Evidence of Chagas disease in seronegative Brazilian patients with megaesophagus

Disagreement between PCR and serological diagnosis of Trypanosoma cruzi infection in blood donors from a Colombian endemic region

Introduction:

Chagas' disease is the leading cause of infectious myocarditis worldwide. This infection caused by Trypanosoma cruzi is usually life-long and asymptomatic; however, the third part of infected people can develop severe or even fatal cardiomyopathy. As the parasitemia in the chronic phase is both low-grade and intermittent, T. cruzi infection is principally detected by serology, although this method has sensitivity and specificity limitations.

Objective:

To determine the level of agreement between serologic and molecular tests in 658 voluntary blood donors from six provinces in the Colombian department of Santander.

Materials and methods:

We evaluated an array of diagnostic technologies by cross-section sampling performing a serological double diagnostic test for T. cruzi antibody detection (Chagas III ELISA™, BiosChile Group, and ARCHITECT Chagas CMIA™, Abbott;, and DNA detection by polymerase chain reaction (PCR). We collected the demographic, clinical, and epidemiological information of participants. The sample size was calculated using Epidat™ and the statistical analysis was done with Stata 12.1™.

Results:

PCR was six times more sensitive in detecting T. cruzi infection than ELISA/CMIA with prevalence values of 1.8% (12/658) and 0.3% (2/658), respectively, and kappa=0.28 (95%CI: -0.03 - 0.59). In contrast, serology showed a sensitivity of 16.7% (95%CI: 2.09 -48.4) and a specificity of 100% (95%CI: 99.4 - 100). All seropositive samples were found to be positive by PCR.

Conclusions:

The implementation of PCR as a complementary method for screening donors could reduce the probability of false negative and the consequent risk of transfusional-transmission of Chagas' disease, especially in endemic regions.

Epidemiological and clinical characteristics of Trypanosoma cruzi infection in dogs (Canis lupus familiaris) from a Chagas Disease-Endemic Urban Area in Colombia

In the last few years, an unusual increase in the number of acute Chagas disease outbreaks, presumably due to oral transmission, has been reported in urban areas in Santander, Colombia. Given the importance of dogs (Canis lupus familiaris) as reservoir hosts and sentinels of T. cruzi infection across different regions of America, we carried out a serological and molecular survey on T. cruzi infection in 215 dogs from the metropolitan area of Bucaramanga, Santander. Serological detection was carried out using enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence antibody test (IFAT), and indirect hemagglutination assay (IHA), while molecular detection was done using a nested PCR (nPCR), targeting the microsatellite region of T. cruzi nuclear DNA. Animals were defined as seropositive when at least two of the three serological tests were positive, and only these animals were evaluated with the nPCR. To discriminate DTU TcI from other DTUs, a multiplex PCR was performed in the T. cruzi-positive samples. Additionally, clinical and hematological traits were evaluated in these hosts. The dog sera showed a seropositivity rate of 27.9 % (60/215), of which 43.3 % (26/60) were positive for nPCR. Statistical analysis indicated that T. cruzi seropositive in dogs was associated with specific socioeconomic sectors and a lack of garbage collection in these municipalities. Hematological analyses showed that T. cruzi infection was associated with anemia and platelet alterations but not with alterations of aspartate aminotransferase (ASAT) and creatine kinase myocardial band (CK-MB). The high seroprevalence of infection and active circulation of T. cruzi I (TcI) in dogs reflect the risk of infection to humans in this area, which should be taken into consideration when Chagas disease control programs are implemented. In addition, T. cruzi infection may take a toll on dog health, which should be considered during dog care and management.

Lack of evidence of seronegative infection in an endemic area of Chagas disease

The diagnosis of Chagas disease is based on the detection of Trypanosoma cruzi (T. cruzi)-specific antibodies. Nonetheless, there is concern about the sensitivity of current serological assays due to reports of T. cruzi PCR positivity among seronegative individuals. The aim of this study was to evaluate if T. cruzi seronegative infections occur in endemic areas. We recruited 2,157 individuals that were identified as having Chagas disease in a public health system database of an endemic region in Brazil. All participants were interviewed and 2,091 had a sample collected for serological and PCR testing. From these, 149 (7.1%) had negative serological results. PCR was positive in 610 samples (31.4%) of the 1,942 seropositive samples but in none of the 149 samples from seronegative participants. True T. cruzi seronegative infections seem to be rare (95% CI 0-3.7) and should not be a concern for blood supply, which relies on antibody screening.

