Ulcerative skin and fin lesions in reared turbot, Scophthalmus maximus (L.)

• Published in: Journal of Fish Diseases
• Main Authors: DEVESA, S., BARJA, J. L., TORANZO, A. E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1989
• Subjects: Scophthalmus maximus; Turbot
• Online Access: http://dx.doi.org/10.1111/j.1365-2761.1989.tb00321.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2761.1989.tb00321.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2761.1989.tb00321.x

Abstract. In this report, the authors describe the evolution of an ulcerative disease that occurred during July and August 1986 in cultured juvenile turbot, Scophthalmus maximus (L.), in northwestern Spain. The daily fish mortality ranged from less than 1 to 7·5%, and the total of cumulative losses were 23·2%. The start of the epizootic was closely associated with a sudden increase of water temperature to values higher than 20·C. Peaks of mortality were observed during the development of the disease. Affected turbot showed erratic swimming, respiratory distress and inappetence. The lesions began as white discoloured foci on the skin, operculum, and base of dorsal and caudal fins which could suffer a total destruction of the interradial membrane. In an advanced stage of this condition, the epithelial surface of the centre of the lesions sloughed off and shallow and haemorrhagic ulcers were produced. Three distinct areas were observed in the ulcerative lesions with a clear predominance of different microorganisms: (1) a peripheric pale zone invaded by a ciliate protozoan resembling Cryptocaryon spp.; (2) an intermediate greyish‐dark area containing large numbers of fastidious myxobacteria which failed to grow in culture media; and (3) a central haemorrhagic zone where we have isolated two halophilic, urease positive Vibrio strains (closely related to V. carchariae ). No microbial involvement was detected in the internal organs of affected fish. The virulence assays conducted with the Vibrio strains failed to reproduce the signs of the disease, either by intraperitoneal inoculation or by water challenge after skin abrasion. The use of alternate baths of formalin/malachite green and nitrofurazone resulted in an effective therapy to control the mortalities.