Validation of a rapid and reliable test for diagnosis of chagas' disease by detection of Trypanosoma cruzi-specific antibodies in blood of donors and patients in Central America

Practical diagnostic algorithms for Chagas disease: a focus on low resource settings

INTRODUCTION

Chagas disease, caused by parasite Trypanosoma cruzi, is the most important neglected tropical disease in the Americas. Two drugs are available for treatment, but access to them is challenging, in part due to complex diagnostic algorithms. These are stage-dependent, involve multiple tests, and are ill-adapted to the reality of vast areas where the disease is endemic. Molecular and serologic tools are used to detect acute and chronic infections, with the performance of the latter showing geographic differences. Breakthroughs in the development of new diagnostic tools include the validation of a loop-mediated isothermal amplification assay for acute infections (T. cruzi-LAMP), and the regional validation of several rapid diagnostic tests (RDTs) for chronic infection, which simplify testing in resource-limited settings. The literature search was carried out in the MEDLINE database until 1 August 2023.

AREAS COVERED

This review outlines existing algorithms, and proposes new ones focused on point-of-care testing.

EXPERT OPINION

Integrating point-of-care testing into existing diagnostic algorithms in certain endemic areas will increase access to timely diagnosis and treatment. However, additional research is needed to validate the use of these techniques across a wider geography, and to better understand the cost-effectiveness of their large-scale implementation.

Trypanosome Infections and Anemia in Cattle Returning from Transhumance in Tsetse-Infested Areas of Cameroon

The objective of this work was to assess the anemic status and the use of an immunological test and PCR-based methods to determine the infection rates of trypanosomes species. Transhumance aims to provide cattle with greener pastures and greater water resources than in the Djerem region during the dry season. Two criteria were used to assess the health status of the animals, the prevalence of trypanosomiasis and the level of anemia. In addition, we have evaluated the effectiveness, in trypanosomiasis detection, of the Very Diag Kit (CEVA Santé animale), a Rapid diagnosis test (RDT) based on immunological identification of T. congolense s.l. and T. vivax, responsible for AAT. Four trypanosome species (Trypanosoma congolense savannah type (Tcs), T. congolense forest type (Tcf), T. brucei s.l. (Tbr) and T. vivax (Tvx)) were identified in cattle sampled in four villages. The overall infection rate determined by PCR (68.6%) was much higher than those generally reported in cattle from the Adamawa region (35 to 50%). Infections (including mixed infections) by Tc s.l. (Tcs + Tcf) were predominant (45.7%). The infection rates were also determined using the Very Diag Kit allowing us to identify Tc s.l. and Tvx in the field in less than 20 min. This method provided, for the global infection, a higher rate (76.5%) than that determined by PCR (68.6%), although it is supposed to be less sensitive than PCR. Tc s.l. infection rate (37.8%) was similar to that (38.8%) determined by PCR (Tcs + Tcf single infections). In contrast, the prevalence of Tvx single infections measured by RDT (18%) was nearly two-fold higher than that (9.4%) measured by PCR. Thus, further comparative analyses seem to be needed in order to more accurately assess the sensitivity and specificity of the Very Diag test under our conditions of use on blood samples. The mean PCVs in trypanosome-infected as well as in uninfected cattle were below 25%, the threshold below which an animal is considered anemic. Our study shows that cattle return from transhumance in poor health. It raises questions about its real benefit, especially since the herds are themselves likely to become vectors of trypanosomiasis and possibly of other diseases. At least, effective measures have to be undertaken to treat all cattle coming back from transhumance.

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.

Diagnosing point-of-care diagnostics for neglected tropical diseases

Inadequate and nonintegrated diagnostics are the Achilles' heel of global efforts to monitor, control, and eradicate neglected tropical diseases (NTDs). While treatment is often available, NTDs are endemic among marginalized populations, due to the unavailability or inadequacy of diagnostic tests that cause empirical misdiagnoses. The need of the hour is early diagnosis at the point-of-care (PoC) of NTD patients. Here, we review the status quo of PoC diagnostic tests and practices for all of the 24 NTDs identified in the World Health Organization's (WHO) 2021-2030 roadmap, based on their different diagnostic requirements. We discuss the capabilities and shortcomings of current diagnostic tests, identify diagnostic needs, and formulate prerequisites of relevant PoC tests. Next to technical requirements, we stress the importance of availability and awareness programs for establishing PoC tests that fit endemic resource-limited settings. Better understanding of NTD diagnostics will pave the path for setting realistic goals for healthcare in areas with minimal resources, thereby alleviating the global healthcare burden.

Levels of anti-B13 antibodies over time in a cohort of chronic infected by Trypanosoma cruzi. Its relationship with specific treatment and clinical status

The immunodominant B13 protein of Trypanosoma cruzi is found on the surface of trypomastigotes and exhibits cross-reactivity with the human cardiac myosin heavy chain; for which antibodies against this parasitic antigen may be involved in the development of disease pathology. In a cohort of chronically T. cruzi-infected adults, undergoing trypanocidal treatment, or not, we, therefore, decided to evaluate the levels of anti-B13 antibodies (ELISA-B13) and its eventual relationship with heart complaints. Two hundred twenty-eight serum samples from 76 chronically infected adults with an average follow-up of 24 years were analyzed. Thirty of them had received trypanocidal treatment. Among treated patients, anti-B13 Ab levels in successive samples showed a significant decrease in reactivity as the years after treatment increased (ANOVA test, p = 0.0049). At the end of the follow-up, 36.7% became non-reactive for ELISA B13. Untreated patients did not have significant variations in the level of anti-B13 antibodies during follow-up. None of the treated patients had electrocardiographic changes compatible with chronic chagasic cardiomyopathy, whereas 21.7% of those undergoing no treatment did show such kind of pathological electrocardiogram tracings. ELISA-B13 was reactive in all cases with heart involvement. Among untreated patients, there were no significant differences in anti-B13 antibodies when comparing individuals without proven pathology with those with chronic chagasic cardiomyopathy. Although treatment with trypanocidal drugs was followed by decreased anti-B13 antibody levels, such assessment was unhelpful in differentiating the evolution of chronic chagasic heart disease.

Evaluation of 2 Lateral Flow Rapid Tests in the Diagnosis of Chagas Disease in the Washington Metropolitan Area

We compared the accuracy of the Stat-Pak and Chagas Detect Plus with a latent class analysis. Sensitivity values of 89.7% and 91.9% and specificities of 97.1% and 80.3%, respectively, were seen in the serodiagnosis of Chagas disease in Hispanic immigrants, revealing the limitations of these tests in diverse populations.

