Norway is the largest producer of farmed Atlantic salmon in the world.
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More bad news for salmon farmers in Norway, as further cases of ISA are reported at facilities owned by Lerøy, SalMar, Måsøval and Mowi, among others.
Reports of further suspected cases of infectious salmon anemia were announced by Mattilsynet, the Norwegian Food Safety Authority, at a SalMar site in Frøya, Trøndelag county on 17 June, and at sites operated by Varde Fiskeopprett, Tombre Fiskeanlegg, Lingalaks and Lerøy Vest Sjø (Lerøy Seafood Group) in Øygarden and Bømlo, Vestland county on 18 and 19 June.
The Authority has also recently established restriction zones at various sites with confirmed cases.
On 18 June, restriction zones were established in Bjørnafjorden, Austevoll and Tysnes municipalities, Vestland county, after ISA was detected at a Lerøy’s facility in sea location 24735 Gulholmen in Bjørnafjorde.
On the same day, a restriction zone was established in Alta municipality, Finnmark, following detection of ISA at a SalMar farm.
One day later, on 19 June, a further restriction zone was implemented in Frøya municipality, Trøndelag, after ISA was found at two separate sites run by Måsøval and Mowi.
When an outbreak of ISA is detected, the Norwegian Food Safety Authority establishes a restriction zone to combat the disease and to limit the further spread of infection. ISA can be spread through movements of infected fish, contaminated water, and contaminated equipment.
Symptoms of ISA in affected salmon include anemia and general signs of circulation problems, such as edema and accumulation of fluid in the abdomen. The disease can also provoke a dark liver, swollen kidneys or spleen, or accumulation of blood in the intestine, according to Mattilsynet.
The virus first invades the mucous membranes on the gills and skin, and then establishes an infection in the cell layer that covers the inside of blood vessels and the heart.
The virus is not transmissable to humans, but is a significant problem for fish health and welfare, and is highly costly for fish farmers, with Norwegian regulations requiring fish at infected sites to be culled early.
Norway aims to eradicate ISA, after Norway's Ministry of Trade and Fisheries decided on 19 April 2022 to introduce an eradication program.