An attempt to vaccinate sheep against Fasciola hepatica using a juvenile fluke antigen sheep antibody complex.

Sheep were injected intramuscularly with a mixture of Freund's complete adjuvant and a precipitated fluke antigen-antibody complex isolated from in vitro cultures of excysted metacercariae of Fasciola hepatica in serum from infected sheep. Control groups of sheep were given Freund's complete adjuvant or were untreated. All sheep were then challenged with 200 metacercariae of F hepatica. Assays of antibody and liver enzymes in serum collected during the experiment indicated that although vaccination with the complex resulted in a pronounced antibody response to its antigenic component(s), there was no apparent effect on the migratory activity of the juvenile flukes in these animals. Failure to confer protection on vaccinated sheep was confirmed at autopsy when no significant difference was found between the worm burden of these animals and the controls.