Assessing Trypanosoma cruzi Parasite Diversity through Comparative Genomics: Implications for Disease Epidemiology and Diagnostics

Chagas disease is an important vector-borne neglected tropical disease that causes great health and economic losses. The etiological agent, Trypanosoma cruzi, is a protozoan parasite endemic to the Americas, comprised by important diversity, which has been suggested to contribute to poor serological diagnostic performance. Current nomenclature describes seven discrete typing units (DTUs), or lineages. We performed the first large scale analysis of T. cruzi diversity among 52 previously published genomes from strains covering multiple countries and parasite DTUs and assessed how different markers summarize this genetic diversity. We also examined how seven antigens currently used in commercial serologic tests are conserved across this diversity of strains. DTU structuration was confirmed at the whole-genome level, with evidence of sub-DTU diversity, associated in part to geographic structuring. We observed very comparable phylogenetic tree topographies for most of the 32 markers investigated, with clear clustering of sequences by DTU, and a few of these markers suggested some degree of intra-lineage diversity. At least three of the currently used antigens represent poorly conserved sequences, with sequences used in tests quite divergent from sequences in many strains. Most markers are well suited for estimating parasite diversity to DTU level, and a few are particularly well-suited to assess intra-DTU diversity. Analysis of antigen sequences across all strains indicates that antigenic diversity is a likely explanation for limited diagnostic performance in Central and North America.

How effective are rapid diagnostic tests for Chagas disease?

Introduction: Diagnosis of chronic Chagas disease relies on the agreement of two conventional serological tests based on distinct antigens. These require cold to preserve reagents and samples, and equipment and trained personnel to run them. Moreover, results turnaround may be delayed for several weeks risking a loss to follow-up of infected subjects, summoning major disadvantages to access diagnosis (and treatment) in many highly endemic areas.Areas covered: Recent studies have shown the versatility of rapid diagnostic tests for the detection of chronic Trypanosoma cruzi infections in referral centers and in field campaigns, with a performance equivalent to that of conventional tools. Remarkably, RDTs do not require cold storage and provide results within an hour. Additionally, they are easy-to-use and can work with a tiny volume of finger-pricked whole blood. Altogether, major advantages toward generalizing their use as an alternative to conventional tests.Expert opinion: Already in 2021, only a small percentage of T. cruzi-infected people are diagnosed and treated. The unsuitability of currently used diagnostics, and of the recommended algorithm, to the conditions found in many regions do not help to fill this gap. RDTs stand as a promising solution, even though geographical validation should precede their implementation.

Rapid Diagnostic Tests for Trypanosoma cruzi Infection: Field Evaluation of Two Registered Kits in a Region of Endemicity and a Region of Nonendemicity in Argentina

Infection by Trypanosoma cruzi (Chagas disease [ChD]) affects around 7 million people in the Americas, most of whom are unaware of their status due to lack of clinical manifestations and poor access to diagnosis. Rapid diagnostic tests (RDTs) are widely used for screening for different infections (HIV, hepatitis B, and syphilis), and their application for ChD would facilitate access to diagnosis, especially in remote areas where health services have scarce resources. We conducted a prospective intervention study in 2018 to evaluate in the field two in vitro RDTs for ChD, authorized by the National Administration of Medicaments, Aliments, and Medical Technologies of Argentina (ANMAT), in areas of endemicity and nonendemicity in Argentina.

Infection by Trypanosoma cruzi (Chagas disease [ChD]) affects around 7 million people in the Americas, most of whom are unaware of their status due to lack of clinical manifestations and poor access to diagnosis. Rapid diagnostic tests (RDTs) are widely used for screening for different infections (HIV, hepatitis B, and syphilis), and their application for ChD would facilitate access to diagnosis, especially in remote areas where health services have scarce resources. We conducted a prospective intervention study in 2018 to evaluate in the field two in vitro RDTs for ChD, authorized by the National Administration of Medicaments, Aliments, and Medical Technologies of Argentina (ANMAT), in areas of endemicity and nonendemicity in Argentina. We recruited 607 volunteers older than 18 years in Salta province and the city of Buenos Aires. The RDTs Ab Standard Diagnostics SD Bioline (SD) and Check Chagas Wiener Lab (WL) were performed in situ with whole-blood samples, and confirmatory serology was done at a reference center. The rate of infection with T. cruzi was 17.8% (108/607). The SD test showed 97.2% sensitivity (95% confidence interval [CI], 93.5 to 100) and 91.7% specificity (95% CI, 96.2 to 99.2%), and the WL test showed 93.4% sensitivity (95% CI, 88.2 to 98.6%) and 99.1% specificity (95% CI, 91.9 to 100%). The sensitivity and specificity for the two RDTs tested were higher than previously reported. These results encourage the use of the tested RDTs in Salta province and for further field studies for the implementation of these RDTs in other epidemiological scenarios. This will be very important to improve access to diagnosis of Chagas and its clinical management as a neglected disease, especially in remote areas with health access barriers.

Development of a New Lateral Flow Assay Based on IBMP-8.1 and IBMP-8.4 Chimeric Antigens to Diagnose Chagas Disease

Despite several available methodologies for Chagas disease (CD) serological screening, the main limitation of chronic CD diagnosis is the lack of effective tools for large-scale screening and point-of-care diagnosis to be used in different CD epidemiological scenarios. Taking into account that developing such a diagnostic tool will significantly improve the ability to identify CD carriers, we aimed at performing a proof-of-concept study (phase I study) to assess the use of these proteins in a point-of-care platform using serum samples from different geographical settings of Brazil and distinct clinical presentations. The diagnostic accuracy study was conducted on a panel of two WHO International Standards (IS) and 14 sera from T. cruzi-positive and 16 from T. cruzi-negative individuals. The results obtained with the test strips were converted to digital images, allowing quantitative comparison expressed as a relative band intensity ratio (RBI). The diagnostic potential and performance were also determined. Regardless of the geographical origin or clinical presentation, all sera with T. cruzi antibodies returned positive both for IBMP-8.1 and IBMP-8.4 chimeric antigens. The area under the ROC curve (AUC) values was 100% for both antigens, demonstrating an outstanding overall diagnostic accuracy (100%). Based on the data, we believe that the lateral flow assays based on these antigens are promising methodologies for screening CD.

Nationwide Exposure of U.S. Working Dogs to the Chagas Disease Parasite, Trypanosoma cruzi

Trypanosoma cruzi is a zoonotic protozoan parasite vectored by triatomine insects that are endemic to the Americas, including the southern United States. Surveillance of domestic dogs for T. cruzi exposure allows for the determination of geographic regions of transmission that are relevant for human and animal health. The U.S. Department of Homeland Security (DHS) working dogs provide critical security and detection services across the country, and many train or work in the southern United States, where they are at risk for T. cruzi exposure. We sampled blood from 1,610 working dogs (predominantly Belgian Malinois, German shepherds, and Labrador retrievers) from six task forces (including the Transportation Security Administration, Customs and Border Protection, Secret Service, and more) and two canine training centers across 41 states from 2015 to 2018. Canine sera that were reactive on at least two independent serological assays were considered positive for anti-T.-cruzi antibodies. In addition, up to three independent polymerase chain reaction (PCR) assays were used to detect and type T. cruzi DNA. Overall seroprevalence was 7.5%, and four dogs (0.25%, n = 1,610) had detectable parasite DNA in the blood, comprising parasite discrete taxonomic units (DTUs) TcIV and a coinfection of TcI/TcIV. Dogs that worked within versus outside of the geographic range of established triatomines showed comparable seroprevalence (7.3% and 9.2%, respectively; P = 0.61). Determining the prevalence of T. cruzi in these working dogs and looking at spatially associated risk factors have practical implications for disease risk management and could assist with improved control measures to protect both animal and human health.

