A systematic review of high quality diagnostic tests for Chagas disease

Chagas Disease across the Ages: A Historical View and Commentary on Navigating Future Challenges

Chagas disease, discovered over a century ago, continues to pose a global health challenge, affecting millions mainly in Latin America. This historical review with commentary outlines the disease's discovery, its evolution into a global concern due to migration, and highlights significant advances in diagnostics and treatment strategies. Despite these advancements, the paper discusses ongoing challenges in eradication, including vector control, congenital transmission, the disease's asymptomatic nature, and socioeconomic barriers to effective management. It calls for a multidisciplinary approach, enhanced diagnostics, improved treatment accessibility, and sustained vector control efforts. The review emphasizes the importance of global collaboration and increased funding to reduce Chagas disease's impact.

Development of a Colorimetric Loop-Mediated Isothermal Amplification Assay for the Detection of Trypanosoma cruzi in Low-Resource Settings

Chagas disease is an inflammatory parasitic infection caused by Trypanosoma cruzi (T. cruzi). Early diagnosis is crucial in guiding treatment and slowing disease progression; however, current diagnostic methods have insufficient detection limits and often require skilled technicians. Molecular tests, especially isothermal nucleic acid assays, are advantageous due to their excellent sensitivity, specificity, speed, and simplicity. Here, we optimized a colorimetric loop-mediated isothermal amplification (LAMP) assay for T. cruzi. We can detect as few as 2 genomic copies/reaction using three different T. cruzi strains. We examined selectivity using other parasitic protozoans and successfully detected T. cruzi DNA extracted from parasites in human whole blood down to 1.2 parasite equivalents/reaction. We also performed a blinded study using canine blood samples and established a 100% sensitivity, specificity, and accuracy for the colorimetric LAMP assay. Finally, we used a heated 3D printer bed and an insulated thermos cup to demonstrate that the LAMP incubation step could be performed with accessible, low-cost materials. Altogether, we have developed a high-performing assay for T. cruzi with a simple colorimetric output that would be ideal for rapid, low-cost screening at the point of use.

Trypanosoma Cruzi antibody screening in North Texas client owned dogs

Despite multiple screening efforts to identify exposures to Trypanosoma cruzi, in dogs across southern USA, no published studies could be found involving client owned dogs in the North Texas Metroplex area. Therefore, a limited screen was conducted for client owned dogs, seeking routine or preventative care, from participating veterinary practices in the greater Dallas-Fort Worth (DFW) Metroplex from 2019 to 2021. Participants, with owner consent, ranged in age, breed, and length of time at recorded residence. Ninety-nine samples were acquired from participating veterinary practices, initially assessed with the Chagas StatPak, and positive samples were confirmed with IFA (indirect fluorescent antibody test) at the Texas Veterinary Medical Diagnostic Lab (TVMDL), College Station, Texas. Six samples were positive with the StatPak and only two were confirmed positive with IFA. Both animals were senior (10 and 8 years) with no owner reports of previous cardiac issues. The results appear reasonable within the context of previous studies and the seropositivity rate of 2% (n = 99) for client owned dogs included in this study are lower than previously reported rates for shelter dogs from the North Texas area.

Five-year serological and clinical evolution of chronic Chagas disease patients in Cochabamba, Bolivia

BACKGROUND

Chagas disease, caused by the parasite Trypanosoma cruzi, is a neglected infectious disease that exerts the highest public health burden in the Americas. There are two anti-parasitic drugs approved for its treatment-benznidazole and nifurtimox-but the absence of biomarkers to early assess treatment efficacy hinders patients´ follow-up.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a longitudinal, observational study among a cohort of 106 chronically T. cruzi-infected patients in Cochabamba (Bolivia) who completed the recommended treatment of benznidazole. Participants were followed-up for five years, in which we collected clinical and serological data, including yearly electrocardiograms and optical density readouts from two ELISAs (total and recombinant antigens). Descriptive and statistical analyses were performed to understand trends in data, as well as the relationship between clinical symptoms and serological evolution after treatment. Our results showed that both ELISAs documented average declines up to year three and slight inclines for the following two years. The recorded clinical parameters indicated that most patients did not have any significant changes to their cardiac or digestive symptoms after treatment, at least in the timeframe under investigation, while a small percentage demonstrated either a regression or progression in symptoms. Only one participant met the "cure criterion" of a negative serological readout for both ELISAs by the final year.

CONCLUSIONS/SIGNIFICANCE

The study confirms that follow-up of benznidazole-treated T. cruzi-infected patients should be longer than five years to determine, with current tools, if they are cured. In terms of serological evolution, the single use of a total antigen ELISA might be a more reliable measure and suffice to address infection status, at least in the region of Bolivia where the study was done. Additional work is needed to develop a test-of-cure for an early assessment of drugs´ efficacy with the aim of improving case management protocols.

Use of sera cell free DNA (cfDNA) and exovesicle-DNA for the molecular diagnosis of chronic Chagas disease

Chagas disease, a neglected tropical disease, is now considered a worldwide health concern as a result of migratory movements from Central and South America to other regions that were considered free of the disease, and where the epidemiological risk is limited to transplacental transmission or blood or organ donations from infected persons. Parasite detection in chronically ill patients is restricted to serological tests that only determine infection by previous infection and not the presence of the parasite, especially in patients undergoing treatment evaluation or in newborns. We have evaluated the use of nucleic acids from both circulating exovesicles and cell-free DNA (cfDNA) from 50 samples twice randomly selected from a total of 448 serum samples from immunologically diagnosed patients in whom the presence of the parasite was confirmed by nested PCR on amplicons resulting from amplification with kinetoplastid DNA-specific primers 121F-122R. Six samples were randomly selected to quantify the limit of detection by qPCR in serum exovesicles. When the nucleic acids thus purified were assayed as a template and amplified with kinetoplastid DNA and nuclear satellite DNA primers, a 100% positivity rate was obtained for all positive samples assayed with kDNA-specific primers and 96% when SAT primers were used. However, isolation of cfDNA for Trypanosoma cruzi and amplification with SAT also showed 100% positivity. The results demonstrate that serum exovesicles contain DNA of mitochondrial and nuclear origin, which can be considered a mixed population of exovesicles of parasitic origin. The results obtained with serum samples prove that both cfDNA and Exovesicle DNA can be used to confirm parasitaemia in chronically ill patients or in samples where it is necessary to demonstrate the active presence of the parasite. The results confirm for the first time the existence of exovesicles of mitochondrial origin of the parasite in the serum of those affected by Chagas disease.

What Do You Need to Know before Studying Chagas Disease? A Beginner's Guide

Chagas disease is one of the most important tropical infections in the world and mainly affects poor people. The causative agent is the hemoflagellate protozoan Trypanosoma cruzi, which circulates among insect vectors and mammals throughout the Americas. A large body of research on Chagas disease has shown the complexity of this zoonosis, and controlling it remains a challenge for public health systems. Although knowledge of Chagas disease has advanced greatly, there are still many gaps, and it is necessary to continue generating basic and applied research to create more effective control strategies. The aim of this review is to provide up-to-date information on the components of Chagas disease and highlight current trends in research. We hope that this review will be a starting point for beginners and facilitate the search for more specific information.

