CYTOPHAGA, FLAVOBACTERIUM, FLEXIBACTER AND CHRYSEOBACTERIUM INFECTIONS IN CULTURED MARINE FISH

Many cases of fin or tail rot, skin ulcer, and jaw erosion were report ed over the years in cultured marine fish. The aetiological role of va rious bacteria belonging to the Flavobacterium-Cytophaga group was fre quently suspected, but only 3 bacterial species pathogenic for marine fish were fully described until now. Flexibacter maritimus was first i dentified in Japan in the late seventies from several fish species rea red in sea water. Subsequently, the disease was recognized in very dif ferent geographic areas such as France, Scotland, Spain, Malta, Tasman ia and California. The pathogenicity of the bacterium was demonstrated experimentally, phenotypic and genomic characteristics as well as vir ulence mechanisms were investigated, and treatment methods were propos ed. Significant losses due to Flexibacter maritimus may occur locally. In Norway, Flexibacter ovolyticus was isolated from the adherent bact erial epiflora of Atlantic halibut eggs and was shown to be an opportu nistic pathogen for halibut eggs and larvae. Chryseobacterium scophtha lmum (first described under the epithet Flavobacterium scophthalmum) w as isolated 10 years ago in Scotland from turbot suffering from gill h yperplasia and haemorrhagic septicaemia. A large collection of strains was studied, and investigations of the disease included experimental infection, histopathology and immunization trials. Until now, Flexibac ter ovolyticus and Chryseobacterium scophthalmum have not been recogni zed in fish species or regions other than those from which they were i nitially isolated.