SOME MODIFICATIONS OF THE FLUORESCENT ANTIBODY TEST IN HUMAN BILHARZIASIS.

Although the fluorescent antibody (FA) test for human bilharziasis described by Sadun and colleagues has proved of great value, its use involves certain difficulties which the author of the present paper has attempted to obviate. The first part of the paper describes a cheap and reproducible method for producing a cercarial antigen conjugated with rhodamine B 200 for use in the indirect FA test. The second part deals with a new modification in which the conjugated cercarial antigen is employed with a bentonite-absorbed FITC antihuman globulin serum and discusses the advantages of this test over the normal FA test.Experience has shown that the use of rhodamine-albumin-coated cercariae, conjugated cercariae or normal fixed cercariae as antigens does not always give valid results when compared with those obtained with the FA test or the ordinary complement-fixation test in bilharziasis. In the third part of this paper, however, the author describes a modification of the complement-fixation test involving the use of a bentonite-absorbed fluorescent antiguinea-pig serum and the RB 200 conjugated cercariae described earlier. This test has given reproducible results in known positive control human sera which have been valid when compared with the Sadun FA test, the conjugated cercarial FA test and the bentonite fluorescent antibody test described in the second part of this paper. In some instances the test results have also been supported by evidence from standard skin tests.