Schistosoma mansoni diagnostic antigens (Sm 31/12): a sero-epidemiological study in the Sudan

A cross-sectional study was performed in a Sudanese village endemic for intestinal schistosomiasis and not located in a control area. Immunological and parasitological diagnosis were compared in 156 individuals. Sera were tested with defined diagnostic Schistosoma mansoni antigens (Sm 31/32, i.e. hemoglobinase and cathepsin), and repeated stool examinations were performed. In immunoblots, 98% of the egg excretors were correctly identified. On the other hand, 75% of the parasitologically negative individuals had anti-Sm 31/32 antibodies. Cross-reactivity of these antigens with other parasites was excluded earlier, and the patients had not received previous chemotherapy. It is concluded that the sensitivity of these defined antigens to detect immunologically infections with S. mansoni compares favourably with stool examinations.