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1.
Growth rates of Atlantic salmon, pink salmon, Arctic char, sea trout and rainbow trout were compared under Norwegian farming conditions. During the juvenile, freshwater period, growth was fastest in pink salmon, followed by rainbow trout and Arctic char. Freshwater growth of sea trout and, especially, Atlantic salmon, was slow. After transfer of smolts or fingerling to sea water, Arctic char failed to survive the autumn. Sea water growth of sea trout was slow, but the three species, rainbow trout, Atlantic salmon and pink salmon, all grew rapidly through all seasons. When in sea water, rainbow trout and pink salmon were regularly attacked by vibriosis, while Atlantic salmon were rarely attacked, and sea trout never. It is concluded that, for commercial farming in Norway, rainbow trout are of value for production of fish of any size up to 3–4 kg, and pink salmon for production of small fish of 0.5–1.5 kg. Atlantic salmon is the only species suitable for production of a very large salmonid, i.e., more than 4–5 kg.  相似文献   

2.
Salmonid alphavirus (SAV) causes pancreas disease (PD) in farmed Atlantic salmon (Salmo salar L.), and exocrine pancreas tissue is a primary target of the virus. Digestive enzymes secreted by the exocrine pancreas break down macromolecules in feed into smaller molecules that can be absorbed. The effect of SAV infection on digestion has been poorly studied. In this study, longitudinal observations of PD outbreaks caused by SAV subtype 2 (SAV2) in Atlantic salmon at two commercial sea sites were performed. The development of PD was assessed by measurement of SAV2 RNA load and evaluation of histopathological lesions typical of PD. Reduced digestion of both protein and fat co‐varied with the severity of PD lesions and viral load. Also, the study found that during a PD outbreak, the pen population comprise several subpopulations, with different likelihoods of being sampled. The body length of sampled fish deviated from the expected increase or steady state over time, and the infection status in sampled fish deviated from the expected course of infection in the population. Both conditions indicate that disease status of the individual fish influenced the likelihood of being sampled, which may cause sampling bias in population studies.  相似文献   

3.
A clinical and histopathological review was carried out of 21 outbreaks of acute infectious pancreatic necrosis (IPN) in Scottish Atlantic salmon, Salmo salar L., farms (13 marine and eight fresh water) during 1991-2004. A distinctive syndrome was evident in both post-smolts in sea water and fry in fresh water, where liver lesions, which had not previously been associated with IPN, became a consistent finding in addition to the more typical pancreatic and intestinal changes. Initial cases were described in post-smolts in Shetland, but by the end of the period of investigation this type of pathology had extended down the West coast of Scotland and into Ireland. Limited viral strain analysis suggested that similar strains were involved in both fresh water and sea water and that these differed from earlier isolates from rainbow trout, Oncorhynchus mykiss (Walbaum). In fresh water, recovered fish frequently developed a greatly distended intestine associated with accumulation of undigested food. In sea water, after the initial, often significant (50% or more), losses, there were many fish which failed to grow and became chronically emaciated and prone to sea louse infection. Although use of transfer diets containing immune enhancers and the selection of IPN resistant broodstock has reduced losses the disease remains a serious cause of economic loss.  相似文献   

4.
The first alphavirus to be isolated from fish was recorded in 1995 with the isolation of salmon pancreas disease virus from Atlantic salmon, Salmo salar L., in Ireland. Subsequently, the closely related sleeping disease virus was isolated from rainbow trout, Oncorhynchus mykiss (Walbaum), in France. More recently Norwegian salmonid alphavirus (SAV) has been isolated from marine phase production of Atlantic salmon and rainbow trout in Norway. These three viruses are closely related and are now considered to represent three subtypes of SAV, a new member of the genus Alphavirus within the family Togaviridae. SAVs are recognized as serious pathogens of farmed Atlantic salmon and rainbow trout in Europe. This paper aims to draw together both historical and current knowledge of the diseases caused by SAVs, the viruses, their diagnosis and control, and to discuss the differential diagnosis of similar pathologies seen in cardiomyopathy syndrome and heart and skeletal muscle inflammation of Atlantic salmon.  相似文献   

