A brand of raw fermented trout has been recalled in Norway after being linked to several Listeria infections.

Haadem Fisk withdrew ‘Hel rakfisk i spann – 4 kilograms’ with lot number 924 due to Listeria contamination. It was sold across the country.

The Norwegian Food Safety Authority (Mattilsynet) warned consumers against eating fish from this batch. Officials would not disclose how many people are ill but Food Safety News understands there are only a small number of potentially linked infections.

Rakfisk is raw fish normally gutted and put into a salt brine and left for weeks or months. For most of the population the main season to eat it is November to February.

After the outbreak was discovered, samples of rakfisk were sent to the Veterinary Institute for analysis which showed a very high concentration of Listeria. There are no indications other products from Haadem Fisk are contaminated but further samples have been taken from production.

Company response
A Haadem Fisk statement identified affected 4-kilogram buckets with lot numbers from 923 to 931.

“There has been a case where listeriosis is suspected after eating rakfisk from Haadem Fisk. Listeria has been found in the bucket that are suspected to have caused the disease and other buckets from the production period. Probably the problem has arisen during production. Therefore, after consultation with Mattilsynet, we recommend that buckets from this lot be discarded or returned to the point of sale.”

Haadem Fisk stressed the importance of good hygiene practices when opening rakfisk buckets, storing products between 0 and 4 degrees C (32 to 39 degrees F) and not eating them after the expiry date.

The company statement said it takes the matter seriously and will take steps to find out what has happened. It has been operating for over half a century without any evidence of listeriosis.

“After this event, all routines will be reviewed, both internally in the company and after the rakfisk has left our production facilities. It has also been decided on our part that the number of laboratory tests should be multiplied in all parts of the production so that one can feel confident that the products from Haadem Fisk have a low risk.”

The Norwegian Food Safety Authority’s advice is people in risk groups, such as the elderly, those with impaired health, pregnant women or weak immune systems should avoid such products.

Heidi Lange, from the Norwegian Institute of Public Health (Folkehelseinstituttet), said the agency has received an isolate from the product that will be whole genome sequenced and compared with patient isolates in its database but so far the agency has not identified any cases.

The traditional Norwegian dish was also behind a Listeria outbreak last year when 13 people fell ill. Most sick people were over 70 years old and had compromised immune systems. The producer, Slidre Ørretsenter, withdrew all varieties of rakfisk from the market at the time but recently filed for bankruptcy.

High levels of Listeria detected
Taran Skjerdal, from the Veterinary Institute, said in the current outbreak it had received food samples from the producer and food authorities.

“First we use detection and enumeration because the higher the dose the more likely it is someone will become ill so the concentration is important. When we have the isolate then we can go on with whole-genome sequencing and compare with patient isolates or other human isolates in Norway and other places to look for some link,” she told Food Safety News.

Skjerdal said analysis found several hundred thousand colony-forming units of Listeria per gram of product.

“According to the dose-response models used today it is above the limit where you have an increased likelihood of listeriosis for normally healthy people. It is the nature of the fermented trout that when something goes wrong it goes terribly wrong,” she said.

“We have two samples where the concentration has been that high when you see that you don’t need to analyze the lot. In the outbreak last year the concentration in illness cases was down to a thousand or less in some cases but we had some samples as high as this or higher.”

Origin of contamination
Rakfisk can be contaminated at several stages of production, according to Skjerdal.

“In production it starts with trout normally from aquaculture but in freshwater, meaning no seawater. Those ponds could be contaminated so it could follow from the fish before it is placed into this bucket and the salt brine goes in. If it is contaminated at that stage there could be rapid growth before the maturation process starts,” she said.

“If there is no contamination there, these buckets are normally not opened unless the producer changes the brine so this is an opportunity for contamination. Several producers don’t open the bucket until they re-pack it in something more consumer-friendly and some send the bucket directly. The consumer can also contaminate the product when they open and close the bucket.

“To get a really high concentration it is likely the contamination has come in early, as you don’t get to this level unless the bacterium has time to grow at the right temperature conditions.”

Skjerdal said rakfisk and Listeria had been studied before by the Veterinary Institute and others.

“Before the European food law introduced a limit of 100 CFU/g, we had another limit of 1,000 CFU/g of Listeria in rakfisk because of its nature. The reason it was so high is it was impossible to avoid high levels due to the way the fish is produced. Then the focus was on how can those levels be detected in fish without analyzing everything. It is possible to analyze the salt brine and not the fish itself. Decades ago there were studies going on about that,” she said.

“Later on it has been studied if protecting flora could be added by washing the bucket in a solution with yogurt because that would introduce lactic acid bacteria which competes well with Listeria. It would not take away the Listeria but it would avoid the high concentration. It is likely studies on that will be taken up again now.

“While we don’t know yet for the ongoing outbreak, for the last one by whole genome sequencing on the strains, it was a different gene sequence compared to other Listeria strains. This may not be unexpected since the production is so different from seafood and agriculture, it appears to be special strains but it is speculation at the moment.”

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