Abstract
BackgroundCurrent available methods for diagnosis of schistosomiasis mansoni lack sufficient sensitivity, which results in underreporting of infectious in areas of low endemicity.Methodology/Principal FindingsWe developed three novel diagnostic methodologies for the direct detection of schistosome infection in serum samples. These three new methods were evaluated with positive patients from a low endemicity area in southeast Brazil. The basis of the assay was the production of monoclonal antibodies against the protein backbone of heavily glycosylated Circulating Cathodic Antigen (CCA). The antibodies were also selected for having no specificity to repeating poly-Lewis x units. Assays based on the detection CCA-protein should not encounter a limitation in sensitivity due to a biological background of this particular epitope. Three diagnostic methodologies were developed and validated, (i) Immunomagnetic Separation based on improved incubation steps of non-diluted serum, (ii) Direct Enzyme-linked Immunosorbent Assay and (iii) Fluorescent Microscopy Analysis as a qualitative assay. The two quantitative assays presented high sensitivity (94% and 92%, respectively) and specificity (100%), equivalent to the analysis of 3 stool samples and 16 slides by Kato-Katz, showing promising results on the determination of cure.Conclusions/SignificanceThe Immunomagnetic Separation technique showed excellent correlation with parasite burden by Cohen coefficient. The qualitative method detected 47 positive individuals out of 50 with the analysis of 3 slides. This easy-to-do method was capable of discriminating positive from negative cases, even for patients with low parasite burden.
Highlights
Schistosomiasis mansoni is a major parasitic disease associated with considerable morbidity and mortality in the developing world and may lead to sequelae of acute and chronic infection [1]
The current study evaluates the potential of three new diagnostic methods for schistosome infection, each based on the direct detection of Cathodic Antigen (CCA) for determining active schistosome infection and to monitor the effectiveness of therapy
Identification of populations to be targeted for individual treatment and broad-spectrum therapy in schistosomiasis-endemic areas, assessment of therapy efficacy, morbidity, and evaluation of control strategies need to be based on reliable and available diagnostic tools [29]
Summary
Schistosomiasis mansoni is a major parasitic disease associated with considerable morbidity and mortality in the developing world and may lead to sequelae of acute and chronic infection [1]. The gold standard for diagnosis of schistosomiasis mansoni is the detection of characteristic parasite eggs in stools. The direct detection of eggs is difficult and not always possible in patients with low parasite burdens, with consequent attainment of low eggshedding rates. Serological tests are widely used to detect antibodies against worm or soluble egg antigens. These assays are unable to differentiate between persistent and inactive infection [2]. While polymerase chain reaction methods can detect schistosomal DNA none of the published PCR methods has been evaluated for utilization in routine diagnosis [3,4]. Current available methods for diagnosis of schistosomiasis mansoni lack sufficient sensitivity, which results in underreporting of infectious in areas of low endemicity
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