5.
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6.
Several different viruses have been associated with myocarditis‐related diseases in the Atlantic salmon aquaculture industry. In this study, we investigated the presence of PMCV, SAV, PRV and the recently identified Atlantic salmon calicivirus (ASCV), alone and as co‐infections in farmed Atlantic salmon displaying myocarditis. The analyses were performed at the individual level and comprised qPCR and histopathological examination of 397 salmon from 25 farms along the Norwegian coast. The samples were collected in 2009 and 2010, 5–22 months post‐sea transfer. The study documented multiple causes of myocarditis and revealed co‐infections including individual fish infected with all four viruses. There was an overall correlation between lesions characteristic of CMS and PD and the presence of PMCV and SAV, respectively. Although PRV was ubiquitously present, high viral loads were with a few exceptions, correlated with lesions characteristic of HSMI. ASCV did not seem to have any impact on myocardial infection by PMCV, SAV or PRV. qPCR indicated a negative correlation between PMCV and SAV viral loads. Co‐infections result in mixed and atypical pathological changes which pose a challenge for disease diagnostic work.  相似文献   

7.
The present study evaluates if abdominal dis-tension caused by a water-filled stomach in seawater farmed rainbow trout, Oncorhynchus mykiss (Walbaum), and Atlantic salmon, Salmo salar L., could be provoked experimentally by live chilling in sea water (0.5 °C). Fifty rainbow trout and 50 salmon were visually classified, either as normal or suffering from the condition. Prior to chilling, no rainbow trout or salmon suffered from a water-filled stomach. During chilling, 25% of the rainbow trout and 2.5% of the salmon developed water-filled stomach. Affected rainbow trout had significantly higher blood plasma osmolality and significantly lower body weight than normal trout. The frequency of trout with a water-filled stomach increased significantly with increasing chilling time and increasing plasma osmolality. The regression coefficients revealed that the proportion of affected rainbow trout in-creased by 0.82% h−1 of chilling and by 0.46% per unit increase in mosmol L−1. The present study revealed that abdominal distension in seawater farmed rainbow trout was far more severe than in Atlantic salmon and could be provoked experimentally by osmoregulatory stress. This is consistent with the observation that water-filled stomach appear only occasionally in seawater farmed Atlantic salmon.  相似文献   

8.
Sequence data from salmonid alphavirus (SAV) strains obtained from farmed marine Atlantic salmon, Salmo salar L. , over a 20-year period between 1991 and 2011 was reviewed to examine the geographical distribution of the genetically defined SAV subtypes in twelve regions across Ireland and Scotland. Of 160 different Atlantic salmon SAV strains examined, 62 belonged to subtype 1, 28 to subtype 2, 34 to subtype 4, 35 to subtype 5 and 1 to subtype 6. SAV subtypes 1, 4 and 6 were found in Ireland, while subtypes 1, 2, 4 and 5 were found in Scotland. In the majority of regions, there was a clear clustering of subtypes, with SAV subtype 1 being the dominant subtype in Ireland overall, as well as in Argyll and Bute in Scotland. SAV subtype 2 predominated in the Shetland and Orkney Islands. The emergence in Atlantic salmon of subtype 2 strains typically associated with sleeping disease in rainbow trout in Argyll and Bute, strongly suggesting transmission of infection between these species, was noted for the first time. SAV subtype 4 was the most common subtype found in the southern Western Isles, while SAV subtype 5 predominated in the northern Western Isles and north-west mainland Scotland. No single strain was dominant on sites in the western Highlands, with a number of sites in this region in particular having more than one subtype detected in different submissions. The significance of these results in relation to aspects of the epidemiology of infection, including transmission, biosecurity and wildlife reservoirs are discussed and knowledge gaps identified.  相似文献   

