Infection was only found in two juvenile salmon during IMR's monitoring.

Little infection found in migrating wild salmon in Norway

The results from the Institute of Marine Research's monitoring last year show that there is probably not much viral and bacterial infection in wild fish in the sea.

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"We found infection in only two fish. It was in young salmon (post smolt) from the Sognefjord where a low amount of the PMC (Piscine Myocarditis) virus was detected," says researcher Abdullah S. Madhun in a news release from IMR .

The PMC virus can cause cardiomyopathy syndrome (CMS), also called heart failure. 

Viruses that can be transmitted from farming

  • Heart disease is chronic and develops slowly. It can cause both reduced animal welfare and acute mortality for the fish. 

  • Heart and muscle inflammation (HSMB) is a contagious viral disease that affects a large proportion of  farmed salmon in the sea phase in all production areas.

  • Bacterial kidney disease (BKD) is a notifiable, serious chronic disease that has been sporadically detected in both farmed and wild fish. 

  • Since 2022, there has been a significant increase in the number of BKD outbreaks in aquaculture. 

  • Last year's results support monitoring findings from previous years.

Madhun points out that the amount of virus found is very low. 

In addition, the fish were tested for PRV1 (the virus that can cause cardiomyopathy) and  R. salmoninarum (the virus that can cause bacterial kidney disease). No fish were found to be infected with these. 

"We generally find very few fish infected with the various infectious agents we investigate."

In total, investigations are being carried out on three different viruses/bacteria, all known to cause serious diseases in farmed fish.

The annual monitoring of such infection was carried out last year on migrating smolts from Ryfylke to Stadt and in West Finnmark, i.e. production areas 2, 3, 4 and 12. A total of 200 fish were examined. The fish were caught as part of the national monitoring of sea lice in wild salmonids (NALO). 

"There is a lot of farming in the areas where we do these surveys, so we assume that if infection with these pathogens was a major problem for migrating smolt, we would find infected fish in these areas.

“Although the results may indicate that transmission from farmed to wild fish is limited, we cannot rule out that wild fish become sick and die before they are registered in our monitoring. The programme mainly captures live fish,” Madhun points out.

The monitoring is carried out on behalf of the Norwegian Food Safety Authority, and the report can be read here.

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