Abstract
Bovine viral diarrhea virus(BVDV)infection occurred on a dairy farm with about 70 milking cows, in a BVDV-free region. A cow with persistent infection(PI)of BVDV, introduced from another region, was identified to be the source of the infection, through antibody and BVDV gene tests performed on all cows raised on the farm. The PI cow was sacrificed, and new PI bovines were identified among calves by virological testing and culled, which led to successful clearance of BVDV from the affected farm. The viral gene was not detected in bulked milk of 13 dairy farms located around this dairy farm. The direct damage caused to the farm was 6 abortions and the sacrifice of a total of 11 animals, namely, the introduced PI cow, which was the source of infection, and 10 newly delivered PI calves. New PI developed in calves that were of gestational age 10-98 days when the PI cow was introduced into the farm, and the incidence was 34.5%(10/29).
