New virus may pose risk to wild salmon

Farmed fish are an increasingly important food source, with a global harvest now at 110 million tons and growing at more than 8 percent a year. But epidemics of infectious disease threaten this vital industry, including one of its most popular products: farmed Atlantic salmon. Perhaps even more worrisome: these infections can spread to wild fish coming in close proximity to marine pens and fish escaping from them.

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. Although studies have indicated an infectious basis, recent efforts to identify the pathogen causing the disease have been unsuccessful. Now, 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. The newly identified virus is related but distinct from previously known reoviruses, which are double-stranded RNA viruses that infect a wide range of vertebrates.

The full study findings are published online in the publication PLoS One.

"Our data provide compelling evidence that HSMI is associated with infection with a new reovirus," says Gustavo Palacios, first author of the study and assistant professor of Epidemiology in the Center.

"While there is no evidence that this could spread to humans, it is a threat to aquaculture and it has the potential to spread to wild salmon," added Dr. Lipkin.

To identify the virus, the Columbia University investigators used 454 high throughput DNA sequencing and bioinformatics, including a new tool called Frequency Analysis of Sequence Data (FASD), pioneered by Raul Rabadan of Columbia's Department of Biomedical Informatics. Investigators in Norway and the U.S. then looked for viral sequences in heart and kidney samples from 29 salmon representing three different HSMI outbreaks and 10 samples from healthy farmed fish. Twenty-eight of the 29 (96.5%) known HSMI samples and none of the 10 healthy salmon samples were positive. The investigators also tested 66 samples obtained from living in nine coastal rivers in Norway. The virus was detected in sixteen of these samples (24.2%), though generally in lower concentrations than found in ailing farmed fish.

"The speed of this process, and the enthusiasm on both sides of the Atlantic created a very fruitful collaboration," says Espen Rimstad, a professor at the Norwegian School of Veterinary Science in Oslo. "Using the expertise of our colleagues at Columbia in high throughput sequencing and advanced bioinformatics, we had within a few weeks the whole genome sequence of a hitherto unknown virus."

Additional research will be needed to confirm that the reovirus is the cause of HSMI. Meanwhile work has already begun in Norway to develop a vaccine to protect farmed .

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Citation: New virus may pose risk to wild salmon (2010, July 9) retrieved 22 April 2019 from
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Jul 10, 2010
Just to pose a little food for thought: Why is it that seemingly viruses always seem to mutate towards doing more harm to their hosts then actually doing any good?
If evolutionary theory is one where things tend to get better and more complex, why don't these little critters get on the ball and start doing better things for their hosts - helping to keep them in prime condition to feed on, instead of making them diseased and eventually killing them off?
Seems like a lame thought till you start examining it closely.

Jul 10, 2010
We knew farmed salmon were a problem back when sea lice were the big issue. How many different diseases from salmon farms will we tolerate before we ban them?

Jul 10, 2010
@ FredHose

Actually the first lifeforms that could reproduce would have likely been similar to simple virus's in terms of scale and structure. We ourselves are the proof that symbiotic relationships between lifeforms evolves and is beneficial. It just happens that to get a relationship that works well for both parties, you might have to wade through a few that don't, or in evolutions case, a few million.

Jul 10, 2010
The easyest thing is to ban things, if they dont farm them then more have to be catched in the wild which is bad for the nature, there are solutions for this problem, lets say GM salmon resistant to this type of viruses, it appears GM can be used for everything and they should.

It's about the ills of monoculture, and commerce's inability to see the forest for the trees. These viruses are not the only diseases that plague farmed(as in MONOCULTURE) fish/shellfish species.

They are constantly infected or under threat of infection by a whole army of pathogens- which they are unable to escape, sinc they are farmed. That means in one place. The role that the ecosystem naturally plays in the health of these animals is entirely replaced with hormone/antibiotic laced food, quantities of which end up decomposing right there on the farm, with the fish. And toxic downstream.

How healthy does anyone think the fish produced in such a system can be, much less as food for us?

Jul 11, 2010

GM is at best a bandaid solution. Pathogens are plentiful and ever evolving. For example, we have only managed to "more or less" eradicate a couple of human diseases after a century plus of medical endeavor. The natural world is prey to just as many -if not more- disease than humans are.

The real problem here is that we have so degraded the natural habitat of these food species, and/or overfished them in the wild, that what would otherwise be resources that existed in equilibrium with their environment, and would be a continuous, renewable source of food, can no longer be sustained, given current practice.

So, we have to turn to this unnatural practice of "aquaculture", which requires that we compensate for the loss of habitat by the use of drugs, chemicals, and manufactured food, all of which have pronounced -magnified- negative effects for the food species, the environment, and humans, GM or no.

The whole system needs rethinking.

Jul 11, 2010
Now there is this thinking that is wrong, critisize everything and not giving any solution, what retinking, (......) to ban farming wont solve anything!

I didn't say ban it.

The process does need rethinking, though, and as currently practiced, should be ENTIRELY REMOVED from direct contact with the natural environment at large, as it is a direct risk in terms of toxin load, and also for the introduction of virulent diseases "incubated" in the captive populations of farmed fish, shellfish, and crustaceans.

All of these are vectors of well-known pathogens that or also of considerable danger to humans, as well. And the feeding and disease prevention measures contribute to local -but more importantly- downstream effects in terms of anoxia, algae blooms, excess phosphate/nitrogen, et c.

Get these facilities out of our waters, and above ground, where their true costs become apparent, and they can't contaminate wild stocks and foul our(yours, mine and their) waters.

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