Application of an eradication protocol to Bovine Viral Diarrea(BVD) in large dairy cattle herds [Applicazione di un protocollo di eradicazione della Diarrea Virale Bovina (BVD) in allevamenti da latte di grandi dimensioni]

The study provided for application of a program for the eradication of BVDV in 28 large dairy herds with a number of animals ranging from 380 to 1,252. The protocol is composed of steps in sequence: collection of blood samples from all animals >6 months; collection of blood samples of newborn animals >6 months every four months; after 3 tests negative for PI animals, serological screening for BVDV NS2-3 antibodies on newborn animals, 6-12 months of age. Detection of PI animals has been performed by PCR for detection of BVDV types 1 and 2 on blood sample pools followed by ELISA BVDV antigen on single blood samples belonging to positive pools. In addition, all the herds applied a protocol of immunization by using BVDV inactivated vaccine. Over three subsequent screenings, corresponding to 12 months, all the PI animals were detected and culled. In a herd, no PI animal has been detected despite the persistence of seropositivity to BVDV NS2-3, considered an indirect demonstration of active viral circulation. Data show the efficacy of the mentioned protocol at eradicating BVDV in large dairy herds. The occasional presence of herds showing serological evidence of viral circulation in absence of PI animals detection must be taken into account when an eradication program to BVDV is applied.