1
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Nielsen SS, Alvarez J, Calistri P, Canali E, Drewe JA, Garin‐Bastuji B, Gonzales Rojas JL, Gortázar C, Herskin MS, Michel V, Miranda Chueca MÁ, Padalino B, Roberts HC, Spoolder H, Ståhl K, Velarde A, Viltrop A, Winckler C, Bron J, Olesen NJ, Sindre H, Stone D, Vendramin N, Antoniou SE, Broglia A, Karagianni AE, Papanikolaou A, Bicout DJ. Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU)2016/429): Infection with salmonid alphavirus (SAV). EFSA J 2023; 21:e08327. [PMID: 37908450 PMCID: PMC10613945 DOI: 10.2903/j.efsa.2023.8327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023] Open
Abstract
Infection with salmonid alphavirus (SAV) was assessed according to the criteria of the Animal Health Law (AHL), in particular the criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as laid out in Article 9 and Article 8 for listing animal species related to infection with SAV. The assessment was performed following the ad hoc method on data collection and assessment developed by AHAW Panel and already published. The outcome reported is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with an uncertain outcome. According to the assessment, it was uncertain whether infection with salmonid alphavirus can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (50-80% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that infection with salmonid alphavirus does not meet the criteria in Section 1 (Category A; 5-10% probability of meeting the criteria) and it is uncertain whether it meets the criteria in Sections 2, 3, 4 and 5 (Categories B, C, D and E; 50-90%, probability of meeting the criteria). The animal species to be listed for infection with SAV according to Article 8 criteria are provided.
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2
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Establishment and Characterization of a Novel Gill Cell Line, LG-1, from Atlantic Lumpfish ( Cyclopterus lumpus L.). Cells 2021; 10:cells10092442. [PMID: 34572091 PMCID: PMC8467979 DOI: 10.3390/cells10092442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 08/19/2021] [Accepted: 09/04/2021] [Indexed: 11/17/2022] Open
Abstract
The use of lumpfish (Cyclopterus lumpus) as a cleaner fish to fight sea lice infestation in farmed Atlantic salmon has become increasingly common. Still, tools to increase our knowledge about lumpfish biology are lacking. Here, we successfully established and characterized the first Lumpfish Gill cell line (LG-1). LG-1 are adherent, homogenous and have a flat, stretched-out and almost transparent appearance. Transmission electron microscopy revealed cellular protrusions and desmosome-like structures that, together with their ability to generate a transcellular epithelial/endothelial resistance, suggest an epithelial or endothelial cell type. Furthermore, the cells exert Cytochrome P450 1A activity. LG-1 supported the propagation of several viruses that may lead to severe infectious diseases with high mortalities in fish farming, including viral hemorrhagic septicemia virus (VHSV) and infectious hematopoietic necrosis virus (IHNV). Altogether, our data indicate that the LG-1 cell line originates from an epithelial or endothelial cell type and will be a valuable in vitro research tool to study gill cell function as well as host-pathogen interactions in lumpfish.
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3
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Aksnes I, Braaen S, Markussen T, Åkesson CP, Villoing S, Rimstad E. Genetically modified attenuated salmonid alphavirus: A potential strategy for immunization of Atlantic salmon. JOURNAL OF FISH DISEASES 2021; 44:923-937. [PMID: 33591590 DOI: 10.1111/jfd.13352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/29/2021] [Accepted: 01/31/2021] [Indexed: 06/12/2023]
Abstract
Pancreas disease (PD) is a serious challenge in European salmonid aquaculture caused by salmonid alphavirus (SAV). In this study, we report the effect of immunization of Atlantic salmon with three attenuated infectious SAV3 strains with targeted mutations in a glycosylation site of the envelope E2 protein and/or in a nuclear localization signal in the capsid protein. In a pilot experiment, it was shown that the mutated viral strains replicated in fish, transmitted to naïve cohabitants and that the transmission had not altered the sequences. In the main experiment, the fish were immunized with the strains and challenged with SAV3 eight weeks after immunization. Immunization resulted in infection both in injected fish and 2 weeks later in the cohabitant fish, followed by a persistent but declining load of the mutated virus variants in the hearts. The immunized fish developed clinical signs and pathology consistent with PD prior to challenge. However, fish injected with the virus mutated in both E2 and capsid showed little clinical signs and had higher average weight gain than the groups immunized with the single mutated variants. The SAV strain used for challenge was not detected in the immunized fish indicating that these fish were protected against superinfection with SAV during the 12 weeks of the experiment.
