Investigations on the safety of the two-step BVD vaccination with killed and modified live BVD-vaccine in pregnant cows

For a first trial ten heifers which were kept in an isolation unit and for a subsequent field trial with 17 cows from a cattle farm situated in the no rthern part of Lower Saxony were chosen. All 27 cattle were found free of B VD-virus and 24 of these were free of BVD neutralising antibodies (nab). 21 of them were in the 1. trimester the remaining six cows in the 2.-3. trime ster of pregnancy. After basic immunisation with killed BVD vaccine between day 38-62 (first trial) and day 1-230 (field trial) of pregnancy no BVD-na b could be detected when the second vaccination with BVD modified live vacc ine (mlv) was accomplished 23 and 33 days later. This second BVD vaccinatio n elicited however an effective anamnestic immune response resulting in hig h antibody titers. The course of the pregnancy in vaccinated cows passed wi thout complications and 23 calves were born clinically healthy. The safety of the two-step vaccination with BVD mlv was demonstrated moreover as no BV D-virus and no BVD nab resulting from transplacental infection could be det ected in precolostral blood samples of the calves born from vaccinated cows . The two-step BVD vaccination which could be a possible alternative within the control of BVD-virus infections according to the official guidelines i s discussed.