Rapid immunochromatographic tests for the diagnosis of chronic Chagas disease in at-risk populations: A systematic review and meta-analysis

BACKGROUND

Despite of a high disease burden, mainly in Latin America, Chagas disease (CD) is underdiagnosed and undertreated. Rapid diagnostic tests (RDTs) might improve the access to diagnosis. The aim of this study is to review the accuracy of commercially available RDTs used in field conditions for the diagnosis of chronic CD in populations at risk, in endemic and non-endemic countries.

METHODS/PRINCIPAL FINDINGS

We undertook a comprehensive search of the following databases: PubMed, SCOPUS, LILACS (last up-date on the 01st July, 2017), without language or date limits. Non-electronic sources have been also searched. This review included clinical studies with cohort recruitment of individuals at risk of T. cruzi exposure, without age limits; adequate reference standards for the diagnosis of CD. We excluded case-control studies and those testing RDTs during acute CD. Data on test accuracies were pooled through a bivariate random-effects model. Only one index test was evaluated separately. Geographical area, commercial brand, disease prevalence, study size, and risk of bias were explored as possible source of heterogeneity. Values of sensitivity and specificity were computed to obtain summary positive/negative likelihood ratios, and summary diagnostic odds ratio. Ten studies were included on six different immunochromatographic RDTs. The pooled sensitivity and specificity of the RDTs resulted 96.6% (95% CI 91.3-98.7%) and 99.3% (95% CI 98.4-99.7%), respectively. Test accuracy was particularly good in endemic areas (98.07%/99.03% of sensitivity/specificity, respectively). One test (Stat-Pak) showed an overall sensitivity of 97% (95% CI 87.6-99.3) and specificity of 99.4% (95% CI 98.6-99.8).

CONCLUSIONS/SIGNIFICANCE

RDTs demonstrated to be sufficiently accurate to recommend their use for screening in endemic areas, even as stand-alone tests. This approach might increase the accessibility to the diagnosis. However, an additional confirmatory test in case of positive result remains a prudent approach.

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.

Widespread Trypanosoma cruzi infection in government working dogs along the Texas-Mexico border: Discordant serology, parasite genotyping and associated vectors

Background

Chagas disease, caused by the vector-borne protozoan Trypanosoma cruzi, is increasingly recognized in the southern U.S. Government-owned working dogs along the Texas-Mexico border could be at heightened risk due to prolonged exposure outdoors in habitats with high densities of vectors. We quantified working dog exposure to T. cruzi, characterized parasite strains, and analyzed associated triatomine vectors along the Texas-Mexico border.

Methodology/Principle findings

In 2015–2016, we sampled government working dogs in five management areas plus a training center in Texas and collected triatomine vectors from canine environments. Canine serum was tested for anti-T. cruzi antibodies with up to three serological tests including two immunochromatographic assays (Stat-Pak and Trypanosoma Detect) and indirect fluorescent antibody (IFA) test. The buffy coat fraction of blood and vector hindguts were tested for T. cruzi DNA and parasite discrete typing unit was determined. Overall seroprevalence was 7.4 and 18.9% (n = 528) in a conservative versus inclusive analysis, respectively, based on classifying weakly reactive samples as negative versus positive. Canines in two western management areas had 2.6–2.8 (95% CI: 1.0–6.8 p = 0.02–0.04) times greater odds of seropositivity compared to the training center. Parasite DNA was detected in three dogs (0.6%), including TcI and TcI/TcIV mix. Nine of 20 (45%) T. gerstaeckeri and T. rubida were infected with TcI and TcIV; insects analyzed for bloodmeals (n = 11) fed primarily on canine (54.5%).

Conclusions/Significance

Government working dogs have widespread exposure to T. cruzi across the Texas-Mexico border. Interpretation of sample serostatus was challenged by discordant results across testing platforms and very faint serological bands. In the absence of gold standard methodologies, epidemiological studies will benefit from presenting a range of results based on different tests/interpretation criteria to encompass uncertainty. Working dogs are highly trained in security functions and potential loss of duty from the clinical outcomes of infection could affect the work force and have broad consequences.

Chagas disease, a potentially deadly cardiac disease of humans, canines and other mammals is caused by the parasite Trypanosoma cruzi. The parasite is primarily transmitted to dogs by ingestion of infected triatomine ‘kissing bug’ vectors or through contact with the insect’s feces. Previous studies concluded that stray and shelter dogs are at high risk of infection in the southern U.S. We proposed that high-value U.S. government working dogs along the Texas-Mexico border may also be at high risk because of their activities in regions with established, infected vector populations. We sampled 528 working dogs along the Texas-Mexico border, and found that 7.4–18.9% of dogs were positive for T. cruzi antibodies and a small proportion (0.6%) also had parasite circulating in the blood. We collected two species of kissing bugs from the canine environments and used molecular approaches to determine that 45% were positive for T. cruzi and the majority had recently fed on canines. We highlight the need for better diagnostic tools for canine Chagas disease research and diagnosis. The widespread burden of T. cruzi infection in the government working dogs could be associated with far-reaching consequences for both animal and human well-being.

Rapid diagnostic tests duo as alternative to conventional serological assays for conclusive Chagas disease diagnosis

Chagas disease is caused by the parasite Trypanosoma cruzi. It affects several million people, mainly in Latin America, and severe cardiac and/or digestive complications occur in ~30% of the chronically infected patients. Disease acute stage is mostly asymptomatic and infection goes undiagnosed. In the chronic phase direct parasite detection is hampered due to its concealed presence and diagnosis is achieved by serological methods, like ELISA or indirect hemagglutination assays. Agreement in at least two tests must be obtained due to parasite wide antigenic variability. These techniques require equipped labs and trained personnel and are not available in distant regions. As a result, many infected people often remain undiagnosed until it is too late, as the two available chemotherapies show diminished efficacy in the advanced chronic stage. Easy-to-use rapid diagnostic tests have been developed to be implemented in remote areas as an alternative to conventional tests. They do not need electricity, nor cold chain, they can return results within an hour and some even work with whole blood as sample, like Chagas Stat-Pak (ChemBio Inc.) and Chagas Detect Plus (InBIOS Inc.). Nonetheless, in order to qualify a rapidly diagnosed positive patient for treatment, conventional serological confirmation is obligatory, which might risk its start. In this study two rapid tests based on distinct antigen sets were used in parallel as a way to obtain a fast and conclusive Chagas disease diagnosis using whole blood samples. Chagas Stat-Pak and Chagas Detect Plus were validated by comparison with three conventional tests yielding 100% sensitivity and 99.3% specificity over 342 patients seeking Chagas disease diagnosis in a reference centre in Sucre (Bolivia). Combined used of RDTs in distant regions could substitute laborious conventional serology, allowing immediate treatment and favouring better adhesion to it.

