Still no source for ISA outbreak

The ISA-virus was discovered on one salmon farm in Shetland at the beginning of January. Two other farms are still under suspicion, although no more outbreaks have been confirmed, Rob Reynard, programme director for aquaculture and aquatic animal health at Fisheries Research Services in Aberdeen told FishfarmingXpert.

In 1998, when ISA last struck on two farms in Scotland - costing the industry £100 million and 200 jobs, the source was never discovered.

“No conclusion of the source was made”, Reynard says.

The ISA virus moves within infected fish or materials, and at the time there were speculations relating to both wild fish and an infected area in another country as the source, he adds.

With the current outbreak in Shetland, there has been guesswork as to whether there could be a connection between the recent salmon lice parasite of Shetland’s west coast, and the ISA-virus found on the site. Reynard says it is hard to work out the direct effect of lice:

“It could be pure coincidental.

"I think it is. There are probably more significant factors,” he says and adds.

“We are three weeks into this investigation and have got a lot more info to collect.

"But we may never know the cause of the outbreak”.

There are 40 registered fish farming sites in the south west Shetland management area, although not all of these sites are currently holding fish. The table below details the current situation.

Reynard agrees the situation could have extremely serious implications for Shetland’s salmon farming industry.

He adds that fish farmers should review their bio-security on their farms to minimize the risk of the emergence of the disease. Although, there is little reason to believe the virus will spread to mainland Scotland: “Evidence indicates that the risk is low,” Reynard said.