High levels of mortalities have been experienced in farmed coho salmon, Oncorhynchus kisuteh (Walbaum), in the Gulf of Ancud, southern Chile. Most affected fish had similar skin lesions ranging from small areas of raised seales through white raised plaques to shallow ulcers. The fish were also generally dark, lethargic and anorexic. However, some affected fish appeared grossly normal with no skin lesions. Internal pathology consisted of varying degrees of ascites, peritonitis and general pallor. Spleens were generally enlarged. Kidneys and hvers were swollen and grey in colour, often with pale foeal lesions. Extensive histopathology was present in affected fish with tissue necrosis, intravaseular neerotic thrombi, large basophilic cells and basophilie granules, some free in the tissues, some contained within eells. The basophilic granules, known locally as the 'UA', or unidentified agent, were thought to be the main aetiological agent, and are likely to be a rickettsia-like organism.

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The present report describes an intestinal disease which causes important losses in farmed turbot. Mortality rates were higher in summer and reached 100% in all tanks where the disease was confirmed. Affected fish showed external signs consisting of anorexia, sunken eyes and a typical prominent bony ridge on the skull. These signs can be considered the pathognomonic signs of the disease, together with the gut lesions seen in the histological study. Pallor of the internal organs, intestinal haemorrhages and the presence of liquid in the intestine were also observed, with ascites in heavily infected fish. Histopathological damage was evident in the gut, with severe enteritis, detachment of epithelium, haemorrhages and inflammation of the subepithelial connective tissue. The myxosporean aetiology was demonstrated in all the fish showing the characteristic signs of disease. Myxosporean stages, including scarce spores, were found in the affected epithelium or free in the intestinal lumen together with epithelial debris. The present study demonstrates the importance of this myxosporean disease which represents a serious threat for turbot culture. This is also the first record of a member of the Myxosporea in turbot.

We compared 18 salmonid alphaviruses (SAV) including the reference F93-125 salmon pancreas disease virus (SPDV) and S49p sleeping disease virus (SDV) isolates by nucleotide sequence analyses of regions within the E1, nsP4 and nsP3 genes, and found these to comprise 3 distinct groups, which we have designated Subtypes 1, 2 and 3: Subtype 1, which comprised SAVs with sequences closely similar to the reference SPDV isolate, included SAVs from pancreas disease (PD) outbreaks in farmed salmon in Ireland and Scotland over a 10 yr period; viruses from recent outbreaks of sleeping disease (SD) in freshwater-reared trout farmed in England, Scotland and France were closely similar to and were grouped with the reference SDV isolate in Subtype 2; 3 viruses isolated from PD-affected salmon in Norway were genetically different from viruses belonging to Subtypes 1 and 2 and have been assigned to Subtype 3; 1 virus isolated from PD-affected salmon in the Western Isles, Scotland, in 2003 showed consistent nucleotide sequence differences from SAV Subtypes 1, 2 and 3, but was more closely related to the Subtype 1 SAVs. The occurrence of the different subtype SAVs appeared to have a geographical basis, which may prove useful in future molecular epidemiology studies of SAV-induced disease outbreaks.KEY WORDS: Salmon pancreas disease · Sleeping disease · Salmonid alphavirus · SAV · Subtypes 1, 2 and 3 Resale or republication not permitted without written consent of the publisherDis Aquat Org 66: [105][106][107][108][109][110][111] 2005 are relatively low (Weston et al. 2002). In contrast, the reference SPDV isolate F93-125 (Nelson et al. 1995) and reference SDV isolate S49p (Castric et al. 1997) showed 91.1% nucleotide sequence identity along their 11919 nucleotide (nt) and 11900 nt genomes respectively (Weston et al. 2002). In a comparative study of alphavirus sequences, Powers et al. (2001) suggested that, on the basis of this limited nucleotide sequence divergence, the 2 reference SPDV and SDV isolates constitute 2 subtypes of a new alphavirus species, for which the name Salmonid alphavirus (SAV) was proposed (Weston et al. 2002).To date, sequence data have been reported for the 2 reference isolates only. The objective of this study was to gain further insight into the molecular diversity exhibited by SAVs with the view to applying our findings epidemiologically. In this paper we compare partial nucleotide sequences of 16 additional SAVs originating in France, Ireland, Norway and the United Kingdom. Our results support the occurrence of 3 genetically different SAV groups, which we have called Subtypes 1, 2 and 3. MATERIALS AND METHODS Viruses.The SAVs compared by nucleotide sequencing in this study mainly comprised viruses present in viraemic serum samples that were submitted to the Veterinary Sciences Division for serological diagnosis, and cell culture isolates (Table 1). In the case of 2 SAVs (F02-67, F02-85), viruses were present in tissue homogenates obtained from clinical outbreaks of SD. The reference F93...