Abstract
Six Holstein calves 6-13 months old which had never been grazed on pasture were inoculated with 1, 000 μg of toxoplasma lysate antigen (TLA) two or three times. They were placed on a pasture contaminated with thicks as a vector of Theileria sergenti 7 weeks after the initial inoculation with TLA emulsion. The lowest RBC was 649×104/μl for the group of TLA emulsion inoculation and 229×104/μl for a control group in grazing. The highest and average rates of parasitized erythrocytes were 2.6% and 0.6%, respectively, for the former group and 10.0% and 3.2% for the latter. When examined for production of antibody against TLA, all the inoculated calves showed an indirect hemagglutination (IHA) antibody titer higher than 1:6 after the initial inoculation with TLA emulsion, except one of three calves inoculated twice with this antigen. The uninoculated control calves also exhibited an increase in IHA antibody titer against TLA after they were placed on pasture. On the other hand, the complement fixation and the indirect immunofluorescence antibody titers against T.sergenti became detectable in one calf inoculated three times with TLA emulsion and the uninoculated control calves 1-5 weeks after the beginning of grazing. No calves possessed serum antibody against Babesia ovata or Anaplasma centrale.
