Resistance of rainbow trout to ulcerative dermal necrosis.

Abstract

THE susceptibility of rainbow trout to ulcerative dermal necrosis1, an infectious disease of some salmonids, has become a matter of importance to fish farmers. We have shown that the aetiological agent of ulcerative dermal necrosis is filterable2 although some workers have suggested that specific bacteria3,4 or fungi5 may be the primary pathogens. Preliminary experiments indicated that rainbow trout exposed to a salmon affected by ulcerative dermal necrosis did not show symptoms of the disease whereas a healthy salmon in the same tank as the trout did. The siphoning technique successfully used to reproduce ulcerative dermal necrosis in salmon2 was adapted to the experiments described here, which were designed to ascertain the susceptibility of rainbow trout to the disease. Further experiments, also described, were carried out to show whether rainbow trout can act as symptomless carriers.