Isolation of a toga-like virus from farmed Atlantic salmon Salmo salar with pancreas disease

Nelson, R.; McLoughlin, M F; Rowley, H M; Platten, Michael; McCormick, Janet

doi:10.3354/dao022025

Cited by 118 publications

(144 citation statements)

References 7 publications

(15 reference statements)

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“…The salmon in 11 of these farms were moderately to strongly infected with Paranucleospora theridion, and their tissues contained low to moderate amounts of SAV. It has been thoroughly demonstrated that SAV play an important role in the development of PD (Nelson et al 1995, McLoughlin et al 1996, and high mortalities have been reported (Taksdal et al 2007, Fringuelli et al 2008. However, as several challenge experiments have shown (McLoughlin et al 1996, Desvignes et al 2002, Christie et al 2007), SAV might not be solely responsible for the PD outbreaks that occur in marine farms for salmonids.…”

Section: Pancreas Diseasementioning

confidence: 99%

“…It is well documented that 'pancreas disease' is associated with the presence of different strains of SAV (Nelson et al 1995, McLoughlin et al 1996, Villoing et al 2000, Hodneland et al 2005, Fringuelli et al 2008). However, the observed disease and mortality in salmon and rainbow trout farms are different from what can be seen in challenge experiments using the different SAV strains .…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

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Diseases of farmed Atlantic salmon Salmo salar associated with infections by the microsporidian Paranucleospora theridion

Nylund¹,

Andersen²,

Sævareid³

et al. 2011

Dis. Aquat. Org.

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The microsporidian Paranucleospora theridion was discovered in Atlantic salmon Salmo salar suffering from proliferative gill disease in a marine farm in western Norway in 2008. The parasite develops in cells of the reticuloendothelial system, cells important for normal immune function. The aim of this study was to see if P. theridion could play a part in some of the diseases with unclear causes in salmon production in Norway, i.e. proliferative gill disease (PGI), pancreas disease (PD), heart and skeletal muscle inflammation (HSMI) and cardiomyopathy syndrome (CMS). P. theridion was present in all areas with salmon farming in Norway, but high prevalence and densities of the parasite in salmon and salmon lice were only seen in southern Norway. This region is also the main area for PGI and PD in Norway. Quantification of pathogens associated with PGI, PD, HSMI and CMS diagnoses showed that P. theridion levels are high in southern Norway, and may therefore play a role in susceptibility and disease development. However, among the different diagnoses, fish with PGI are particularly heavily infected with P. theridion. Therefore, P. theridion appears as a possible primary agent in cases with high mortality in connection with PGI in western Norway. KEY WORDS: Paranucleospora theridion · Atlantic salmon · Microsporidia · Proliferative gill disease · PGI · Pancreas disease · PD Resale or republication not permitted without written consent of the publisherDis Aquat Org 94: [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] 2011 Clavochlamydia salmonicola , Atlantic salmon paramyxovirus (Kvellestad et al. 2005), and salmon gill poxvirus . These agents may all contribute to the gill pathology, hypertrophia, hyperplasia, inflammation and necrosis of gill tissues, but it is not known whether they are primary pathogens or secondary invaders.It is well documented that 'pancreas disease' is associated with the presence of different strains of SAV (Nelson et al. 1995, McLoughlin et al. 1996, Villoing et al. 2000, Hodneland et al. 2005, Fringuelli et al. 2008). However, the observed disease and mortality in salmon and rainbow trout farms are different from what can be seen in challenge experiments using the different SAV strains . The explanations for this could be presence of different pathogens or other stress factors that may trigger the disease or be the primary cause of disease, reducing SAV to a secondary cause of the observed mortality in farms. Lack of comparable mortality and to a certain extent also pathology has also been observed when comparing challenge experiments using CMS and HSMI homogenates with the observed situation in salmon farms affected by these 2 diseases (Kongtorp et al. 2004a, Fritsvold et al. 2009. Hence, the trigger or primary causes for these diseases could be environmental factors or other pathogens.Paranucleospora theridion was first discovered in farmed Atlantic salmon suffering from gill disease in western Norway in (A. Nylund et al. 2009a,b, S. Nylund et al. 2009. Th...