Identification of a triatomine infected with Trypanosoma cruzi in an urban area of the state of Veracruz, Mexico: A comprehensive study

Chagas disease, considered a neglected disease, was initially confined to rural localities in endemic areas; however, in recent years through the process of urbanization and migration of infected people, the disease is gaining importance in urban environments. The presence of the vector in urban areas in most cases is due to the passive transport of vectors, but recently, its presence seems to be linked to vector adaptation processes associated with climate change. This paper reports the occurrence of an infected triatomine in the peridomicile of a house in an urban area of Córdoba, Veracruz, Mexico, where the species found is described, the molecular characteristics and resistance to BZN and NFX of the Trypanosoma cruzi isolate obtained, as well as serological data of the dwelling inhabitants. These urban disease scenarios make it possible to generate new scientific knowledge and enable the creation of new control strategies for Chagas disease vectors.

Accuracy of Diagnostic Tests for the Detection of Chagas Disease: A Systematic Review and Meta-Analysis

The present systematic review and meta-analysis about the accuracy of diagnostic tests aim to describe the findings of literature over the last thirty years for the diagnosis of Chagas disease (CD). This work aimed to determine the accuracy of diagnostic techniques for CD in the disease's acute and chronic phases. The PubMed database was searched for studies published between 1990 and 2021 on CD diagnostics. Fifty-six published studies that met the criteria were analyzed and included in the meta-analysis, evaluating diagnostic accuracy through sensitivity and specificity. For Enzyme-Linked Immunosorbent Assay (ELISA), Fluorescent Antibody Technique (IFAT), Hemagglutination Test (HmT), Polymerase Chain Reaction (PCR), and Real-Time Polymerase Chain Reaction (qPCR) diagnosis methods, the sensitivity had a median of 99.0%, 78.0%, 75.0%, 76.0%, and 94.0%, respectively; while specificity presented a median of 99.0%, 99.0%, 99.0%, 98.0%, and 98.0%, respectively. This meta-analysis showed that ELISA and qPCR techniques had a higher performance compared to other methods of diagnosing CD in the chronic and acute phases, respectively. It was concluded utilizing the Area Under the Curve restricted to the false positive rates (AUCFPR), that the ELISA diagnostic test presents the highest performance in diagnosing acute and chronic CD, compared to serological and molecular tests. Future studies focusing on new CD diagnostics approaches should be targeted.

Rapid diagnostic tests and ELISA for diagnosing chronic Chagas disease: Systematic revision and meta-analysis

OBJECTIVE

To determine the diagnostic validity of the enzyme-linked immunosorbent assay (ELISA) and Rapid Diagnostic Tests (RDT) among individuals with suspected chronic Chagas Disease (CD).

METHODOLOGY

A search was made for studies with ELISA and RDT assays validity estimates as eligibility criteria, published between 2010 and 2020 on PubMed, Web of Science, Scopus, and LILACS. This way, we extracted the data and assessed the risk of bias and applicability of the studies using the QUADAS-2 tool. The bivariate random effects model was also used to estimate the overall sensitivity and specificity through forest-plots, ROC space, and we visually assessed the heterogeneity between studies. Meta-regressions were made using subgroup analysis. We used Deeks' test to assess the risk of publication bias.

RESULTS

43 studies were included; 27 assessed ELISA tests; 14 assessed RDTs; and 2 assessed ELISA and RDTs, against different reference standards. 51.2 % of them used a non-comparative observational design, and 46.5 % a comparative clinical design ("case-control" type). High risk of bias was detected for patient screening and reference standard. The ELISA tests had a sensitivity of 99% (95% CI: 98-99) and a specificity of 98% (95% CI: 97-99); whereas the Rapid Diagnostic Tests (RDT) had values of 95% (95% CI: 94-97) and 97% (95% CI: 96-98), respectively. Deeks' test showed asymmetry on the ELISA assays.

CONCLUSIONS

ELISA and RDT tests have high validity for diagnosing chronic Chagas disease. The analysis of these two types of evidence in this systematic review and meta-analysis constitutes an input for their use. The limitations included the difficulty in extracting data due to the lack of information in the articles, and the comparative clinical-type design of some studies.

Gold Nanoshells-Based Lateral Flow Assay for the Detection of Chagas Disease at the Point-of-Care

Chagas disease is a neglected parasitic infection and a major public health problem in the Americas. It remains underdiagnosed in the United States and internationally due to the lack of affordable testing and disparities in healthcare, particularly for those most at risk. We describe a proof-of-concept lateral flow immunoassay employing a recombinant Chagas multiantigen conjugated to gold nanoshells (AuNS) to detect circulating human anti-Chagas IgG antibodies. This is one of the first lateral flow immunoassays to capitalize on the larger surface area of AuNS compared with nanoparticles that can help amplify low-magnitude signals. Results were compared with 42 positive and negative Chagas serum samples, of which a subset of 27 samples was validated against an ELISA (Hemagen®). The sensitivity and specificity of our assay were 83% and 95%, respectively. These results suggest that an AuNS-based rapid testing for Chagas disease could facilitate in-field screening/diagnosis with a performance comparable to commercial methods.

Evaluation of the Chagas Western Blot IgG Assay for the Diagnosis of Chagas Disease

Chagas disease is a debilitating and often fatal pathology resulting from infection by the protozoan parasite Trypanosoma cruzi. In its recommendations, the World Health Organization states that the diagnosis of T. cruzi infection is usually based on the detection of antibodies against T. cruzi antigens and performed with two methodologically different assays. An inconclusive result can be resolved with a third “confirmatory” assay. The objective of this article is to evaluate the effectiveness of the Chagas Western Blot IgG assay (LDBio Diagnostics, Lyon, France) as a confirmatory serologic test. The Chagas Western Blot IgG assay was performed with native antigens derived from a T. cruzi strain of the TcVI genotype. Retrospective sera were provided by two parasitology laboratories (France and Argentina). The sensitivity, specificity, positive predictive value and negative predictive value of the Chagas blot were all 100% in our sera collection. The Chagas blot is an easy and qualitative method for the diagnosis of Chagas disease, with results in less than 2 h. This immunoblot has potential as a supplemental test for the confirmation of the presence of antibodies against T. cruzi in serum specimens. Nonetheless, the very good initial results presented here will need to be confirmed in larger studies.

Geographic variations in test reactivity for the serological diagnosis of Trypanosoma cruzi infection

Chagas disease is a neglected disease caused by Trypanosoma cruzi parasites. Most diagnosis is based on serological tests, but the lack of a gold standard test complicates the measurement of test performance. To overcome this limitation, we used samples from a cohort of well-characterized T. cruzi-infected women to evaluate the reactivity of two rapid diagnostic tests and one enzyme-linked immunosorbent assay (ELISA). Our cohort was derived from a previous study on congenital transmission of T. cruzi and consisted of 481 blood/plasma samples from Argentina (n = 149), Honduras (n = 228), and Mexico (n = 104), with at least one positive T. cruzi PCR. Reactivity of the three tests ranged from 70.5% for the Wiener ELISA to 81.0% for the T-Detect and 90.4% for the Stat-Pak rapid tests. Test reactivity varied significantly among countries and was highest in Argentina and lowest in Mexico. When considering at least two reactive serological tests to confirm seropositivity, over 12% of T. cruzi infection cases from Argentina were missed by serological tests, over 21% in Honduras, and an alarming 72% in Mexico. Differences in test performance among countries were not due to differences in parasitemia, but differences in antibody levels against ELISA antigens were observed. Geographic differences in T. cruzi parasite strains as well as genetic differences among human populations both may contribute to the discrepancies in serological testing. Improvements in serological diagnostics for T. cruzi infections are critically needed to ensure an optimum identification of cases.

