infection by Trypanosoma cruzi, morbidity and mortality vary from asymptomatic cases to severe clinical forms of the disease. It has been found that there is no specific clinical profile in newborns infected by T. cruzi, since during intrauterine development diverse pathological changes take place, causing alterations in the serological and parasitological profiles. Some intrinsic factors of the host, such as: the placental barrier and the ability of both, mother and fetus, to develop a specific immune response to control parasite multiplication, could be involved in such differences. Another possibility includes the genetic polymorphism of T. cruzi, since it is considered that strains of greater virulence can cross the placenta more easily and are more pathogenic to the fetus and/or the neonate.

Epidemiology of American trypanosomiasis (Chagas disease)

Trypanosoma cruzi, the cause of American trypanosomiasis, or Chagas disease, is a protozoan parasite that is enzootic and endemic in much of the Americas, where it infects a wide variety of wild and domestic mammals as well as many species of triatomine vectors, in addition to humans. Historically, vector-borne transmission of T. cruzi has been the most important mechanism through which humans have become infected with the parasite, but transmission by blood transfusion and congenital transmission also have been important. In many of the endemic countries transmission of T. cruzi has improved markedly in recent years as vector control and donor screening programs have been implemented on a widespread basis. In the United States autochthonous transmission of T. cruzi appears to be extremely rare. Five persons are known to have become infected with T. cruzi through organ transplants here, and prior to the implementation of blood donor screening in 2007 five instances of transmission by transfusion had been reported. Current estimates put the total number of T. cruzi-infected persons living in the United States at 300,000, essentially all of whom are immigrants from the endemic countries. The obstacles that stand in the way of the total elimination of T. cruzi transmission throughout the endemic range are economic and political, and no major technological advances are needed to accomplish this goal.

Vertical transmission of Trypanosoma cruzi in the Province of Choapa, IV Region, Chile: Preliminary Report (2005-2008)

Congenital Chagas disease acquired special importance in Chile after the certification of the control of Triatoma infestans and transmission by blood donors affected with Trypanosoma cruzi. In order to establish adequate protocols for intervention and control in infected mother-neonate pairs in endemic zones of Chagas disease, we present partial results (2005-2008) of a pilot project which is being carried out in the Province of Choapa, IV Region, Chile, whose objectives are: determine the current prevalence of the disease in pregnant women, estimate the incidence of vertical transmission of T. cruzi to newborns, determine the lineages of the parasite present in mothers who do and do not transmit the disease, determine the prevalence of Chagas disease in maternal grandmothers of neonates and study placental histopathology. Preliminary results indicated that in this study period, 3.7% of the women who gave birth in the Province have Chagas disease and 2.5% of their newborns were infected. The most frequent T. cruzi genotypes found in mothers studied during pregnancy were TCI and TCIId, either alone or in mixed infections. A high percentage (74.3%) of the grandmothers studied was infected with the parasite. In 29 placentas from mothers with Chagas disease we observed edema, necrosis, fibrinoid deposits and slight lymphoplasmocyte infiltration. In three placentas we found erythroblastosis and in one of them amastigote forms of T. cruzi; this was one of the cases of congenital infection. The evaluation of the diagnostic and control protocols generated will allow us to determine if it has been possible to modify the natural history of vertical transmission of T. cruzi in Chile.

Infection and invasion mechanisms of Trypanosoma cruzi in the congenital transmission of Chagas' disease: a proposal

Chagas' disease is produced by the haemophlagelated protozoan Trypanosoma cruzi and transmitted by haematophages insects such as Triatoma infestans (vinchuca). Due to vector control, congenital transmission gains importance and is responsible for the presence and expansion of this disease in non-endemic areas. The mechanisms of congenital infection are uncertain. It has been suggested that the parasite reaches the fetus through the bloodstream by crossing the placental barrier, and that congenital Chagas' disease is the result of complex interactions between the immune response, placental factors, and the parasite's characteristics. We review the cellular and molecular mechanisms of infection and invasion of the parasite and how immune and placental factors may modulate this process. Finally, we propose a possible model for the vertical transmission of Chagas' disease.

