J.M. Groff J.K. Morrison W. T. Yasutake R.A. Holt M.L. Kent 1989 <p><i>C. psychrophila </i><span>infections of the cranium and anterior vertebrae in salmonid fishes were associated with ataxia, spiral swimming along the axis of the fish, and death. The syndrome was observed in 2-10% of underyearling coho salmon </span><i>Oncorhynchus kisutch, </i><span>rainbow trout</span><i>Salmo gairdneri, </i><span>and steelhead trout </span><i>S. gairdneri </i><span>at several private, state, and federal hatcheries in Washington and Oregon, USA, between 1963 and 1987. Affected fish did not recover and ultimately died. Histological examination consistently revealed subacute to chronic periostitis, osteitis, meningitis, and ganglioneuritis. Inflammation and periosteal proliferation of the anterior vertebrae at the junction of the vertebral column with the cranium with extension into the cranial case was a consistent feature. The adjacent nervous tissue, particularly the medulla, was often compressed by the proliferative lesion, and this may have caused the ataxia. Though bacteria were seldom observed in these lesions. </span><i>C. psychrophila</i><span>was isolated in culture from the cranial cavity of all affected fish that were tested. Epidemiological observations suggested that this bacterium is the causative agent because the spiral swimming behaviour and lesions were observed only in populations that had recovered from acute </span><i>C. psychrophila </i><span>infections.</span></p> application/pdf 10.3354/dao006011 en Inter-Research Spiral swimming behavior due to cranial and vertebral lesions associated with <i>Cytophaga psychrophila</i> infections in salmonid fishes article