Towards a New Strategy for Diagnosis of Congenital Trypanosoma cruzi Infection

Evaluation and validation of a PrintrLab-based LAMP assay to identify Trypanosoma cruzi in newborns in Bolivia: a proof-of-concept study

BACKGROUND

Vertical transmission of Trypanosoma cruzi represents approximately 20% of new Chagas disease cases. Early detection and treatment for women of childbearing age and newborns is a public health priority, but the lack of a simple and reliable diagnostic test remains a major barrier. We aimed to evaluate the performance of a point-of-care loop-mediated isothermal amplification (LAMP) assay for the detection of T cruzi.

METHODS

In this proof-of-concept study, we coupled a low-cost 3D printer repurposed for sample preparation and amplification (PrintrLab) to the Eiken T cruzi-LAMP prototype to detect vertically transmitted T cruzi, which we compared with standardised PCR and with the gold-standard algorithm (microscopy at birth and 2 months and serological study several months later). We screened pregnant women from two hospitals in the Bolivian Gran Chaco province, and those who were seropositive for T cruzi were offered the opportunity for their newborns to be enrolled in the study. Newborns were tested by microscopy, LAMP, and PCR at birth and 2 months, and by serology at 8 months.

FINDINGS

Between April 23 and Nov 17, 2018, 986 mothers were screened, among whom 276 were seropositive for T cruzi (28·0% prevalence, 95% CI 25·6-31·2). In total, 224 infants born to 221 seropositive mothers completed 8 months of follow-up. Congenital transmission was detected in nine of the 224 newborns (4·0% prevalence, 1·9-7·5) by direct microscopy observation, and 14 more cases were diagnosed serologically (6·3%, 3·6-10·3), accounting for an overall vertical transmission rate of 10·3% (6·6-15·0; 23 of 224). All microscopy-positive newborns were positive by PrintrLab-LAMP and by PCR, while these techniques respectively detected four and five extra positive cases among the remaining 215 microscopy-negative newborns.

INTERPRETATION

The PrintrLab-LAMP yielded a higher sensitivity than microscopy-based analysis. Considering the simpler use and expected lower cost of LAMP compared with PCR, our findings encourage its evaluation in a larger study over a wider geographical area.

FUNDING

Inter-American Development Bank.

Mother-to-child Chagas disease transmission: The challenge of detection and prevention in areas without the risk of vectorial transmission

Chagas disease (CD) is caused by the parasite Trypanosoma cruzi. Although it is endemic in many Latin American (LA) countries, mother-to-child transmission has caused it to expand to other countries and continents. In places where vector transmission is controlled or absent, the epidemiological importance of T. cruzi transmission of the infected mother to her child during pregnancy or childbirth (i.e., perinatal CD) increases. In countries where CD is not endemic, CD screening should be performed in pregnant or fertile women who are native to LA countries or whose mothers are native to LA countries. Diagnosis is established by detecting anti-T. cruzi IgG antibodies in a serum or plasma sample. Antiparasitic treatment cannot be offered during pregnancy, and since the majority of infected newborns are asymptomatic at birth, a diagnosis is made by direct observation or concentration (microhematocrit) or by using molecular testing techniques. Once the infected child receives a diagnosis, it is essential to offer treatment (benznidazole/nifurtimox) as soon as possible, with good tolerance and effectiveness in the first year of life. Even if the diagnosis is negative at birth, the newborn must be followed up for at least the first 9 months of life.