Shelter cats host infections with multiple Trypanosoma cruzi discrete typing units in southern Louisiana

Trypanosoma cruzi is a zoonotic parasite endemic in the southern US and the Americas, which may frequently infect dogs, but limited information is available about infections in cats. We surveyed a convenience sample of 284 shelter cats from Southern Louisiana to evaluate T. cruzi infection using serological and PCR tests. Parasites from PCR positive cats were also genotyped by PCR and deep sequencing to assess their genetic diversity. We detected a seropositivity rate for T. cruzi of at least 7.3% (17/234), and 24.6% of cats (70/284) were PCR positive for the parasite. Seropositivity increased with cat age (R² = 0.91, P = 0.011), corresponding to an incidence of 7.2% ± 1.3 per year, while PCR positivity decreased with age (R² = 0.93, P = 0.007). Cats were predominantly infected with parasites from TcI and TcVI DTUs, and to a lesser extent from TcIV and TcV DTUs, in agreement with the circulation of these parasite DTUs in local transmission cycles. These results indicate that veterinarians should have a greater awareness of T. cruzi infection in pets and that it would be important to better evaluate the risk for spillover infections in humans.

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

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

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

Chagas Disease in the United States: A Perspective on Diagnostic Testing Limitations and Next Steps

Chagas disease is a neglected tropical disease that affects an estimated 300,000 people in the United States. This perspective piece reviews diagnostic challenges and proposes next steps to address these shortfalls.

Genetic diversity of Trypanosoma cruzi parasites infecting dogs in southern Louisiana sheds light on parasite transmission cycles and serological diagnostic performance

Background

Chagas disease is a neglected zoonosis of growing concern in the southern US, caused by the parasite Trypanosoma cruzi. We genotyped parasites in a large cohort of PCR positive dogs to shed light on parasite transmission cycles and assess potential relationships between parasite diversity and serological test performance.

Methodology/principal findings

We used a metabarcoding approach based on deep sequencing of T. cruzi mini-exon marker to assess parasite diversity. Phylogenetic analysis of 178 sequences from 40 dogs confirmed the presence of T. cruzi discrete typing unit (DTU) TcI and TcIV, as well as TcII, TcV and TcVI for the first time in US dogs. Infections with multiple DTUs occurred in 38% of the dogs. These data indicate a greater genetic diversity of T. cruzi than previously detected in the US. Comparison of T. cruzi sequence diversity indicated that highly similar T. cruzi strains from these DTUs circulate in hosts and vectors in Louisiana, indicating that they are involved in a shared T. cruzi parasite transmission cycle. However, TcIV and TcV were sampled more frequently in vectors, while TcII and TcVI were sampled more frequently in dogs.

Conclusions/significance

These observations point to ecological host-fitting being a dominant mechanism involved in the diversification of T. cruzi-host associations. Dogs with negative, discordant or confirmed positive T. cruzi serology harbored TcI parasites with different mini-exon sequences, which strongly supports the hypothesis that parasite genetic diversity is a key factor affecting serological test performance. Thus, the identification of conserved parasite antigens should be a high priority for the improvement of current serological tests.

Chagas disease is a neglected zoonosis of growing concern in the southern US, caused by the parasite Trypanosoma cruzi. Here we analyzed the parasite genetic diversity in a large cohort of infected dogs to better understand parasite transmission cycles and assess potential relationships between parasite diversity and serological test performance. We used DNA sequencing of a well characterized T. cruzi genetic marker to assess parasite diversity. We confirmed the presence of T. cruzi lineages TcI and TcIV, and report TcII, TcV and TcVI for the first time in US dogs. Parasite lineages TcIV TcII and TcVI appeared more frequent in dogs compared to insect vectors. Dogs with negative, discordant or confirmed positive T. cruzi serology harbored genetically different TcI parasites, which shows that parasite genetic diversity is a key factor affecting serological test performance. Thus, the identification of parasite antigens conserved across strains and lineages should be a high priority for the improvement of current serological tests.

Optimization and evaluation of the ARCHITECT Chagas assay and in-house ELISA for Chagas disease in clinical settings in Japan

Approximately 250,000 immigrants from Latin America live in Japan and it is estimated that 1500-3000 of them are potentially infected with Trypanosoma cruzi, the cause of Chagas disease. Therefore, the establishment of a standardized diagnostic method for Chagas disease in Japan is urgently needed. In this study, we optimized and evaluated the ARCHITECT Chagas assay and in-house ELISA for Chagas disease in clinical settings. In particular, we evaluated the performance of ARCHITECT Chagas as well as ELISA with whole-cell lysates and three recombinant proteins (TcF, TcBCDE, and CP1 + CP3) using 93 Chagas disease-positive serum samples and 108 Chagas disease-positive samples. The sensitivities of ARCHITECT Chagas, whole-cell lysate, TcF, TcBCDE, and CP1 + CP3 ELISA were respectively 100%, 100%, 98.9%, 98.9%, and 89.2% and the corresponding specificities were 100%, 99.1%, 99.1%, 100%, and 99.1%. False-positive results were obtained for whole-cell lysate, TcF, and CP1 ± CP3 ELISA. This is the first evidence that OD cut-off values optimized for in-house ELISA are similar in terms of sensitivity and specificity to those of the ARCHITECT Chagas test, supporting the use of these in-house assays as diagnostic tests for Chagas disease in the clinical setting in Japan.

Large granular lymphocytosis in a cynomolgus macaque (Macaca fascicularis) with a subclinical Trypanosoma cruzi infection

A 5.25-year-old cynomolgus macaque (Macaca fascicularis) was found to have a marked leukocytosis due to a lymphocytosis on routine quarantine laboratory data prior to inclusion in a preclinical research study. The majority of lymphocytes were characterized as intermediate to large with round to convoluted nuclei, coarse to clumped chromatin, rare prominent nucleoli, and moderate amounts of lightly basophilic cytoplasm that frequently contained small magenta granules and/or clear vacuoles. The animal had tested negative for several viruses and other etiologic agents found in nonhuman primates 1 week prior to shipment to the research facility. However, further evaluation of the blood smear revealed rare hemoflagellates, and later testing using real-time PCR and ELISA was confirmatory for Trypanosoma cruzi (T cruzi). Trypanosoma cruzi is a zoonotic pathogen responsible for Chagas disease in people and can have negative consequences on study results when positive animals are inadvertently used for preclinical research. This case report describes a marked large granular lymphocytosis in an otherwise healthy macaque as the only indication of infection with T cruzi in an animal believed to be negative for the infection. Additionally, it highlights the diagnostic limitations of screening tests to rule out diseases in animals intended to be used in preclinical studies.

Chagas Disease Infection Prevalence and Vector Exposure in a High-Risk Population of Texas Hunters

Chagas disease, caused by the vector-borne parasite Trypanosoma cruzi, remains one of the most significant neglected tropical diseases affecting the Americas. Identifying high-risk populations is important for understanding Chagas disease transmission and directing public health resources. We recently hypothesized that Texas hunters may be at an elevated risk for contracting Chagas disease because of opportunities for vector exposure and contact with blood of infected reservoirs. To assess their unique exposure risks, we conducted a statewide screening program of Texas hunters. A total of 885 study participants were interviewed and tested for T. cruzi infection; 18 screened positive on a rapid, point-of-care test; however, none were found positive through confirmatory testing. We did find a high prevalence of reported direct contact with wildlife blood as well as triatomine and other arthropod disease vectors. This large-scale screening program represents a novel approach to better understand the vector-borne disease risk in this unique population.

Chagas Disease in the New York City Metropolitan Area

Background

Chagas disease, caused by the parasite Trypanosoma cruzi, once considered a disease confined to Mexico, Central America, and South America, is now an emerging global public health problem. An estimated 300 000 immigrants in the United States are chronically infected with T. cruzi. However, awareness of Chagas disease among the medical community in the United States is poor.

