Three groups of SPF pigs aged 6-7 weeks were vaccinated respectively with BVD (S) prepared by 10% of infected spleen in cattle, with BVD(T) prepared by two passages in BT cells, and with BVD (T) + LPC mixture
The two groups of pigs respectively vaccinated w」th BVD (S) or BVD (T) were clinically normal, but the BVD (T) + LPC mixture group showed 1-2 days of slight fever reaction postvaccination.
Those tested pigs were challenged with ALD virulent virus 6 weeks postvaccination.
The pigs vaccinated with BVD (T) or BVD (S) showed fever reaction after ALD challenge and some pigs anorexia but recovered soon. On the contray pigs vaccinated with BVD (T)+ LPC mixture were quite normal after challenge.
The pigs vaccinated with BVD(S) orBVD (T) did not produce HC antibody before ALD challenge. But pigs with BYD (T) + LPC vaccination produced trace HC antibody 6 days postvaccination and had a hig titer of Log 3.01 just before challenge.
The pigs vaccinated with BVD (S) or BVD (T) virus rapidly induced HC antibody after challenge. Average HC antibody titer in these two groups were 1.5 and 2.24 one week, 2. 83 and 2. 86 two weeks, and 3. 13 and 2. 96 three weeks postchallenge. While most pigs of BVD CT)+ LPC group kept the same titer around 3.31 after challenge.
BVD antibody titer was rapidly produced in pigs vaccinated with BVD(S) or BVD(T) after HC challenge and reached 3.85 or above three weeks postchallenge. But pigs vaccinated with BVD (T) + LPC mixture did not produce BYD antibody as quickly as BVD (S) or BYD (T) group and only did reach 1. 83 three weeks postchallenge. The reason might be that the challenge ALD virus was influenced by existing HC neutralizing antibody.
Similar pathological changes were found in BVD (S), BVD (T) orBVD (T) + LPC groups. Tonsils ar.d lymphoid tissues of all vaccinated pigs were prominenly lymphoid hyperplasia, but with occasional hemorrhage in lymphoid tissue.