Immunization of cattle with a Babesia bigemina antigen in Freund's complete adjuvant.

Three adult intact cattle and five splenetomized calves were immunized against Babesia bigemina by the subcutaneous injection of an adjuvant-vaccine given twice at 3- and 4-week intervals, respectively. The antigen consisted of B bigemina parasites and erythrocytic stroma. The vaccinated adults plus one control, and the vaccinated splenectomized calves plus four comparable controls were challenge exposed at 67 and 33 days, respectively, after the last vaccine injection. All control animals died of acute babesiosis. The intact vaccinated adult cows showed only minimal response and little or no drop in packed cell volume. Three of five vaccinated splenectomized calves showed a moderate response to challenge exposure and recovered rapidly.