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A novel totivirus and piscine reovirus (PRV) in Atlantic salmon (Salmo salar) with cardiomyopathy syndrome (CMS)

Marie Løvoll1, Jannicke Wiik-Nielsen2, Søren Grove1, Christer R Wiik-Nielsen1, Anja B Kristoffersen3, Randi Faller1, Trygve Poppe4, Joonil Jung5, Chandra S Pedamallu5, Alexander J Nederbragt6, Matthew Meyerson7, Espen Rimstad8 and Torstein Tengs9*

Author Affiliations

1 Section for immunoprophylaxis, National Veterinary Institute, P.O. Box 750 Sentrum, 0106 Oslo, Norway

2 Section for fish health, National Veterinary Institute, P.O. Box 750 Sentrum, 0106 Oslo, Norway

3 Section for epidemiology, National Veterinary Institute, P.O. Box 750 Sentrum, 0106 Oslo, Norway

4 Department of basic sciences and aquatic medicine, Norwegian School of Veterinary Science, P.O. Box 8146 Dep, 0033 Oslo, Norway

5 Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA

6 Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, 0316 Oslo, Norway

7 Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA

8 Department of food safety and infection biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep, 0033 Oslo, Norway

9 Section for virology and serology, National Veterinary Institute, P.O. Box 750 Sentrum, 0106 Oslo, Norway

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Virology Journal 2010, 7:309  doi:10.1186/1743-422X-7-309

Published: 10 November 2010

Abstract

Background

Cardiomyopathy syndrome (CMS) is a severe disease affecting large farmed Atlantic salmon. Mortality often appears without prior clinical signs, typically shortly prior to slaughter. We recently reported the finding and the complete genomic sequence of a novel piscine reovirus (PRV), which is associated with another cardiac disease in Atlantic salmon; heart and skeletal muscle inflammation (HSMI). In the present work we have studied whether PRV or other infectious agents may be involved in the etiology of CMS.

Results

Using high throughput sequencing on heart samples from natural outbreaks of CMS and from fish experimentally challenged with material from fish diagnosed with CMS a high number of sequence reads identical to the PRV genome were identified. In addition, a sequence contig from a novel totivirus could also be constructed. Using RT-qPCR, levels of PRV in tissue samples were quantified and the totivirus was detected in all samples tested from CMS fish but not in controls. In situ hybridization supported this pattern indicating a possible association between CMS and the novel piscine totivirus.

Conclusions

Although causality for CMS in Atlantic salmon could not be proven for either of the two viruses, our results are compatible with a hypothesis where, in the experimental challenge studied, PRV behaves as an opportunist whereas the totivirus might be more directly linked with the development of CMS.