Clinical trials for Chagas disease: etiological and pathophysiological treatment

Chagas disease (CD) is caused by the flagellate protozoan Trypanosoma cruzi. It is endemic in Latin America. Nowadays around 6 million people are affected worldwide, and 75 million are still at risk. CD has two evolutive phases, acute and chronic. The acute phase is mostly asymptomatic, or presenting unspecific symptoms which makes it hard to diagnose. At the chronic phase, patients can stay in the indeterminate form or develop cardiac and/or digestive manifestations. The two trypanocide drugs available for the treatment of CD are benznidazole (BZ) and nifurtimox (NFX), introduced in the clinic more than five decades ago. WHO recommends treatment for patients at the acute phase, at risk of congenital infection, for immunosuppressed patients and children with chronic infection. A high cure rate is seen at the CD acute phase but better treatment schemes still need to be investigated for the chronic phase. There are some limitations within the use of the trypanocide drugs, with side effects occurring in about 40% of the patients, that can lead patients to interrupt treatment. In addition, patients with advanced heart problems should not be treated with BZ. This is a neglected disease, discovered 114 years ago that still has no drug effective for their chronic phase. Multiple social economic and cultural barriers influence CD research. The high cost of the development of new drugs, in addition to the low economical return, results in the lack of investment. More economic support is required from governments and pharmaceutical companies on the development of more research for CD treatment. Two approaches stand out: repositioning and combination of drugs, witch drastically decrease the cost of this process, when compared to the development of a new drug. Here we discuss the progress of the clinical trials for the etiological and pathophysiological treatment for CD. In summary, more studies are needed to propose a new drug for CD. Therefore, BZ is still the best option for CD. The trials in course should clarify more about new treatment regimens, but it is already possible to indicate that dosage and time of treatment need to be adjusted.

Domestic Triatoma spp. Infections with Trypanosoma cruzi, Household Infestations, and Molecular Identification in Oaxaca, México

In Latin America, Mexico is the country with the second highest annual estimated number of Chagas disease cases, caused by Trypanosoma cruzi, due to vector-borne transmission. The state of Oaxaca is the location of the first documented human cases of Chagas disease in Mexico and contained the highest T. cruzi seropositive rate (3.5%) from blood donors. Here, entomological surveys, from 2017 to 2019, were conducted to collect triatomines in 124 villages of 60 municipalities. Four principal domestic Triatoma spp. (Hemiptera: Triatominae), Triatoma phyllosoma, T. barberi, T. mazzotti, and T. dimidiata, of Oaxaca, Mexico were identified by morphology and molecular analysis of the barcode region of the cytochrome oxidase 1 (cox1 or COI or CO1) gene. A total of 41 out of 83 T. phyllosoma specimens examined by microscopy were positive for T. cruzi (49%), 49 out of 171 for T. barberi (28%), 31 out of 177 for T. mazzotti (17%), and none out of 10 for T. dimidiata (0%). Overall, the infestation index was 3.1% of households containing at least one triatomine; the crowding index was a mean of two Triatoma spp./household; and the colonization index was 0.38 for households based on presence of nymphs. Geographical distribution of triatomines in Oaxaca at the municipality level and endophilic behavior is also reported. Precise identification, endophilic habits, and infection rates of these triatomines are paramount for vector control programs of the Ministry of Health of Oaxaca and beyond.

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

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

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

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

Evaluation of the Performance of the Loopamp Trypanosoma cruzi Detection Kit for the Diagnosis of Chagas Disease in an Area Where It Is Not Endemic, Spain

In Spain, PCR is the tool of choice for the diagnosis of congenital Chagas disease (CD) and serology for diagnosing chronic CD. A loop-mediated isothermal amplification test for Trypanosoma cruzi DNA detection showed good analytical performance and ease of use.