[Screening for congenital infection by Trypanosoma cruzi in France]

The importance of congenital transmission of Chagas' disease increases with its emergence in communities infected with Trypanosoma cruzi, but where vector transmission has never existed or is fully controlled through vector control campaigns. In both endemic and non-endemic areas, the rates of mother-to-child transmission (MTCT) could be the same, by 5%, generating a constant source of new cases of the disease. Risk factors for vertical transmission are not fully elucidated, but the effectiveness of the adaptive immune response and the genetic susceptibility of both the mother and the child are suspected. Besides the risk of miscarriage or premature birth, neonatal infection by T. cruzi causes an acute form of Chagas disease, which may be accompanied by a severe infectious syndrome that can causes death if not treated early. This form of the disease is a real public health priority because it is frequent, severe, identifiable and curable. Indeed, almost all newborns diagnosed and treated before the end of their first year of life will be definitely cured. In all non-endemic areas, detection of cases of congenital Chagas disease is hampered by a very low prevalence of the disease in the general population of pregnant women, the lack of symptoms in most infected women and the disregard of these problems from health personnel in charge of monitoring pregnancy. Secondary prevention firstly consists in identifying infected women (with history of exposure and positive serology for Chagas disease) and secondly to look for the parasite in newborns from infected mothers. No primary prevention is indeed possible during pregnancy, since the only two drugs are toxic and possibly teratogenic. However, after birth, treatment could be offered to all infected women in order to prevent late complications of the disease and to make an attempt at breaking the chain of MTCT in future pregnancies.

[The first case of congenital Chagas' disease analyzed by AP-PCR in Colombia]

INTRODUCTION

The main route of Chagas disease transmission is through vectors of the insect family Reduviidae. However, the parasite can also be transmitted from infected mothers to their fetus in utero. Until now, no cases of congenital Chagas disease have been reported in Colombia.

OBJECTIVE

A congenital Chagas disease case occurred in Moniquirá County, Boyacá, Colombia. It was confirmed by comparing strains isolated from the mother and her baby using polymerase chain reaction (PCR) with arbitrary primers.

MATERIALS AND METHODS

The parasite DNA was extracted from positive blood cultures of the afflicted mother and her son. The species confirmation and group detection were performed by PCR. The strain genotypes were determined by AP-PCR with two oligonucleotides based on the genes for the b-globin (5'-CCTCACCTTCTTTCATGGAG-3') and 16S RrNA (5'-ACGGGCAGTGTGTACAAGACC-3'), in different reactions.

RESULTS

The T. cruzi strains isolated from the blood cultures of the mother and her son showed the same amplification profile by the two AP-PCR tests; this corresponded with profiles of the T. cruzi I strains used as controls. However, T. cruzi II was also found in the blood culture from the newborn.

CONCLUSIONS

This is the first case of Chagas disease transmission reported in Moniquirá, demonstrating that this form of transmission occurs in Colombia. The presence of both groups of T. cruzi in the newborn sample suggests mixed infection in the mother as well, with a higher prevalence of T. cruzi I, at least in the mother's blood culture.

[Congenital Chagas disease in Geneva: diagnostic and clinical aspects]

Chagas disease, a parasitic infection with Trypanosoma cruzi, recently emerged in Europe and in Switzerland. Mother-to-child infection represents a major mode of transmission in non endemic areas. In 2008, 305 Latin American pregnant women consulting at the Geneva University Hospitals were screened by serology. Overall prevalence was 2% and 8.8% in Bolivian women. All infected women were in the indeterminate form of the chronic phase. Two newborns were congenitally infected. Considering the potential for vertical transmission and the risk of long-term complications, screening programs for persons at risk need to be implemented.

