Immunization of sheep against Theileria hirci infection with schizonts propagated in tissue culture

Two experiments were carried out. In the first, three groups of lambs were inoculated subcutaneously with 3 X 10(6) schizonts of different passages (3, 30 and 63) of Theileria hirci propagated in tissue culture. Severe reactions were observed in lambs inoculated with organisms derived from the 3rd passage. In the second experiment, four groups were inoculated with 5 X 10(5), 3 X 10(6), 1 X 10(7) and 5 X 10(8) schizonts of the 63rd passage. No clinical reactions or parasites were detected in lambs inoculated with 5 X 10(5) schizonts. Mild reactions were observed in lambs inoculated with 3 X 10(6), 1 X 10(7), and 5 X 10(7) schizonts. Lambs inoculated with 3 X 10(6) schizonts were resistant to challenge with a virulent strain. The indirect fluorescent antibody (IFA) test was used to determine the antibody titre.