Apparent chronic bacterial myeloen-cephalitis in hatchery-reared juvenile coho salmon Oncorhynchus kisutch in Alaska

Abstract

Chronic losses in juvenile coho salmon Oncorhynchus kisutch at 2 Alaskan hatcheries were associated with neurologic disorders and with chronic myeloencephalitis of apparent bacterial etiology. The syndrome occurred as a sequela to bacterial coldwater disease, which also occurs in Alaska. This case report appears to represent an extension of the geographic range of occurrence of the chronic neurologic form of coldwater disease, earlier cases of which have been reported in Washington and Oregon. Clinical signs are similar to whirling disease and nutritional blacktail, both of which must be considered in the differential diagnosis.