Rising ISA outbreaks under investigation

An investigation has been ordered into the rising number of Infectious Salmon Anaemia (ISA) outbreaks along the Norwegian coast. More than 15 confirmed cases have been logged so far this year, many of them during the last two months and it is giving cause for concern. Additional suspected infections are also under investigation. Troms and Finnmark appear to be the worst hit regions, although areas towards the south of the country have been affected.

Sites operated by Cermaq and Norway Royal Salmon are among the companies where cases have been confirmed or suspected during the last few days.

Now the Norwegian Food Safety Authority, supported by the country’s Veterinary Authority, is carrying out a probe. While not harmful to humans, ISA is highly infectious among fish and spreads quickly. There is not one single cause. Some put this pathogen spread down to intensive fish farming practices, along with workboats moving fish between sites and the discharge of untreated blood. Another school of thought thinks sea warming could be playing a part.

ISA was first reported in Norway in 1984, but has since hit most salmon producing countries including Scotland. The disease may appear as a systemic and lethal condition characterised by severe anaemia and haemorrhages in several organs. There is no effective treatment at present to prevention is all important.

Either way, it is usually very costly for companies, and for smaller independent businesses in particular, because cages have to be emptied, the stock destroyed and restrictions placed on movement. A recent outbreak is believed to have led to the loss of fish worth over 40 million kroner (£3.4 million) at one site near Tromso.

The Veterinary Authority told Intrafish Norway it was following developments closely but did not want to speculate on a cause at the moment as ISA was a complex issue.

Observers say some of the outbreaks are quite isolated while others may have spread from farm to farm. However, a small number of cases have been found in areas which had been set aside from breeding following earlier outbreaks. Meanwhile, the industry is being urged to increase its prevention measures.