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In order to test the efficacy of antibody-mediated immunologic methods for the diagnosis of schistosomiasis (immediate intradermal and serologic tests) and to compare them with a cell-mediated immunologic reaction (the delayed intradermal test), 350 subjects were examined. Approximately half of them were from the West Indian island of St. Lucia, all with proven schistosomiasis mansoni on fecal examination, and the other half were comparable subjects from St. Vincent, an island 30 miles distant where schistosomiasis has never been found. Five different antigens utilized in the intradermal tests (prepared from Schistosoma mansoni cercariae, adult worms and eggs, and from S. haematobium and S. japonicum eggs) were injected blindly in a randomized manner. The antigens were almost equally and highly sensitive in the immediate skin reaction in the adult St. Lucians (89-95%, with the exception of S. haematobium, 74%), but were far less sensitive in the children. There was a large number of false positive immediate responses among the Vincentians, e.g., 44 of 171 subjects tested with the S. mansoni cercarial antigen. Delayed skin reactions, which among the St. Lucians reached a peak of 66% positivity with S. mansoni adult worm antigen, were less sensitive than the immediate reactions, but appeared to be more specific. Among the St. Lucians there were relatively few false positive delayed reactions with the heterologous antigens (S. haematobium and S. japonicum eggs), while the Vincentians had very few false positive reactions with the homologous and none with the heterologous antigens. Of the three serologic tests (complement fixation, cholesterol-lecithin flocculation, and fluorescent antibody), the first two were insensitive and non-specific; the third was the only one that provided results which were at all acceptable.
External Staff, Medical Research Council, seconded to Rockefeller Foundation.
Now at the School of Public Health, University of Texas, Houston, Texas 77025.
Staff member, Rockefeller Foundation.