Antibody test is sometimes necessary for the diagnosis of acute human metagonimiasis because eggs may not be detected in stool. The antibody test (ELISA) was evaluated for its significance by reacting human sera from clinically diagnosed metagonimiasis, fascioliasis, clonorchiasis and paragonimiasis with 4 crude extracts of Metagonimus yokogawai (metacercariae), adults of Fasciola hepatica, Clonorchis sinensis and Paragonimus westermani. By ELISA, 10 of 11 metagonimiasis sera showed the highest absorbance (abs.) to the homologous antigen. Cross reactions to M. yokogawai antigen occurred most frequently in clonorchiasis sera. The antigenic protein fractions in M. yokogawai metacercarial extract were observed by SDS-PAGE/immunoblot using patients and control sera together with experimental cat sera. Out of 14 protein bands in the extract, 11 bands were reacting. Cross reacting bands to other trematodiasis sera were frequently observed. Of the reacting bands, 66 and 22 kDa proteins were recognized as specific for metagonimiasis.
