Human fascioliasis in Cajamarca/Peru. II. Humoral antibody response and antigenaemia.

Four immunoassays (IgG ELISA, indirect haemagglutination = IHA, IgM ELISA and antigen ELISA) for determination of humoral antibody and of circulating antigen, respectively, were applied to sera of 45 Peruvian fascioliasis patients who were identified by demonstration of Fasciola eggs in faeces. All of the sera were reactive by at least one of the assays. Sensitivity rates were 0.98 for IgG ELISA, 0.56 for IHA, 0.51 for IgM ELISA and 0.20 for antigen ELISA. Among those 34 patients who were followed up after praziquantel therapy there was a different pattern of immunoassay results between patients who stopped excreting eggs after therapy and those who continued to pass eggs. Cure was indicated by disappearance of both IgM antibody and antigen levels during three months after treatment, whereas persistence of infection corresponded to new or re-occurrence of IgM antibody and/or circulating antigen during the period of observation. Since there was no apparent relation of immunoassay results to therapy, it is presumed that the Peruvian patients did not respond to praziquantel at all.