Vince McDonagh

Heart of the matter

Fish may be good for our health, but they suffer cardio problems themselves

BY VINCE MCDONAGH

ONE of the biggest threats to farmed salmon is not what you might expect. Every year, hundreds of thousands, possibly millions, of fi sh die from a li� le-discussed cardiac disease, cardiomyopathy syndrome (CMS). In short: heart failure.

The disease made its entry into Norwegian salmon farms in the mid 1980s and later spread to the Faroe Islands, Scotland and Ireland. Now the authori� es are increasing their eff orts to try to fi nd out why this killer syndrome is on the increase.

Salmon mortality in Norway is alarmingly high. It is es� mated that around 50 million salmon die every year from various causes, many as a result of CMS.

No part of the country’s long coastline is immune, but the western part of Norway appears to be the hardest hit.

It is also reckoned that cases o� en rise following lice treatment procedures, sugges� ng stress may be a factor. Scotland also has a problem. Mowi revealed in its third-quarter report, published in October, that incidents of CMS at its Sco� sh farms remain are s� ll too high. Neighbouring companies have also suff ered in the past. Edgar Brun, Director of Fish Health and Welfare at the Norwegian Veterinary Ins� tute, told

Above: Examining fi sh (Photo: SAIC) Left: Edgar Brun Opposite from top: Health check for a salmon (Photo: SAIC); Ida Beitnes-Johansen

“The industry must take some of the blame”

the state broadcaster NRK recently that he believed there had been too much a� en� on on salmon lice. He is calling for the focus to be widened.

He says there are so many other diseases that are contribu� ng to the high mortality rate for farmed salmon and this has overshadowed the discussion around other types of infec� on. It is � me, he argues, to take them more seriously.

Ida Beitnes Johansen, an associate professor at NMBU Veterinary College, has been selected to fi nd some of the answers and mostly importantly why some fi sh get sick while others remain healthy. She says fi sh grow up in a highly controlled environment and it may be that stress is an important contributory cause. Trygve Poppe, Professor Emeritus of Fish Health at the Norwegian School of Veterinary Science, believes the industry must take some of the blame for the country’s high fi sh mortality. He also told NRK the fact that so many salmon and trout die prematurely was not worthy of a cultured na� on like Norway . Firda Seafood CEO Ola Braanaas also believes there is an issue, adding that his company has introduced a number of measures that have resulted in reduced mortality. He says the company hopes to reduce losses to 5% within two years, with an eventual goal of zero deaths.

High mortality rates are costly for businesses – es� mated at around £130m a year – because the disease o� en aff ects large and mature fi sh coming up to harvest.

The Veterinary Ins� tute also believes the real cost could be almost twice as high as is es� mated because CMS is not a no� fi able disease.

In Vestland county, virus infec� on was registered last year in 35 fi sh farms – up from 28 in 2018 and 24 in 2017.

More worryingly, a number of CMS cases have been reported where the disease occurs signifi cantly earlier in the life cycle of a salmon, o� en fi ve months a� er release into the sea, when fi sh are as small as 100-300 grams.

According to scien� sts, this means that there is a risk of suff ering CMS in a plant throughout almost the en� re produc� on cycle, resul� ng in major consequences for both opera� ons and fi nances.

So far, outbreaks tend to be confi ned largely (but not exclusively) to farmed salmon. Some locali� es appear to be aff ected more than others, which leads scien� sts to believe there are reservoirs of infec� on they do not yet know about.

Clinical microscopic fi ndings include infl ammatory changes in the inner, spongy part of the anterior and cardiac chambers, while the compact ventricular wall is usually normal.

In severe cases, the changes can be so extensive that the atrial wall ruptures, which has given the disease its more popular and frightening name – heart crack.

So far there is no vaccine or eff ec� ve treatment for CMS, but scien� sts are thought to be making progress. And that, for now, seems to be the best hope. FF A new service that automa� cally alerts salmon farmers to non-no� fi able diseases such as CMS, pasteurellosis and other problems in their area was launched by the fi sh health company Manolin earlier in the year. This is thought to be the fi rst and only available system to no� fy farmers about the risk in their area of non-no� fi able diseases – those that are not tracked by the regulators. Manolin’s industry member data shows that non-no� fi able diseases caused fewer than 1% of total mortali� es from 2012 to 2016, but increased to 10% 2019 and 9% in 2020. According to a Norwegian Veterinary Ins� tute 2020 report, The Health Situati on in Norwegian Aquaculture, the number of locali� es diagnosed with cardiomyopathy syndrome more than tripled between 2010 and 2020, from 49 to 154.

Above: Tony Chen, CEO Manolin

A BLOOD TEST FOR HEART ISSUES

Meanwhile, a group of aquaculture researchers in Scotland is aiming to develop a simple and cost-eff ec� ve mass-tes� ng tool that can quickly and proac� vely detect and diff eren� ate between a range of cardiac condi� ons in salmon. The consor� um will seek to study specifi c blood biomarkers that indicate the presence of cardiomyopathies such as heart and skeletal muscle infl amma� on, cardiomyopathy syndrome and pancreas disease. Assessing the diseases with high precision is diffi cult with current diagnos� c techniques, par� cularly when they are at their early stages. Bringing together experts from the University of Glasgow, University of Edinburgh, Cooke Aquaculture Scotland, Life Diagnos� cs Ltd, Moredun Research Ins� tute, Benchmark Gene� cs Ltd, and the Sustainable Aquaculture Innova� on Centre (SAIC), the project will deliver a new tool that is simple to use for fi sh health professionals, easily deployable at fi sh farms, and brings immediate and prac� cal advantages in disease preven� on, earlier treatment, stock management and breeding for disease resistance. Professor David Eckersall, an expert in veterinary biochemistry at the University of Glasgow, says: “Similar types of tests for cardiac biomarkers are deployed and used rou� nely in other species of animals. A big part of this project will be transla� ng what we know about detec� ng and diagnosing cardiomyopathies in other animals to fi sh.”