Thirty five-week-old healthy Newzealand meet rabbits were used for bacteria infection. Bb infections were performed as the following: Finally, the dosage was 4.6×109CFU, and the ear vein was used in rabbits in the challenge group. Blood samples were collected for anticoagulant blood cell assay and serum isolation and preservation at 7 days after challenge. Six rabbits in the attack group died 10 days after the attack. All rabbits were euthanatized at the end of the experiment. Nine of the rabbits in each group were taken for spleen extraction.