Spatial and Temporal Genetic Homogeneity of Orf Viruses Infecting Japanese Serows (Capricornis crispus)

概要

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This study genetically characterized orf viruses (ORFVs) isolated from recent outbreaks in Japanese serows (Capricornis crispus) in 2007 and 2008, and from earlier outbreaks from 1985 to 2001. Nucleotide sequences of genes for the viral envelope, vascular endothelial growth factor (VEGF), and virus interferon resistance (VIR) were determined in two ORFVs isolated from recent outbreaks and in eight from earlier outbreaks. No deletions or insertions were observed in these genes. Surprisingly, the amino acid sequences of the envelope and VIR genes were identical among the 10 ORFVs, and only one amino acid substitution in the VEGF gene was found in one of the two recent ORFVs (2007). Genotyping by differential PCR for the A32L gene, which encodes an ATPase, classified all of the 10 ORFVs into the same genotype. In an ORFV isolated from a sheep in 1970, the three sequenced genes were almost the same as in the ORFVs isolated from Japanese serows, and the ORFV in 1970 was classified into the same genotype as the ORFVs from Japanese serows. These results suggest that recent outbreaks in Japanese serows are caused by ORFVs genetically closely related to the viruses in earlier outbreaks and that these genetically stable ORFVs have circulated among Japanese serows over a long period of time.