[Vectorial and congenital transmission of Trypanosoma cruzi in Las Lomitas, Formosa]

Chagas disease, caused by Trypanosoma cruzi, is a major cause of morbidity and mortality in Latin America. The objective of this study was to describe the rate of infestation in four aboriginal communities in Las Lomitas (Great Chaco Region), Formosa, Argentina; the rate of infection in children residing in these communities, in blood donors and in pregnant women who received care at the Hospital Las Lomitas, as well as the rate of congenital infection in children born to women infected during the study period. The rate of infestation of 172 households evaluated in 2006 reached 32%. Prevalence of infection among 445 people was 17.5% and in children under 5 years old it was 8.6%. The rate of infection reached 18.6% in blood donors and 29.1% in pregnant women. The rate of infection among 47 children born to infected women, and living in residences under vectorial surveillance was 17.0%. These infections were considered as congenital. This study showed indexes compatible with active vectorial transmission at the beginning. After vectorial control with insecticides the infestation rate has been reduced to 3.3%. The local health system has introduced high impact procedures of primary and secondary prevention in order to prevent new cases and to treat infected people.

[Part II. Chagas disease in adults, infancy and adolescence]

The different stages of Chagas disease in adults: acute, undetermined or latent and chronic phases are described. This document contains guidelines for etiological diagnosis of Chagas disease and its treatment. In chronic phase, as cardiac and digestive system (esophagus and colon) are affected, symptoms and signs, evolution of the disease, laboratory analysis and treatment are described. The following topics in congenital Chagas disease are boarded: its prevalence in pregnant women, the importance of mother phase of disease, repercussions of the parasite transmission to the fetus, the frequency of transmission, how the infection to the fetus is produced, the importance of chronic infection in consecutive pregnancies, and clinical consequences to the newborn infant including symptoms of congenital disease. Concomitance with human immunodeficiency virus is commented. No vertically transmitted Chagas disease in infancy and adolescents has similar clinical manifestations as in adults. Direct and indirect laboratory tests of infection are described and an algorithm for diagnosis and follow up of vertical transmission of Trypccnosoma cruzi is presented.

Effects of parasitic infections in pregnant women

This review focuses on the parasitic diseases which occur frequently in the tropics and which affect pregnant women. Clinical disease of the mother during pregnancy, vertical transmission of parasites and transplacental passage of soluble parasitic antigens are discussed in relation to their immunopathological significance for the fetus. The incidences of congenital malaria, African trypanosomiasis and Chagas' disease are reviewed, together with vertical transmission of filarial infection, involvement of the female genital tract in schistosomiasis, and fulminant colitis due to Entamoeba histolytica infection during pregnancy.

The value of molecular studies for the diagnosis of congenital Chagas disease in northeastern Argentina

Polymerase chain reaction (PCR) as a diagnostic tool for congenital Chagas disease is scarcely used. To assess the usefulness of PCR, a study in neonates was carried out to compare PCR with standard methods; that is bloodstream parasites by microhematocrit, and/or seroconversion by two conventional procedures. Seventeen neonates, born to mothers with positive Trypanosoma cruzi serology were analyzed by serologic, parasitological and molecular procedures, in blood samples taken at birth, and when aged 2-4 and 9 months. For a better comparison of sensitivity between both parasitological methods (microhematocrit and PCR), the number of samples of neonates studied at birth extended to 121. In children followed-up until 9 months of age, a 100% correlation between PCR and routine diagnosis was found, with PCR showing its highest sensitivity from Month 2 onwards. Comparative analysis between both parasitological methods, on samples taken at birth, showed a higher sensitivity of PCR respect the microhematocrit (P < 0.0008).

Soluble tumor necrosis factor (TNF) receptors (sTNF-R1 and -R2) in pregnant women chronically infected with Trypanosoma cruzi and their children

Most congenital transmissions of Trypanosoma cruzi are not detected. As the levels of mediators regulating the immune response might be different in the absence or in the presence of transmission, we explored the levels of tumor necrosis factor (TNF) and soluble TNF receptors TNF-R1 and -R2 in T. cruzi-infected pregnant women and the neonates. We previously found that the circulating levels of TNF were higher in non-transmitting than in transmitting pregnant women. This observation has now been extended to the spontaneous release of TNF by peripheral blood leukocytes (PBLs) that was also higher in non-transmitting than in transmitting pregnant women. As their mothers, non-infected neonates had higher circulating levels of TNF than congenitally infected children. The circulating levels of sTNF-R1 increased in non-transmitting and transmitting mothers and in infected and non-infected neonates. The circulating levels of sTNF-R2 were approximately 60% higher in infected than in non-infected neonates (1,635 +/- 101 and 1,027 +/- 100 pg/mL, respectively) and remained higher at 1 year of age. This important increase, only observed in infected neonates, could be useful to orientate to the presence of vertical transmission of T. cruzi infection.

