The first isolation of border disease virus (BDV) in Japan was from a pig farm of the farrow-to-finish type that did not keep small ruminants or cattle. The infection was detected during the course of sero-surveillance for classical swine fever virus (CSFV). The infected pigs had no clinical symptoms of CSFV or other disease; nevertheless, a high sero-positive rate of 58.5% was identified. A pig persistently infected with the BDV was found and suspected to be the cause of sero-prevalence in the farm. The isolated BDV was genetically close to BDV strains from New Zealand, but there was no epidemiological evidence concerning the route(s) of the invasion into the farm.
Serological tests are useful for monitoring of animals for CSFV. However, care should be taken when interpreting the test results, because cross-reactions will occur among pestiviral species. It is therefore important that PCR be used for detecting pestiviral agents and a subsequent genetic analysis should be performed for differentiation between CSFV and ruminant pestiviruses.
(Viral Disease and Epidemiology Research Division)
References:
Kawanishi, N. et al (2014) Veterinary Microbiology 171: 210-214
