Background The Kato-Katz technique is recommended worldwide for the diagnosis of intestinal schistosomiasis, detecting parasite eggs in feces of infected people. However, new tests have been developed in order to facilitate diagnosis, e.g. by detection of specific antigens secreted by schistosomes, such as the circulating cathodic antigen (CCA). The aim of this study was to evaluate the performance of the point-of-care circulating cathodic antigen test (POC-CCA) compared to the Kato-Katz technique in a low prevalence area in the Amazon Region, located in the municipality of Primavera, State of Pará, Brazil. Methods Positivity rates of the POC-CCA test and the Kato-Katz technique were calculated. The sensitivity, specificity, accuracy and kappa coefficient were determined by comparing both methods. The reference standard was established using 16 Kato-Katz slides, 12 of the first fecal sample, two of the second and two of the third one. The study also included the concordance between POC-CCA results and different numbers and combinations of Kato-Katz slides. Results The prevalence of schistosomiasis according to the reference standard or POC-CCA test reached a rate of 9.4% or 23.9%, respectively, among a total of 372 participants. The positivity rates by the Kato-Katz technique increased from 2.4 to 9.4%, according to the increase in the number of slides examined and fecal samples collected. A sensitivity of 55.6%, specificity 76.9%, accuracy 76% and κ coefficient of 0.06 was observed by comparing one slide of the first sample and POC-CCA. Comparing 6 slides from three different samples, two slides of each, with POC-CCA resulted in a sensitivity of 58.3%, specificity 78.4%, accuracy 77% and κ coefficient of 0.16. Finally, the comparison of 16 slides from three different samples with POC-CCA revealed a sensitivity of 65.7%, specificity 80.4%, accuracy 79%, and κ coefficient of 0.27. Conclusions The immunochromatographic test has the potential to be an important tool to combat schistosomiasis because of its practicality and applicability but should be applied with caution in low prevalence areas and in programs that aim to eliminate this disease. Trial registration CAAE#21824513.9.0000.5091 . January 31st, 2014. Electronic supplementary material The online version of this article (10.1186/s40249-019-0551-7) contains supplementary material, which is available to authorized users.
Introduction: Schistosomiasis is a poverty-related disease that affects people in 78 countries worldwide. This study aimed to evaluate the point-of-care circulating cathodic antigen (POC-CCA) test performance using sensitive parasitological methods as a reference standard (RS) in individuals before and after treatment. Methods: The RS was established by combining the results of 16 Kato-Katz slides and the Helmintex ® method. Positivity rates of the POC-CCA test and Kato-Katz and Helmintex ® methods were calculated before treatment and 30 days afterward. Furthermore, the sensitivity, specificity, accuracy, and kappa coefficient before treatment were determined by comparing the methods. The cure rate was defined 30 days after treatment. Results: Among the 217 participants, the RS detected a total of 63 (29.0%) positive individuals. The POC-CCA test identified 79 (36.4%) infections. The evaluation of POC-CCA test performance in relation to the RS revealed a sensitivity of 61.9%, specificity of 74.0%, accuracy of 70.5%, and kappa coefficient of 0.33. Out of the 53 remaining participants after treatment, a total of 45 (81.1%) showed egg negative results, and 8 (18.9%) were egg positive according to the RS. A total of 5 (9.4%) egg-positive and 37 (69.8%) egg-negative individuals were positive by the POC-CCA test. Conclusions: Our data show that the POC-CCA test has potential as an auxiliary tool for the diagnosis of Schistosoma mansoni infection, yielding better results than 16 Kato-Katz slides from three different stool samples. However, the immunochromatographic test lacks sufficient specificity and sensitivity for verifying the cure rate after treatment.
In Brazil, schistosomiasis occurrence is related to the presence of the etiological agent Schistosoma mansoni. The presence of mollusks for Biomphalaria genus is a necessary condition for development of the parasite cycle. In Pará state, the species B. schrammi, B. kuhniana, B. straminea and B. glabrata have already been identified, with reports of the last two occurring in Belé m. The aim of this study was to determine the spatial distribution of Biomphalaria species in Belé m, Pará , Brazil, identifying risk areas for schistosomiasis transmission. Biannual malacological surveys were carried out between September 2013 and October 2017 in 35 neighborhoods of Belé m. The collection points were georeferenced using a Global Positioning System (GPS) receiver and the Kernel Density Estimation (KDE) was used to the spatial analysis. The mollusks, after measurement, were exposed to light to verify the presence of S. mansoni cercariae. Subsequently, mollusks were sacrificed and fixed for dissection and morphological identification of species. The surveys resulted in a total of 10,803 mollusks collected, of which 9,367 (86.70%) specimens were examined. Among the analyzed mollusks, 5,820 (62.14%) were identified as B. glabrata and 3,547 (37.86%) as B. straminea. The presence of the parasite was observed in 208 (2.22%) specimens, all B. glabrata. Positive mollusks were found in six neighborhoods: Guamá (51 mollusks/24.5%), Sacramenta (47 mollusks/22.6%), Telé grafo (47 mollusks/22.6%), Terra Firme (36 mollusks/17.3%), Condor (20 mollusks/9.6%) and Barreiro (7 mollusks/3.4%). This study confirms that B. glabrata species actively participates as intermediate host in the disease maintenance in Belé m. The KDE allowed to analyze the spatial distribution of collection sites and consequently to determine possible risk areas of schistosomiasis transmission in Belé m. The development of maps identifying sites with schistosomiasis positive snails may support efforts of this municipality by directing activities related to endemic disease control.
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