Susceptibility of juvenile Atlantic cod Gadus morhua to viral haemorrhagicsepticaemia virus isolated from wild-caught Atlantic cod

A European strain of viral haemorrhagic septicaemia virus (VHSV) isolated f rom wild-caught cod Gadus morhua (H16/7/95) was shown to cause clinical dis ease and mortality in excess of 80% in juvenile Atlantic cod when administe red by the intra-peritoneal (i.p.) route. No virus was recovered from cod c ohabiting with experimentally infected fish at a ratio of 1:1, and no VHSV- associated mortality was demonstrated following immersion infection. Extern al signs of disease in cod were the presence of exophthalmia and ascites. V irus was identified as VHSV by enzyme-linked immunosorbent assay (ELISA) an d was recovered from both brain and organ pools (kidney, liver and spleen) of 100% of i.p, infected cod mortalities. Virus was also detected using an indirect immunofluorescence test on tissue imprints of kidney, Liver, splee n and brain taken from moribund fish. The fact that cod were not susceptibl e to VHSV following waterborne exposure raises important questions surround ing the propagation, maintenance and impact of a naturally occurring reserv oir of virus in the marine environment.