Segregation of bovine diarrhea virus into genotypes.
Sequence analysis of the 5′ untranslated end of the viral genome from isolates of bovine viral diarrhoea virus (BVDV) identified 2 groups termed BVDV I and BVDV II. Phylogenetic analysis suggested that these 2 groups were as different from each other as reference BVDV strains (NADL, SD-1 and Osloss) are from swine fever virus. Polymerase chain reactions, using the 5′ untranslated region and the genomic region coding for the p125 polypeptide identified 76 of 140 isolates as BVDV II. BVDV I isolates were those commonly used in vaccine production, diagnostic tests and research. BVDV II isolates were predominantly from fetal bovine sera, persistently infected calves born to dams vaccinated against BVDV, and cattle that had died from an acute form of BVDV termed haemorrhagic syndrome.