In Spain, PCR is the tool of choice for the diagnosis of congenital Chagas disease (CD) and serology for diagnosing chronic CD. A loop-mediated isothermal amplification test for Trypanosoma cruzi DNA detection showed good analytical performance and ease of use. We aimed to evaluate the performance of the Loopamp Trypanosoma cruzi detection kit (Eiken Chemical Co. Ltd., Japan) (Tcruzi-LAMP) for congenital and chronic CD diagnosis using well-characterized samples. We included samples from 39 congenital and 174 chronic CD cases and from 48 uninfected children born to infected mothers and 34 nonchagasic individuals. The sensitivity, specificity, and accuracy of Tcruzi-LAMP were estimated using standard case definitions for congenital CD (positive result by parasitological or PCR tests or serology after 9 months of age) and chronic CD (positive serology by at least two tests). The Tcruzi-LAMP results were read by visual examination and a real-time fluorimeter. For congenital CD, Tcruzi-LAMP sensitivity was 97% for both types of reading; specificity was 92% by visual examination and 94% by fluorimeter. For chronic CD, sensitivity was 47% and specificity 100%. The accuracy in congenital CD was >94% versus 56% in chronic CD. The agreement of Tcruzi-LAMP with PCR tests was better in congenital CD (kappa, 0.86 to 0.91) than in chronic CD (kappa, 0.67 to 0.83). The Loopamp Trypanosoma cruzi detection kit showed good performance for the diagnosis of congenital CD. Tcruzi-LAMP, like PCR, can be useful for the screening and early diagnosis of congenital infection.

Epidemiology of congenital Chagas disease 6 years after implementation of a public health surveillance system, Catalonia, 2010 to 2015

Background

Chagas disease is endemic in Latin America and affects 8 million people worldwide. In 2010, Catalonia introduced systematic public health surveillance to detect and treat congenital Chagas disease.

Aim

The objective was to evaluate the health outcomes of the congenital Chagas disease screening programme during the first 6 years (2010–2015) after its introduction in Catalonia.

Methods

In a surveillance system, we screened pregnant women and newborns and other children of positive mothers, and treated Chagas-positive newborns and children. Diagnosis was confirmed for pregnant women and children with two positive serological tests and for newborns with microhaematocrit and/or PCR at birth or serology at age 9 months.

Results

From 2010 to 2015, the estimated screening coverage rate increased from 68.4% to 88.6%. In this period, 33,469 pregnant women were tested for Trypanosoma cruzi and 937 positive cases were diagnosed. The overall prevalence was 2.8 cases per 100 pregnancies per year (15.8 in Bolivian women). We followed 82.8% of newborns until serological testing at age 9–12 months and 28 were diagnosed with Chagas disease (congenital transmission rate: 4.17%). Of 518 siblings, 178 (34.3%) were tested and 14 (7.8%) were positive for T. cruzi. Having other children with Chagas disease and the heart clinical form of Chagas disease were maternal risk factors associated with congenital T. cruzi infection (p < 0.05).

Conclusion

The increased screening coverage rate indicates consolidation of the programme in Catalonia. The rate of Chagas disease congenital transmission in Catalonia is in accordance with the range in non-endemic countries.

ARCHITECT Chagas® as a single test candidate for Chagas disease diagnosis: evaluation of two algorithms implemented in a non-endemic setting (Barcelona, Spain)

OBJECTIVES

To evaluate two algorithms for the diagnosis of chronic and congenital Chagas disease (CD), both including the chemiluminescent microparticle immunoassay ARCHITECT Chagas® (CMIA) as a single test but with an amended signal-to-cut-off ratio (S/CO) of ≥6, instead of an S/CO of ≥1 as indicated by the manufacturer.

METHODS

The study encompassed two panels of retrospective samples: 831 sera from 786 adolescents and adults (panel A), and 96 sera from 35 newborn infants with CD-infected mothers (panel B). A CMIA-negative result was deemed conclusive, whereas samples with an S/CO ≥ 0.8 were confirmed by a second test (BioELISA Chagas, ELISAr).

RESULTS

In panel A, seropositivity was 13% (102/786); 10 samples gave discordant results for CMIA and ELISAr, all of which were CMIA positive and had CD confirmed through a previous diagnosis by two positive serological tests. In panel B, all newborns were considered non-infected based on both a progressive decrease in antibody titres over time and negative real-time PCR results. CMIA still gave positive results in two infants aged 10 months but no S/CO values ≥6 were observed from 4 months on.

CONCLUSIONS

CMIA is a firm candidate for use as a single CD diagnostic test in non-endemic countries. The algorithm with the ≥6 S/CO is as an efficient method for chronic CD diagnosis. CMIA could also be used as a single test to screen infants for congenital infection at the age of 10 months or even earlier if applying the corrected cut-off ratio, although further studies are required.