Congenital Trypanosoma cruzi infection in a non-endemic area

In May 2004, after launching a screening programme to detect Trypanosoma cruzi infection in the Latin American population, a case of congenital infection in a 2-year-old boy was discovered in Barcelona. Few cases of congenital transmission have been described in non-endemic areas and little is known about the epidemiological and clinical features of congenital Chagas disease in this context. The increase in Latin American immigrants in Europe and the USA requires greater epidemiological surveillance and appropriate diagnostic techniques for managing T. cruzi infections.

Evidence of congenital transmission of Trypanosoma cruzi in a vector-free area of Bolivia

A seroprevalence survey of Trypanosoma cruzi was carried out in two areas of South Bolivia. Triatoma infestans, the main vector of Tryp. cruzi, was abundant in the first area, but absent in the second one. Titration of Tryp. cruzi antibodies was carried out in children aged 6-24 months and their mothers. The seroprevalence of Chagas' disease was significantly higher in the area with the vector, but also high in the second area. Chagas' infection in children under 2 years old could be linked to congenital transmission of parasites during pregnancy and/or delivery, despite active vector control in both areas.

Direct molecular profiling of minicircle signatures and lineages of Trypanosoma cruzi bloodstream populations causing congenital Chagas disease

Congenital transmission of Trypanosoma cruzi may occur in some or all the gestations from a T. cruzi-infected mother. Variable rates of congenital transmission have been reported in different geographical areas where different parasitic strains predominate, suggesting that parasitic genotypes might play a role in the risk of congenital transmission. Moreover, in cases of transmission it is unknown if the whole maternal T. cruzi population or certain clones are preferentially transmitted by the transplacental route. In this study, bloodstream T. cruzi lineages were identified in blood samples from congenitally infected children, transmitting and non-transmitting mothers and unrelated Chagas disease patients, using improved PCR strategies targeted to nuclear genomic markers. T. cruzi IId was the prevalent genotype among 36/38 PCR-positive congenitally infected infants, 5/5 mothers who transmitted congenital Chagas disease, 12/13 mothers who delivered non-infected children and 28/34 unrelated Chagas disease patients, all coming from endemic localities of Argentina and Bolivia. These figures indicate no association between a particular genotype and vertical transmission. Furthermore, minicircle signatures from the maternal and infants' bloodstream trypanosomes were profiled by restriction fragment length polymorphism of the 330-bp PCR-amplified variable regions in seven cases of mothers and congenitally infected infants. Minicircle signatures were nearly identical between each mother and her infant/s and unique to each mother-infant/s case, a feature that was also observed in twin deliveries. Moreover, allelic size polymorphism analysis of microsatellite loci from populations transmitted to twins showed that all clones from the maternal polyclonal population were equally infective to both siblings.

Comparison of Trypanosoma cruzi lineages and levels of parasitic DNA in infected mothers and their newborns

To better understand the factors involved in maternal-fetal transmission of Trypanosoma cruzi, we compared DNA levels-obtained by use of quantitative real-time PCR and parasitic genotypes determined by PCR amplification followed by hybridization-in Bolivian mothers and their congenitally infected newborns. Mothers and their neonates displayed markedly different parasitic DNA levels, as most maternal estimated parasitemias (> 90%) were < 10 parasites/mL, whereas those of 76% of their newborns were > 1,000 parasites/mL. Comparison of T. cruzi TcII sublineages infecting mothers and newborns showed identity, without evidence of mixed infection in mothers or neonates. Analysis of minor variants of TcIId-genotyped parasites using sequence class probes hybridizing with hypervariable domains of kDNA minicircles showed discrepancies in half of mother/newborn pairs.

