Abstract
BackgroundThe Kato-Katz is the most common diagnostic method for Schistosoma mansoni infection. However, the day-to-day variability in host egg-excretion and its low detection sensitivity are major limits for its use in low transmission zones and after widespread chemotherapy. We evaluated the accuracy of circulating cathodic antigen (CCA) urine-assay as a diagnostic tool of S. mansoni. In comparison, a low sensitive CCA test (CCA-L) was assessed.MethodologyThe study was conducted in three settings: two foci with single S. mansoni infections (settings A and B), and one mixed S. mansoni – S. haematobium focus (setting C). Stool and urine samples were collected from school-children on three consecutive days. Triplicate Kato-Katz readings were performed per stool sample. Each urine sample was tested with one CCA and only the first urine sample was subjected to CCA-L. Urine samples were also examined for S. haematobium eggs using the filtration method and for microhaematuria using urine reagent strips. Overall, 625 children provided three stool and three urine samples.Principal FindingsConsidering nine Kato-Katz thick smears as ‘reference’ diagnostic test, the prevalence of S. mansoni was 36.2%, 71.8% and 64.0% in settings A, B and C, respectively. The prevalence of S. haematobium in setting C was 12.0%. The sensitivities of single Kato-Katz, CCA and CCA-L from the first stool or urine samples were 58%, 82% and 46% in setting A, 56.8%, 82.4% and 68.8% in setting B, and 49.0%, 87.7% and 55.5% in setting C. The respective specificities were 100%, 64.7% and 100%; 100%, 62.3% and 91.3%; and 100%, 42.5% and 92.0%. Mixed infection with S. haematobium did not influence the CCA test results for S. mansoni diagnosis.Conclusions/SignificanceUrine CCA revealed higher sensitivity than CCA-L and triplicate Kato-Katz, and produced similar prevalence as nine Kato-Katz. It seems an attractive method for S. mansoni diagnosis.
Highlights
Schistosomiasis remains of significant public health importance worldwide, with an estimated 207 million people infected
We evaluated the commercially available point-of-contact circulating cathodic antigen (CCA) as a potential tool for the screening of S. mansoni infections
Our results showed that urine CCA assay had a better sensitivity for detecting S. mansoni infections than single and triplicate Kato-Katz thick smears
Summary
Schistosomiasis remains of significant public health importance worldwide, with an estimated 207 million people infected. The disease is caused by six species of blood flukes: Schistosoma haematobium, S. mansoni, S. japonicum, S. intercalatum, S. guineensis and S. mekongi. S. haematobium causes urogenital schistosomiasis while the other species cause intestinal disease. The development of preventive chemotherapy strategy, the greater access to praziquantel and the increased resources for control have amplified treatment possibilities to the majority of people who need it [4]. Significant progress has been made in the control of schistosomiasis within the past ten years, though this falls short of the target set by World Health Assembly Resolution 54.19 adopted in 2001, which aimed to reach at least 75% of all school-aged children at risk of morbidity by 2010 [5]. The Kato-Katz is the most common diagnostic method for Schistosoma mansoni infection. A low sensitive CCA test (CCA-L) was assessed
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