We have reported the isolation of a paramyxovirus from stocks of adult chinook salmon (Oncorhynchus tshawytscha) returning to coastal rivers of Oregon, USA (Winton et al 1985). The isolates were obtained from kidney and spleen tissues using the chinook salmon embryo cell line, CHSE-214. Initial cytopathic effect (CPE) was slow to develop, requiring 28 days incubation at 18°C. The virus replicated in CHSE-214, chum heart (CHH-1), kokanee ovary (K0-6), coho salmon embryo (CSE-119), and fathead minnow (FHM) cell lines where it produced a lytic type of CPE.

The virus was stable at pH 3-11 and iodo-deoxyuridine did not inhibit wiral replication. Infectivity was lost after treatment with chloroform indicating the presence of essential lipids. The density of virions in CsCl was 1.2 g/ml. The virus hemagglutinated cells of 11 of 14 species of birds, mammals, and fish tested. Electron microscopy of infected cells revealed enveloped particles 125-250 nm in dia. containing coiled nucleocapsids and examination of freon-treated virions showed the nucleocapsid was a helix approximately 18 nm in dia. and > 1000 nm in length (Winton et al 1985).

In addition to causing hemagglutination, members of the Paramyxoviridae are known for the ability to establish persistent infections of cell lines (Choppin and Compans 1975). The purpose of this study was to determine if the paramyxovirus isolates from salmon were able to establish persistent infections in fish cell lines and to study the nature of the infection.