Clubbing and necrosis gill (CNG) syndrome in sea-caged Atlantic salmon, Salmo salar L., in Tasmania: an initial report

In autumn 1993, an outbreak of gill disease occurred in Atlantic salmon, Salmo salar L., smolts farmed in the Huon estuary in southern Tasmania, Australia. Histologically, the presumptive primary lesion appeared as focal, sometimes full thickness, gill necrosis, which showed no host reaction in the initial stages. Healing of these damaged areas gave rise to conspicuous expanded tips or clubbing of gill filaments. The term clubbing and necrosis gill (CNG) syndrome is suggested to include both these histological features. Fusion of lamellae proximally along the filament, often with vascular dilation, was also a feature of the condition. Similar lesions have been described previously in the literature, but the initial necrosis followed by the very prominent clubbing of filaments was sufficiently different from previous descriptions to warrant designation of this condition as a distinct entity.