[Congenital Chagas disease: from the laboratory to public health]

Trypanosoma cruzi, the protozoan agent of Chagas disease can be transmitted from mother to foetus. The incidence of congenital infection is estimated to be at least 15,000 cases per year in Latin-America. Its incidence in the non endemic countries (U.S.A., Europe, Japan) is not known. Thanks to multidisciplinary studies performed in Bolivia, it has been possible to specify the epidemiologic and clinical features of congenital Chagas disease. The transplacental route, as well as the role of some parasitic (genotype and parasitic charge) or host factors (capacity of maternal and fetal/neonatal immune responses, particularly the generation of CD8T cells with cytotoxic and IFN-gamma-producing capacities) in mother-to-fetus transmission of infection and/or development of congenital Chagas disease, have been also studied. Altogether, these data have allowed the development of a strategy to control T. cruzi congenital infection, which has been validated by WHO and is applied in various Latin American countries.

Congenital Chagas disease in Bolivia is not associated with DNA polymorphism of Trypanosoma cruzi

This study aims to typify the Trypanosoma cruzi (sub)lineage(s) in umbilical cord blood of congenitally infected Bolivian newborns, using PCR amplifications of "Region Markers", mini-exon or kDNA fragments followed by hybridization or sequencing. New probes were also designed to distinguish three variants within the TcIId sublineage. The IIb, IId, or IIe T. cruzi sublineages, as well as different variants of the IId sublineage, were detected in infected neonates, whereas mixed infections were not found. The frequencies of the IId sublineage were similar in neonates (95.1%) and adults of the same area (94.1%). The IId-infected newborns displayed either asymptomatic, or severe and fatal clinical forms of congenital Chagas disease, as well as low or high parasitemia. Altogether these data show that T. cruzi DNA polymorphism, based on the presently available markers, is not associated with the occurrence of congenital infection or the development of severe clinical forms of congenital Chagas disease.

Human congenital infection with Trypanosoma cruzi induces phenotypic and functional modifications of cord blood NK cells

We studied the phenotype and activity of cord blood natural killer (NK) cells in newborns congenitally infected with Trypanosoma cruzi. We found that the proportion of CD56(bright) NK cells was significantly decreased in cord blood from these newborns, suggesting they may have been recruited to secondary lymphoid organs. The remaining CD56(bright) NK cells exhibited a defective ability in the production of interferon (IFN)-gamma following in vitro activation with interleukin (IL)-12 + IL-2 or IL-12 + IL-15 cytokines, as compared with NK cells from uninfected newborns. In addition, cord blood NK cells from congenitally infected newborns stimulated with cytokines have a decreased release of granzyme B (GrB) when incubated with K562 target cells. This defect in cytotoxic effector function is associated with a reduced surface expression of activating NK receptors (NKp30, NKp46, and NKG2D) on CD56(dim) NK cells compared with uninfected newborns. These alterations of fetal NK cells from congenitally infected newborns may reflect a down-regulation of the NK cell response after an initial peak of activation and could also be the result of T. cruzi modulating the immune response.

Are maternal re-infections with Trypanosoma cruzi associated with higher morbidity and mortality of congenital Chagas disease?

BACKGROUND

Comparing two surveys performed in Bolivia in 1992-1994 and 1999-2001, we reported a significant decrease in the proportions of severe and mortal forms of congenital Chagas disease. This might be due to a reduction of vectorial density (VD) in maternal residence area, raising the question of a possible causal relationship between such VD, maternal parasitaemia and prognosis of congenital infection with Trypanosoma cruzi.

METHOD

Comparisons of haematological and parasitological data obtained from Bolivian mothers infected with T. cruzi, and of clinical and biological data obtained from their infected and uninfected newborns, stratified according to VD in the area of maternal residence.

