Eradication of BVDV in cattle: the Norwegian project.

The intention of this collaborative project was eradication of pestivirus from the Norwegian cattle population of about 30,000 dairy and beef herds, primarily by identification and culling of persistently infected (PI) animals. Testing was performed in four tiers, with examination for pestivirus antibodies by indirect ELISA in (1) bulk milk, (2) pooled milk from primiparous dairy cows and (3) pooled blood from young stock. The herds positive in the third tier were examined for pestivirus antigen in blood from all antibody-negative individuals by -antigen-capture ELISA, and these animal composed tier (4). Following culling of the PI animals, a herd was considered free from pestivirus when pooled blood from young stock was antibody-negative on two sampling occasions three months apart. Number of herds with PI animals peaked at about 3000 (10 per cent) in the 2nd project year, then decreased steadily; only three herds (0.01 per cent) contained PI animals 10 years later. Solid, continuous information flow to all relevant partners was crucial to project success. The project saved losses of between 50 million and 200 million Norwegian crowns (NOK) annually (approximately 4.5 million to 18 million GBP). Project running costs for 10 years were 52.4 million NOK. Following project completion, surveillance of the Norwegian cattle population for pestivirus has continued.