Use of a partially purified Fasciola gigantica worm antigen in the serological diagnosis of human fascioliasis in Egypt.

Crude extracts of Fasciola gigantica adult worms, when used as an antigen in indirect hemagglutination (IHA) and counterimmunoelectrophoresis (CIEP) tests, detected all independently diagnosed human F. gigantica and F. hepatica infections but cross-reacted with sera of patients with schistosomiasis and amebiasis. Fractionation of this crude worm extract using Sephadex G-200 chromatography demonstrated four major protein peaks. Antigen from the crest and descending portion of peak II (mol. wt. approximately 20 x 10(3)) and all of peak III (mol. wt. approximately 6 x 10(3)) were pooled and used as a source of partially purified antigen. This partially purified fraction, when used in the CIEP test, reacted with sera from patients with fascioliasis but not those from schistosomiasis or amebiasis patients, whether undiluted or concentrated fivefold, but failed to react by IHA with fascioliasis sera. It reacted with undiluted sera from all individuals passing F. gigantica eggs except one, a possibly spurious infection, and with eight of 20 sera from individuals passing F. hepatica eggs, while the remaining 12 sera became positive after fivefold concentration. It also reacted with two sera from individuals passing eggs of both Fasciola species and with five of 11 sera from individuals negative microscopically but positive serologically with the crude antigen.