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Affiliation(s)
- Ida Aksnes
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Oslo, Norway
| | - Stine Braaen
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Oslo, Norway
| | - Turhan Markussen
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Oslo, Norway
| | | | | | - Espen Rimstad
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Oslo, Norway
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4
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Tighe AJ, Gallagher MD, Carlsson J, Matejusova I, Swords F, Macqueen DJ, Ruane NM. Nanopore whole genome sequencing and partitioned phylogenetic analysis supports a new salmonid alphavirus genotype (SAV7). DISEASES OF AQUATIC ORGANISMS 2020; 142:203-211. [PMID: 33331288 DOI: 10.3354/dao03546] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Salmon pancreas disease virus, more commonly known as salmonid alphavirus (SAV), is a single-stranded positive sense RNA virus and the causative agent of pancreas disease and sleeping disease in salmonids. In this study, a unique strain of SAV previously isolated from ballan wrasse was subjected to whole genome sequencing using nanopore sequencing. In order to accurately examine the evolutionary history of this strain in comparison to other SAV strains, a partitioned phylogenetic analysis was performed to account for variation in the rate of evolution for both individual genes and codon positions. Partitioning the genome alignments almost doubled the observed branch lengths in the phylogenetic tree when compared to the more common approach of applying one model of substitution across the genome and significantly increased the statistical fit of the best-fitting models of nucleotide substitution. Based on the genomic data, a valid case can be made for the viral strain examined in this study to be considered a new SAV genotype. In addition, this study adds to a growing number of studies in which SAV has been found to infect non-salmonid fish, and as such we have suggested that the viral species name be amended to the more inclusive 'piscine alphavirus'.
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Affiliation(s)
- Andrew J Tighe
- Fish Health Unit, Marine Institute, Oranmore H91 R673, Ireland
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5
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Gallagher MD, Karlsen M, Petterson E, Haugland Ø, Matejusova I, Macqueen DJ. Genome Sequencing of SAV3 Reveals Repeated Seeding Events of Viral Strains in Norwegian Aquaculture. Front Microbiol 2020; 11:740. [PMID: 32390982 PMCID: PMC7193772 DOI: 10.3389/fmicb.2020.00740] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 03/30/2020] [Indexed: 01/14/2023] Open
Abstract
Understanding the dynamics of pathogen transfer in aquaculture systems is essential to manage and mitigate disease outbreaks. The goal of this study was to understand recent transmission dynamics of salmonid alphavirus (SAV) in Norway. SAV causes significant economic impacts on farmed salmonids in European aquaculture. SAV is classified into six subtypes, with Norway having ongoing epidemics of SAV subtypes 2 and 3. These two viral subtypes are present in largely distinct geographic regions of Norway, with SAV2 present in Trondelag, SAV3 in Rogaland, Sogn og Fjordane, and Hordaland, and Møre og Romsdal having outbreaks of both subtypes. To determine likely transmission routes of Norwegian SAV an established Nanopore amplicon sequencing approach was used in the current study. After confirming the accuracy of this approach for distinguishing subtype level co-infections of SAV2 and SAV3, a hypothetical possibility in regions of neighboring epidemics, twenty-four SAV3 genomes were sequenced to characterize the current genetic diversity of SAV3 in Norwegian aquaculture. Sequencing was performed on naturally infected heart tissues originating from a range of geographic locations sampled between 2016 and 2019. Phylogenetic analyses revealed that the currently active SAV3 strains sampled comprise several distinct lineages sharing an ancestor that existed ∼15 years ago (95% HPD, 12.51-17.7 years) and likely in Hordaland. At least five of these lineages have not shared a common ancestor for 7.85 years (95% HPD, 5.39-10.96 years) or more. Furthermore, the ancestor of the strains that were sampled outside of Hordaland (Sogn of Fjordane and Rogaland) existed less than 8 years ago, indicating a lack of long-term viral reservoirs in these counties. This evident lack of geographically distinct subclades is compatible with a source-sink transmission dynamic explaining the long-term movements of SAV around Norway. Such anthropogenic transport of the virus indicates that at least for sink counties, biosecurity strategies might be effective in mitigating the ongoing SAV epidemic. Finally, genomic analyses of SAV sequences were performed, offering novel insights into the prevalence of SAV genomes containing defective deletions. Overall, this study improves our understanding of the recent transmission dynamics and biology of the SAV epidemic affecting Norwegian aquaculture.
