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Melanized focal changes in skeletal muscle in farmed Atlantic salmon after natural infection with Piscine orthoreovirus (PRV).

https://arctichealth.org/en/permalink/ahliterature301317
Source
J Fish Dis. 2019 Jun; 42(6):935-945
Publication Type
Journal Article
Date
Jun-2019
Author
Håvard Bjørgen
Randi Haldorsen
Øyvind Oaland
Agnar Kvellestad
Dhamotharan Kannimuthu
Espen Rimstad
Erling Olaf Koppang
Author Affiliation
Institute of Basic Science and Aquatic Medicine, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
Source
J Fish Dis. 2019 Jun; 42(6):935-945
Date
Jun-2019
Language
English
Publication Type
Journal Article
Keywords
Animals
Aquaculture
Fish Diseases - pathology - virology
Melanins
Muscle, Skeletal - pathology - virology
Norway
Orthoreovirus - pathogenicity
RNA, Viral - genetics
Reoviridae Infections - pathology - veterinary
Salmo salar - virology
Abstract
Melanized focal changes in skeletal muscle of farmed Atlantic salmon (Salmo salar) are a major quality problem. The aetiology is unknown, but infection with Piscine orthoreovirus (PRV) has been associated with the condition. Here, we addressed the pathogenesis of red and melanized focal changes and their association with PRV. First, a population of farmed fish (PRV-negative prior to sea transfer) was sequentially investigated throughout the seawater period. The fish were autopsied and tested for PRV infection. Muscular changes were described by macroscopy and histology, and a classification system was established. Second, in an experimental infection trial, PRV was injected intramuscularly to induce changes. The farmed fish was gradually infected with PRV. Red focal changes occurred throughout the observation period with a low prevalence regardless of PRV status. Melanized changes were highly diverse and their prevalence increased during the trial. Changes of low macroscopic grade and histological category were more prevalent in PRV-negative fish. Diffuse granulomatous melanized changes only occurred after PRV infection. No muscular changes were observed in the experimentally challenged fish. Our studies do not indicate that PRV infection causes red focal changes, but seems important in the development of granulomatous melanized changes.
PubMed ID
30972792 View in PubMed
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Molecular detection and genotyping of Aphanomyces astaci directly from preserved crayfish samples uncovers the Norwegian crayfish plague disease history.

https://arctichealth.org/en/permalink/ahliterature258768
Source
Vet Microbiol. 2014 Sep 17;173(1-2):66-75
Publication Type
Article
Date
Sep-17-2014
Author
Trude Vrålstad
David A Strand
Frédéric Grandjean
Agnar Kvellestad
Tore Håstein
Ann Kristin Knutsen
Trond Taugbøl
Ida Skaar
Source
Vet Microbiol. 2014 Sep 17;173(1-2):66-75
Date
Sep-17-2014
Language
English
Publication Type
Article
Keywords
Animals
Aphanomyces - classification - genetics - pathogenicity
Astacoidea - parasitology
DNA - genetics
Genotype
Genotyping Techniques
History, 20th Century
History, 21st Century
Microsatellite Repeats
Norway
Real-Time Polymerase Chain Reaction
Abstract
Aphanomyces astaci causes crayfish plague in European freshwater crayfish, but most historical epizootics lack agent isolation and identification. Although declared as crayfish plague outbreaks by the Norwegian Competent Authorities, only presumptive diagnoses without agent isolation exist from Norwegian epizootics until 2005. Molecular methods now allow both A. astaci detection and genotype determination from preserved samples. We therefore aimed to (1) investigate molecularly if A. astaci was involved in a selection of mass-mortality events in Norwegian noble crayfish populations from 1971 to 2004, and (2) determine the eventually involved A. astaci genotype groups both from these historical and also more recent mass-mortality events. DNA was extracted directly from presumptively infected crayfish tissues, and screened by A. astaci specific qPCR. A representative selection of positive samples was confirmed by ITS-sequencing. Finally, genotype determination was performed with microsatellite markers that distinguish all known A. astaci genotype groups. The molecular examination detected A. astaci in crayfish materials from all examined mass-mortality events. The first event in 1971-1974 was caused by the A. astaci genotype group A, presumably the first genotype group that entered Europe more than 150 years ago. All later outbreaks were caused by the A. astaci genotype group B which was introduced to Europe by importation of signal crayfish in the 1960s. The results suggest that molecular methods can verify the involvement of A. astaci in the vast majority of observed crayfish mass mortalities in Europe whenever preserved materials exist. Moreover, microsatellite genotyping can reveal at least parts of the underlying epidemiology.
PubMed ID
25124447 View in PubMed
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Piscine orthoreovirus (PRV) in red and melanised foci in white muscle of Atlantic salmon (Salmo salar).

