Fig 1.
Flowchart describing the workflow for the diagnosis of intestinal schistosomiasis in an endemic population within the district of Brejo do Amparo, Januária, Minas Gerais, Brazil.
Fecal samples were examined with the Kato-Katz technique with one fecal sample and two (SPL1 K1-K2), six (SPL1 K1-K6), 12 (SPL1 K1-K12), and 14 thick-smears (SPL1 K1-K14), or with three fecal samples with two slides each (SPL1-3 K1-K2), saline gradient, Helmintex and spontaneous sedimentation technique (HPJ). Further, individual urine samples were analyzed with the point-of-care rapid urine test (POC-CCA) that detects the circulating cathodic antigen of Schistosoma mansoni. The numbers in brackets indicate the number of individuals tested with each method.
Table 1.
Selected socio-economic parameters and demographics of the study population in a rural community of Brejo do Amparo, Januária, Minas Gerais, Brazil.
Fig 2.
Classification of Schistosoma mansoni-infected individuals according to their parasitic load.
A: Individual egg counts of one fecal sample analyzed with two Kato-Katz slides and classification of egg-positive individuals according to their parasite load. Infection intensity was determined by the number of eggs per gram of feces (EPG) and was classified as light (1–99 EPG, triangles), moderate (100–399 EPG, squares) or heavy (≥400 EPG, circles). Individual EPG values are plotted on a logarithmic scale and the horizontal bars indicate the mean EPG value in each category. B: Boxplots showing the median, interquartile ranges, and 95% intervals of the parasite load (EPG) by the different age groups and indicated on a logarithmic scale. Non-parametric Kruskal-Wallis test revealed no statistical significance between age groups (p > 0.05).
Table 2.
Prevalence of Schistosoma mansoni infection and other intestinal parasites in a rural community of the Municipality of Januária, Minas Gerais, Brazil.
Fig 3.
Prevalence of intestinal schistosomiasis and sensitivity of the Kato-Katz method, according to the number of examined slides and stool samples.
Prevalence of Schistosoma mansoni infection (white bars), as determined by the analysis of one fecal sample with two (SPL1 K1-K2), six (SPL1 K1-K6), 12 (SPL1 K1-K12) or 14 slides (SPL1 K1-K14), or obtained with the analysis of two slides prepared from each of three fecal samples (SPL1-3 K1-K2). The sensitivity of the different numbers of Kato-Katz slides examined (black bars) was calculated in relation to the reference standard, which included the combined results of 18 Kato-Katz slides, the saline gradient, and the Helmintex methods.
Table 3.
Performance of different parasitological and immunochromatographic methods for the detection of intestinal schistosomiasis in comparison with the reference standard (18 Kato-Katz slides, saline gradient, and Helmintex).
Fig 4.
Prevalence profile of intestinal schistosomiasis in an endemic population divided by different age groups according to the different parasitological methods.
Black circles indicate the prevalence profile in the population considering the sum of all parasitological methods used (reference standard: 18 Kato-Katz slides, saline gradient, and Helmintex); grey squares indicate the prevalence profile considering the recommended two KK slides from one fecal sample. Prevalence values (%) for each age group are indicated.
Table 4.
Sensitivity of different diagnostic methods for the detection of intestinal schistosomiasis considering the parasite load, as defined by egg counts of two Kato-Katz slides.
Table 5.
Performance of the rapid urine test for circulating cathodic antigen of Schistosoma mansoni (POC-CCA), as compared with the reference standard of a positive result in any of the used parasitological methods.
Fig 5.
Performance of the rapid urine test (POC-CCA) for the diagnosis of Schistosoma mansoni infection.
A: Photograph showing the different reactions possible with the POC-CCA: negative, trace, weak (+), medium (++) and strong (+++). B: Distribution of the POC-CCA results in individuals from an endemic area classified as negative (n = 116) or positive (n = 112) for S. mansoni infection by extensive parasitological testing (Reference standard: 18 Kato-Katz slides, saline gradient, and Helmintex); total n = 228). Data indicate the percentages of POC-CCA reactivities in each group of parasitologically negative or positive individuals. Red circles indicate discordant results in comparison with the reference standard (false positive: 28 and 2%; or false negative: 35%).
Table 6.
Prevalence, sensitivity and specificity of different diagnostic tests when combined with the Kato-Katz method, as compared with the reference standard (18 Kato-Katz slides, saline gradient, and Helmintex).