Abstract

Cytophaga psychrophila infections of the cranium and anterior vertebrae in salmonid fishes were associated with ataxia, spiral swimming along the long axis of the fish, and death. The syndrome was observed in 2 to 10% of underyearling coho salmon, rainbow trout and steelhead trout at several private, state, and federal hatcheries in Washington and Oregon, USA. Epizootiological observations suggested that C. psychrophila is the etiologic agent of the disease because the spiral swimming behavior and lesions were only observed in populations which had recovered from acute infections, known as "cold-water disease". Shortened abstract.