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Piscine orthoreovirus (PRV) in red and melanised foci in white muscle of Atlantic salmon (Salmo salar).

Bjørgen H, Wessel Ø, Fjelldal PG, Hansen T, Sveier H, Sæbø HR, Enger KB, Monsen E, Kvellestad A, Rimstad E, Koppang EO - Vet. Res. (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Basic Science and Aquatic Medicine, School of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway. havard.bjorgen@nmbu.no.

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.

No MeSH data available.


Related in: MedlinePlus

RT-qPCR analysis for PRV in blood (A) and white skeletal muscle (B). Fish groups with melanised, red or no changes are coloured brown, red, and grey, respectively. (A) Detection in blood presented by box plot with whiskers indicating max/min of the Ct-values from Group A (n = 25), B (n = 35), E (n = 20), F (n = 42), G (n = 43) and H (n = 10). The percent of fish in each group with melanised focal changes are displayed. (B) Samples from red or melanised focal changes (+) and non-affected areas (−) from the same individual. Box plot and whiskers showing max/min of the Ct-values from Group C with red focal changes (n = 6), and from Groups A (n = 9) and E (n = 14) with melanised focal changes. Only non-affected tissue (−) could be tested from groups without changes; i.e. Groups F (n = 6) and G (n = 6). Analyses were performed using Wilcoxon matched pairs signed rank test. *p < 0.05.
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Fig7: RT-qPCR analysis for PRV in blood (A) and white skeletal muscle (B). Fish groups with melanised, red or no changes are coloured brown, red, and grey, respectively. (A) Detection in blood presented by box plot with whiskers indicating max/min of the Ct-values from Group A (n = 25), B (n = 35), E (n = 20), F (n = 42), G (n = 43) and H (n = 10). The percent of fish in each group with melanised focal changes are displayed. (B) Samples from red or melanised focal changes (+) and non-affected areas (−) from the same individual. Box plot and whiskers showing max/min of the Ct-values from Group C with red focal changes (n = 6), and from Groups A (n = 9) and E (n = 14) with melanised focal changes. Only non-affected tissue (−) could be tested from groups without changes; i.e. Groups F (n = 6) and G (n = 6). Analyses were performed using Wilcoxon matched pairs signed rank test. *p < 0.05.

Mentions: The PRV loads in blood samples of Groups A, B, E-H were assessed by RT-qPCR (Figure 7A). All groups in which melanised changes were found (Groups A, B, E) contained RT-qPCR PRV positive fish. High PRV loads were detected in Group A (Ct 20.7 ± 0.8) and Group E (Ct 20.7 ± 1.4), in which prevalences of melanised changes were 40% and 90%, respectively. The viral load was much lower in Group B (Ct 32.8 ± 1.7) where melanised changes were much less prevalent (3%). High levels of PRV were also detected in Group F (Ct 20.6 ± 1.2) and Group G (Ct 21.4 ± 1.4) where melanised focal changes were absent. The wild fish of Group H were the only group negative for both PRV and melanised changes. Overall, the load of PRV in blood was not correlated with the presence of melanised changes.Figure 7


Piscine orthoreovirus (PRV) in red and melanised foci in white muscle of Atlantic salmon (Salmo salar).

Bjørgen H, Wessel Ø, Fjelldal PG, Hansen T, Sveier H, Sæbø HR, Enger KB, Monsen E, Kvellestad A, Rimstad E, Koppang EO - Vet. Res. (2015)

RT-qPCR analysis for PRV in blood (A) and white skeletal muscle (B). Fish groups with melanised, red or no changes are coloured brown, red, and grey, respectively. (A) Detection in blood presented by box plot with whiskers indicating max/min of the Ct-values from Group A (n = 25), B (n = 35), E (n = 20), F (n = 42), G (n = 43) and H (n = 10). The percent of fish in each group with melanised focal changes are displayed. (B) Samples from red or melanised focal changes (+) and non-affected areas (−) from the same individual. Box plot and whiskers showing max/min of the Ct-values from Group C with red focal changes (n = 6), and from Groups A (n = 9) and E (n = 14) with melanised focal changes. Only non-affected tissue (−) could be tested from groups without changes; i.e. Groups F (n = 6) and G (n = 6). Analyses were performed using Wilcoxon matched pairs signed rank test. *p < 0.05.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4562189&req=5

Fig7: RT-qPCR analysis for PRV in blood (A) and white skeletal muscle (B). Fish groups with melanised, red or no changes are coloured brown, red, and grey, respectively. (A) Detection in blood presented by box plot with whiskers indicating max/min of the Ct-values from Group A (n = 25), B (n = 35), E (n = 20), F (n = 42), G (n = 43) and H (n = 10). The percent of fish in each group with melanised focal changes are displayed. (B) Samples from red or melanised focal changes (+) and non-affected areas (−) from the same individual. Box plot and whiskers showing max/min of the Ct-values from Group C with red focal changes (n = 6), and from Groups A (n = 9) and E (n = 14) with melanised focal changes. Only non-affected tissue (−) could be tested from groups without changes; i.e. Groups F (n = 6) and G (n = 6). Analyses were performed using Wilcoxon matched pairs signed rank test. *p < 0.05.
Mentions: The PRV loads in blood samples of Groups A, B, E-H were assessed by RT-qPCR (Figure 7A). All groups in which melanised changes were found (Groups A, B, E) contained RT-qPCR PRV positive fish. High PRV loads were detected in Group A (Ct 20.7 ± 0.8) and Group E (Ct 20.7 ± 1.4), in which prevalences of melanised changes were 40% and 90%, respectively. The viral load was much lower in Group B (Ct 32.8 ± 1.7) where melanised changes were much less prevalent (3%). High levels of PRV were also detected in Group F (Ct 20.6 ± 1.2) and Group G (Ct 21.4 ± 1.4) where melanised focal changes were absent. The wild fish of Group H were the only group negative for both PRV and melanised changes. Overall, the load of PRV in blood was not correlated with the presence of melanised changes.Figure 7

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Basic Science and Aquatic Medicine, School of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway. havard.bjorgen@nmbu.no.

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.

No MeSH data available.


Related in: MedlinePlus