A study in a flock of 100 sheep was carried out to detect animals pers
istently infected with Border Disease Virus (BDV). From buffy coats of
animals without neutralizing antipestivirus antibodies, 6 non cytopat
hic pestiviruses were isolated in cell cultures. Using 3 monoclonal an
tibodies, the 6 viruses were initially characterized as BDV strains.