Disease Pathways From Farmed to Wild Salmon Confirmed.

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DN.NO Today, published an exposé by Harald Berglihn confirming that there is now “no doubt of the spread of deadly virus from farmed fish to wild fish”.

This has long been thought of as the primary source of mortality in wild salmon, the plethora and concentration of diseases in feedlots does not simply disintegrate in close proximity of sea pens. Government computer modelling has, somewhat conservatively, shown that dispersal patterns of chemical and organic detritus can pollute up to 10km from farms and still hold the potential to affect the life of molluscs and invertebrates.

The worldwide prevalence of water borne disease is a serious concern, and enhancing the understanding of major pathogen sources and their significant impacts on water resources is crucial. It is known however, that some diseases and viruses can live for months in sea water without a host and simply drift around in the currents and tides. One can only imagine the effects on wild salmonid populations. More work is desperately required.

Professor Are Nylund at the Department of Biosciences at the University of Bergen has researched fish diseases and especially ILA (infectious salmon anaemia) for over 30 years. It was he who, after the catastrophic ILA outbreak in Chile, which set the industry back many years, documented that the infection came with roe from Norway.

The highly contagious and lethal salmon disease ILA that ravaged the Chilean aquaculture industry a few years ago, is now known to be transmitted from farmed salmon to wild fish. It’s bad news for the wild salmon and goes some way to explain the plummet in numbers in the vicinity of farms and on migratory routes, from rivers on the west and east of Scotland.

In the tradition of the “merchant of doubt”, a large Norwegian fish breeding company replied by stamping Nylund’s research as unethical and reported Nylund and his research team to the National Investigation Committee for Misconduct in Research. Since then, several other reports confirmed that Nylund was absolutely right.

Nylund has led the group that has researched the spread of the virus itself (ILAV) between farmed salmon and wild salmon and recently published an article in the renowned American magazine Plos One.

ILA and ILAV:

Infectious salmon anemia (ILA) is a serious and contagious viral disease found mainly in salmon.

The virus (ILAV) is similar to the influenza virus that affects birds and mammals.

The ILAV virus primarily attacks the blood vessels of the salmon and causes severe bleeding and death.

The disease ILA can cause major losses to the aquaculture industry.

Source: DN / Veterinærinstituttet.

New virus variants:

The article shows that the virus has evolved after the aquaculture industry came to Norway.

“Three new groups of ILAV viruses have been established, which we now increasingly find in the wild salmon. This means that we are in no doubt that the spread of infection by ILAV goes from farmed fish to wild fish and that the reservoir for the infection is thus in fish farms.”, he says.

The virus, like the avian flu virus, occurs in a low and a high virulence variant. By high virulent it is meant that it causes disease.

“In the chicken industry, all the animals are slaughtered immediately on the discovery of the low-virulence variant because of the danger that it may mutate and become highly virulent. In the aquaculture industry, salmon are only slaughtered at the discovery of the highly virulent variety.“, Nyund says.

He believes it would have been a disaster for the industry if all farmed salmon also with low virulent ILAV were to be slaughtered.

“We strongly recommend that the administration put a strategy to get rid of ILAV completely. Then one has to start with ILAV-free broodfish which is kept in land-based plant and then put out virus-free smolt in feedlots with the least possible pressure of infection. It will take time; maybe 10-15 years, but that’s the only way to go.” thinks Nylund.

Are Nylund is a fish health professor at the University of Bergen.

Danger to wild salmon:

Is there a risk that the highly virulent variant can establish itself in the rivers with great negative consequences for the wild salmon?

“Yes, we did infection tests already in the 90’s where trout were infected with high virulent ILAV. Trout do not die from this virus, but 75–80 percent of them become carriers of the infectious virus. So one can imagine that the highly virulent virus can spread to salmon fry in the rivers. This can have major negative consequences for the population if this happens.” says Nylund.

The fish health professor believes it is time that not only salmon lice in the fish farming cages, but also the pressure from the aquaculture industry, come in as a parameter in the so-called traffic light scheme that determines where the aquaculture industry can grow.

“I think today’s traffic light system is quite hopeless with big flaws. It should be based on the total infection pressure against the wild salmon and not just the number of salmon lice in the fish farms. Farming is too important an industry for Norway for it not to be properly managed.” he believes.

The sheer biomass of dead salmon in Scottish farms due to disease, year on year is staggering. Yet our Government and salmon farming industry and it‘s sycophants continue to peddle the same old rhetoric of “many contributing factors” in the demise of wild salmonids. They revel in the idea that no single sea louse has been tracked from farmed fish to wild fish, therefore to some extent admonishing salmon farming from being the No.1 contributor.

The emphasis put on sea lice has long been a “red herring”. Indeed, it has even been used as a scapegoat in quackery publications to cast doubt on whether salmon farms do any damage at all.

While Government ministers queue up for the PR photo opportunity at Fisheries Management Scotland’s “Wild Salmon Matter” campaign, the same politicians are simply buying time for the salmon farming industry and guilty of organised environmental crime. Very sad.


Fuente: https://www.fishybusiness.co.uk/blog/disease-pathways-from-farmed-to-wild-salmon-confirmed


 

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