Chagas disease is a neglected tropical disease caused by the parasite Trypanosoma cruzi. It affects 6–7 million people, mainly in Latin America. An initial asymptomatic phase make the infection go undiagnosed and untreated, silently progressing into its chronic stage. About 30% of the chronically infected patients end up developing life-threatening disruption of the heart and/or gut tissues. Two drugs are available but their efficacy diminishes the longer a person has been infected. Therefore, it is of paramount importance to achieve an early diagnosis to start treatment before symptoms advance. In the chronic stage parasite presence is intermittent and diagnosis is made by serological assays that detect parasite-specific immunoglobulins. Problem is that conventional serological techniques are laborious and require equipment and trained personnel unavailable in remote regions with high disease prevalence. To circumvent those inconveniences easy-to-use rapid diagnostic tests were developed. They return results within an hour and some work with whole blood as sample allowing diagnosis out of digital puncture. We propose that conventional assays could be substituted by whole blood-friendly rapid tests in order to achieve a conclusive Chagas disease diagnosis in remote regions. This would ease access to treatment increasing adherence rates to it.

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.

Epidemiology and Molecular Typing of Trypanosoma cruzi in Naturally-Infected Hound Dogs and Associated Triatomine Vectors in Texas, USA

BACKGROUND

Trypanosoma cruzi is the etiologic agent of Chagas disease throughout the Americas. Few population-level studies have examined the epidemiology of canine infection and strain types of T. cruzi that infect canines in the USA. We conducted a cross-sectional study of T. cruzi infection in working hound dogs in south central Texas, including analysis of triatomine vectors collected within kennel environments.

METHODOLOGY/PRINCIPLE FINDINGS

Paired IFA and Chagas Stat-Pak serological testing showed an overall seroprevalence of 57.6% (n = 85), with significant variation across kennels. Dog age had a marginally significant effect on seropositivity, with one year of age increase associated with a 19.6% increase in odds of being seropositive (odds ratio 95% CI 0.996-1.435; p = 0.055). PCR analyses of blood revealed 17.4% of dogs harbored parasite DNA in their blood, including both seronegative and seropositive dogs. Molecular screening of organs from opportunistically sampled seropositive dogs revealed parasite DNA in heart, uterus, and mammary tissues. Strain-typing showed parasite discrete typing units (DTU) TcI and TcIV present in dog samples, including a co-occurrence of both DTUs in two individual dogs. Bloodmeal analysis of Triatoma gerstaeckeri and Triatoma sanguisuga insects collected from the kennels revealed exclusively dog DNA. Vector infection with T. cruzi was 80.6% (n = 36), in which T. gerstaeckeri disproportionately harbored TcI (p = 0.045) and T. sanguisuga disproportionately harbored TcIV (p = 0.029). Tracing infection status across dog litters showed some seropositive offspring of seronegative dams, suggesting infection of pups from local triatomine vectors rather than congenital transmission.

CONCLUSIONS/SIGNIFICANCE

Canine kennels are high-risk environments for T. cruzi transmission, in which dogs likely serve as the predominant parasite reservoir. Disease and death of working dogs from Chagas disease is associated with unmeasured yet undoubtedly significant financial consequences because working dogs are highly trained and highly valued.

Serological based monitoring of a cohort of patients with chronic Chagas disease treated with benznidazole in a highly endemic area of northern Argentina

This study aimed to evaluate well-documented diagnostic antigens, named B13, 1F8 and JL7 recombinant proteins, as potential markers of seroconversion in treated chagasic patients. Prospective study, involving 203 patients treated with benznidazole, was conducted from endemic areas of northern Argentina. Follow-up was possible in 107 out of them and blood samples were taken for serology and PCR assays before and 2, 3, 6, 12, 24 and 36 months after treatment initiation. Reactivity against Trypanosoma cruzi lysate and recombinant antigens was measured by ELISA. The rate of decrease of antibody titers showed nonlinear kinetics with an abrupt drop within the first three months after initiation of treatment for all studied antigens, followed by a plateau displaying a low decay until the end of follow-up. At this point, anti-B13, anti-1F8 and anti-JL7 titers were relatively close to the cut-off line, while anti-T. cruzi antibodies still remained positive. At baseline, 60.8% (45/74) of analysed patients tested positive for parasite DNA by PCR and during the follow-up period in 34 out of 45 positive samples (75.5%) could not be detected T. cruzi DNA. Our results suggest that these antigens might be useful as early markers for monitoring antiparasitic treatment in chronic Chagas disease.

Mother-to-Child Transmission of Chagas Disease in El Salvador

To estimate the incidence (any mother to child) and rate (from seropositive mother to child) of mother-to-child transmission of Trypanosoma cruzi, a serological census was conducted, targeting pregnant women and infants born to seropositive mothers, in four municipalities of El Salvador. Of 943 pregnant women, 36 (3.8%) were seropositive for T. cruzi. Of 36, 32 proceeded to serological tests of their infants when they became 6-8 months of age. Six infants seropositive at the age of 6-8 months further proceeded to second-stage serological test at the age of 9-16 months. As the result, one infant was congenitally infected. Thus, serological tests at the age of 6-8 months produced five false positives. To ensure earlier effective medication only for true positives, identification of seropositive infants at the age of 9-16 months is crucial. Incidence and rate of mother-to-child transmission were 0.14 (per 100 person-years) and 4.0%, respectively. Estimated number of children infected through mother-to-child transmission in El Salvador (170 per year) was much higher than that of human immunodeficiency virus (HIV; seven per year). It is recommended that serological testing for T. cruzi be integrated into those for HIV and syphilis as part of antenatal care package.

Chagas parasite detection in blood images using AdaBoost

The Chagas disease is a potentially life-threatening illness caused by the protozoan parasite, Trypanosoma cruzi. Visual detection of such parasite through microscopic inspection is a tedious and time-consuming task. In this paper, we provide an AdaBoost learning solution to the task of Chagas parasite detection in blood images. We give details of the algorithm and our experimental setup. With this method, we get 100% and 93.25% of sensitivity and specificity, respectively. A ROC comparison with the method most commonly used for the detection of malaria parasites based on support vector machines (SVM) is also provided. Our experimental work shows mainly two things: (1) Chagas parasites can be detected automatically using machine learning methods with high accuracy and (2) AdaBoost + SVM provides better overall detection performance than AdaBoost or SVMs alone. Such results are the best ones known so far for the problem of automatic detection of Chagas parasites through the use of machine learning, computer vision, and image processing methods.

