Cold-water disease is a serious infection of hatchery-reared salmonid fish which was originally recognised in North America. In the spring of 1948, severe epizootics occurred in fish populations at temperatures below 10°C, and Cytophaga psychrophila was isolated as the causative agent. Since 1984, C. psychrophila infections have caused serious losses in rainbow trout hatcheries in some European countries and this disease is generally regarded as "trout fry anaemia syndrome". The severity and disease signs of cold-water disease depend on the stage of development of the fish. Juveniles are primarily affected and they exhibit lesions after they begin feeding. The lesions may occur around the caudal fin or dorsal fin and survivors may develop scoliosis. Hatcheries usually treat affected fish with oxytetracycline, although this is not effective against the chronic form of the disease.