Salmon Killer Disease Mystery Solved

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The identity of a mysterious disease that’s raged through European salmon farms, wasting the hearts and muscles of infected fish, has been revealed…

The researchers eventually arrived at the 10-gene virus they called piscine reovirus, or PRV. The virus was described July 9 in Public Library of Science One.


“If the potential hosts are in close proximity, it goes through them like wildfire,”

Infected fish are physically stunted, and their muscles are so weakened that they have trouble swimming or even pumping blood. The disease is often fatal, and the original outbreak has been followed by 417 others in Norway and the United Kingdom. Every year there’s more of the disease, and it’s now been seen in wild fish, suggesting that farm escapees are infecting already-dwindling wild stocks

Piscine reovirus (PRV) in hearts of Atlantic salmon coincide with Heart and Skeletal Muscle Inflammation (HSMI)

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 "Heart and skeletal muscle inflammation (HSMI) is one example of an emerging disease in farmed Atlantic salmon (Salmo salar L). Since the first recognition as a disease in 1999 it has become a widespread and economically important disease in Norway.

The disease was recently found to be associated with infection with a novel reovirus, piscine reovirus (PRV).

"Our results confirm the association between PRV and HSMI, and strengthen the hypothesis of PRV being the causative agent of HSMI."



"Aquaculture is the fastest growing food production sector in the world. However, the increased production has been accompanied by the emergence of infectious diseases. Heart and skeletal muscle inflammation (HSMI) is one example of an emerging disease in farmed Atlantic salmon.


"The immunohistochemical detection of PRV is an informative, supportive tool for diagnostic histopathology of HSMI".

                                                    -VETERINARY RESEARCH 2012

Heart and Skeletal Muscle Inflammation of Farmed Salmon Is Associated with Infection with a Novel Reovirus

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Atlantic salmon mariculture has been associated with epidemics of infectious diseases that threaten not only local production, but also wild fish coming into close proximity to marine pens and fish escaping from them.


Heart and skeletal muscle inflammation (HSMI) is a frequently fatal disease of farmed Atlantic salmon. Here we provide evidence that HSMI is associated with infection with piscine reovirus (PRV).


Measures must be taken to control PRV not only because it threatens domestic salmon production but also due to the potential for transmission to wild salmon populations.

What’s Killing Farmed Salmon? New Virus May Also Pose Risk to Wild Salmon

"Heart and skeletal muscle inflammation (HSMI), an often fatal disease, was first detected in salmon on a farm in Norway in 1999, and has now been reported in 417 fish farms in Norway as well as in the United Kingdom."

"The disease destroys heart and muscle tissue and kills up to 20 percent of infected fish."

"… using cutting-edge molecular techniques, an international team led by W. Ian Lipkin, MD, the John Snow Professor of Epidemiology and director of the Center for Infection and Immunity at Columbia University's Mailman School of Public Health, has found evidence that the disease may be caused by a previously unknown virus"

"Our data provide compelling evidence that HSMI is associated with infection with a new reovirus"  


"these infections can spread to wild fish coming in close proximity to marine pens”

                                               - SCIENCE DAILY

Piscine reovirus (PRV) in wild Atlantic salmon and sea-trout in Norway

Journal of Fish Diseases

“PRV is a newly discovered reovirus associated with heart and skeletal muscle inflammation (HSMI), a serious and commercially important disease affecting farmed Atlantic salmon in Norway.”

“Since 1999, HSMI has been detected in all salmon-producing counties in Norway.”

“The diagnosis of HSMI is based on histological examination of changes in heart and skeletal muscle”

“HSMI is associated with a reovirus with the proposed name Piscine reovirus (PRV)."

"It is generally acknowledged that aquaculture can influence diseases in wild fish populations either by increasing the number of available hosts and thereby altering the equilibrium between host and parasite (Mennerat et al. 2010), or by introducing pathogens into new geographical areas (Peeler et al. 2011)."

“For HSMI, the identification of PRV as a possible causative agent has made it possible to screen both wild and farmed populations by real-time RT-PCR”

“one would expect HSMI-affected fish with severe heart and skeletal muscle lesions to have reduced cardiovascular capacity (Kongtorp et al. 2004b, 2006) and thus be less capable of returning to rivers, being caught and sampled. In general, diseased wild fish are difficult to sample because they display abnormal behaviour or reduced swimming capacity and will be removed by predators or otherwise disappear in the mass of water” (McVicar 1997; Bergh 2007)."

“The abundance and distribution of PRV in wild salmonid populations described in this article could place limitations on management of the virus in commercial aquaculture, as will the newly discovered presence of the virus in wild marine fish” (Wiik-Nielsen et al. 2012)."

                                              -JOURNAL OF FISH DISEASES, 2012

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