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.

Seroprevalence of Trypanosoma cruzi among mothers and children in rural Mayan communities and associated reproductive outcomes

Our objective was to determine the seroprevalence of Trypanosoma cruzi infection among mothers and children in two rural Mayan communities in Yucatan, Mexico and examine sociodemographic characteristics and adverse reproductive outcomes associated with maternal infection. We performed household surveys in the communities of Sudzal and Teya. Mothers were interviewed, and blood samples were obtained to perform rapid tests and enzyme-linked immunosorbent assays (ELISAs). We surveyed 390 mothers and 685 children. The overall seroprevalence was 2.3% among mothers and 0.4% among children. In Sudzal, we found a seroprevalence of 4.4% among mothers and 0.7% in children. In Teya, we found a seroprevalence of 0.9% among mothers and 0.3% among children. Compared with uninfected mothers, seropositive mothers reported more stillbirths (relative risk = 4.7; 95% confidence interval = 2.1-10.4). T. cruzi infection is present in these communities, and infected children indicate active transmission. Seropositivity in mothers is associated with a history of adverse reproductive outcomes.

Comparative evaluation of 11 commercialized rapid diagnostic tests for detecting Trypanosoma cruzi antibodies in serum banks in areas of endemicity and nonendemicity

Chagas disease is one of the main public health issues in Latin America. Increasingly during the past few decades, Trypanosoma cruzi infection has been detected in North America, Europe, and the Western Pacific, mainly as a result of population movement. The limited availability of rapid serological diagnostic tests hinders rapid diagnosis and early treatment in areas of endemicity and nonendemicity. In collaboration with 11 national reference laboratories (NRLs) from different geographical areas, we evaluated the performances of commercialized serological rapid diagnostic tests (RDT) for T. cruzi infection. Eleven commercialized T. cruzi infection RDTs were evaluated on a total of 474 samples extensively tested with at least three different techniques for Chagas disease, maintained at controlled low temperatures, and stored in the serum banks of the 11 NRLs. We measured the sensitivity, specificity, and concordance of each RDT and provided an additional questionnaire to evaluate its ease of use. The selected RDTs in this study were performed under controlled laboratory conditions. Out of the 11 RDTs, we found 8 of them to be useful, with the cassette format favored over the strip. We did not observe significant differences in RDT performances in the different regions. Overall, the performance results were lower than those disclosed by the manufacturers. The results of this evaluation validate the possibility of using RDTs to diagnose Chagas disease, thereby decreasing the time to treatment at a primary health care facility for patients who are willing to be treated. Further studies should be conducted in the laboratory and in the field to confirm these data, expressly to evaluate reproducibility in resource-limited settings, or using whole blood in clinical settings in areas of endemicity and nonendemicity.

Regional variation in the correlation of antibody and T-cell responses to Trypanosoma cruzi

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is a major cause of morbidity and mortality in Central and South America. Geographic variations in the sensitivity of serologic diagnostic assays to T. cruzi may reflect differences in T. cruzi exposure. We measured parasite-specific T-cell responses among seropositive individuals in two populations from South America with widely varying antibody titers against T. cruzi. Antibody titers among seropositive individuals were significantly lower in Arequipa, Peru compared with Santa Cruz, Bolivia. Similarly, the proportion of seropositive individuals with positive T-cell responses was lower in Peru than Bolivia, resulting in overall lower frequencies of interferon-γ (IFNγ)-secreting cells from Peruvian samples. However, the magnitude of the IFNγ response was similar among the IFNγ responders in both locations. These data indicate that immunological discrepancies based on geographic region are reflected in T-cell responses as well as antibody responses.

Antibodies against Mycobacterial proteins as biomarkers for HIV-associated smear-negative tuberculosis

Serology data are limited for patients with sputum smear-negative HIV-associated active tuberculosis (TB). We evaluated the serum antibody responses against the mycobacterial proteins MPT51, MS, and echA1 and the 38-kDa protein via enzyme-linked immunosorbent assay (ELISA) in South African (S.A.) HIV-positive (HIV(+)) smear-negative TB patients (n = 56), U.S. HIV(+) controls with a positive tuberculin skin test (TST(+); n = 21), and S.A. HIV-negative (HIV(-)) (n = 18) and HIV(+) (n = 24) controls. TB patients had positive antibody reactivity against MPT51 (73%), echA1 (59%), MS (36%), and the 38-kDa protein (11%). Little reactivity against MPT51 and echA1 was observed in control groups at low risk for TB, i.e., S.A. HIV(-) (0% and 6%, respectively), and at moderate risk for TB development, i.e., U.S. HIV(+) TST(+) controls (14% and 10%, respectively). By contrast, more reactivity was detected in the S.A. HIV(+) control group at higher risk for TB (25% and 45%, respectively). Our data hold promise that antibody detection against MPT51 and echA1 might have adjunctive value in the detection of HIV(+) smear-negative TB and might reflect increasing Mycobacterium tuberculosis infection activity in asymptomatic HIV(+) individuals.

Rickettsiae, protozoa, and opisthokonta/metazoa

Rhizobiales (formerly named Rickettsiales) cause in rare instances meningitis and meningovasculitis, respectively. In case of history of exposure, infection by Rhizobiales needs to be considered since both diagnosis and therapy may be extremely difficult and pathogen-specific. The same applies to protozoa; in this chapter, Babesia species, free-living amoebae and Entamoeba histolytica infection, including severe meningitis and brain abscess, infection by Trypanosoma species (South American and African trypanosomiasis) are discussed with respect to history, epidemiology, clinical signs, and symptoms as well as differential diagnosis and therapy. Parasitic flatworms and roundworms, potentially able to invade the central nervous system, trematodes (flukes), cestodes (in particular, Cysticercus cellulosae), but also nematodes (in particular, Strongyloides spp. in the immunocompromised) are of worldwide importance. In contrast, filarial worms, Toxocara spp., Trichinella spp., Gnathostoma and Angiostrongylus spp. are seen only in certain geographically confined areas. Even more regionally confined are infestations of the central nervous system by metazoa, in particular, tongue worms (=arthropods) or larvae of flies (=maggots). The aim of this chapter is (1) to alert the neurologist to these infections, and (2) to enable the attending emergency neurologist to take a knowledgeable history, with an emphasis on epidemiology, clinical signs, and symptoms as well as therapeutic management possibilities.

