Genetic typing of bovine pestiviruses from England and Wales.

Using RNA purified directly from stored clinical specimens, a collection of 62 pestiviruses were typed by RT-PCR and sequencing within the 5'-untranslated region of the genome. All the specimens had been obtained in 1966/1967 from diary cattle in England and Wales. Eight further pestiviruses, grown in cell culture, were characterised in the same way. Seven of these viruses were representatives of a panel of British isolates, obtained from cattle ten years before. The eighth was the virus used in a British bovine viral diarrhoea (BVD) vaccine. Most of the viruses were genetically unique and were of BVDV type Ia. One recent isolate was BVDV type Ib, two others were intermediate between Ia and Ib. No BVDV type II or border disease virus (BDV) isolates were found. There was no overall association between geographical and phylogenetic clustering, suggesting long-distance virus dispersal, presumably via trading of infected cattle. The sequences of the recently obtained cattle viruses were very similar or, in one case, identical to the older isolates in the region studied. Their close similarity to some previously characterised pestiviruses from British sheep suggests that a common pool of BVDV Ia is shared by these two livestock species, although another pestivirus--BVDV--is confined to sheep. The British cattle viruses were mostly distinct from continental European isolates, but more similar to type Ia isolates from North American cattle.