9.
A cohort study was initiated in the spring of 2006 to investigate epidemiological aspects and pathogenesis of salmonid alphavirus (SAV) subtype 3 infections and pancreas disease (PD). The aims were to assess involvement of the freshwater production phase, the extent and frequency of subclinical infections and to follow PD‐affected populations throughout the entire seawater production cycle, as well as investigate possible risk factors for PD outbreaks. Fish groups from 46 different Atlantic salmon freshwater sites in six counties were sampled once prior to seawater transfer and followed onto their seawater sites. A total of 51 Atlantic salmon seawater sites were included, and fish groups were sampled three times during the seawater production phase. SAV subtype 3 was not identified by real‐time RT‐PCR from samples collected in the freshwater phase, nor were any SAV‐neutralizing antibodies or histopathological changes consistent with PD. In the seawater phase, SAV was detected in samples from 23 of 36 (63.9%) studied sites located within the endemic region. No SAV subtype 3 was detected in samples from seawater sites located outside the endemic region. The cumulative incidence of PD during the production cycle amongst sites with SAV detected was 87% (20 of 23 sites). Average fish weight at time of PD diagnosis ranged from 461 to 5978 g, because of a wide variation in the timing of disease occurrence throughout the production cycle. Mortality levels following a PD diagnosis varied greatly between populations. The mean percentage mortality was 6.9% (±7.06) (range 0.7–26.9), while the mean duration of increased mortality following PD diagnosis was 2.8 months (±1.11) (range 1–6).  相似文献   

10.
Sleeping disease (SD), a disease of freshwater-reared rainbow trout, Oncorhynchus mykiss (Walbaum), was histologically compared to pancreas disease (PD), a disease of sea water-reared Atlantic salmon, Salmo salar L. Some weeks after injection of kidney homogenates from SD- or PD-affected fish in rainbow trout, the fish successively developed pancreatic, heart and muscular lesions in both populations, although the SD-injected population was the most affected. An acquired protection was observed against PD and SD after an initial injection with PD- or SD-infective material. This acquired cross-protection and the similar histopathologies in PD and SD suggest the two diseases could be caused by a similar or identical agent.  相似文献   

11.
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12.
Viral diseases represent serious challenge in marine farming of Atlantic salmon (Salmo salar L). Pancreas disease (PD) caused by a salmonid alphavirus (SAV) is by far the most serious in northern Europe. To control PD, it is necessary to identify virus transmission routes. One aspect to consider is whether the virus is transported as free particles or associated with potential vectors. Farmed salmonids have high lipid content in their tissue which may be released into the environment from decomposing dead fish. At the seawater surface, the effects of wind and ocean currents are most prominent. The aim of this study was primarily to identify whether the lipid fraction leaking from dead infected salmon contains SAV. Adipose tissue from dead SAV‐infected fish from three farming sites was submerged in beakers with sea water in the laboratory and stored at different temperature and time conditions. SAV was identified by real‐time RT‐PCR in the lipid fractions accumulating at the water surface in the beakers. SAV‐RNA was also present in the sea water. Lipid fractions were transferred to cell culture, and viable SAV was identified. Due to its hydrophobic nature, fat with infective pathogenic virus at the surface may contribute to long‐distance transmission of SAV.  相似文献   

13.
Pancreas disease (PD) caused by salmonid alphavirus (SAV) has a significant negative economic impact in the salmonid fish farming industry in northern Europe. Until recently, only SAV subtype 3 was present in Norwegian fish farms. However, in 2011, a marine SAV 2 subtype was detected in a fish farm outside the PD‐endemic zone. This subtype has spread rapidly among fish farms in mid‐Norway. The PD mortality in several farms has been lower than expected, although high mortality has also been reported. In this situation, the industry and the authorities needed scientific‐based information about the virulence of the marine SAV 2 strain in Norway to decide how to handle this new situation. Atlantic salmon post‐smolts were experimentally infected with SAV 2 and SAV 3 strains from six different PD cases in Norway. SAV 3‐infected fish showed higher mortality than SAV 2‐infected fish. Among the SAV 3 isolates, two isolates gave higher mortality than the third one. At the end of the experiment, fish in all SAV‐infected groups had significantly lower weight than the uninfected control fish. This is the first published paper on PD to document that waterborne infection produced significantly higher mortality than intraperitoneal injection.  相似文献   

