A comparative analysis of the microbiological quality of three turbot (Scophthalnus maximus) farms (A, B, and C) located in Galicia (northwest Spain) is given. The microbial load and types of bacteria in the internal organs (liver and kidney) of apparently healthy fish was monitored over a year, and all the disease problems occurring during this survey were analyzed. The percentage of healthy turbot in which positive bacterial growth was obtained was relatively high in the three ongrowing facilities. Farm A exhibited the poorest conditions of fish health with an average of 42% fish infected, while farm B showed the best microbiological quality with 27% of turbot harbouring bacteria in the internal organs. In all three farms, a wide range of bacteria was found in healthy turbot with Vibrio (V. splendidus-V pelagius, Vfisheri-V harveyi and Vibrio spp.) and Pseudomonas spp. being the predominant groups comprising at least 80% of the total bacterial isolates in each farm. The highest number of pathological problems (22) with the most diverse bacterial flora occurred in farm A. Vibrio spp. and Pseudomonas spp. were the most prevalent bacteria recovered from diseased turbot. Haemorrhages in palate and jaws, tail and fins, and ulcerative lesions were the most frequent external clinical signs of diseased fish recorded in the three farms. However, it was not possible to associate a particular bacterial species with a specific pathology. Routine use in farm A of oxolinic acid and nitrofurantoin may have led to the development in the Vibrio strains of resistances to both chemotherapeutants (up to 25%).

Abslracl. 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 tish mortality ranged from less than 1 to 7-5%, and the total ot cumulative losses were 23-2%. The start of the epizootic was closely associated with a sudden increase of water temperature to values higher than 20X. Peaks of mortality were observed during the development ol the disease. Affected turbot showed erratic swimming, respiratory distress and inappetcncc. The lesions began as white discoloured foci on the skin, operculum, and base of dorsal and caudal tins which could suffer a total destruction of the intcrradial membrane. In an advanced stage of this condition, the epithelial surface of the centre of the lesions sloughed off and shallow and hacmorrhagic 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 myxobaeteria 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. carcharlae). 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, cither 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.

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The lesions of an enterocoeeal septieaemia occurring in turbot, Scophthalmus maximus (L.), eultured in several farms in northwest Spain are described. The agent of this septicaemia was identified previously as an Enterococcus-Wko. bacterium. Two main patterns of lesions were observed in the diseased turbot: a focal form characterized by exophthalmia, muscular haemorrhages, aeute branchitis, and suppurative inflammation of periorbital tissues, eyeball, meninges and brain; and another generalized form with similar lesions, but showing more extensive haemorrhages, ulceration and purulent inflammation of the skin, desquamative enteritis, and necrosis of spleen and kidney. Fatty changes of the liver were observed in all turbot examined (diseased and controls), which indicates that these alterations were not related to the infection. Experimentally inoculated turbot developed lesions eorresponding to the generalized form of the natural disease. Although the Enterococcus strain was recovered in pure culture from all the organs. Gram-positive bacteria eould not be visualized histologically in the lesions of muscle and brain.

ABSTRACT. Skin papillomas, mainly composed of epidermal hyperplasia and visceral tulnors involving the pancreatic and occasionally the blle ducts, were observed in a population of juvenile turbot Scophthalmus maximus reared in a fishfarm located in the northwest of Spain. By electron microscopy, the epidermal hyperplastic tissue had Malpighian cells with irregular nuclei and abundant glycogenlike particles and free ribosomes in the cytoplasm. In visceral tumors, proliferation of the pancreatic ductular epithelia1 cells was acconlpanied by growth of surrounding smooth muscle cells and connective tissue. Pancreatic acinar cells were vacuolated. Some affected fish also presented lesions in the liver, spleen and kidney. Attempts to isolate virus using different fish cell-lines were negatlve Similarly, no viral particles were observed by electron microscopy. However, bacteriological analysis revealed the presence of the Vibrio fischeri -V harveyi group in the internal organs of the majority of affected fish. which supports a possible contribution of these bacteria in the development of mortality. High pressure liquid chromatography analysis has not detected the presence of allatoxin B, in tissues. At present the origin of these tumors in turbot remains unclear