Application of dipstick dye immunoassay (DDIA) kit for the diagnosis of schistosomiasis mekongi

The dipstick dye immunoassay (DDIA), developed in China for the detection of antibodies against Schistosoma japonicum, relies on soluble egg antigen (SEA) labelled with a colloidal dye. This assay is not only rapid, simple and inexpensive, but also particularly useful for screening in the field. In order to determine whether S. japonicum antigens are sufficiently cross-reactive to make the assay applicable for the diagnosis also of S. mekongi a DDIA approach based on the S. japonicum SEA was tried in cohorts of healthy and infected people living in areas non-endemic and endemic with regard to schistosomiasis mekongi in Cambodia and Laos. A sensitivity of 97.1% was recorded when testing Cambodian subjects, correctly diagnosing 33 out of 34 infected people. When the assay was applied in Laos, a sensitivity of 98.6% (69/70) was found. None of 114 residents living in a non-endemic area in Cambodia tested positive. A cross-reaction of 18.3% was found in patients infected with Opisthorchis viverrini. The results support the notion that the DDIA using S. japonicum SEA antigens can safely be implemented for the diagnosis of schistosomiasis mekongi, but care is needed in the interpretation of results obtained from areas that are co-endemic for O. viverrini.