RESULTS

i) Blood hematocrit rates or hemoglobin amounts were within the normal ranges and similar in all the maternal groups, whatever the VD in their areas of residence; ii) mothers living in high VD areas displayed a higher frequency of hemocultures positive for T. cruzi; iii) newborns congenitally infected with T. cruzi, but not uninfected babies born from infected mothers, displayed higher frequencies of very low Apgar scores, low birth weights, prematurity, respiratory distress syndrome or anasarca, as well as higher mortality rates when their mothers lived in areas of high VD.

CONCLUSION

Frequent bites of blood sucking Reduvidae during pregnancy do not induce maternal anaemia, but, likely through multiple maternal re-infections with T. cruzi, increase maternal parasitemia and worsen congenital Chagas disease. Maternal dwelling in areas of high VD is associated with a serious increased risk of severe and mortal congenital Chagas disease.

EARLY DIAGNOSIS OF CONGENITAL TRYPANOSOMA CRUZI INFECTION USING PCR, HEMOCULTURE, AND CAPILLARY CONCENTRATION, AS COMPARED WITH DELAYED SEROLOGY

Congenital Trypanosoma cruzi infection is a highly pathogenic and underreported condition. Early recognition is essential for effective treatment. Umbilical chord blood from newborns (n = 302) to infected mothers was analyzed with microhematocrit, hemoculture, and PCR methods. Each subject was then followed serologically. In calibrated suspensions of T. cruzi in blood, the sensitivity of PCR was 27-fold higher than hemoculture. However, this advantage was not reflected during routine testing of samples from maternities, partly because of the uneven distribution of few parasites in small samples. Levels of detection of congenital infection were 2.9% (8/272) for microhematocrit, 6.3% (18/287) for hemoculture, 6.4% (15/235) for PCR, and 8.9% (27/302) for cumulated results. Evaluation against the standard of delayed serology indicates that the regular application of PCR, hemoculture, and microhematocrit to blood samples allows the rapid detection of about 90% of the congenitally infected newborns, in samples that can be obtained before the mother and child leave the maternity ward.

High prevalence of congenital Trypanosoma cruzi infection and family clustering in Salta, Argentina

OBJECTIVE

Trypanosoma cruzi, the causative agent of Chagas' disease, is transmitted mainly by insect vectors, but congenital and transfusion-borne infections occasionally occur. The factors that are involved in transmission from mother to offspring are not well understood. The objective of this study was to study the presence of T cruzi infection in children who were born to infected mothers and in the children's siblings to evaluate the epidemiologic risk factors associated with congenital transmission of Chagas' disease.

METHODS

Congenital T cruzi infection was studied in 340 children who were born to chronically infected mothers in Salta, Argentina. Infection was detected in 31 children, who were selected for additional study as infected index cases (IIC). Of the 309 noninfected children, 31 were taken as noninfected index cases (NIIC). We compared the prevalence of congenital T cruzi transmission in the remaining siblings of the IIC and NIIC. Data and blood samples were collected in house-to-house visits. Diagnosis of infection was established mainly by serologic methods, indirect hemmagglutination, and enzyme-linked immunosorbent assay.

RESULTS

The prevalence was 31.4% (32 of 102 children) for IIC siblings, whereas no infected siblings were found in families with NIIC (0 of 112). Clustering of congenital infection was found in 14 families, in which >1 child was infected. Second-generation congenital transmission (from grandmother to mother to newborn) was established in 4 families. The association among low weight at birth, prematurity, and congenital transmission was highly significant. An important observation was the absence of pathologic findings in a high proportion of infected children. The detection of asymptomatic infections was a consequence of population screening, as opposed to hospital-based diagnosis, for which symptomatic cases predominate. Congenital transmission was associated with the geographic origin of mothers: women from areas where insect vectors proliferate were less likely to give birth to infected offspring than women from areas under active vector control.

CONCLUSIONS

Siblings of an infant infected with T cruzi are at high risk for infection themselves and, even in the absence of symptoms, should also be screened for infection. The findings of family clustering of infection and of second-generation congenital infection in vector-free areas suggest that new modalities of transmission, other than classic vector-borne spread, may occur both in endemic and in nonendemic areas.

