Diagnosis of Schistosomiasis by Reagent Strip Test for Detection of Circulating Cathodic Antigen

Abstract

A newly developed reagent strip assay for the diagnosis of schistosomiasis based on parasite antigen detection in urine of infected individuals was evaluated. The test uses the principle of lateral flow through a nitrocellulose strip of the sample mixed with a colloidal carbon conjugate of a monoclonal antibody specific for Schistosoma circulating cathodic antigen (CCA). The strip assay to diagnose a group of highly infected schoolchildren in Mwanza, Tanzania, demonstrated a high sensitivity and association with the intensity of infection as measured both by egg counts, and by circulating anodic antigen and CCA levels determined by enzyme-linked immunosorbent assay. A specificity of ca. 90% was shown in a group of schistosome-negative schoolchildren from Tarime, Tanzania, an area where schistosomiasis is not endemic. The test is easy to perform and requires no technical equipment or special training. The stability of the strips and the conjugate in the dry format lasts for at least 3 months at ambient temperature in sealed packages, making it suitable for transport and use in areas where schistosomiasis is endemic. This assay can easily be developed to an end-user format.Diagnosis of schistosomiasis, one of the major parasitic diseases in tropical areas, is usually performed by parasitological (microscopic detection of eggs), and/or immunological methods (antibody and antigen detection) (11). The demonstration of parasite eggs in urine or feces directly indicates the presence of the worms, but the disadvantages of this approach include a high fluctuation in egg counts, easily missed low infections, and a relatively time-consuming methodology. Immunological methods such as enzyme-linked immunosorbent assays (ELISAs) usually require more advanced laboratory settings but may yield a higher sensitivity (particularly for antibody detection). However, for antibody detection, specificity may be a problem, and the efficacy of treatment remains difficult to determine since specific antibodies continue to be present long after the worms have disappeared. In this respect, detection of parasite antigens (such as circulating anodic antigen [CAA] and circulating cathodic antigen [CCA]) by ELISA (1, 3, 11) shows many advantages, such as the demonstration of active infections or of the effect of treatment, and has a high specificity. However, ELISA procedures (total assay time of ca. 3 h) remain relatively slow, even in an optimized and standardized format, and they require skilled personnel and well-equipped laboratories. In most studies involving the CAA and/or CCA ELISA on serum and urine samples, the best diagnostic performance was achieved with the urine CCA assay, with sensitivities ranging from 80 to 100% (11). For this reason and because of the relative ease of obtaining urine samples, we have investigated ways to develop a rapid field-applicable test for the detection of CCA in the urine of schistosome-infected individuals. Here, we describe the development of a lateralflow assay with carbon-labeled anti-CCA monoclon...

Performance of POC-CCA® in diagnosis of schistosomiasis mansoni in individuals with low parasite burden

“…This indicates that levels of serum and urine CCA and CAA decrease significantly some weeks after treatment, constituting a biomarker for schistosomiasis cure. Additional studies have found that detection of CCA and CAA offers some advantages for schistosomiasis diagnosis, such as the identification of active infections and a good diagnostic performance, particularly in highly infected individuals (11) (12) .…”

Field-based evaluation of a reagent strip test for diagnosis of Schistosomiasis mansoni by detecting circulating cathodic antigen (CCA) in urine in low endemic area in Ethiopia

“…Because of less field applicability of the ELISA-based method for the diagnosis of schistosomiasis at a community level, reagent strip/dipstick based assay has INTRODUCTION D iagnosis of intestinal schistosomiasis by demonstrating the parasites' eggs in feces using convectional techniques like Kato and formol-ether concentration has been claimed for its low sensitivity in case of low intensity of infection, post-treatment situations as well as for egg output fluctuation (De Vlas & Gryseels, 1992;Gryseels & De Vlas, 1996;Engels et al, 1996;Kongs et al, 2001). Detection of specific antibodies induced against the different stages of the parasite using immunological techniques has been suggested as a solution to minimize the risk of low sensitivity of the parasitological techniques (Rossi et al, been developed for the diagnosis of both intestinal and urinary schistosomiasis by detecting CCA of the parasites in urine of infected individuals regardless of species specificity, according to the information provide by the manufacturer (B.V. European, Veterinary Laboratory, The Netherlands) and Van Dam et al (2004). The test has been found to be highly sensitive and specific in detecting CCA in the urine of Schistosoma mansoni -infected individuals in high endemic areas of the disease (Van Etten et al, 1994;Van Dam et al, 2004;Stothard et al, 2006).…”

“…Detection of specific antibodies induced against the different stages of the parasite using immunological techniques has been suggested as a solution to minimize the risk of low sensitivity of the parasitological techniques (Rossi et al, been developed for the diagnosis of both intestinal and urinary schistosomiasis by detecting CCA of the parasites in urine of infected individuals regardless of species specificity, according to the information provide by the manufacturer (B.V. European, Veterinary Laboratory, The Netherlands) and Van Dam et al (2004). The test has been found to be highly sensitive and specific in detecting CCA in the urine of Schistosoma mansoni -infected individuals in high endemic areas of the disease (Van Etten et al, 1994;Van Dam et al, 2004;Stothard et al, 2006). On the other hand, the test was found to be valueless in the diagnosis of schistosomiasis haematobium (Stothard et al, 2006).…”

Diagnosing schistosomiasis: where are we?

“…To date, currently available CCA tests have been shown to have moderate to good reliability in detecting S. mansoni 54,[61][62][63][64][65] but poor performance in detecting S. haematobium 61,[66][67][68][69] . Recently, the Bill & Melinda Gates Foundation sponsored evaluation studies on the accuracy of the urine CCA tests for determining schistosomiasis prevalence in young children in African countries.…”

“…The detection of circulating anodic antigen (CAA) and circulating cathodic antigen (CCA) in serum and urine, using the ELISA 52,53 or dipstick platforms 54 , and antigen capture with monoclonal antibodies 55 have been the most widely studied methods. Their main advantages are high specificity, positive correlation with worm burden, and the possibility for estimation of infection intensity [56][57][58] .…”