Full-length sequence determination and isolation of infectious particles of an atypical porcine pestivirus from wild boars in Ishikawa Prefecture, Japan.

Atypical porcine pestivirus (APPV), the causative agent of congenital tremor (CT) type A-II, is a single-stranded (+) RNA virus classified in the genus Pestivirus of the family Flaviviridae that infects domestic pigs and wild boars. While surveys and studies on APPV infection in pigs are ongoing, information on APPV in wild boars is lacking. In Japan, there have been no reports of APPV infection in wild boars. We therefore screened serum samples from 333 wild boars to determine the prevalence of APPV in Ishikawa Prefecture. APPV-RNA was detected in two samples, and the complete viral genome was sequenced from one of these samples. Infectious particles were isolated from the same serum sample. Phylogenetic analysis classified the APPV detected in wild boars as genotype 3, which is consistent with the genotype previously reported in Japanese domestic pigs. Replication kinetics assays showed that wild boar-derived APPV exhibited lower replication efficiency than pig-derived APPV, although this efficiency improved with successive passaging of infected cells. The complete APPV sequence and infectious particles obtained from wild boar-derived serum for the first time in Japan are considered useful for future research on APPV.