ABSTRACT. Bovine viral diarrhea virus 2 (BVDV-2) strains demonstrated in cattle, sheep, and adventitious contaminants of biological products have been evaluated by the palindromic nucleotide substitutions (PNS) method at the three variable loci (V1, V2 and V3) in the 5' untranslated region (UTR), to determine their taxonomical status. Variation in conserved genomic sequences was used as parameter for epidemiological evaluation of the species in relation with geographical distribution, animal host and virulence. Four genotypes, BVDV-2a, BVDV-2b, BVDV-2c, and BVDV-2d have been identified within the species. Taxonomical segregation corresponded to geographical distribution of genotype variants. Genotype 2a was present worldwide, and was the only circulating also in sheep, in addition to cattle. Genotypes 2b, 2c and 2d were restricted to South America. Contamination of biological products was related to genotypes 2a and 2d. Genetic variation could be related with chronological diffusion of the BVDV-2 species variants in different geographic areas. Chronologically, the species emerged in North America in 1978, spreading in UK and Japan, continental Europe, South America and New Zealand. Correlation between clinical features related with isolation of BVDV-2 strains and genetic variation indicated that subgenotype 1, variant 4 of genotype 2a was related with hemorrhagic syndrome. These observations suggest that evaluation of genomic secondary structure, by identifying markers for expression of virus biological activities and species evolutionary history, may be applied as useful tool for epidemiological evaluation of the BVDV-2 species, and possibly for other species of the genus Pestivirus. KEY WORDS: BVDV-2, genoepidemiology, palindromic nucleotide substitutions, pestivirus.

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The 5'-untranslated region (5 '-UTR) of the 'Giraffe' strain of pestivirus was sequenced for comparison with those of other pestiviruses from cattle, sheep, goats, and swine. A phylogenetic tree constructed with these strains suggested that the 'Giraffe' strain was allocated to a new taxon. This observation was also confirmed by a newly proposed method based on palindromic nucleotide substitutions (PNS) at the three variable regions in the 5 '-UTR. Other reported pestivirus strains isolated from deer were assigned as bovine viral disease virus (BVDV)-1 according to the PNS as well as phylogenetic analysis, suggesting that BVDV-1 strains can cross-infect deer as well as cattle, sheep, goats, and swine, and that wild deer may serve as a reservoir of BVDV-1. We also identified the genovar of a deer isolate, SH9/11, as BVDV-1c by the PNS method.

ABSTRACT. Bovine viral diarrhea virus 2 (BVDV-2) strains, isolated from sheep showing clinical symptoms of border disease, have been evaluated by the palindromic nucleotide substitution (PNS) method at the three variable loci (V1, V2 and V3) in the 5'-untranslated region (UTR) of genomic RNA. The characteristic two base-pairings common to the BVDV-2 species, a C-G pairing which was common to the V1 locus, and a G*U pairing common to the V2 locus, were observed in all tested strains. Strains BD-78 and C413 were identified by a unique C-G pairing at position 4 from the bottom of the V2 stem region, which is characteristic to BVDV-2b. BVDV2d characteristic U-A pairing at position 18 of the V1 stem region was observed in five strains, Lees, 167 237, 168 149, 173 157 and 175 375. No strains have been assigned to the genotypes BVDV-2a or BVDV-2c. Furthermore, the investigation at the level of the 5'-UTR excluded the application in sheep of the proposed BVDV-2 genetic virulence markers described in cattle. The two specific positions of uracil and cytosine nucleotides related to low or high virulence where indifferently present in the ovine BVDV-2 strains responsible of border disease.

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