MOLECULAR CHARACTERIZATION OF OVINE PESTIVIRUSES

Forty-two ovine pestivirus isolates, collected over a period of 18 yea rs, were compared by phylogenetic analysis, The viruses were mostly fi eld isolates from Britain;two others originated from Sweden and two fr om New Zealand, RT-PCR products were obtained from two genomic regions , one within the 5'-noncoding (5'-NC) region, and the other encompassi ng parts of the p20 (N-pro) and C coding regions, Direct sequencing of the 5'-NC PCR products, followed by computer-assisted phylogenetic an alysis, divided the ovine pestiviruses into three main genotypes, The results demonstrated that sheep may naturally be infected not only wit h border disease virus (BDV), but also with bovine viral diarrhoea vir us (BVDV) types I and II, The BDV isolates segregated into two princip al subtypes represented by the Moredun strain from Scotland and the 13 7/4 strain from England, The BVDV-I group was composed of three cluste rs, two of them represented by BVDV reference strains NADL and Osloss, respectively, and the third by ovine isolates D1120/1 and D1432/P, Th e grouping of ovine pestiviruses, based on comparative nucleotide sequ ence analysis of the 5'-NC region, was confirmed by comparative analys is of the p20 (N-pro) and C coding regions, performed both at the nucl eotide and at the amino acid level, The presence of three genotypes in sheep, including BVDV-I and BVDV-II, indicates the inadequacy of the current host-species-based nomenclature and classification of pestivir uses.