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Affiliation(s)
- Michael D. Gallagher
- School of Biological Sciences, University of Aberdeen, Aberdeen, United Kingdom
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Edinburgh, United Kingdom
| | | | | | | | - Iveta Matejusova
- Marine Laboratory, Marine Scotland Science, Aberdeen, United Kingdom
| | - Daniel J. Macqueen
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Edinburgh, United Kingdom
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6
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Ruane NM, Swords D, Morrissey T, Geary M, Hickey C, Collins EM, Geoghegan F, Swords F. Isolation of salmonid alphavirus subtype 6 from wild-caught ballan wrasse, Labrus bergylta (Ascanius). JOURNAL OF FISH DISEASES 2018; 41:1643-1651. [PMID: 30051469 DOI: 10.1111/jfd.12870] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 06/25/2018] [Accepted: 06/25/2018] [Indexed: 06/08/2023]
Abstract
The use of cleaner fish as a biological control for sea lice in Atlantic salmon aquaculture has increased in recent years. Wild-caught wrasse are commonly used as cleaner fish in Europe. In Ireland, samples of wrasse from each fishing area are screened for potential pathogens prior to their deployment into sea cages. Salmonid alphavirus was isolated from a pooled sample of ballan wrasse, showing no signs of disease, caught from the NW of Ireland. Partial sequencing of the E2 and nsP3 genes showed that it was closely related to the previously reported SAV subtype 6. This represents only the second isolation of this subtype and the first from a wild fish species, namely ballan wrasse.
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Affiliation(s)
- Neil M Ruane
- Fish Health Unit, Marine Institute, County Galway, Ireland
| | - David Swords
- Fish Health Unit, Marine Institute, County Galway, Ireland
| | | | - Michelle Geary
- Fish Health Unit, Marine Institute, County Galway, Ireland
| | - Cathy Hickey
- Fish Health Unit, Marine Institute, County Galway, Ireland
| | | | | | - Fiona Swords
- Fish Health Unit, Marine Institute, County Galway, Ireland
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7
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Abstract
Salmonid alphavirus (SAV), genus Alphavirus, family Togaviridae, is a single-stranded RNA virus affecting Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). It is known to be responsible for pancreas disease (PD) and sleeping disease (SD) which are increasing problems, causing high fish mortality and economic losses in the European aquaculture industry. Pancreas disease was first described in Atlantic salmon in Scotland in 1976 and a similar disease caused by the closely related sleeping disease virus was first described in rainbow trout in France. There have also been reports of salmonid alphavirus infections from other European countries, including Ireland, England, Norway, Germany, Italy, and Spain. Salmonid alphaviruses have been classified into six subtypes (SAV1–6). SAV1 and SAV4–6 cause pancreas disease in Atlantic salmon in Ireland or Scotland, SAV2 is the causative agent of sleeping disease in rainbow trout, and SAV3 has been detected in Atlantic salmon in Norway. The aim of this paper was to summarise current knowledge of infections caused by salmonid alphavirus and diagnostic methods including the newest techniques, and to briefly describe prevention from SAV infections by vaccination.