Trypanosoma cruzi Detection in Colombian Patients with a Diagnosis of Esophageal Achalasia

Achalasia is a motility disorder of the esophagus that might be secondary to a chronic Trypanosoma cruzi infection. Several studies have investigated esophageal achalasia in patients with Chagas disease (CD) in Latin America, but no related studies have been performed in Colombia. The goals of the present study were to determine the presence of anti-T. cruzi antibodies in patients with esophageal achalasia who visited a referral hospital in Bogotá, Colombia, and to detect the presence of the parasite and its discrete typing units (DTUs). This cross-sectional study was conducted in adult patients (18-65 years old) who were previously diagnosed with esophageal achalasia and from whom blood was drawn to assess antibodies against T. cruzi using four different serological tests. Trypanosoma cruzi DNA was detected by conventional polymerase chain reaction (cPCR) and quantitative polymerase chain reaction (qPCR). In total, 38 patients, with an average age of 46.6 years (standard deviation of ±16.2) and comprising 16 men and 22 women, were enrolled. Five (13.15%) patients were found to be positive for anti-T. cruzi antibodies by indirect immunofluorescence assay (IFA), and two patients who were negative according to IFA were reactive by both enzyme-linked immunosorbent assay and immunoblot (5.3%). Parasite DNA was detected in two of these seven patients by cPCR and in one of these by qPCR. The parasite DTU obtained was TcI. In summary, this study identified T. cruzi in Colombian patients with esophageal achalasia, indicating that digestive compromise could also be present in patients with chronic CD.

Serological and molecular inquiry of Chagas disease in an Afro-descendant settlement in Mato Grosso do Sul State, Brazil

Furnas do Dionísio is a Brazilian Afro-descendant settlement in the city of Jaraguari, 21.4 miles from Campo Grande, Mato Grosso do Sul, Brazil. Approximately 96 families live in this quilombola (Maroon) settlement, also known in Brazil as a remnant community of descendants of African slaves. Recent studies found 20% of households were infested by triatomines, 18% of insects captured in the community were infected by Trypanosoma cruzi, and 22.7% of dogs presented T. cruzi antibodies. The low prevalence of Chagas disease observed in humans in Mato Grosso do Sul State is attributed to its arrival via colonist migration and subsequent transplacental transmission. In order to gain a better understanding of the T. cruzi cycle in residents of the study community, serological and molecular tests were carried out to diagnose Chagas disease. In the present study, 175 residents between 2 and 80 years old were included. A total of 175 participants were interviewed and 170 provided blood samples, which were tested for T. cruzi antibodies with serological tests. Molecular diagnosis was performed in 167 participants by PCR (KDNA) and NPCR (satellite DNA) tests. One of the 170 samples tested positive for all serological tests performed. The overall frequency of Chagas disease in the community was low (0.6%). Interview responses revealed that 66.3% knew of triatomine insects and 65.7% reported having had no contact with them. Physical improvements to residences, together with vector surveillance and control by the State and municipal governments and local ecological conservation contribute to the low frequency of the Chagas disease in this quilombola community.

The detection of Trypanosoma cruzi by nested-PCR in elderly patients: relationship to the clinical and epidemiological profile

Chagas disease, which is caused by Trypanosoma cruzi, is transmitted primarily by triatomine bugs, although the incidence of new cases has decreased as a result of vector control. In Brazil, most of those affected have the chronic form of the disease and are generally elderly individuals who require appropriate clinical follow-up. In this work, we undertook a descriptive study in which 85 patients were interviewed and blood samples were collected for molecular analyses based on the amplification of parasite satellite DNA. The cardiac form of the disease was the most prevalent among the patients and hypertension was the most frequent comorbidity; polypharmacy was detected in 34% of the cases. Serological tests were positive in 95% of cases while 36% were positive in nested-polymerase chain reaction. These findings indicate an increased use of medications and a larger number of age-related diseases in elderly patients with Chagas disease, even in patients with low parasitemia. We conclude that elderly patients with Chagas disease require special attention and that further studies should be done with elderly individuals who carry this disease.