Methods

We review our experience managing 60 patients with Chagas disease in hospitals throughout the New York City metropolitan area and describe screening, clinical manifestations, EKG findings, imaging, and treatment.

Results

The most common country of origin of our patients was El Salvador (n = 24, 40%), and the most common detection method was by routine blood donor screening (n = 21, 35%). Nearly half of the patients were asymptomatic (n = 29, 48%). Twenty-seven patients were treated with either benznidazole or nifurtimox, of whom 7 did not complete therapy due to side effects or were lost to follow-up. Ten patients had advanced heart failure requiring device implantation or organ transplantation.

Conclusions

Based on our experience, we recommend that targeted screening be used to identify at-risk, asymptomatic patients before progression to clinical disease. Evaluation should include an electrocardiogram, echocardiogram, and chest x-ray, as well as gastrointestinal imaging if relevant symptoms are present. Patients should be treated if appropriate, but providers should be aware of adverse effects that may prevent patients from completing treatment.

Chagas Disease Serological Test Performance in U.S. Blood Donor Specimens

Chagas disease affects an estimated 300,000 individuals in the United States. Diagnosis in the chronic phase requires positive results from two different IgG serological tests. Three enzyme-linked immunosorbent assays (ELISAs) (Hemagen, Ortho, and Wiener) and one rapid test (InBios) are FDA cleared, but comparative data in U.S. populations are sparse. We evaluated 500 seropositive and 300 seronegative blood donor plasma samples. Country of birth was known for 255 seropositive specimens, which were grouped into regions as follows: Mexico (n = 94), Central America (n = 88), and South America (n = 73). Specimens were tested by the four FDA-cleared IgG serological assays. Test performance was evaluated by two comparators and latent class analysis. InBios had the highest sensitivity (97.4% to 99.3%) but the lowest specificity (87.5% to 92.3%). Hemagen had the lowest sensitivity (88.0% to 92.0%) but high specificity (99.0% to 100.0%). The level of sensitivity was intermediate for Ortho (92.4% to 96.5%) and Wiener (94.0% to 97.1%); both had high specificity (98.8% to 100.0% and 96.7% to 99.3%, respectively). The levels of antibody reactivity and clinical sensitivity were lowest in donors from Mexico, intermediate in those from Central America, and highest in those from South America. Our findings provide an initial evidence base to improve laboratory diagnosis of Chagas disease in the United States. The best current testing algorithm would employ a high-sensitivity screening test followed by a high-specificity confirmatory test.

Complementary Paths to Chagas Disease Elimination: The Impact of Combining Vector Control With Etiological Treatment

Background

The World Health Organization’s 2020 goals for Chagas disease are (1) interrupting vector-borne intradomiciliary transmission and (2) having all infected people under care in endemic countries. Insecticide spraying has proved efficacious for reaching the first goal, but active transmission remains in several regions. For the second, treatment has mostly been restricted to recently infected patients, who comprise only a small proportion of all infected individuals.

Methods

We extended our previous dynamic transmission model to simulate a domestic Chagas disease transmission cycle and examined the effects of both vector control and etiological treatment on achieving the operational criterion proposed by the Pan American Health Organization for intradomiciliary, vectorial transmission interruption (ie, <2% seroprevalence in children <5 years of age).

Results

Depending on endemicity, an antivectorial intervention that decreases vector density by 90% annually would achieve the transmission interruption criterion in 2–3 years (low endemicity) to >30 years (high endemicity). When this strategy is combined with annual etiological treatment in 10% of the infected human population, the seroprevalence criterion would be achieved, respectively, in 1 and 11 years.

Conclusions

Combining highly effective vector control with etiological (trypanocidal) treatment in humans would substantially reduce time to transmission interruption as well as infection incidence and prevalence. However, the success of vector control may depend on prevailing vector species. It will be crucial to improve the coverage of screening programs, the performance of diagnostic tests, the proportion of people treated, and the efficacy of trypanocidal drugs. While screening and access can be incremented as part of strengthening the health systems response, improving diagnostics performance and drug efficacy will require further research.

Insights from quantitative and mathematical modelling on the proposed WHO 2030 goals for Chagas disease

Chagas disease (CD) persists as one of the neglected tropical diseases (NTDs) with a particularly large impact in the Americas. The World Health Organization (WHO) recently proposed goals for CD elimination as a public health problem to be reached by 2030 by means of achieving intradomiciliary transmission interruption (IDTI), blood transfusion and transplant transmission interruption, diagnostic and treatment scaling-up and prevention and control of congenital transmission. The NTD Modelling Consortium has developed mathematical models to study Trypanosoma cruzi transmission dynamics and the potential impact of control measures. Modelling insights have shown that IDTI is feasible in areas with sustained vector control programmes and no presence of native triatomine vector populations. However, IDTI in areas with native vectors it is not feasible in a sustainable manner. Combining vector control with trypanocidal treatment can reduce the timeframes necessary to reach operational thresholds for IDTI (<2% seroprevalence in children aged <5 years), but the most informative age groups for serological monitoring are yet to be identified. Measuring progress towards the 2030 goals will require availability of vector surveillance and seroprevalence data at a fine scale, and a more active surveillance system, as well as a better understanding of the risks of vector re-colonization and disease resurgence after vector control cessation. Also, achieving scaling-up in terms of access to treatment to the expected levels (75%) will require a substantial increase in screening asymptomatic populations, which is anticipated to become very costly as CD prevalence decreases. Further modelling work includes refining and extending mathematical models (including transmission dynamics and statistical frameworks) to predict transmission at a sub-national scale, and developing quantitative tools to inform IDTI certification, post-certification and re-certification protocols. Potential perverse incentives associated with operational thresholds are discussed. These modelling insights aim to inform discussions on the goals and treatment guidelines for CD.

Antiparasitic effect of (-)-α-bisabolol against Trypanosoma cruzi Y strain forms

Chagas disease is caused by Trypanosoma cruzi and affects about 7 million people worldwide. Benznidazole and nifurtimox have low efficacy and high toxicity. The present study was designed to identify the trypanocidal effect of (-)-α-Bisabolol (BIS) and investigate its mechanism. Epimastigotes and trypomastigotes were cultured with BIS and the viable cells were counted. BIS antiamastigote effect was evaluated using infected LLC-MK2 cells. MTT assay was performed to evaluate BIS cytotoxicity. Growth recovery was assessed to evaluate BIS effect after short times of exposure. BIS mechanism was investigated through flow cytometry, with 7-AAD and Annexin V-PE. DCFH-DA, rhodamine 123 (Rho123) and acridine orange (AO). Finally, enzymatic and computational assays were performed to identify BIS interaction with T. cruzi GAPDH (tcGAPDH). BIS showed an inhibitory effect on epimastigotes after all tested periods, as well on trypomastigotes. It caused cytotoxicity on LLC-MK2 cells at higher concentrations, with selectivity index (SeI) = 26.5. After treatment, infected cells showed a decrease in infected cells, the number of amastigotes per infected cell and the survival index (SuI). Growth recovery demonstrated that BIS effect causes rapid death of T. cruzi. Flow cytometry showed that BIS biological effect is associated with apoptosis induction, increase in cytoplasmic ROS and mitochondrial transmembrane potential, while reservosome swelling was observed at a late stage. Also, BIS action mechanism may be associated to tcGAPDH inhibition. Altogether, the results demonstrate that BIS causes cell death in Trypanosoma cruzi Y strain forms, with the involvement of apoptosis and oxidative stress and enzymatic inhibition.