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8
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Gao S, Shi W, Wang Y, Guo M, Duan K, Song A, Lian G, Ren T, Li Y, Tang L, Sun L, Liu M. Establishment and evaluation of an indirect immunofluorescence assay for the detection of salmonid alphavirus. Lett Appl Microbiol 2018; 66:293-299. [DOI: 10.1111/lam.12834] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 11/21/2017] [Accepted: 11/21/2017] [Indexed: 11/28/2022]
Affiliation(s)
- S. Gao
- College of Animal Science and Technology; Northeast Agricultural University; Harbin, Heilongjiang China
| | - W. Shi
- College of Animal Science and Technology; Northeast Agricultural University; Harbin, Heilongjiang China
| | - Y.T. Wang
- College of Animal Science and Technology; Northeast Agricultural University; Harbin, Heilongjiang China
| | - M.T. Guo
- College of Animal Science and Technology; Northeast Agricultural University; Harbin, Heilongjiang China
| | - K.X. Duan
- College of Animal Science and Technology; Northeast Agricultural University; Harbin, Heilongjiang China
| | - A.C. Song
- College of Animal Science and Technology; Northeast Agricultural University; Harbin, Heilongjiang China
| | - G.H. Lian
- College of Animal Science and Technology; Northeast Agricultural University; Harbin, Heilongjiang China
| | - T. Ren
- Beijing Entry-exit Inspection and Quarantine Bureau; Beijing China
| | - Y.J. Li
- Department of Preventive Veterinary Medicine; College of Veterinary Medicine; Northeast Agricultural University; Harbin Heilongjiang China
| | - L.J. Tang
- Department of Preventive Veterinary Medicine; College of Veterinary Medicine; Northeast Agricultural University; Harbin Heilongjiang China
| | - L. Sun
- College of Animal Science and Technology; Northeast Agricultural University; Harbin, Heilongjiang China
| | - M. Liu
- College of Animal Science and Technology; Northeast Agricultural University; Harbin, Heilongjiang China
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9
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Wallace IS, McKay P, Murray AG. A historical review of the key bacterial and viral pathogens of Scottish wild fish. JOURNAL OF FISH DISEASES 2017; 40:1741-1756. [PMID: 28718925 DOI: 10.1111/jfd.12654] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/07/2017] [Accepted: 04/08/2017] [Indexed: 06/07/2023]
Abstract
Thousands of Scottish wild fish were screened for pathogens by Marine Scotland Science. A systematic review of published and unpublished data on six key pathogens (Renibacterium salmoninarum, Aeromonas salmonicida, IPNV, ISAV, SAV and VHSV) found in Scottish wild and farmed fish was undertaken. Despite many reported cases in farmed fish, there was a limited number of positive samples from Scottish wild fish, however, there was evidence for interactions between wild and farmed fish. A slightly elevated IPNV prevalence was reported in wild marine fish caught close to Atlantic salmon, Salmo salar L., farms that had undergone clinical IPN. Salmonid alphavirus was isolated from wild marine fish caught near Atlantic salmon farms with a SAV infection history. Isolations of VHSV were made from cleaner wrasse (Labridae) used on Scottish Atlantic salmon farms and VHSV was detected in local wild marine fish. However, these pathogens have been detected in wild marine fish caught remotely from aquaculture sites. These data suggest that despite the large number of samples taken, there is limited evidence for clinical disease in wild fish due to these pathogens (although BKD and furunculosis historically occurred) and they are likely to have had a minimal impact on Scottish wild fish.
