Isolation of an epitheliotropic herpesvirus from white sturgeon Acipenser transmontanus

Mortality among juvenile white sturgeon Acipenser transmontanus was associated with infections of the integument and oropharyngeal mucosa with a previously unrecognized herpesvirus.There was acanthosis and necrosis of the affected epithelium.No other tissues were found to be infected with the white sturgeon herpesvirus (WSHV) The virus was isolated from infected fish using a recently estabhshed cell line from the skin of white sturgeon (WSSK-l).There was no evidence for virus replication in 2 other lines from the white sturgeon heart (WSH-l) and spleen (WSS-2) nor in the CHSE-214 and EPC lines derived from chinook salmon Oncorhynchus tshawytscha and common carp Cyprinus carpio, respectively.Cytopathic effects in WSSK-1 cells were characterized by syncytia 2 to 4 d after inoculation of cells at 15OC.The virus grew in WSSK-1 cells at 10, 15 and 20°C but not at 5 or 25°C.Virions detected in both infected tissues and WSSK-1 cells were characteristic of herpesviruses: hexagonal capsids (mean diameter of 110 nm) had a deeply staining core surrounded by the tegument and an external envelope with a diameter of 230 nm.Experimentally induced infections and mortality of juvenile white sturgeon followed bath exposure to the virus grown in WSSK-1 cells.The association of WSHV with mortality among farm-reared and experimentally infected fish indicated that the virus can be one cause of mortality often observed in the early rearing phases of juvenile white sturgeon.