Chagas disease as example of a reemerging parasite

Trypanosoma cruzi, the protozoan that causes Chagas disease, is primarily transmitted by three main Triatomine vectors in endemic areas. However, the infection has become a potential emerging disease because the vector is found in non-endemic areas, there is migration of infected asymptomatic people that can infect the vector, become blood donors, or pass the disease vertically (congenital infections). Lastly, the disease can be acquired through contaminated food (oral transmission). This review will present the different transmission pathways, clinical manifestations, diagnostic modalities and treatment considerations of Chagas disease.

Repeated cross-sectional study of Trypanosoma cruzi in shelter dogs in Texas, in the context of Dirofilaria immitis and tick-borne pathogen prevalence

BACKGROUND

Vector-borne diseases have an adverse impact on health of dogs, and infected dogs can be sentinels for human infection. Infection with Trypanosoma cruzi, an agent of Chagas disease, causes fatal heart disease in dogs across the southern United States but has been neglected from wide-scale prevalence studies.

OBJECTIVES

To determine the prevalence of exposure to T. cruzi, Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi, and infection with Dirofilaria immitis among dogs in shelters across Texas and to identify risk factors for T. cruzi seropositivity.

ANIMALS

Six hundred and eight dogs.

METHODS

This repeated cross-sectional study was performed by collecting blood from ~30 dogs during each of the 3 visits to 7 shelters. We tested serum for antibodies to T. cruzi using 2 tests in series and for antibodies to Ehrlichia spp., Anaplasma spp., and B. burgdorferi and D. immitis antigen using the IDEXX SNAP 4DX Plus point-of-care test. DNA was extracted from blood clots and tested for T. cruzi DNA and strain type via quantitative polymerase chain reactions (qPCR). We used logistic regression to assess risk factors.

RESULTS

One hundred ten (18.1%) of 608 dogs were seropositive for T. cruzi. Prevalence of exposure to the other vector-borne agents was: Ehrlichia spp. 3.6%; Anaplasma spp. 6.9%; B. burgdorferi 0.2%; and D. immitis infection 16.0%. Six of 559 (1.1%) dogs were qPCR-positive for T. cruzi.

CONCLUSIONS AND CLINICAL IMPORTANCE

T. cruzi seroprevalence was comparable to D. immitis prevalence and higher than seroprevalence of the tick-borne pathogens. T. cruzi is an underrecognized health threat to dogs across Texas and possibly other southern states where triatomine vectors are endemic.

Motility-based label-free detection of parasites in bodily fluids using holographic speckle analysis and deep learning

Parasitic infections constitute a major global public health issue. Existing screening methods that are based on manual microscopic examination often struggle to provide sufficient volumetric throughput and sensitivity to facilitate early diagnosis. Here, we demonstrate a motility-based label-free computational imaging platform to rapidly detect motile parasites in optically dense bodily fluids by utilizing the locomotion of the parasites as a specific biomarker and endogenous contrast mechanism. Based on this principle, a cost-effective and mobile instrument, which rapidly screens ~3.2 mL of fluid sample in three dimensions, was built to automatically detect and count motile microorganisms using their holographic time-lapse speckle patterns. We demonstrate the capabilities of our platform by detecting trypanosomes, which are motile protozoan parasites, with various species that cause deadly diseases affecting millions of people worldwide. Using a holographic speckle analysis algorithm combined with deep learning-based classification, we demonstrate sensitive and label-free detection of trypanosomes within spiked whole blood and artificial cerebrospinal fluid (CSF) samples, achieving a limit of detection of ten trypanosomes per mL of whole blood (~five-fold better than the current state-of-the-art parasitological method) and three trypanosomes per mL of CSF. We further demonstrate that this platform can be applied to detect other motile parasites by imaging Trichomonas vaginalis, the causative agent of trichomoniasis, which affects 275 million people worldwide. With its cost-effective, portable design and rapid screening time, this unique platform has the potential to be applied for sensitive and timely diagnosis of neglected tropical diseases caused by motile parasites and other parasitic infections in resource-limited regions.

A scoping review on the field validation and implementation of rapid diagnostic tests for vector-borne and other infectious diseases of poverty in urban areas

BACKGROUND

Health personnel face challenges in diagnosing vector-borne and other diseases of poverty in urban settings. There is a need to know what rapid diagnostic technologies are available, have been properly assessed, and are being implemented to improve control of these diseases in the urban context. This paper characterizes evidence on the field validation and implementation in urban areas of rapid diagnostics for vector-borne diseases and other diseases of poverty.

MAIN BODY

A scoping review was conducted. Peer-reviewed and grey literature were searched using terms describing the targeted infectious diseases, diagnostics evaluations, rapid tests, and urban setting. The review was limited to studies published between 2000 and 2016 in English, Spanish, French, and Portuguese. Inclusion and exclusion criteria were refined post hoc to identify relevant literature regardless of study design and geography. A total of 179 documents of the 7806 initially screened were included in the analysis. Malaria (n = 100) and tuberculosis (n = 47) accounted for the majority of studies that reported diagnostics performance, impact, and implementation outcomes. Fewer studies, assessing mainly performance, were identified for visceral leishmaniasis (n = 9), filariasis and leptospirosis (each n = 5), enteric fever and schistosomiasis (each n = 3), dengue and leprosy (each n = 2), and Chagas disease, human African trypanosomiasis, and cholera (each n = 1). Reported sensitivity of rapid tests was variable depending on several factors. Overall, specificities were high (> 80%), except for schistosomiasis and cholera. Impact and implementation outcomes, mainly acceptability and cost, followed by adoption, feasibility, and sustainability of rapid tests are being evaluated in the field. Challenges to implementing rapid tests range from cultural to technical and administrative issues.

CONCLUSIONS

Rapid diagnostic tests for vector-borne and other diseases of poverty are being used in the urban context with demonstrated impact on case detection. However, most evidence comes from malaria rapid diagnostics, with variable results. While rapid tests for tuberculosis and visceral leishmaniasis require further implementation studies, more evidence on performance of current tests or development of new alternatives is needed for dengue, Chagas disease, filariasis, leptospirosis, enteric fever, human African trypanosomiasis, schistosomiasis and cholera.

The challenge of discordant serology in Chagas disease: The role of two confirmatory techniques in inconclusive cases

Serodiscordance in Chagas disease (CD) remains a challenge since individuals with inconclusive results are clinically complicated to manage. This work, conducted outside the endemic area, aims to compare two different confirmatory techniques for the diagnosis of CD in individuals without a definitive diagnosis, to analyze the performance of the screening techniques in this group of patients, and to describe the serological follow-up of these subjects over time. Sera from 48 individuals with repeatedly discordant results by one recombinant enzyme immunoassay (r-ELISA) and one native ELISA (n-ELISA), were included in the study. Confirmatory procedures were performed through TESA-blot, using trypomastigote antigens of Trypanosoma cruzi, and in-house WB (IH-WB) using a lysate from T. cruzi epimastigotes. Of the 48 sera, TESA-blot confirmed 22 (45.8%) cases and IH-WB 17 (35.4%). Both techniques showed a substantial agreement (k = 0.604). Confirmation defined as the positivity of one of the ELISA and at least one of the confirmatory tests was reached in 24/48 (50%) cases. We found a great dispersion of r-ELISA index values, especially among individuals with confirmatory negative results, ranging from 0.03-6.2. Additionally, n-ELISA yielded a better performance than r-ELISA in this cohort of patients, showing a significantly greater agreement with the confirmatory methods. Our results indicate that either confirmatory test could be an efficient tool to solve inconclusive cases regardless of which form of the parasite's life cycle they use. Also, most individuals remain with discordant serology throughout the short-term follow-up period time of study. Finally, we consider that it is necessary to establish a reference test feasible and commercialized in all areas to solve the problem of inconclusive results.

