牛ウイルス性下痢・粘膜病生ワクチンの乳牛における抗体応答と胎子感染

Abstract

The antibody response and possibility of fetal infection were assessed in cows that had been vaccinated with a bovine viral diarrhea-mucosal disease live virus vaccine (No.12-43 strain). The seroconversion rate was examined in 92 vaccinated cows. In those cows which had antibody titer of 4 or lower at the time of vaccination, the seroconversion rate reached almost 100%, while in those with antibody titer of 8 or higher, the rate tended to be lower in the cows which showed higher antibody levels against the No.12 and Nose strains. Twenty-six antibody-negative cows were vaccinated and their antibody titers were determined two months later. The mean antibody titers (n=26) against the No.12, Nose, and KS86-1 strains were 4806.5, 1170.0, and 121.4, respectively. Rises in antibody titer were also recognized against field-isolated virus strains obtained from cattle in Hokkaido, and the mean antibody titers against three isolates were 460.2, 135.0, and 131.5. The mean antibody titer (n=6) determined one year after the vaccination was 512 against the No.12 and Nose strains, and 64 against the K (+) strain. In some cases, however, in spite of a high antibody level against the KS86-1 strain, a significant rise in antibody titer was recognized when antibody levels against the No.12 and Nose strains were low. This suggested that some field strains may greatly be different serologically from vaccine strains.Eight antibody-negative pregnant cows were vaccinated, and all of them showed a significant rise in antibody titer after vaccination. Furthermore, antibody to the No.12 strain was detected in 5 pre-colostrol calves born to these 8 cows, suggesting fetal infection.The present findings indicated that the live virus vaccine used in this study induced an antibody response effective enough for prevention of bovine viral diarrhea-mucosal disease, although the use for pregnant cows should be avoided.