BOVINE VIRUS DIARRHEA VIRUS - DETECTION OF DANISH DAIRY HERDS WITH PERSISTENTLY INFECTED ANIMALS BY MEANS OF A SCREENING-TEST OF 10 YOUNG STOCK

In each of 42 Danish dairy herds, ten young stock aged 8-18 months were tested for antibodies against bovine virus diarrhoea virus (BVDV). At the same time a bulk milk sample from each herd was examined for antibodies against BVDV. The herds could be divided into two distinct groups: (1) Group A (24 herds) had three or less antibody carriers among the ten young stock sampled from each herd and were considered 'slightly infected'; (2) Group B (18 herds) had eight or more antibody carriers in the 'spot' sample and were therefore considered 'heavily infected'. Persistently infected animals were not found in two Group A herds studied by a subsequent total herd blood test but were detected in five Group B herds in which all animals in the herds were subsequently tested. Bulk milk titers were generally higher in Group B than in Group A herds. However, there was considerable variation, and in most cases it was not possible to distinguish the two herd categories from one another by means of bulk milk titers.