Trypanosoma cruzi genetic diversity: Something new for something known about Chagas disease manifestations, serodiagnosis and drug sensitivity

The genetic diversity of Trypanosoma cruzi, the protozoan agent of Chagas disease, is widely recognized. At present, T. cruzi is partitioned into seven discrete typing units (DTUs), TcI-TcVI and Tcbat. This article reviews the present knowledge on the parasite population structure, the evolutionary relationships among DTUs and their distinct, but not exclusive ecological and epidemiological associations. Different models for the origin of hybrid DTUs are examined, which agree that genetic exchange among T. cruzi populations is frequent and has contributed to the present parasite population structure. The geographic distribution of the prevalent DTUs in humans from the southern United States to Argentina is here presented and the circumstantial evidence of a possible association between T. cruzi genotype and Chagas disease manifestations is discussed. The available information suggests that parasite strains detected in patients, regardless of the clinical presentation, reflect the principal DTU circulating in the domestic transmission cycles of a particular region. In contrast, in several orally transmitted outbreaks, sylvatic strains are implicated. As a consequence of the genotypic and phenotypic differences of T. cruzi strains and the differential geographic distribution of DTUs in humans, regional variations in the sensitivity of the serological tests are verified. The natural resistance to benznidazole and nifurtimox, verified in vivo and in vitro for some parasite stocks, is not associated with any particular DTU, and does not explain the marked difference in the anti-parasitic efficacy of both drugs in the acute and chronic phases of Chagas disease. Throughout this review, it is emphasized that the interplay between parasite and host genetics should have an important role in the definition of Chagas disease pathogenesis, anti-T. cruzi immune response and chemotherapy outcome and should be considered in future investigations.

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.

Next-generation ELISA diagnostic assay for Chagas Disease based on the combination of short peptidic epitopes

Chagas Disease, caused by the protozoan Trypanosoma cruzi, is a major health and economic problem in Latin America for which no vaccine or appropriate drugs for large-scale public health interventions are yet available. Accurate diagnosis is essential for the early identification and follow up of vector-borne cases and to prevent transmission of the disease by way of blood transfusions and organ transplantation. Diagnosis is routinely performed using serological methods, some of which require the production of parasite lysates, parasite antigenic fractions or purified recombinant antigens. Although available serological tests give satisfactory results, the production of reliable reagents remains laborious and expensive. Short peptides spanning linear B-cell epitopes have proven ideal serodiagnostic reagents in a wide range of diseases. Recently, we have conducted a large-scale screening of T. cruzi linear B-cell epitopes using high-density peptide chips, leading to the identification of several hundred novel sequence signatures associated to chronic Chagas Disease. Here, we performed a serological assessment of 27 selected epitopes and of their use in a novel multipeptide-based diagnostic method. A combination of 7 of these peptides were finally evaluated in ELISA format against a panel of 199 sera samples (Chagas-positive and negative, including sera from Leishmaniasis-positive subjects). The multipeptide formulation displayed a high diagnostic performance, with a sensitivity of 96.3% and a specificity of 99.15%. Therefore, the use of synthetic peptides as diagnostic tools are an attractive alternative in Chagas’ disease diagnosis.

Chagas disease, caused by the parasite Trypanosoma cruzi, is a life-long and debilitating illness of major significance throughout Latin America, and an emergent threat to global public health. Diagnostic tests are key tools to support disease surveillance, and to ultimately help stop transmission of the parasite. However currently available diagnostic methods have several limitations. Identification of novel biomarkers with improved diagnostic characteristics is a main priority. Recently, we conducted a large-scale screening looking for new T. cruzi antigens using short peptides displayed on a solid support at high-density. This led to the identification of several hundred novel antigenic epitopes. In this work we validated the serodiagnostic performance of 27 of these against an extended panel of human serum samples. Based on this analysis, we developed a proof-of-principle multiplex diagnostic kit by combining different validated reactive peptides. Overall, our data support the applicability of high-density peptide microarrays for the rapid identification and mapping epitopes that could be readily translated into novel and useful tools for diagnosis of Chagas disease.

Prevalence and Seroprevalence of Trypanosoma cruzi Infection in a Military Population in Texas

Recent biosurveillance findings at Joint Base San Antonio (JBSA), a large military installation located in south-central Texas, indicate the potential for vector-borne human Chagas disease. A cross-sectional study was conducted to determine the prevalence and seroprevalence of Trypanosoma cruzi infection in highest risk subpopulations on the installation, including students and instructors who work and sleep in triatomine-endemic field settings. Real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and indirect immunofluorescent antibody assay were performed on enrolled subjects (N = 1,033), none of whom tested positive for T. cruzi or anti-T. cruzi antibodies. Current countermeasures used during field training on JBSA appear to be sufficient for preventing autochthonous human Chagas disease.

Trypanosoma cruzi (Agent of Chagas Disease) in Sympatric Human and Dog Populations in "Colonias" of the Lower Rio Grande Valley of Texas

AbstractThe zoonotic, vector-borne parasite Trypanosoma cruzi causes Chagas disease throughout the Americas, but human and veterinary health burdens in the United States are unknown. We conducted a cross-sectional prevalence study in indigent, medically underserved human and cohabiting canine populations of seven south Texas border communities, known as colonias. Defining positivity as those samples that were positive on two or more independent tests, we found 1.3% seroprevalence in 233 humans, including one child born in the United States with only short-duration travel to Mexico. Additionally, a single child with no travel outside south Texas was positive on only a single test. Among 209 dogs, seroprevalence was 19.6%, but adjusted to 31.6% when including those dogs positive on only one test and extrapolating potential false negatives. Parasite DNA was detected in five dogs, indicating potential parasitemia. Seropositive dogs lived in all sampled colonias with no difference in odds of positivity across age, sex, or breed. Colonia residents collected two adult Triatoma gerstaeckeri and one nymph triatomine from around their homes; one of three bugs was infected with T. cruzi, and blood meal hosts were molecularly determined to include dog, human, and raccoon. Dogs and the infected vector all harbored T. cruzi discrete typing unit I, which has previously been implicated in human disease in the United States. Colonias harbor active T. cruzi transmission cycles and should be a priority in outreach and vector control initiatives.

Virus-like Particle Display of the α-Gal Epitope for the Diagnostic Assessment of Chagas Disease

The α-Gal antigen [Galα(1,3)Galβ(1,4)GlcNAcα] is an immunodominant epitope displayed by infective trypomastigote forms of Trypanosoma cruzi, the causative agent of Chagas disease. A virus-like particle displaying a high density of α-Gal was found to be a superior reagent for the ELISA-based serological diagnosis of Chagas disease and the assessment of treatment effectiveness. A panel of sera from patients chronically infected with T. cruzi, both untreated and benznidazole-treated, was compared with sera from patients with leishmaniasis and from healthy donors. The nanoparticle-α-Gal construct allowed for perfect discrimination between Chagas patients and the others, avoiding false negative and false positive results obtained with current state-of-the-art reagents. As previously reported with purified α-Gal-containing glycosylphosphatidylinositol-anchored mucins, the current study also showed concentrations of anti-α-Gal IgG to decrease substantially in patients receiving treatment with benznidazole, suggesting that the semiquantitative assessment of serum levels of this highly abundant type of antibody can report on disease status in individual patients.