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Affiliation(s)
- I S Wallace
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
| | - P McKay
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
| | - A G Murray
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
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10
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Herath TK, Ashby AJ, Jayasuriya NS, Bron JE, Taylor JF, Adams A, Richards RH, Weidmann M, Ferguson HW, Taggart JB, Migaud H, Fordyce MJ, Thompson KD. Impact of Salmonid alphavirus infection in diploid and triploid Atlantic salmon (Salmo salar L.) fry. PLoS One 2017; 12:e0179192. [PMID: 28949966 PMCID: PMC5614425 DOI: 10.1371/journal.pone.0179192] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 05/25/2017] [Indexed: 11/26/2022] Open
Abstract
With increasing interest in the use of triploid salmon in commercial aquaculture, gaining an understanding of how economically important pathogens affect triploid stocks is important. To compare the susceptibility of diploid and triploid Atlantic salmon (Salmo salar L.) to viral pathogens, fry were experimentally infected with Salmonid alphavirus sub-type 1 (SAV1), the aetiological agent of pancreas disease (PD) affecting Atlantic salmon aquaculture in Europe. Three groups of fry were exposed to the virus via different routes of infection: intraperitoneal injection (IP), bath immersion, or cohabitation (co-hab) and untreated fry were used as a control group. Mortalities commenced in the co-hab challenged diploid and triploid fish from 11 days post infection (dpi), and the experiment was terminated at 17 dpi. Both diploid and triploid IP challenged groups had similar levels of cumulative mortality at the end of the experimental period (41.1% and 38.9% respectively), and these were significantly higher (p < 0.01) than for the other challenge routes. A TaqMan-based quantitative PCR was used to assess SAV load in the heart, a main target organ of the virus, and also liver, which does not normally display any pathological changes during clinical infections, but exhibited severe degenerative lesions in the present study. The median viral RNA copy number was higher in diploid fish compared to triploid fish in both the heart and the liver of all three challenged groups. However, a significant statistical difference (p < 0.05) was only apparent in the liver of the co-hab groups. Diploid fry also displayed significantly higher levels of pancreatic and myocardial degeneration than triploids. This study showed that both diploid and triploid fry are susceptible to experimental SAV1 infection. The lower virus load seen in the triploids compared to the diploids may possibly be related to differences in cell metabolism between the two groups, however, further investigation is necessary to confirm this and also to assess the outcome of PD outbreaks in other developmental stages of the fish when maintained in commercial production systems.
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Affiliation(s)
- Tharangani K. Herath
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
- Department of Animal Production, Welfare and Veterinary Sciences, Harper Adams University, Newport, Shropshire, United Kingdom
- * E-mail:
| | - Angela J. Ashby
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
- Fish Vet Group, Inverness, Scotland, United Kingdom
| | | | - James E. Bron
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
| | - John F. Taylor
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
| | - Alexandra Adams
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
| | | | - Manfred Weidmann
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
| | - Hugh W. Ferguson
- Marine Medicine Programme, School of Veterinary Medicine, St. George’s University, Grenada, West Indies
| | - John B. Taggart
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
| | - Herve Migaud
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
| | | | - Kim D. Thompson
- Institute of Aquaculture, University of Stirling, Stirling, United Kingdom
- Moredun Research Institute, Edinburgh, United Kingdom
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11
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Røsaeg MV, Sindre H, Persson D, Breck O, Knappskog D, Olsen AB, Taksdal T. Ballan wrasse (Labrus bergylta Ascanius) is not susceptible to pancreas disease caused by salmonid alphavirus subtype 2 and 3. JOURNAL OF FISH DISEASES 2017; 40:975-978. [PMID: 27859355 DOI: 10.1111/jfd.12572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 09/23/2016] [Accepted: 09/23/2016] [Indexed: 06/06/2023]
Affiliation(s)
- M V Røsaeg
- SalMar ASA, Kverva, Norway
- Norwegian University of Life Sciences, Oslo, Norge
| | - H Sindre
- Norwegian Veterinary Institute, Oslo, Norge
| | - D Persson
- Norwegian University of Life Sciences, Oslo, Norge