An automatic algorithm for the detection of Trypanosoma cruzi parasites in blood sample images

Chagas disease is a tropical parasitic disease caused by the flagellate protozoan Trypanosoma cruzi (T. cruzi) and currently affecting large portions of the Americas. One of the standard laboratory methods to determine the presence of the parasite is by direct visualization in blood smears stained with some colorant. This method is time-consuming, requires trained microscopists and is prone to human mistakes. In this article we propose a novel algorithm for the automatic detection of T. cruzi parasites, in microscope digital images obtained from peripheral blood smears treated with Wright's stain. Our algorithm achieved a sensitivity of 0.98 and specificity of 0.85 when evaluated against a dataset of 120 test images. Experimental results show the versatility of the method for parasitemia determination.

A scientometric evaluation of the Chagas disease implementation research programme of the PAHO and TDR

The Special Programme for Research and Training in Tropical Diseases (TDR) is an independent global programme of scientific collaboration cosponsored by the United Nations Children's Fund, the United Nations Development Program, the World Bank, and the World Health Organization. TDR's strategy is based on stewardship for research on infectious diseases of poverty, empowerment of endemic countries, research on neglected priority needs, and the promotion of scientific collaboration influencing global efforts to combat major tropical diseases. In 2001, in view of the achievements obtained in the reduction of transmission of Chagas disease through the Southern Cone Initiative and the improvement in Chagas disease control activities in some countries of the Andean and the Central American Initiatives, TDR transferred the Chagas Disease Implementation Research Programme (CIRP) to the Communicable Diseases Unit of the Pan American Health Organization (CD/PAHO).

This paper presents a scientometric evaluation of the 73 projects from 18 Latin American and European countries that were granted by CIRP/PAHO/TDR between 1997 and 2007. We analyzed all final reports of the funded projects and scientific publications, technical reports, and human resource training activities derived from them. Results about the number of projects funded, countries and institutions involved, gender analysis, number of published papers in indexed scientific journals, main topics funded, patents inscribed, and triatomine species studied are presented and discussed.

The results indicate that CIRP/PAHO/TDR initiative has contributed significantly, over the 1997–2007 period, to Chagas disease knowledge as well as to the individual and institutional-building capacity.

Congenital transmission of Trypanosoma cruzi in Argentina, Honduras, and Mexico: study protocol

BACKGROUND

Trypanosoma cruzi has been divided into Discrete Typing Units I and non-I (II-VI). T. cruzi I is predominant in Mexico and Central America, while non-I is predominant in most of South America, including Argentina. Little is known about congenital transmission of T. cruzi I. The specific aim of this study is to determine the rate of congenital transmission of T. cruzi I compared to non-I.

METHODS/DESIGN

We are conducting a prospective study to enroll at delivery, 10,000 women in Argentina, 7,500 women in Honduras, and 13,000 women in Mexico. We are measuring transmitted maternal T. cruzi antibodies by performing two rapid tests in cord blood (Stat-Pak, Chembio, Medford, New York, and Trypanosoma Detect, InBios, Seattle, Washington). If at least one of the results is positive, we are identifying infants who are congenitally infected by performing parasitological examinations on cord blood and at 4-8 weeks, and serological follow-up at 10 months. Serological confirmation by ELISA (Wiener, Rosario, Argentina) is performed in cord and maternal blood, and at 10 months. We also are performing T. cruzi standard PCR, real-time quantitative PCR and genotyping on maternal venous blood and on cord blood, and serological examinations on siblings. Data are managed by a Data Center in Montevideo, Uruguay. Data are entered online at the sites in an OpenClinica data management system, and digital pictures of data forms are sent to the Data Center for quality control. Weekly reports allow for rapid feedback to the sites.

Immunogenicity of mycobacterial vesicles in humans: identification of a new tuberculosis antibody biomarker

Biomarkers for active tuberculosis (TB) are urgently needed. Mycobacteria produce membrane vesicles (MVs) that contain concentrated immune-modulatory factors that are released into the host. We evaluated the human immune responses to BCG and Mycobacterium tuberculosis MVs to characterize the antibody responses and identify potentially novel TB biomarkers. Serological responses to MVs were evaluated by ELISAs and immunoblots with sera from 16 sputum smear-positive, 12 smear-negative HIV uninfected pulmonary TB patients and 16 BCG vaccinated Tuberculin skin-test positive controls with and without latent tuberculosis infection. MVs from both BCG and M. tuberculosis induced similar responses and were strongly immunogenic in TB patients but not in controls. Several MV-associated antigens appear to induce robust antibody responses, in particular the arabinomanan portion of the cell wall glycolipid lipoarabinomannan. Three proteins at ≈ 36, 25, and 23 kDa were simultaneously recognized by sera from 16/16 smear-positive, 9/12 smear-negative TB patients and 0/16 controls. These results provide promise and encouragement that antibody responses to proteins enriched in MVs of pathogenic mycobacteria may constitute a novel TB biomarker signature that could have diagnostic information.

Evaluation of in-house ELISA using Trypanosoma cruzi lysate and recombinant antigens for diagnosis of Chagas disease and discrimination of its clinical forms

The aim of this work was to investigate the potential usefulness of Trypanosoma cruzi lysate, recombinant protein JL7, and peptides P013, R13, JL18, JL19, and P0β as serological markers for human Chagas disease. We analyzed 228 sera from Brazilian Chagas disease patients classified into four clinical groups and 108 from non-chagasic patients. We defined the diagnostic sensitivity, specificity, and Kappa index measured by enzyme-linked immunosorbent assay (ELISA). As previously described, the highest values of diagnostic parameters were achieved for T. cruzi lysate and JL7; peptide P013 showed high specificity but low sensitivity. The other peptides resulted in lower sensitivity and specificity in our ELISA than T. cruzi lysate and JL7 protein. Antibodies against JL7 protein were mainly detected in sera from patients with severe chagasic cardiomyopathy, compared with those from the indeterminate form, whereas peptides failed to discriminate between the clinical forms of the disease.

Antibody responses to mycobacterial antigens in children with tuberculosis: challenges and potential diagnostic value

The identification of easily detectable biomarkers for active tuberculosis (TB) is a global health priority. Such biomarkers would be of particular value in childhood TB, which poses greater diagnostic challenges than adult TB. Serum antibodies can be detected by simple formats that provide extremely rapid results. However, attempts to develop accurate serodiagnostic tests for TB have been unsuccessful. Whereas antibody responses to mycobacterial antigens in adult TB have been studied extensively and reviewed, the same cannot be said for serologic data in pediatric populations. Here we appraise studies on serological responses in childhood TB and discuss findings and limitations in the context of the developing immune system, the age range, and the spectrum of TB manifestations. We found that the antibody responses to mycobacterial antigens in childhood TB can vary widely, with sensitivities and specificities ranging from 14% to 85% and from 86% to 100%, respectively. We conclude that the limitations in serodiagnostic studies of childhood TB are manifold, thereby restricting the interpretation of currently available data. Concerns about the methodology used in published studies suggest that conclusions about the eventual value of serodiagnosis cannot be made at this time. However, the available data suggest a potential adjunctive value for serology in the diagnosis of childhood TB. Despite the difficulties noted in this field, there is optimism that the application of novel antigens and the integration of those factors which contribute to the serological responses in childhood TB can lead to useful future diagnostics.