Molecular Diagnosis of Chagas Disease in Colombia: Parasitic Loads and Discrete Typing Units in Patients from Acute and Chronic Phases

BACKGROUND

The diagnosis of Chagas disease is complex due to the dynamics of parasitemia in the clinical phases of the disease. The molecular tests have been considered promissory because they detect the parasite in all clinical phases. Trypanosoma cruzi presents significant genetic variability and is classified into six Discrete Typing Units TcI-TcVI (DTUs) with the emergence of foreseen genotypes within TcI as TcIDom and TcI Sylvatic. The objective of this study was to determine the operating characteristics of molecular tests (conventional and Real Time PCR) for the detection of T. cruzi DNA, parasitic loads and DTUs in a large cohort of Colombian patients from acute and chronic phases.

METHODOLOGY/PRINCIPAL FINDINGS

Samples were obtained from 708 patients in all clinical phases. Standard diagnosis (direct and serological tests) and molecular tests (conventional PCR and quantitative PCR) targeting the nuclear satellite DNA region. The genotyping was performed by PCR using the intergenic region of the mini-exon gene, the 24Sa, 18S and A10 regions. The operating capabilities showed that performance of qPCR was higher compared to cPCR. Likewise, the performance of qPCR was significantly higher in acute phase compared with chronic phase. The median parasitic loads detected were 4.69 and 1.33 parasite equivalents/mL for acute and chronic phases. The main DTU identified was TcI (74.2%). TcIDom genotype was significantly more frequent in chronic phase compared to acute phase (82.1% vs 16.6%). The median parasitic load for TcIDom was significantly higher compared with TcI Sylvatic in chronic phase (2.58 vs.0.75 parasite equivalents/ml).

CONCLUSIONS/SIGNIFICANCE

The molecular tests are a precise tool to complement the standard diagnosis of Chagas disease, specifically in acute phase showing high discriminative power. However, it is necessary to improve the sensitivity of molecular tests in chronic phase. The frequency and parasitemia of TcIDom genotype in chronic patients highlight its possible relationship to the chronicity of the disease.

Chagas Disease: A Solvable Problem, Ignored

Chagas disease is the highest impact parasitic disease in the Americas, yet remains virtually unknown and untreated, despite the fact that the infection is curable and the global problem of Chagas disease is manageable. The causes of this situation and how it can be changed are the focus of this communication.

Molecular mechanisms of myocarditis caused by Trypanosoma cruzi

PURPOSE OF REVIEW

American trypanosomiasis, or Chagas disease, is a lifelong and persistent infection caused by the protozoan Trypanosoma cruzi and is the most significant cause of morbidity and mortality in South and Central America. Owing to immigration and additional risks from blood transfusion and organ transplantation, the number of reported cases of Chagas disease has increased recently in Europe and the USA. The disease is caused by a moderate to intense lasting inflammatory response that triggers local expression of inflammatory mediators and activates and recruits leukocytes to various tissues to eliminate the parasites.

RECENT FINDINGS

This long-term inflammatory process triggers biochemical, physiological and morphological alterations and clinical changes in the digestive, nervous and cardiac (e.g. myocarditis, arrhythmias, congestive heart failure, autonomic dysfunctions and microcirculatory disturbances) systems. Indeed, the pathogenesis of Chagas disease is intricate and multifactorial, and the roles of the parasite and the immune response in initiating and maintaining the disease are still controversial.

SUMMARY

In this review, we discuss the current knowledge of 'strategies' employed by the parasite to persist in the host and host defence mechanisms against Trypanosoma cruzi infection, which can result in equilibrium (absence of the disease) or disease development, mainly in the cardiac systems.

Sensing parasites: Proteomic and advanced bio-detection alternatives

Parasitic diseases have a great impact in human and animal health. The gold standard for the diagnosis of the majority of parasitic infections is still conventional microscopy, which presents important limitations in terms of sensitivity and specificity and commonly requires highly trained technicians. More accurate molecular-based diagnostic tools are needed for the implementation of early detection, effective treatments and massive screenings with high-throughput capacities. In this respect, sensitive and affordable devices could greatly impact on sustainable control programmes which exist against parasitic diseases, especially in low income settings. Proteomics and nanotechnology approaches are valuable tools for sensing pathogens and host alteration signatures within microfluidic detection platforms. These new devices might provide novel solutions to fight parasitic diseases. Newly described specific parasite derived products with immune-modulatory properties have been postulated as the best candidates for the early and accurate detection of parasitic infections as well as for the blockage of parasite development. This review provides the most recent methodological and technological advances with great potential for bio-sensing parasites in their hosts, showing the newest opportunities offered by modern "-omics" and platforms for parasite detection and control.

Commercial enzyme-linked immunosorbent assay versuspolymerase chain reaction for the diagnosis of chronic Chagas disease: a systematic review and meta-analysis

Chronic Chagas disease diagnosis relies on laboratory tests due to its clinical characteristics. The aim of this research was to review commercial enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) diagnostic test performance. Performance of commercial ELISA or PCR for the diagnosis of chronic Chagas disease were systematically searched in PubMed, Scopus, Embase, ISI Web, and LILACS through the bibliography from 1980-2014 and by contact with the manufacturers. The risk of bias was assessed with QUADAS-2. Heterogeneity was estimated with the I2 statistic. Accuracies provided by the manufacturers usually overestimate the accuracy provided by academia. The risk of bias is high in most tests and in most QUADAS dimensions. Heterogeneity is high in either sensitivity, specificity, or both. The evidence regarding commercial ELISA and ELISA-rec sensitivity and specificity indicates that there is overestimation. The current recommendation to use two simultaneous serological tests can be supported by the risk of bias analysis and the amount of heterogeneity but not by the observed accuracies. The usefulness of PCR tests are debatable and health care providers should not order them on a routine basis. PCR may be used in selected cases due to its potential to detect seronegative subjects.

Highly discordant serology against Trypanosoma cruzi in central Veracruz, Mexico: role of the antigen used for diagnostic

Background

Chagas disease is a parasitic disease caused by the protozoan parasite Trypanosoma cruzi. In Mexico, the burden of the disease is difficult to estimate and improving surveillance for Chagas disease is an important priority. We aimed here at determining the seroprevalence of T. cruzi infection in humans in a rural community in Veracruz.

Methods

Serum samples (196) were analyzed for T. cruzi infection using five enzyme-linked immunosorbent assay (ELISA) tests: two in-house tests based on crude parasite extract and three commercial ELISA kits. Because of highly discordant results, we further explored the importance of parasite antigens and strains by western-blot analysis.

Results

A total of 74 samples (37.7 %) were reactive with at least one ELISA, but discordance among tests was very high. The best agreement was between Chagatest recombinant and Chagatek ELISA (Kappa index = 0.798). The agreement between other combinations of tests ranged from 0.038 to 0.518. Discordant samples were confirmed by western-blot analysis using up to nine parasite strains, giving a seroprevalence of 33.7 %.

Conclusions

Commercial tests had a very limited ability to detect T. cruzi infection in the study population. In-house tests based on crude parasite antigens showed a greater sensitivity but were still unable to detect all cases of T. cruzi infection, even when based on a local parasite strain. The high seroprevalence confirmed the hyper-endemicity of T. cruzi infection in the region. Reliable epidemiological surveillance of Chagas disease will require the development of improved diagnostic tests.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1072-2) contains supplementary material, which is available to authorized users.