Canine trypanosomiasis in an endemic Costa Rican community: Demonstration of the active infection cycle

A cross-sectional study was conducted to determine the prevalence of canine trypanosomiasis in an endemic community of Costa Rica. The indirect hemagglutination and indirect immunofluorescence assay yielded positive results in 6.4% (20/314) of canine samples analyzed; polymerase chain reaction (PCR) and light microscopy yielded positive results in one dog. Subsequently, a longitudinal study was carried out with 55 negative T. cruzi canines in the cross-sectional study. These dogs were divided into two groups: Group 1, which consisted of 25 individuals that lived in dwellings where triatomines were found in their homes; and Group 2, which consisted of 30 dogs that lived in dwellings where triatomines were not found during the previous study in their homes. Seroconversion occurred in six dogs (10.9%) in Group 1 in the first months of the year (dry season); these dogs remained seropositive until the end of the study. Only one of the six seropositive canines was also found positive once in T. cruzi PCR. The analysis of the amplified T. cruzi sequences of dogs and triatomines showed that all of them belonged to the TcI lineage. It is recommended that residents be made aware of the need to eliminate vectors in their homes and their surroundings.

Serological evaluation for Chagas disease in migrants from Latin American countries resident in Rome, Italy

Background

Chagas disease (CD) is a systemic parasitic infection caused by the protozoan Trypanosoma cruzi, whose chronic phase may lead to cardiac and intestinal disorders. Endemic in Latin America where it is transmitted mainly by vectors, large-scale migrations to other countries have turned CD into a global health problem because of its alternative transmission routes through blood transfusion, tissue transplantation, or congenital. Aim of this study was to compare the performance of two commercially available tests for serological diagnosis of CD in a group of Latin American migrants living in a non-endemic setting (Rome, Italy). The study was based on a cross-sectional analysis of seroprevalence in this group. Epidemiological risk factors associated to CD were also evaluated in this study population.

Methods

The present study was conducted on 368 subjects from the Latin American community resident in Rome. Following WHO guidelines, we employed a diagnostic strategy based on two tests to detect IgG antibodies against T. cruzi in the blood (a lysate antigen-based ELISA and a chemiluminescent microparticle CMIA composed of multiple recombinant antigens), followed by a third test (an immunochromatographic assay) on discordant samples.

Results

Our diagnostic approach produced 319/368 (86.7%) concordant negative and 30/368 (8.1%) concordant positive results after the first screening. Discrepancies were obtained for 19/368 (5.2%) samples that were tested using the third assay, obtaining 2 more positive and 17 negative results. The final count of positive samples was 32/368 (8.7% of the tested population). Increasing age, birth in Bolivia, and previous residence in a mud house were independent factors associated with T. cruzi positive serology.

Conclusions

Serological diagnosis of CD is still challenging, because of the lack of a reference standard serological assay for diagnosis. Our results reaffirm the importance of performing CD screening in non-endemic countries; employing a fully automated and highly sensitive CMIA assay first could be a cost- and resource-effective strategy for mass screening of low-risk patients. However, our results also suggest that the WHO strategy of using two different serological assays, combined with epidemiological information, remains the best approach for patients coming from endemic countries.

Introducing automation to the molecular diagnosis of Trypanosoma cruzi infection: A comparative study of sample treatments, DNA extraction methods and real-time PCR assays

BACKGROUND

Polymerase chain reaction (PCR) has become a useful tool for the diagnosis of Trypanosoma cruzi infection. The development of automated DNA extraction methodologies and PCR systems is an important step toward the standardization of protocols in routine diagnosis. To date, there are only two commercially available Real-Time PCR assays for the routine laboratory detection of T. cruzi DNA in clinical samples: TCRUZIDNA.CE (Diagnostic Bioprobes Srl) and RealCycler CHAG (Progenie Molecular). Our aim was to evaluate the RealCycler CHAG assay taking into account the whole process.