14.
Epidemiological investigations into the pancreas disease (PD) of farmed salmon were conducted on populations of Atlantic salmon reared in Ireland during 2003 and 2004. The investigations surveyed all marine salmon farms operating in Ireland through a detailed questionnaire with follow-up farm visits. Information was gathered on 21 populations of fish in 2003 and 14 populations in 2004. Thirteen of the 21 populations suffered PD in 2003 and 12 of the 14 in 2004. The mean mortality due to PD on affected farms was 18.8% in 2003 and 14.8% in 2004 and the loss of growth due to PD was estimated at 11.4% over the 2-year period. The highest risk periods for outbreaks of PD were early summer and early autumn and the farms most seriously affected by PD mortality were in the western counties of Ireland. Factors which showed an indication of association with a PD outbreak or high mortality during a PD outbreak were: livestock movement to another sea site, high feeding rate prior to any PD outbreak, the presence of another PD positive farm in the same water body, greater than 250000 fish on a site, a previous history of PD on a site, a high sea lice burden, and sites located in the western regions of Ireland which reared a specific strain of salmon.  相似文献   

15.
Heart and skeletal muscle inflammation (HSMI) caused by piscine orthoreovirus (PRV) and pancreas disease (PD) caused by salmonid alphavirus (SAV) are among the most prevalent viral diseases of Atlantic salmon farmed in Norway. There are limited data about the impact of disease in farmed salmon on wild salmon populations. Therefore, the prevalence of PRV and SAV in returning salmon caught in six sea sites was determined using real‐time RT‐PCR analyses. Of 419 salmon tested, 15.8% tested positive for PRV, while none were positive for SAV. However, scale reading revealed that 10% of the salmon had escaped from farms. The prevalence of PRV in wild salmon (8%) was significantly lower than in farm escapees (86%), and increased with fish length (proxy for age). Sequencing of the S1 gene of PRV from 39 infected fish revealed a mix of genotypes. The observed increase in PRV prevalence with fish age and the lack of phylogeographic structure of the virus could be explained by virus transmission in the feeding areas. Our results highlight the need for studies about the prevalence of PRV and other pathogens in Atlantic salmon in its oceanic phase.  相似文献   

16.
Infectious pancreatic necrosis virus (IPNV) is an aquabirnavirus that causes serious diseases in a variety of fish species worldwide. It has been isolated from a large number of healthy fresh and marine water fish. Prior to this study, there was no record of the presence of IPNV infection in Kenya. Here, the presence of IPNV in farmed rainbow trout and tilapia was examined in Nyeri County of central Kenya. Head kidney samples taken from five rainbow trout and three tilapia farms and stored in RNALater® were processed by PCR followed by sequencing of a segment A fragment covering nucleotide positions 2,120–2,343 bp. IPNV was detected in all the farms sampled with infection ratios ranging from 0.3 to 0.78 although the infections were not associated with any specific clinical signs of disease. These findings were supported by immunohistochemistry staining of the virus in the kidney and exocrine pancreas of rainbow trout. Sequence alignment and phylogenetic analysis revealed that the Kenyan isolates were identical to European isolates, suggesting a common origin. These findings highlight the need for better biosecurity procedures with more stringent surveillance programmes and control for fish diseases, especially focusing on imported breeding materials to Kenya.  相似文献   