Old and new challenges in Chagas disease

Chagas disease, caused by the parasite Trypanosoma cruzi, is a neglected disease, which can lead to cardiomyopathy, arrhythmias, megaviscera, and more rarely, polyneuropathy in up to 30-40% of patients around 20 to 30 years after acute infection. Although it is endemic in the Americas, global population movements mean that it can be located wherever migrants from endemic areas settle. The disease was first described 100 years ago and still challenges clinicians worldwide, since diagnostic, therapeutic, and prognostic methods remain insufficient. Furthermore, factors such as HIV co-infection, immunosuppressive drugs, transplantation, and neoplastic disease can alter the natural course of the infection. We present the case of a Bolivian woman with chronic T cruzi infection diagnosed at our clinic in Madrid, Spain, who subsequently developed non-Hodgkin lymphoma. Our report illustrates the challenges of an increasingly common infection seen in non-endemic countries, and highlights both daily management dilemmas and associated difficulties that arise.

Hispano-Americans in Europe: what do we know about their health status and determinants? A scoping review

Background

Policy makers and health practitioners are in need of guidance to respond to the growing geographic mobility of Hispano-American migrants in Europe. Drawing from contributions from epidemiology, social sciences, demography, psychology, psychiatry and economy, this scoping review provides an up-to-date and comprehensive synthesis of studies addressing the health status and determinants of this population. We describe major research gaps and suggest specific avenues of further inquiry.

Methods

We identified systematically papers that addressed the concepts “health” and “Hispano Americans” indexed in five data bases from Jan 1990 to May 2014 with no language restrictions. We screened the 4,464 citations retrieved against exclusion criteria and classified 193 selected references in 12 thematic folders with the aid of the reference management software ENDNOTE X6. After reviewing the full text of all papers we extracted relevant data systematically into a table template to facilitate the synthesising process.

Results

Most studies focused on a particular disease, leaving unexplored the interlinkages between different health conditions and how these relate to legislative, health services, environmental, occupational, and other health determinants. We elucidated some consistent results but there were many heterogeneous findings and several popular beliefs were not fully supported by empirical evidence. Few studies adopted a trans-national perspective and many consisted of cross-sectional descriptions that considered “Hispano-Americans” as a homogeneous category, limiting our analysis. Our results are also constrained by the availability and varying quality of studies reviewed.

Conclusions

Burgeoning research has produced some consistent findings but there are huge gaps in knowledge. To prevent unhelpful generalisations we need a more holistic and nuanced understanding of how mobility, ethnicity, income, gender, legislative status, employment status, working conditions, neighbourhood characteristics and social status intersect with demographic variables and policy contexts to influence the health of the diverse Hispano-American populations present in Europe.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-1799-x) contains supplementary material, which is available to authorized users.

Interruption of vector transmission by native vectors and "the art of the possible"

In a recent article in the Reader’s Opinion, advantages and disadvantages of the certification processes of interrupted Chagas disease transmission (American trypanosomiasis) by native vector were discussed. Such concept, accepted by those authors for the case of endemic situations with introduced vectors, has been built on a long and laborious process by endemic countries and Subregional Initiatives for Prevention, Control and Treatment of Chagas, with Technical Secretariat of the Pan American Health Organization/World Health Organization, to create a horizon target and goal to concentrate priorities and resource allocation and actions. With varying degrees of sucess, which are not replaceable for a certificate of good practice, has allowed during 23 years to safeguard the effective control of transmission of Trypanosoma cruzi not to hundreds of thousands, but millions of people at risk conditions, truly “the art of the possible.”

Mapping antigenic motifs in the trypomastigote small surface antigen from Trypanosoma cruzi

The trypomastigote small surface antigen (TSSA) is a mucin-like molecule from Trypanosoma cruzi, the etiological agent of Chagas disease, which displays amino acid polymorphisms in parasite isolates. TSSA expression is restricted to the surface of infective cell-derived trypomastigotes, where it functions as an adhesin and engages surface receptors on the host cell as a prerequisite for parasite internalization. Previous results have established TSSA-CL, the isoform encoded by the CL Brener clone, as an appealing candidate for use in serology-based diagnostics for Chagas disease. Here, we used a combination of peptide- and recombinant protein-based tools to map the antigenic structure of TSSA-CL at maximal resolution. Our results indicate the presence of different partially overlapping B-cell epitopes clustering in the central portion of TSSA-CL, which contains most of the polymorphisms found in parasite isolates. Based on these results, we assessed the serodiagnostic performance of a 21-amino-acid-long peptide that spans TSSA-CL major antigenic determinants, which was similar to the performance of the previously validated glutathione S-transferase (GST)-TSSA-CL fusion molecule. Furthermore, the tools developed for the antigenic characterization of the TSSA antigen were also used to explore other potential diagnostic applications of the anti-TSSA humoral response in Chagasic patients. Overall, our present results provide additional insights into the antigenic structure of TSSA-CL and support this molecule as an excellent target for molecular intervention in Chagas disease.

Diagnostic reliability of an immunochromatographic test for Chagas disease screening at a primary health care centre in a rural endemic area

Many patients with Chagas disease live in remote communities that lack both equipment and trained personnel to perform a diagnosis by conventional serology (CS). Thus, reliable tests suitable for use under difficult conditions are required. In this study, we evaluated the ability of personnel with and without laboratory skills to perform immunochromatographic (IC) tests to detect Chagas disease at a primary health care centre (PHCC). We examined whole blood samples from 241 patients and serum samples from 238 patients. Then, we calculated the percentage of overall agreement (POA) between the two groups of operators for the sensitivity (S), specificity (Sp) and positive (PPV) and negative (NPV) predictive values of IC tests compared to CS tests. We also evaluated the level of agreement between ELISAs and indirect haemagglutination (IHA) tests. The readings of the IC test results showed 100% agreement (POA = 1). The IC test on whole blood showed the following values: S = 87.3%; Sp = 98.8%; PPV = 96.9% and NPV = 95.9%. Additionally, the IC test on serum displayed the following results: S = 95.7%; Sp = 100%; PPV = 100% and NPV = 98.2%. Using whole blood, the agreement with ELISA was 96.3% and the agreement with IHA was 94.1%. Using serum, the agreement with ELISA was 97.8% and the agreement with IHA was 96.6%. The IC test performance with serum samples was excellent and demonstrated its usefulness in a PHCC with minimal equipment. If the IC test S value and NPV with whole blood are improved, then this test could also be used in areas lacking laboratories or specialised personnel.

Emerging and reemerging neglected tropical diseases: a review of key characteristics, risk factors, and the policy and innovation environment

In global health, critical challenges have arisen from infectious diseases, including the emergence and reemergence of old and new infectious diseases. Emergence and reemergence are accelerated by rapid human development, including numerous changes in demographics, populations, and the environment. This has also led to zoonoses in the changing human-animal ecosystem, which are impacted by a growing globalized society where pathogens do not recognize geopolitical borders. Within this context, neglected tropical infectious diseases have historically lacked adequate attention in international public health efforts, leading to insufficient prevention and treatment options. This subset of 17 infectious tropical diseases disproportionately impacts the world's poorest, represents a significant and underappreciated global disease burden, and is a major barrier to development efforts to alleviate poverty and improve human health. Neglected tropical diseases that are also categorized as emerging or reemerging infectious diseases are an even more serious threat and have not been adequately examined or discussed in terms of their unique risk characteristics. This review sets out to identify emerging and reemerging neglected tropical diseases and explore the policy and innovation environment that could hamper or enable control efforts. Through this examination, we hope to raise awareness and guide potential approaches to addressing this global health concern.