METHODOLOGY/PRINCIPAL FINDINGS

We assessed the usefulness of an automated DNA extraction system based on magnetic particles (EZ1 Virus Mini Kit v2.0, Qiagen) combined with a commercially available Real-Time PCR assay targeting satellite DNA (SatDNA) of T. cruzi (RealCycler CHAG), a methodology used for routine diagnosis in our hospital. It was compared with a well-known strategy combining a commercial DNA isolation kit based on silica columns (High Pure PCR Template Preparation Kit, Roche Diagnostics) with an in-house Real-Time PCR targeting SatDNA. The results of the two methodologies were in almost perfect agreement, indicating they can be used interchangeably. However, when variations in protocol factors were applied (sample treatment, extraction method and Real-Time PCR), the results were less convincing. A comprehensive fine-tuning of the whole procedure is the key to successful results. Guanidine EDTA-blood (GEB) samples are not suitable for DNA extraction based on magnetic particles due to inhibition, at least when samples are not processed immediately.

CONCLUSIONS/SIGNIFICANCE

This is the first study to evaluate the RealCycler CHAG assay taking into account the overall process, including three variables (sample treatment, extraction method and Real-Time PCR). Our findings may contribute to the harmonization of protocols between laboratories and to a wider application of Real-Time PCR in molecular diagnostic laboratories associated with health centers.

The Trypomastigote Small Surface Antigen from Trypanosoma cruzi Improves Treatment Evaluation and Diagnosis in Pediatric Chagas Disease

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi Assessment of parasitological cure upon treatment with available drugs relies on achieving consistent negative results in conventional parasitological and serological tests, which may take years to assess. Here, we evaluated the use of a recombinant T. cruzi antigen termed trypomastigote small surface antigen (TSSA) as an early serological marker of drug efficacy in T. cruzi-infected children. A cohort of 78 pediatric patients born to T. cruzi-infected mothers was included in this study. Only 39 of the children were infected with T. cruzi, and they were immediately treated with trypanocidal drugs. Serological responses against TSSA were evaluated in infected and noninfected populations during the follow-up period using an in-house enzyme-linked immunosorbent assay (ELISA) and compared to conventional serological methods. Anti-TSSA antibody titers decreased significantly faster than anti-whole parasite antibodies detected by conventional serology both in T. cruzi-infected patients undergoing effective treatment and in those not infected. The differential kinetics allowed a significant reduction in the required follow-up periods to evaluate therapeutic responses or to rule out maternal-fetal transmission. Finally, we present the case of a congenitally infected patient with an atypical course in whom TSSA provided an early marker for T. cruzi infection. In conclusion, we showed that TSSA was efficacious both for rapid assessment of treatment efficiency and for early negative diagnosis in infants at risk of congenital T. cruzi infection. Based upon these findings we propose the inclusion of TSSA for refining the posttherapeutic cure criterion and other diagnostic needs in pediatric Chagas disease.

Molecular diagnostics for Chagas disease: up to date and novel methodologies

INTRODUCTION

Chagas disease is caused by the parasite Trypanosoma cruzi. It affects 7 million people, mainly in Latin America. Diagnosis is usually made serologically, but at some clinical scenarios serology cannot be used. Then, molecular detection is required for early detection of congenital transmission, treatment response follow up, and diagnosis of immune-suppression reactivation. However, present tests are technically demanding and require well-equipped laboratories which make them unfeasible in low-resources endemic regions. Areas covered: Available molecular tools for detection of T. cruzi DNA, paying particular attention to quantitative PCR protocols, and to the latest developments of user-friendly molecular diagnostic methodologies. Expert commentary: In the absence of appropriate biomarkers, molecular diagnosis is the only option for the assessment of treatment response. Besides, it is very useful for the early detection of acute infections, like congenital cases. Since current Chagas disease molecular tests are restricted to referential labs, research efforts must focus in the implementation of easy-to-use diagnostic tools in order to overcome the access to diagnosis gap.