Distribution pattern of bovine viral diarrhoea virus strains in intensive cattle herds in Italy

The genetic variation of bovine viral diarrhoea virus (BVDV) was studied by comparative nucleotide sequence analysis of 26 Italian field strains colle cted during the period 1995-2000 in 18 cattle herds. A fragment within the 5'-untranslated region (UTR) was sequenced directly from gel-purified produ cts obtained by reverse transcription polymerase chain reaction. BVDV-1b (n = 14), -1c (n = 1), -1d (n = 1) and BVDV-2 (n = 2) strains have been isola ted. Most herds were infected by BVDV-1b. Pairwise similarity and cluster a nalysis of the remaining BVDV-1 isolates (n = 8) did not provide a clear-cu t assignation to defined BVDV-1 groups. This is the first time that a BVDV- 2 isolation was reported in Italy. Among BVDV-2 reference strains, Italian BVDV-2 isolates showed the highest sequence similarity with the CD87 strain . Both BVDV-2 strains were isolated in two, healthy animals from different herds. The 5'-UTR sequence of one of the two BVDV-2 strains was identical t o a German BVDV field strain. Complete nucleotide homology was found only a mong BVDV strains isolated from the same herd, showing a herd-specific clus tering. Moreover, 99.6% homology was observed between strains from herds li nked by livestock trade. Despite the small number of BVDV isolates analysed , it revealed a high level of genetic diversity among Italian field BVDV st rains. (C) 2001 Elsevier Science B.V. All rights reserved.