Quantitative detection of schistosomal circulating anodic antigen by a magnetic bead antigen capture enzyme-linked immunosorbent assay (MBAC-EIA) before and after mass chemotherapy.

The magnetic bead antigen capture enzyme-linked immunosorbent assay (MBAC-EIA) has been applied to detect schistosomal circulating anodic antigen (CAA) in pre- and post-treatment sera from 55 individuals in a Schistosoma mansoni control project in the Blue Nile valley of western Ethiopia. The amounts of CAA detected by this assay were positively correlated with the numbers of eggs per gram of faeces (epg). A significant reduction in CAA levels as measured by the MBAC-EIA was observed after mass chemotherapy. The sensitivity was 88-89% in clinically significant cases excreting more than 100 epg. In light infections, however, the sensitivity was lower. None of 32 uninfected Norwegian blood donors or 12 Ethiopian immigrants to Norway were positive. The specificity was thus estimated to be 100%. The test is rapid (1-2 h) and simple to perform without sophisticated equipment and could therefore, with slight modification, be used as a reliable method of diagnosis at field level in endemic areas undergoing mass chemotherapy campaigns or population surveys.