Differential parasitological, molecular, and serological detection of Trypanosoma cruzi I, II, and IV in blood of experimentally infected mice

Trypanosoma cruzi is the etiological agent of American trypanosomiasis (Chagas' disease), which affects 6-7 million people worldwide, mainly in Latin America. It presents great genetic and biological variability that plays an important role in the clinical and epidemiological features of the disease. Our working hypothesis is that the genetic diversity of T. cruzi has an important impact on detection of the parasite using diagnostic techniques. The present study evaluated the diagnostic performance of parasitological, molecular, and serological techniques for detecting 27 strains of T. cruzi that belonged to discrete typing units (DTUs) TcI (11 strains), TcII (four strains), and TcIV (12 strains) that were obtained from different hosts in the states of Amazonas and Paraná, Brazil. Blood samples were taken from experimentally infected mice and analyzed by fresh blood examination, hemoculture in Liver Infusion Tryptose (LIT) medium, polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay (ELISA). Polymerase chain reaction presented the best detection of TcI, with 80.4% positivity. For all of the detection methods, the animals that were inoculated with TcII presented the highest positivity rates (94.1-100%). ELISA that was performed 7 months after inoculation presented a higher detection ability (95.4%) for TcIV. Intra-DTU comparisons showed that the reproducibility of the majority of the results that were obtained with the different methods was weak for TcI and good for TcII and TcIV. Our data indicate that the detection capability of different techniques varies with the DTUs of the parasites in mammalian blood. The implications of these findings with regard to the diagnosis of human T. cruzi infection are discussed.

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.

Detection of Trypanosoma cruzi DNA in blood by PCR is associated with Chagas cardiomyopathy and disease severity

BACKGROUND

The significance of detection of Trypanosoma cruzi DNA in blood of antibody-positive patients for risk of development of Chagas heart disease is not well established. The objective of this study was to compare detection of T. cruzi DNA with known clinical and laboratory markers of Chagas cardiomyopathy (CC) severity.

METHODS

This is a case-control study nested within a retrospective cohort developed in Brazil to understand the natural history of Chagas disease. The study enrolled 499 T. cruzi seropositive blood donors (SP-BD) and 488 frequency matched seronegative control donors (SN-BD) who had donated between 1996 and 2002, and 101 patients with clinically diagnosed CC. In 2008-2010 all enrolled subjects underwent a health questionnaire, medical examination, electrocardiograms and echocardiograms and polymerase chain reaction (PCR) analyses. A blinded panel of three cardiologists adjudicated the outcome of CC. Trypanosoma cruzi kinetoplast minicircle sequences were amplified by real-time PCR using an assay with a sensitivity of one parasite per 20 mL of blood. All testing was performed on coded samples.

RESULTS

Rates of PCR detection of T. cruzi DNA were significantly (P = 0.003) higher in CC patients and SP-BD diagnosed with CC (79/105 [75.2 %]) compared with SP-BD without CC (143/279 [51.3%]). The presence of parasitaemia was significantly associated with known markers of disease progression such as QRS and QT interval duration, lower left ventricular ejection fraction, higher left ventricular index mass, and elevated troponin and NTpro-BNP levels.

CONCLUSION

Trypanosoma cruzi PCR positivity is associated with presence and severity of cardiomyopathy, suggesting a direct role of parasite persistence in disease pathogenesis.

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.

Serological profiles and evaluation of parasitaemia by PCR and blood culture in individuals chronically infected by Trypanosoma cruzi treated with benzonidazole

OBJECTIVE

To evaluate the serological and parasitological status of patients with chronic Chagas disease (CD) after chemotherapy with benzonidazole.

METHODS

Retrospective study of patients treated with benzonidazole (5 mg/kg/day for 60 days) between 1980 and 2010. Twenty-nine patients who had CD confirmed by two reagent immunological tests and/or one positive xenodiagnosis before treatment were included. Conventional serology (ELISA and IIF) and parasitological tests (haemoculture and N-PCR) were performed.

RESULTS

At the time of treatment, the mean age of patients was 36 ± 7.24 years (20-39 years) and the time post-treatment varied from 1 to 29 years. After chemotherapy, all individuals had reagent ELISA and 93.1% had positive results for the IIF test. T. cruzi DNA was detected by N-PCR in 48.3%. Negative results were observed in 41.4% and inconclusive ones in 10.3%. Haemoculture was negative for all individuals.

CONCLUSIONS

Our results suggest that N-PCR may be useful in the early identification of therapeutic failure of CD. Although it is difficult to determine parasitological cure in negative N-PCR cases, we can infer that this condition represents a declination of parasitaemia as a favourable consequence of aetiological treatment.