Vaccination of calves with bovine herpesvirus 1 vaccines originating from contaminated batches did not result in infection with bovine virus diarrhoevirus

The aim of the experiment was to study whether bovine herpesvirus 1 (BHV1) marker vaccine batches known to be contaminated with bovine virus diarrhoea virus (BVDV) type 1 could cause BVD in cattle. For this purpose, four grou ps of cattle were used. The first group (n = 4 calves, the positive control group), was vaccinated with vaccine from a batch contaminated with BVDV ty pe 2. The second group (n = 4 calves, the negative control group), was vacc inated with vaccine from a batch that was not contaminated with BVDV. The t hird group (n = 39 calves, was vaccinated with a vaccine from one of four b atches contaminated with BVDV type 1 (seronegative experimental group). The fourth group n = 6 seropositive heifers), was vaccinated with a vaccine fr om one of three batches known to be contaminated with BVDV type 1. All catt le were vaccinated with an overdose of the BHV1 marker vaccine. At the star t of the experiment, all calves except those from group 4 were seronegative for BVDV and BHV1. The calves from group 4 had antibodies against BVDV, we re BVDV-free and seronegative to BHV1. After vaccination, the positive cont rol calves became severely ill, had fever for several days, and BVDV was is olated from nasal swabs and white blood cells. In addition, these calves pr oduced antibodies to BVDV and BHV1. No difference in clinical scores of the other groups was seen, nor were BVDV or BVDV-specific antibody responses d etected in these calves; however, they did produce antibodies against BHV1. The remainder of each vaccine vial used was examined for the presence of i nfectious BVDV in cell culture. From none of the vials was BVDV isolated af ter three subsequent passages. This indicated that BVDV was either absent f rom the vials or was present in too low an amount to be isolated. Thus vacc ination of calves with vaccines from BHV1 marker vaccine batches contaminat ed with BVDV type 1 did not result in BVDV infections.