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Section: Pancreas Diseasementioning

confidence: 99%

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

Diseases of farmed Atlantic salmon Salmo salar associated with infections by the microsporidian Paranucleospora theridion

Nylund¹,

Andersen²,

Sævareid³

et al. 2011

Dis. Aquat. Org.

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“…Acute and chronic pancreatic lesions in exocrine pancreatic tissue may also be present in diseased fish (McLoughlin et al, 2002). The virus responsible for pancreas disease in Ireland and Scotland have been isolated and identified as an alphavirus, and the name salmon pancreas disease virus (SPDV) was suggested (Nelson et al, 1995; 2000; Weston et al, 1999). Because pancreas disease affected fish from Norway show similar clinical symptoms and gross pathology, it has been of the common opinion that pancreas disease in the British Isles and Norway is caused by the same virus.…”

Section: Introductionmentioning

confidence: 99%

Sensitive and specific detection of Salmonid alphavirus using real-time PCR (TaqMan®)

Hodneland

Endresen

2006

Journal of Virological Methods

134

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Pancreas disease is responsible for major economic losses in the European salmonid farming industry. It was previously believed that a single subtype (salmon pancreas disease virus) of the virus species Salmonid alphavirus (SAV) was responsible for all outbreaks of pancreas disease in the UK and Norway. However, the recent discovery that pancreas disease in Norway is caused by a new and distinct subtype of salmonid alphavirus, exclusively found in Norway, has advocated the need for better diagnostic tools. In the present paper, three real-time PCR assays for all known subtypes of salmonid alphavirus have been developed; the Q nsP1 assay is a broad-spectrum one that detects RNA from all subtypes, the Q SPDV assay specifically detects the salmon pancreas disease virus subtype, and the Q NSAV assay only detects the new Norwegian salmonid alphavirus subtype.The results demonstrated the assays to be highly sensitive and specific, detecting <0.1 TCID 50 of virus stocks. Regression analysis and standard curves calculated from the C t -values from 10-fold serial dilutions of virus stocks showed that the assays were highly reproducible over a wide range of RNA input. Thirty-nine field samples were tested in triplicate and compared with traditional RT-PCR. Overall, the real-time assays detected 35 positive compared to 29 positives in standard RT-PCR, and were thus shown to be more sensitive for detecting salmonid alphaviruses in field samples.

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“…Since then it has also been described in North America (Kent & Elston 1987), Ireland (Murphy et al 1992) and Norway (Poppe & Breck 1989). The condition is now known to be caused by infection with an alphavirus that is closely related to the virus responsible for sleeping disease (SD) in farmed rainbow trout Oncorhynchus mykiss (Nelson et al 1995, McLoughlin et al 1996, 2002, Castric et al 1997, Weston et al 1999, Villoing et al 2000. The name salmonid alphavirus (SAV) has been proposed for this closely related group of viruses (Weston et al 2002).…”

Section: Introductionmentioning

confidence: 99%

“…Because of the difficulties inherent in isolating the virus from tissues of affected fish (Nelson et al 1995), traditionally, these histopathological changes have been the basis on which PD is diagnosed. More recently, tests capable of screening large numbers of sera for the presence of both SAV viraemia and virus neutralising antibodies have been developed and evaluated for routine diagnostic and epidemiological use (Graham et al 2003, Jewhurst et al 2004.…”

Section: Introductionmentioning

confidence: 99%

Sub-clinical infection of farmed Atlantic salmon Salmo salar with salmonid alphavirus a prospective longitudinal study

Graham¹,

Jewhurst²,

McLoughlin³

et al. 2006

Dis. Aquat. Org.