Prevalencia de la enfermedad de Chagas en puérperas y transmisión congénita en una zona endémica del Perú

OBJECTIVES

To determine the prevalence of antibodies against Trypanosoma cruzi in puerperal women and to assess possible congenital transmission of Chagas' disease in the department of Arequipa, Peru, where the disease is endemic.

METHODS

Women who had given birth between December 2001 and July 2002 in three hospitals (two urban and one rural) and four health centers (three rural and one urban) of the department of Arequipa, Peru, were studied. The serological study included screening all the puerperal women in order to detect antibodies against T. cruzi through indirect immunofluorescence (IIF), with confirmatory testing done with enzyme-linked immunosorbent assay (ELISA) testing and the titration of immunoglobulin G (IgG) antibodies by IIF. IIF tests to screen for immunoglobulin M (IgM) antibodies were done with the seropositive women and their newborns, and infection was evaluated through xenodiagnosis (evaluated at 30 and 60 days) and the direct micromethod of Freilij et al. The results were analyzed in terms of the presence of the vector and of cases of Chagas' disease in the places where the puerperal women had been born and where they were living. Two neonatologists clinically evaluated the newborns in order to detect abnormalities and signs of congenital Chagas' disease.

RESULTS

The overall prevalence of Chagas' disease in the 3 000 puerperal women studied was 0.73%. Prevalence was highest in two health centers located in rural areas (2.2% in El Pedregal and 4.1% in La Joya) (P=0.018). The disease was associated with previous direct contact with the vector (P<0.05) and with having been born in an area considered endemic (P<0.01). Four (20%) of the 20 seropositive puerperal women were also positive by xenodiagnosis. However, none of the women was aware of her infectious carrier state, and none showed the characteristic symptoms or signs of acute or chronic Chagas' disease. IgM antibodies were not detected in any of the puerperal women. One neonate (whose mother did not have evidence of parasitemia) presented an IgM titer of 1/8, but in later controls neither IgM nor IgG antibodies were detected. Parasites were not detected in the blood of the neonates by either of the two testing methods used. Of the 20 neonates evaluated, one presented microcephaly and hepatosplenomegaly; although the child had specific IgG antibodies against T. cruzi at birth, the antibodies were not present at the age of two months. The growth and development of the other 19 newborns were normal.

CONCLUSIONS

The prevalence of Chagas' disease in puerperal women of the department of Arequipa, Peru, is low. No cases of intrauterine congenital transmission were found. We recommend carrying out studies on prenatal detection that evaluate more mothers and in which women who give birth at home also participate.

Use of the placental perfusion model to evaluate transplacental passage of Trypanosoma cruzi

OBJECTIVE

To determine whether Trypanosoma cruzi could be identified in placental cells in vitro and in placental tissue using a human ex vivo perfusion model.

STUDY DESIGN

A placental cell line was incubated with trypomastigotes for progressive time periods. Trypomastigotes were also infused as a bolus into the maternal circulation of a placental perfusion model. Maternal and fetal perfusates, and placental tissue, were analyzed for parasitic DNA using polymerase chain reaction; perfused specimens were also examined histologically.

RESULTS

Intracytoplasmic amastigotes were identified in trophoblast of the incubated cell line by 24-48 hours. Following placental perfusion, T cruzi DNA was identified in all postinoculation maternal perfusate samples and postinoculation placental tissue specimens; preinoculation controls were negative.

CONCLUSION

This is the first description of the use of the human placental perfusion model to study congenital Chagas' disease, including the presence and time course of early parasitic invasion of the placenta.

Chagas' disease: study of congenital transmission in cases of acute maternal infection

We studied three pregnant women with acute chagasic infection. Two patients, infected in the third trimester of pregnancy, had uninfected children. The third patient, infected earlier, had an infected newborn. These results encourage research on risk factors of transmission and on medical decisions concerning pregnant women with acute Chagas' disease.