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 gelfiltration 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 $\text{Echinococcus granulosus}$ and from uninfected sheep. Of 34 sheep with $\text{E. granulosus}$ infection 31 were positive with the cathodic antigen while of 85 sheep without $\text{E. granulosus}$ 8 were (falsely) positive. Many false positives appeared to be associated with heavy infections of $\text{Taenia ovis}$ or $\text{T. hydatigena}$ 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 $\text{E. granulosus}$ infections in sheep.