- FoMas - Fiskehelse og miljø, Haugesund, Norway
| | - O Breck
- Marine Harvest Norway AS, Bergen, Norway
| | - D Knappskog
- MSD Animal Health, Bergen, Norway
- Vaxxinova Norway AS, Bergen, Norway
| | - A B Olsen
- Norwegian Veterinary Institute, Oslo, Norge
| | - T Taksdal
- Norwegian Veterinary Institute, Oslo, Norge
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12
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Jansen MD, Bang Jensen B, McLoughlin MF, Rodger HD, Taksdal T, Sindre H, Graham DA, Lillehaug A. The epidemiology of pancreas disease in salmonid aquaculture: a summary of the current state of knowledge. JOURNAL OF FISH DISEASES 2017; 40:141-155. [PMID: 27136332 DOI: 10.1111/jfd.12478] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/12/2016] [Accepted: 02/18/2016] [Indexed: 05/13/2023]
Abstract
Pancreas disease (PD) is a viral disease caused by Salmonid alphavirus (SAV) that affects farmed Atlantic salmon (Salmo salar L.) and rainbow trout (Oncorhynchus mykiss (Walbaum)) in the seawater phase. Since its first description in Scotland in 1976, a large number of studies have been conducted relating to the disease itself and to factors contributing to agent spread and disease occurrence. This paper summarizes the currently available, scientific information on the epidemiology of PD and its associated mitigation and control measures. Available literature shows infected farmed salmonids to be the main reservoir of SAV. Transmission between seawater sites occurs mainly passively by water currents or actively through human activity coupled with inadequate biosecurity measures. All available information suggests that the current fallowing procedures are adequate to prevent agent survival within the environment through the fallowing period and thus that a repeated disease outbreak at the same site is due to a new agent introduction. There has been no scientific evaluation of currently used on-site biosecurity measures, and there is limited information on the impact of available mitigation measures and control strategies.
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Affiliation(s)
- M D Jansen
- Norwegian Veterinary Institute, Oslo, Norway
| | | | | | - H D Rodger
- Vet-Aqua International, Oranmore, Ireland
| | - T Taksdal
- Norwegian Veterinary Institute, Oslo, Norway
| | - H Sindre
- Norwegian Veterinary Institute, Oslo, Norway
| | - D A Graham
- Animal Health Ireland, Carrick on Shannon, Ireland
| | - A Lillehaug
- Norwegian Veterinary Institute, Oslo, Norway
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13
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Simons J, Bruno DW, Ho YM, Murray W, Matejusova I. Common dab, Limanda limanda (L.), as a natural carrier of salmonid alphavirus (SAV) from waters off north-west Ireland. JOURNAL OF FISH DISEASES 2016; 39:507-510. [PMID: 25865360 DOI: 10.1111/jfd.12376] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 02/27/2015] [Indexed: 06/04/2023]
Affiliation(s)
- J Simons
- Marine Scotland Science, Aberdeen, UK
| | - D W Bruno
- Marine Scotland Science, Aberdeen, UK
| | - Y-M Ho
- Marine Scotland Science, Aberdeen, UK
| | - W Murray
- Marine Scotland Science, Aberdeen, UK
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14
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Herath TK, Ferguson HW, Weidmann MW, Bron JE, Thompson KD, Adams A, Muir KF, Richards RH. Pathogenesis of experimental salmonid alphavirus infection in vivo: an ultrastructural insight. Vet Res 2016; 47:7. [PMID: 26743442 PMCID: PMC4705579 DOI: 10.1186/s13567-015-0300-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 05/23/2015] [Indexed: 12/27/2022] Open
Abstract
Salmonid alphavirus (SAV) is an enveloped, single-stranded,
positive sense RNA virus belonging to the family Togaviridae. It causes economically devastating disease in cultured salmonids. The characteristic features of SAV infection include severe histopathological changes in the heart, pancreas and skeletal muscles of diseased fish. Although the presence of virus has been reported in a wider range of tissues, the mechanisms responsible for viral tissue tropism and for lesion development during the disease are not clearly described or understood. Previously, we have described membrane-dependent morphogenesis of SAV and associated apoptosis-mediated cell death in vitro. The aims of the present study were to explore ultrastructural changes associated with SAV infection in vivo. Cytolytic changes were observed in heart, but not in gill and head-kidney of virus-infected fish, although they still exhibited signs of SAV morphogenesis. Ultrastructural changes associated with virus replication were also noted in leukocytes in the head kidney of virus-infected fish. These results further describe the presence of degenerative lesions in the heart as expected, but not in the gills and in the kidney.
