The value of different antigens in the diagnosis of chronic bilharziasis by the skin and complement fixation tests.

Abstract

Summary Extracts prepared from the hepatopancreas of infected snails and from adult worms of S. mansoni and F. hepatica were tested in skin and complement fixation tests on a total of 70 patients with chronic bilharziasis and 304 control subjects. Skin tests with a saline extract of S. mansoni worms diagnosed 90 per cent of the cases and yielded only 1.2 per cent “false positives” while for the snail liver extract, the figures were 89 per cent and 27 per cent and the F. hepatica extract gave 66 per cent and 11 per cent respectively. The Schistosoma and Fasciola antigens were without after effects while the snail liver extract gave rise to many late and painful reactions. For the complement fixation test, the S. mansoni extract also proved superior, diagnosing 86.5 per cent of cases of bilharziasis and being doubtful or positive in 1 per cent of controls. The snail liver antigen reacted positively with 54 per cent of patients' sera and F. hepatica extracts were without activity. When skin tests and complement fixation tests were performed together in bilharzial patients, with the snail or with the Schistosoma antigens, positive results were always obtained with either or both tests. Treatment of the chronic patients had no effect on their reaction to the skin tests with these two antigens. In the complement fixation test, no clear cut effect was observed when the S. mansoni antigen was used but with the snail liver extract the proportion of negative reactors was high in a group of treated patients. Individuals who were examined both before and after treatment with the Schistosoma antigen showed a rise of titer in the C.F.T. in some cases, a fall in others, while in the majority there was no change. The value of different antigens and of technics of preparation, preservation and use are critically discussed in the light of the relevant literature. The use of an extract of Schistosoma mansoni worms is recommended for the skin and complement fixation tests in the diagnosis of bilharziasis.