Congenital and oral transmission of American trypanosomiasis: an overview of physiopathogenic aspects

Chagas disease or American trypanosomiasis is a pathology affecting about 8-11 million people in Mexico, Central America, and South America, more than 300 000 persons in the United States as well as an indeterminate number of people in other non-endemic countries such as USA, Spain, Canada and Switzerland. The aetiological agent is Trypanosoma cruzi, a protozoan transmitted by multiple routes; among them, congenital route emerges as one of the most important mechanisms of spreading Chagas disease worldwide even in non-endemic countries and the oral route as the responsible of multiple outbreaks of acute Chagas disease in regions where the vectorial route has been interrupted. The aim of this review is to illustrate the recent research and advances in host-pathogen interaction making a model of how the virulence factors of the parasite would interact with the physiology and immune system components of the placental barrier and gastrointestinal tract in order to establish a response against T. cruzi infection. This review also presents the epidemiological, clinical and diagnostic features of congenital and oral Chagas disease in order to update the reader about the emerging scenarios of Chagas disease transmission.

Sensitivity and specificity of an operon immunochromatographic test in serum and whole-blood samples for the diagnosis of Trypanosoma cruzi infection in Spain, an area of nonendemicity

Trypanosoma cruzi infection is an imported parasitic disease in Spain, and the majority of infected individuals are in the chronic phase of the disease. This study evaluated the sensitivity and specificity of the Operon immunochromatographic test (ICT-Operon; Simple Stick Chagas and Simple Chagas WB [whole blood]; Operon S.A., Spain) for different biological samples. Well-characterized serum samples were obtained from chagasic patients (n = 63), nonchagasic individuals (n = 95), visceral leishmaniasis patients (n = 38), and malaria patients (n = 55). Noncharacterized specimens were obtained from Latin American immigrants and individuals at risk with a clinical and/or epidemiological background: these specimens were recovered serum or plasma samples (n = 450), whole peripheral blood (n = 94), and capillary blood (n = 282). The concordance of the results by enzyme-linked immunosorbent assay and indirect immunofluorescence test was considered to be the "gold standard" for diagnosis. Serum and plasma samples were analyzed by Stick Chagas, and whole blood was analyzed by Simple Chagas WB. The sensitivity and specificity of the ICT-Operon in well-characterized samples were 100% and 97.9%, respectively. No cross-reactivity was found with samples obtained from visceral leishmaniasis patients. In contrast, a false-positive result was obtained in 27.3% of samples from malaria patients. The sensitivities of the rapid test in noncharacterized serum or plasma, peripheral blood, and capillary blood samples were 100%, 92.1%, and 86.4%, respectively, while the specificities were 91.6%, 93.6%, and 95% in each case. ICT-Operon showed variable sensitivity, depending on the kind of sample, performing better when serum or plasma samples were used. It could therefore be used for serological screening combined with any other conventional test.

Acute and congenital Chagas disease

The acute phase of Chagas disease lasts 4-8 weeks and is characterized by microscopically detectable parasitaemia. Symptoms are usually mild with severe acute disease occurring in less than 1% of patients. Orally transmitted Trypanosoma cruzi outbreaks can have more severe acute morbidity and higher mortality than vector-borne infection. Congenital T. cruzi infection occurs in 1-10% of infants of infected mothers. Most congenital infections are asymptomatic or cause non-specific signs, requiring laboratory screening for detection. A small proportion of congenital infections cause severe morbidity with hepatosplenomegaly, anaemia, meningoencephalitis and/or respiratory insufficiency, with an associated high mortality. Infected infants are presumed to carry the same 20-30% lifetime risk of cardiac or gastrointestinal disease as other infected individuals. Most control programs in Latin America employ prenatal serological screening followed by microscopic examination of cord blood from infants of seropositive mothers. Recent data confirm that polymerase chain reaction (PCR) is more sensitive and detects congenital infections earlier than conventional techniques. For infants not diagnosed at birth, conventional serology is recommended at at 6 to 9 months of age. In programs that have been evaluated, less than 20% of at risk infants completed all steps of the screening algorithm. A sensitive, specific and practical screening test for newborns is needed to enable Chagas disease to be added to newborn screening programs.

Parasitic infections and myositis

Infectious myositis may be caused by a wide variety of bacterial, fungal, viral, and parasitic agents. Parasitic myositis is most commonly a result of trichinosis, cystericercosis, or toxoplasmosis, but other parasites may be involved. A parasitic cause of myositis is suggested by history of residence or travel to endemic area and presence of eosinophilia. The diagnosis of parasitic myositis is suggested by the clinical picture and radiologic imaging, and the etiologic agent is confirmed by parasitologic, serologic, and molecular methods, together with histopathologic examination of tissue biopsies. Therapy is based on the clinical presentation and the underlying pathogen. Drug resistance should be put into consideration in different geographic areas, and it can be avoided through the proper use of anti-parasitic drugs.

Do commercial serologic tests for Trypanosoma cruzi infection detect Mexican strains in women and newborns?

We sought to determine the serological test that could be used for Trypanosoma cruzi seroprevalence studies in Mexico, where lineage I predominates. In a previous study among pregnant women and their newborns in the states of Yucatan and Guanajuato, we reported a 0.8-0.9% of prevalence for T. cruzi -specific antibodies by Stat-Pak and Wiener ELISA. We have expanded this study here by performing an additional non-commercial ELISA and confirming the seropositives with Western blot, using whole antigens of a local parasite strain. We found a seroprevalence of 0.6% (3/500) in Merida and 0.4% in Guanajuato (2/488). The 5 seropositive umbilical cord samples reacted to both non-commercial ELISA and Western blot tests, and only 1 of the maternal samples was not reactive to non-commercial ELISA. A follow-up of the newborns at 10 mo was performed in Yucatan to determine the presence of T. cruzi antibodies in children as evidence of congenital infection. None of the children was seropositive. One newborn from an infected mother died at 2 wk of age of cardiac arrest, but T. cruzi infection was not confirmed. The T. cruzi seroprevalence data obtained with both commercial tests (Stat-Pak and ELISA Wiener) are similar to those from non-commercial tests using a local Mexican strain of T. cruzi.