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Affiliation(s)
- Tharangani K Herath
- Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.
| | - Hugh W Ferguson
- School of Veterinary Medicine, St George's University, St. George, Grenada, West Indies.
| | - Manfred W Weidmann
- Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.
| | - James E Bron
- Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.
| | - Kimberly D Thompson
- Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK. .,Moredun Research Institute, Pentlands Science Park, Bush Loan Penicuik, Edinburgh, UK.
| | - Alexandra Adams
- Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.
| | - Katherine F Muir
- Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.
| | - Randolph H Richards
- Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.
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15
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16
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Karlsen M, Andersen L, Blindheim SH, Rimstad E, Nylund A. A naturally occurring substitution in the E2 protein of Salmonid alphavirus subtype 3 changes viral fitness. Virus Res 2014; 196:79-86. [PMID: 25445347 DOI: 10.1016/j.virusres.2014.11.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 11/09/2014] [Accepted: 11/12/2014] [Indexed: 10/24/2022]
Abstract
Phylogenetic analyses of the Salmonid alphavirus subtype 3 (SAV3) epizootic have suggested that a substitution from proline to serine in the receptor binding protein E2 position 206 has occurred after the introduction of virus from a wild reservoir to farmed salmonid fish in Norway. We modelled the 3D structure of P62, the uncleaved E3-E2 precursor, of SAVH20/03 based on its sequence homology to the Chikungunya virus (CHIKV), and studied in vitro and in vivo effects of the mutation using reverse genetics. E2(206) is located on the surface of the B-domain of E2, which is associated with receptor attachment in alphaviruses. Recombinant virus expressing the E2(206S) codon replicated slower and produced significantly less genomic copies than virus expressing the ancestral E2(206P) codon in vitro in Bluegill Fry (BF2) cells. The E2(206S) mutant was out-competed by the E2(206P) mutant after 5 passages in an in vitro competition assay, confirming that the substitution negatively affects the efficacy of virus multiplication in cell culture. Both mutants were highly infectious to Atlantic salmon (Salmo salar), produced similar viral RNA loads in gills, heart, kidney and brain, and induced similar histopathologic changes in these organs. The E2(206S) mutant produced a less persistent infection in salmon and was shed more rapidly to water than the E2(206P) mutant. Reduced generation time through more rapid shedding could therefore explain why a serine in this position became dominant in the viral population after SAV3 was introduced to farmed salmon from the wild reservoir.
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Affiliation(s)
- Marius Karlsen
- Department of Biology, University of Bergen, Thor Møhlens gt 55, 5020 Bergen, Norway.
| | - Linda Andersen
- Department of Biology, University of Bergen, Thor Møhlens gt 55, 5020 Bergen, Norway
| | - Steffen H Blindheim
- Department of Biology, University of Bergen, Thor Møhlens gt 55, 5020 Bergen, Norway
| | - Espen Rimstad
- Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine and Biosciences, Norwegian University of Life Sciences, P.O. 8146 Dep, 0033 Oslo, Norway
| | - Are Nylund
- Department of Biology, University of Bergen, Thor Møhlens gt 55, 5020 Bergen, Norway
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