https://arctichealth.org/en/permalink/ahliterature271725
Source
Vet Res. 2015;46:89
Publication Type
Article
Date
2015
Author
Håvard Bjørgen
Øystein Wessel
Per Gunnar Fjelldal
Tom Hansen
Harald Sveier
Håkon Rydland Sæbø
Katrine Bones Enger
Eirik Monsen
Agnar Kvellestad
Espen Rimstad
Erling Olaf Koppang
Source
Vet Res. 2015;46:89
Date
2015
Language
English
Publication Type
Article
Keywords
Animals
Aquaculture
Fish Diseases - epidemiology - virology
Muscle, Skeletal - virology
Norway - epidemiology
Orthoreovirus - isolation & purification
Prevalence
Reoviridae Infections - epidemiology - veterinary - virology
Salmo salar
Abstract
Melanised focal changes (black spots) are common findings in the white skeletal muscle of seawater-farmed Atlantic salmon (Salmo salar). Fillets with melanised focal changes are considered as lower quality and cause large economic losses. It has been suggested that red focal changes (red spots) precede the melanised focal changes. In the present work, we examined different populations of captive and wild salmon for the occurrence of both types of changes, which were investigated for the presence of different viruses by immunohistochemistry and RT-qPCR. The occurrence of red or melanised foci varied significantly between the populations, from none in wild fish control group, low prevalence of small foci in fish kept in in-house tanks, to high prevalence of large foci in farm-raised salmon. Large amounts of Piscine orthoreovirus (PRV) antigen were detected in all foci. No other viruses were detected. Red focal changes contained significantly higher levels of PRV RNA than apparently non-affected areas in white muscle of the same individuals. Some changes displayed a transient form between a red and melanised pathotype, indicating a progression from an acute to a chronic manifestation. We conclude that PRV is associated with the focal pathological changes in the white muscle of farmed Atlantic salmon and is a premise for the development of focal melanised changes.
Notes
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PubMed ID
26346256 View in PubMed
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Vertebral column deformity with curved cross-stitch vertebrae in Norwegian seawater-farmed Atlantic salmon, Salmo salar L.

https://arctichealth.org/en/permalink/ahliterature307203
Source
J Fish Dis. 2020 Mar; 43(3):379-389
Publication Type
Journal Article
Date
Mar-2020
Author
Cathrine Trangerud
Håvard Bjørgen
Erling Olaf Koppang
Randi Nygaard Grøntvedt
Hege Kippenes Skogmo
Nina Ottesen
Agnar Kvellestad
Author Affiliation
Department of Companion Animal Clinical Sciences, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
Source
J Fish Dis. 2020 Mar; 43(3):379-389
Date
Mar-2020
Language
English
Publication Type
Journal Article
Keywords
Animals
Fish Diseases - epidemiology - pathology
Norway - epidemiology
Prevalence
Salmo salar - abnormalities
Spinal Diseases - epidemiology - pathology - veterinary
Spine - abnormalities
Abstract
Pathological changes in the vertebral column of farmed Atlantic salmon in Norway have been reported since the 1990s. Based on the characteristic radiographic findings, we here present a vertebral column deformity named "curved cross-stitch vertebrae" that mainly affects the middle aspect of the vertebral column. Sixty fish, from the west/northwest coast of mid-Norway, were sampled at slaughter and examined by radiography, computed tomography (CT), necropsy, macrophotography, and histology. The vertebral deformities were radiographically graded as mild, moderate, or marked. The main differences between these grades of changes were defined by increased curving of the peripheries of endplates, reduced intervertebral spaces, and vertical displacement of the vertebrae. The curved rims of endplates were located peripheral to a continuous and approximately circular borderline. The CT studies revealed small, multifocal, hypo-attenuating, round to crescent-shaped areas in the notochord, compatible with the presence of gas. Additionally, histology revealed that the axial parts of endplates had circular zones with perforations, through which either notochordal tissue prolapsed into the vertebrae or vascularized fibrochondroid proliferations extended from the vertebrae into the notochord. Inflammation was present in many vertebral bodies. To the best of our knowledge, this is the first report of gas in the notochord of fish.
PubMed ID
31970816 View in PubMed
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