A re-evaluation of the slide flocculation test for the diagnosis of schistosomiasis with adult worms as antigen.

The present study was conducted to determine whether extracts from adult Schistosoma mansoni could be coated onto cholesterol-lecithin crystals. Of particular interest was the use of stunted schistosomes (SS) recovered from rabbits. The reactions obtained with this antigen in this slide flocculation (SF) test were compared with those employing antigens from cercariae and mature adult worms. The stunted schistosome SF test (SFSS) showed a high sensitivity and specificity while cercarial antigen showed extensive cross reaction with Trichinella spiralis, Ascaris lumbricoides, and Echinococcus granulosus antisera. Both SS and cercarial antigens reacted with syphilitic sera, but the former only with high titer sera. The antigen from mature adult worms could not be coated onto cholesterol crystals, a finding which is in agreement with previous investigations. The relative simplicity of the SFSS test and its apparent high sensitivity and specificity indicates that the test may be an ideal epidemiological tool for schistosomiasis surveys. The results obtained should encourage additional study of the procedure involved and investigation into the role of lipids in flocculation tests. In addition, the findings should stimulate immunological studies of the stunted schistosomes.