A novel totivirus and piscine reovirus (PRV) in Atlantic salmon (Salmo salar) with cardiomyopathy syndrome (CMS).
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.
Section for virology and serology, National Veterinary Institute, P,O, Box 750 Sentrum, 0106 Oslo, Norway.
Marie
M
Løvoll
Jannicke
J
Wiik-Nielsen
Søren
S
Grove
Christer R
CR
Wiik-Nielsen
Anja B
AB
Kristoffersen
Randi
R
Faller
Trygve
T
Poppe
Joonil
J
Jung
Chandra S
CS
Pedamallu
Alexander J
AJ
Nederbragt
Matthew
M
Meyerson
Espen
E
Rimstad
Torstein
T
Tengs
D000818:Animals; D009202:Cardiomyopathies / Q000662:veterinary* / Q000821:virology; D005393:Fish Diseases / Q000821:virology*; D006321:Heart / Q000821:virology; D006651:Histocytochemistry; D017403:In Situ Hybridization; D008853:Microscopy; D008969:Molecular Sequence Data; D009206:Myocardium / Q000473:pathology; D012367:RNA, Viral / Q000235:genetics; D012087:Reoviridae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D012088:Reoviridae Infections / Q000662:veterinary* / Q000821:virology; D020317:Salmo salar / Q000821:virology*; D017422:Sequence Analysis, DNA; D019197:Totivirus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*
D012367:RNA, Viral