Sera of Sudanese patients with active infections of Schistosoma mansoni or S. haematobium were tested in immunoblots for their reactivity with Mr31/32 000 proteins of adult S. mansoni (Sm31/32). All sera from patients with intestinal (n=123) and all but one from those with urinary schistosomiasis (n=35) had antibodies against Sm31/32. These and additional data suggest that both specificity and sensitivity of Sm31/32 to detect schistosome infections are close to 100%. Antibodies against these proteins developed also in monkeys after experimental infection with S. haematobium. Sm31/32 antigens reacted in immunoblots as a doublet with most S. haematobium-patient sera and as a broad band with many S. mansoni-sera suggesting that at least two components are present in the molecular weight region of Mr31/32 000. The data demonstrate the potential use of Sm31/32 from adult worms to diagnose patients with intestinal or urinary schistosomiasis in endemic areas.
