The use of a cathodic antigen in the immunoelectrophoretic serodiagnosis of Echinococcus granulosus in sheep.

An antigen was prepared from purified sheep hydatid-cyst fluid by gel-filtration on Sephadex G-200 followed by chromatography on DEAE-cellulose. In each case the first-peak material was used. This antigen, which migrated cathodically, was concentrated and used in immunoelectrophoretic analyses of 4X concentrated sera from sheep experimentally and naturally infected with Echinococcus granulosus and from uninfected sheep. Of 34 sheep with E. granulosus infection 31 were positive with the cathodic antigen while of 85 sheep with E. granulosus 8 were (falsely) positive. Many false positives appeared to be associated with heavy infections of Taenia ovis or T. hydatigena larvae. The "arc 5' immunoelectrophoresis test, which is the most specific immuno-diagnostic test for echinococcus infection in humans, was not able to specifically identify E. granulosus infections in sheep.