These studies indicate the importance of the problem of BVDV contamination in fetal calf serum and several conclusions can be made: first, veterinary diagnostic laboratories should avoid the use of fetal calf serum in diagnostic procedures for pestivirus infections, second, there is a significant risk that adventitious BVDV from fetal calf serum may lead to contaminations in the veterinary biologicals industry (see Section on 'Other substances of animal/human origin and non-animal derived substances'), and third, the results indicate a very high rate of fetal infection with BVDV, possibly reflecting a failure in hygiene issues or in control measures (Bolin et al., 1991) .