Introduction - The control of bovine viral diarrhea (BVD) infection is based on three main pillars: implementation of bio-safety measures, test and cull of persistently infected animals (PI) and adoption of a vaccine protocol to prevent transplacental infection (fetal protection). Aim - The aim of this study is to verify, in field conditions, the efficacy of a combined approach that provides for detection and removal of PI animals and vaccination with a vaccine with the claim of fetal protection to BVDV. Materials and methods - The study lasted 9 years (November 2008-December 2017), was carried out in three farms located in the Province of Modena (Italy) and involved about 4,800 animals. Anamnestic data pointed out that in all the farms a BVD vaccination protocol was in place for at least 8 years (2001-2008) with both inactivated and modified-live vaccines. At the beginning of the study, all animals over 5 months of age were tested, in pool of 20 animals, for the detection of BVDV by RT-PCR. Subsequently, in the screening phase, PI research by RT-PCR was performed on all newborn calves. Moreover, BVDV detection in bulk milk was performed as well on a four-monthly basis. Regarding vaccination protocol, the animals were vaccinated with a modified-live vaccine (Mucosiffa®), namely heifers every six months and cows in the post-partum. Results and discussion - During the study, three PI animals were identified. These animals were born from non-PI cows vaccinated with an inactivated vaccine. During the period when the animals were vaccinated with the modified-live vaccine, no PI animals were detected. All the tests on bulk milk were negative for BVD antigen. Conclusion - The combined approach of vaccination with a modified-live vaccine, associated with test and cull of PI calves, allowed the control of BVD infection, as demonstrated by absence of new PI calves and BVDV circulation assessed by RT-PCR in bulk milk.
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