Chagas disease: changes in knowledge and management

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

Research needs for Chagas disease prevention

We present an overview of the two main strategies for the primary (vector control) and secondary (patient care) prevention of Chagas disease (CD). We identify major advances, knowledge gaps, and key research needs in both areas. Improved specific chemotherapy, including more practical formulations (e.g., paediatric) or combinations of existing drugs, and a better understanding of pathogenesis, including the relative weights of parasite and host genetic makeup, are clearly needed. Regarding CD vectors, we find that only about 10-20% of published papers on triatomines deal directly with disease control. We pinpoint the pitfalls of the current consensus on triatomine systematics, particularly within the Triatomini, and suggest how some straightforward sampling and analytical strategies would improve research on vector ecology, naturally leading to sounder control-surveillance schemes. We conclude that sustained research on CD prevention is still crucial. In the past, it provided not only the know-how, but also the critical mass of scientists needed to foster and consolidate CD prevention programmes; in the future, both patient care and long-term vector control would nonetheless benefit from more sharply focused, problem-oriented research.

Validation of a rapid immunochromatographic assay for diagnosis of Trypanosoma cruzi infection among Latin-American Migrants in Geneva, Switzerland

Chagas' disease is a global public health problem due to the recent exchange of population between Latin America and other regions, including Europe. The recent development of rapid diagnostic tests (RDTs) for Trypanosoma cruzi infection may improve patient access to diagnosis and care worldwide. We evaluated the diagnostic accuracy of the Chagas Stat-Pak RDT in a cohort of undocumented Latin-American migrants living in Geneva, Switzerland. Study participants were enrolled in a primary health care center. The Chagas Stat-Pak test was performed independently on blood and serum samples. A combination of two commercialized enzyme-linked immunosorbent assay (ELISA)-based serological tests was used for comparison (reference standard). A total of 999 adults (median age, 36 years) were included in the study; the majority were women (83%) and originally from Bolivia (47%) or Brazil (25%). A total of 125 participants (12.5%) were diagnosed with T. cruzi infection; with the exception of three individuals, all individuals diagnosed with T. cruzi were originally from Bolivia. The sensitivity and specificity of the Chagas Stat-Pak test on blood samples were 95.2% (95% confidence interval [95% CI], 89.2% to 97.9%) and 99.9% (95% CI, 99.3% to 100%), respectively. When the test was performed on serum samples, the sensitivity was 96% (95% CI, 91% to 98.3%), and the specificity was 99.8% (95% CI, 99.2% to 99.9%). The concordance of test results for blood and serum samples was 99.7%. Both negative and positive predictive values were above 98%. The Chagas Stat-Pak is an accurate diagnostic test for T. cruzi infection among Latin-American migrants living in Europe. The mild deficit in sensitivity should be interpreted in light of its ease of use and capacity to provide immediate results, which allow more people at risk to have access to diagnosis and care both in countries where Chagas' disease is endemic and in countries where this disease is not endemic.

Rapid detection of Trypanosoma cruzi in human serum by use of an immunochromatographic dipstick test

We evaluated a commercially available immunochromatographic dipstick test to detect Trypanosoma cruzi infection in 366 human serum samples with known serological results from Argentina, Ecuador, Mexico, and Venezuela. One hundred forty-nine of 366 (40.7%) and 171/366 (46.7%) samples tested positive by dipstick and serology, respectively. Dipstick sensitivity was calculated to be 84.8% (range between countries, 77.5 to 95%), and specificity was 97.9% (95.9 to 100%).

Therapy, diagnosis and prognosis of chronic Chagas disease: insight gained in Argentina

The purpose of this review is to describe research findings regarding chronic Chagas disease in Argentina that have changed the standards of care for patients with Trypanosoma cruzi infection. Indirect techniques (serological tests) are still the main tools for the primary diagnosis of infection in the chronic phase, but polymerase chain reaction has been shown to be promising. The prognosis of patients with heart failure or advanced stages of chagasic cardiomyopathy is poor, but a timely diagnosis during the initial stages of the disease would allow for prescription of appropriate therapies to offer a better quality of life. Treatment of T. cruzi infection is beneficial as secondary prevention to successfully cure the infection or to delay, reduce or prevent the progression to disease and as primary disease prevention by breaking the chain of transmission. Current recommendations have placed the bulk of the diagnostic and treatment responsibility on the Primary Health Care System. Overall, the current research priorities with respect to Chagas disease should be targeted towards (i) the production of new drugs that would provide a shorter treatment course with fewer side effects; (ii) the development of new tools to confirm cure after a full course of treatment during the chronic phase and (iii) biomarkers to identify patients with a high risk of developing diseases.

Evaluation of the Chagas Stat-Pak assay for detection of Trypanosoma cruzi antibodies in wildlife reservoirs

An immunochromatographic assay (Chagas Stat-Pak) was evaluated for the detection of Trypanosoma cruzi antibodies in 4 species of wildlife reservoirs. Antibodies to T. cruzi were detected in raccoons (Procyon lotor) (naturally and experimentally infected) and degus (Octodon degu) (experimentally-infected) using the Chagas Stat-Pak. In naturally exposed wild raccoons, the Chagas Stat-Pak had a sensitivity and specificity of 66.7-80.0% and 96.3%, respectively. Compared with indirect immunofluorescent antibody assay results, seroconversion as determined by Chagas Stat-Pak was delayed for experimentally infected raccoons, but occurred sooner in experimentally infected degus. The Chagas Stat-Pak did not detect antibodies in naturally or experimentally infected Virginia opossums (Didelphis virginiana) or in experimentally infected short-tailed opossums (Monodelphis domestica). These data suggest that the Chagas Stat-Pak might be useful in field studies of raccoons and degus when samples would not be available for more-conventional serologic assays. Because this assay did not work on either species of marsupial, the applicability of the assay should be examined before it is used in other wild species.

Antibody drop in newborns congenitally infected by Trypanosoma cruzi treated with benznidazole

OBJECTIVE

To compare the drop of Chagas antibody titres between non-infected and congenitally infected newborns treated by two doses of benznidazole, aiming at evaluating the recovery time and giving recommendations regarding serological criteria of recovery.

METHODS

During a clinical trial, the drop of Trypanosoma cruzi antibody titres measured by ELISA tests was followed during the first year of life in congenitally infected newborns treated with different doses of benznidazole and compared to T. cruzi antibody titres in non-parasitaemic newborns. Confirmation of recovery was given by two negative serological tests: Chagas Stat-Pak (CSP) (immunochromatography) and Chagatest v3.0 (ELISA).

RESULTS

In non-parasitaemic infants of infected mothers, antibodies of maternal origin disappeared in <8 months while in infected infants, T. cruzi antibodies decreased more slowly and disappeared in 9-16 months allowing to confirm the recovery. All CSP tests were negative before the ninth month while about 10% of ELISA tests remained positive at the 12th month.

CONCLUSIONS

Recovery may be confirmed in most cases at 10 months. The CSP test was compared to Chagatest v3.0 ELISA and appeared to give a reliable response. The decrease rate of antibodies does not depend on treatment modes.