Mucosal disease-like syndrome in a calf persistently infected by Hobi-like pestivirus.

A calf persistently infected with Hobi-like pestivirus displayed severe clinical signs and subsequently died. Gross lesions and histopathological changes were suggestive of hemorrhagic and necrotic inflammation involving several tissues. A Hobi-like pestivirus pair was isolated from the dead calf, i.e., cytopathogenic (CP) and noncytopathogenic (NCP) strains strictly related to each other and to Italian prototype isolates at the genetic level. Two biotype-specific real-time reverse transcription-PCR assays determined the time of the emergence of the CP virus as 1 month before the calf's death. This highest RNA titers were reached in lymphoid and nervous system tissues, whereas only traces of CP viral RNA were found in blood. In contrast, great NCP virus loads were present in all tissues and biological fluids. The present report provides new insights into the pathogenesis and molecular mechanisms of this emerging group of pestiviruses.