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A prospective longitudinal study of salmonid alphavirus infection in farmed Atlantic salmon Salmo salar L. was initiated in post-transfer smolts on a UK farm in July 2004 and continued for 320 d. Sampling was concentrated on a single caged population (C4) with serum and tissue samples collected and tested for viraemia, virus neutralising (VN) antibodies and viral nucleic acid by real time RT-PCR and by histopathology; 380 sera collected between Days 0 (D0) and 139 (D139) were consistently negative for both viraemia and VN antibodies. The first evidence of infection was detected on D146, when 4 out of 20 fish were found to be viraemic and 1 of 20 to be antibodypositive. On D153 only 2 of 20 fish was viraemic and 1 antibody positive. At the next sampling (D158) no viraemic or antibody positive fish were detected. Thereafter, one or two viraemic fish were detected on 6 occasions, including on D320. The prevalence of antibody-positive fish remained low (0 to 5%) until D192 after which time it rose irregularly to a peak of 57.9% on D320. Real time RT-PCR testing of sera was more sensitive than screening for viraemia, detecting a peak of 35% positive on D153 before declining. Histological lesions diagnostic for pancreas disease (PD) were observed at D146 and D153 only. In addition, mild cardiac and to a lesser extent brain lesions were frequently found after virus was detected, but not in earlier samples. No clinical signs or mortalities attributable to PD occurred throughout the study. This is the first detailed report of sub-clinical infection and highlights the usefulness of longitudinal surveys and the detection of virus and antibodies as diagnostic and epidemiological tools. KEY WORDS: Salmonid alphavirus · Pancreas disease · Longitudinal survey · Sub-clinical infection · Viraemia · Serology · RT-PCR Resale or republication not permitted without written consent of the publisherDis Aquat Org 72: 193-199, 2006 ological studies in Ireland between 1989 and 1994 found that mortality levels on sites varied widely from a low of 0.1% to as high as 63% (Crockford et al. 1999). However, overall there was a significant downward trend in PD-related mortalities during this period that continued in the second half of the 1990s. A similar observation was reported from Scotland (Bruno 2004). However, in recent years PD has re-emerged as a significant cause of mortality and economic loss in the Irish industry and there is evidence of a similar trend in both Scotland and Norway (G Ritchie pers. comm.).Both field and experimental infections of salmon with SAV isolates from outbreaks of PD are characterised clinically by sequential histopathological changes that include pancreatic and cardiomyocytic necrosis and skeletal myopathy (McLoughlin et al. 1996(McLoughlin et al. , 2002. Because of the difficulties inherent in isolating the virus from tissues of affected fish (Nelson et al. 1995), traditionally, these histopathological changes have been the basis on which PD is diagnosed. More recently, tests capable of scree...

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Isolation of a toga-like virus from farmed Atlantic salmon Salmo salar with pancreas disease

Cited by 118 publications

References 7 publications

Diseases of farmed Atlantic salmon Salmo salar associated with infections by the microsporidian Paranucleospora theridion

Diseases of farmed Atlantic salmon Salmo salar associated with infections by the microsporidian Paranucleospora theridion

Sensitive and specific detection of Salmonid alphavirus using real-time PCR (TaqMan®)

Sub-clinical infection of farmed Atlantic salmon Salmo salar with salmonid alphavirus a prospective longitudinal study

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Isolation of a toga-like virus from farmed Atlantic salmon Salmo salar with pancreas disease

Cited by 118 publications

References 7 publications

Diseases of farmed Atlantic salmon Salmo salar associated with infections by the microsporidian Paranucleospora theridion

Diseases of farmed Atlantic salmon Salmo salar associated with infections by the microsporidian Paranucleospora theridion

Sensitive and specific detection of Salmonid alphavirus using real-time PCR (TaqMan®)

Sub-clinical infection of farmed Atlantic salmon Salmo salar with salmonid alphavirus a prospective longitudinal study

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Sub-clinical infection of farmed Atlantic salmon Salmo salar with salmonid alphavirus a prospective longitudinal study