17.
Laboratory studies were carried out to investigate the cultural characteristics of salmonid alphaviruses (SAV) from Atlantic salmon (AS, Salmo salar) and rainbow trout (RT, Oncorhynchus mykiss), particularly in relation to cell line and temperature. In an initial study, SAV was isolated from 12 viraemic sera and passaged in Chinook salmon embryo (CHSE‐214) cells at 15 °C. Geometric mean titres (GMT) after initial isolation were found to be significantly higher (P < 0.05) relative to those after two or four passages. Primary isolation of SAV was conducted from 12 viraemic sera (six AS and six RT) in seven different cell lines at 15 °C: CHSE‐214, rainbow trout gonad (RTG‐2), TO (derived from Atlantic salmon head kidney leucocytes), salmon head kidney (SHK‐1), blue fin‐2 (BF‐2), fat head minnow (FHM) and Epithelioma papulosum cyprini (EPC). Overall, significant differences were found between cell lines in both the numbers of strains where growth was detected and in the GMT obtained. For both AS and RT strains, GMT values were significantly (P < 0.01) higher in both TO and BF‐2 cells relative to the others, including CHSE‐214 and RTG‐2, the cell lines conventionally used for SAV. The effects of temperature of incubation (4, 10, 15 and 20 °C) on growth in TO, CHSE‐214 and RTG‐2 were investigated. In TO and RTG‐2 growth was optimal at 15 °C, whereas in CHSE‐214 results at 10 and 15 °C were more similar. Little or no growth was detected at 4 or 20 °C.  相似文献   

18.
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19.
Brook trout, rainbow trout, and Atlantic salmon were acclimated to sea water (30‰ S) and placed during autumn in floating cages in a concrete tide pool. The salmon (mean length ca 26 cm in mid-October) grew about 2 cm before they stopped feeding in December. The brook trout (19 cm) and rainbow trout (21 cm) grew little, if any, during December. Feeding by the rainbow trout and salmon continued until temperature fell below 1°C. The brook trout fed little, if any, during December while temperature fell from 4 to 1°C. Brook trout, particularly the mature individuals, had high mortality rates from the time they were put into sea water. Blood plasma osmolalities indicated that brook trout, but not the other species, were under severe osmotic stress in sea water. Most of the fish (all three species) died in a 4-day period during early January when the water cooled to ?0.7 to ?0.8°C. A temperature of ?0.7°C is a reasonable approximation of the lower lethal temperature for these salmonids at 30‰ salinity. Based on our observations, it is not practicable to hold the above species in sea water which is likely to get colder than 1°C because of poor growth and the risk of mortality.  相似文献   

20.
Coldwater Vibrio species isolated from Atlantic salmon, Salmo salar L., during winter ulcer disease outbreaks at saltwater sites in Norway and Iceland were characterized phenotypically, tested for virulence, and used to evaluate the efficacy of multivalent, oil-adjuvanted vaccines. The intraperitoneal (i.p.) injection of rainbow trout, Oncorhynchus mykiss (Walbaum), in fresh water with one bacteria species isolated during winter ulcer outbreaks, V. ‘viscosus’, produced rapid mortality and disease signs which resembled those observed during natural outbreaks [105 colony-forming units (cfu) fish??1]. Another species, V. ‘wodanis’, was not virulent to rainbow trout (103–106 cfu fish??1). Although vaccination of rainbow trout with a mineral-oil-adjuvanted, injectable vaccine containing V. anguillarum (serotypes 01 and 02), V. salmonicida and Aeromonas salmonicida did not provide protection against injection challenge with V. viscosus, vaccines which included V. viscosus produced significant protection in Atlantic salmon and rainbow trout. Atlantic salmon vaccinated with an oil-adjuvanted vaccine containing V. viscosus, V. wodanis and atypical A. salmonicida produced a relative percentage survival (RPS) of 97% when challenged i.p. with V. viscosus, demonstrating cross-protection between strains from Iceland and Norway. Short-term efficacy was demonstrated in rainbow trout by injection challenge at 21 and 43 days post-vaccination with an oil-adjuvanted vaccine containing V. viscosus, V. anguillarum (01/02), V. salmonicida and A. salmonicida, which produced an RPS of 96–99%. Rainbow trout challenged with V. viscosus at 52 and 362 days post-vaccination produced an RPS of 93% and 79%, indicating that vaccination provided long-term protection. In a similar manner, rainbow trout injected i.p. with 0.2 mL of a vaccine containing the five bacteria species and infectious pancreatic necrosis virus produced a 90% RPS when challenged with V. viscosus 66 days later. The high RPS under a severe challenge burden, along with disease signs in experimental freshwater challenges which resembled the saltwater disease condition, indicated that V. viscosus is a contributing factor to winter ulcer and that vaccination will protect against the disease.  相似文献   

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