‘Very little’ infection between farmed and wild salmon, study finds
New research has shown there is probably little viral and bacterial infection passing from farmed salmon to wild fish in the sea.
The study was carried out by the Norwegian Institute of Marine Research, which has just published its findings.
Institute researcher Abdullah S. Madhun said: “We found infection in only two fish. It was in young salmon (post smolt) from the Sognefjord where a low amount of the PMC virus was detected.”
The PMC virus can cause cardiomyopathy syndrome (CMS), also known as heart failure. The disease is chronic and develops slowly. It can cause both reduced animal welfare and acute mortality in fish.
Madhun points out that the amount of virus found was very low.
In addition, the fish were tested for PRV1 (the virus that can cause heart and skeletal muscle inflammation (HSMI)) and R. salmoninarum (the bacterium that can cause bacterial kidney disease (BKD). No fish were found to be infected with either of these.
The report says heart and muscle inflammation 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 farmed fish. Last year’s results support surveillance findings from previous years.”
“We generally find very few fish infected with the various infectious agents we investigate", says Madhun.
Investigations were carried out on three different viruses/bacteria, all known to cause serious diseases in farmed fish.
The annual monitoring of such infection took place last year on migrating young salmon (smolt) from Ryfylke to Stadt and in West Finnmark.
Madhun pointed out: “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 program mainly captures live fish.”
The monitoring was carried out on behalf of the Norwegian Food Safety Authority.
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