A splenectomized cattle was experimentally infected with Babesia bigemina (Bb) isolated in Taiwan. The infected cattle was bled for Bb collection when the concentration of Bb in blood was counted to be
103 to 104/ml at 4-7 days post infection (Pl). The red cells from the half volume of blood obtained from infected cattle were lysed. The Bbs were concentrated and were frozen and thawed for their inactivation. Eventially, the inactivated immunogen (II) was prepared by adding DEAE-dextran into that Bb preparation. An activated immunogen (AI) was prepared from the rest part of blood by concentrating and mixing it with phosphate buffer saline containing glucose and calf serum.
An attempt to evaluate their safety and immunogenecity of both immunogens described above was made on 2 groups of cattle. The II was used to immunize both groups of cattle in farms with and without Bb contamination, so was the AI. The results showed that some cattle without Bb contamination produced a complement fixation antibody (CF Ab) titer of around x4 at 2 weeks PI with 11. The CF Ab titer was in-creasing up to x4 to x8 at 4 weeks PI and dropping down to nil at 12 weeks PI. However, the CF Ab in the cattle with Bb contamination was found to be not evident following the inoculation of cattle with II.
When the cattle was immunized with AI, different results were obtained.
The Cf Ab response in cattle without Bb contamination was detecatable at 2 weeks Pl and the highest titer was detected at 8 weeks PI. A CF Ab titer of X4 was still detectable at 20 weeks PI. On the other hand, the production of CF Ab in cattle with Bb contamination could be detected until 8th week Pl The CF Ab titer in cattle with Bb centamination were not fluctuate in the comparison to that in cattle without Bb contamination.
Most of cattle inoculated with AI did not show any abnormal response with the exception of a few cattle that revealed fever. Generally, parasitemia was found at 2 weeks PI. It's peak was detected at 4 weeks PI and parasite (Bb) was found disapparently. On the basis of these results. it would be suggested that the immunogens prepared in this study are safe and their immunogenecity is highly evident. Furthermore, the AI can strongly induce Ab response in cattle.