Abstract
During the period 2003 to 2006, nine isolates and two detected genes of the bovine viral-diarrhea virus (BVDV) were recovered from six persistently infected (PI) cattle in Okayama Prefecture or commercial importedbovine fetal serum (FBS). Phylogenetic analysis of the 5' non-coding region (5'NCR) of the isolates whichare derived from PI cattle were classified as subtype BVDV-la (two isolates), lb (two isolates) and lc (threeisolates), and the isolates and detected genes derived from FBSs were classified as subtype BVDV-lb (1 isolate: derived from El Salvador), ld (1 isolate: derived from Canada) and lc (detected 2 genes: derived from Canada), respectively. Sequence analysis of the E2 gene suggested that the BVDV that was derived from Hokkaido was transmitted via a public pasture in Okayama Prefecture, and suggested that inappropriate active BVDV vaccine inoculation of the cattle in early pregnancy produced the PI calf. These results suggested thatanalysis of the E2 gene, which is more varied, in comparison with 5'NCR is useful in the epidemiological investigationof field BVDV isolates. The results of an examination of FBS suggested that BVDV-ld, which has beenisolated in Europe, has already been transmitted to Canada. This data demonstrated that BVDV-ld couldinvade Japan in the future through imported cattle.
