INFECTIOUS SALMON ANEMIA (ISA)

THE FACTS

Infectious Salmon Anemia (ISA) is a virus that is highly contagious in the marine environment, spread through the water between Atlantic salmon within a grow-out site, and carried by the water from one site to another
ISA is highly lethal to Atlantic salmon, but does not harm humans, according to all sources.
ISA was only discovered in wild Atlantic salmon in 1999, but has been known in farmed Atlantic salmon from a much earlier date
ISA was unknown to science prior to epidemics in the Norwegian salmon farming industry in 1984
Disease symptoms include the salmon becoming lethargic or moribund, lifting of scales, protuberance of the eyes, skin lesions, pale gills, and internal hemorrhages.

ISA is found on both sides of the Atlantic Ocean, and at times has caused massive losses for salmon farmers in Norway,Scotland, and the Faroes.
Norwegian salmon farms were the first to be affected, and, by 1990, 101 salmon farms were infected
In Scotland, an outbreak in 1998 spread so that, by the following year, 11 sites were infected, and a further 24 sites were suspected of being infected, a total of 10% of Scotland’s salmon farms. Since then there have been outbreaks from time to time.
In the Faroe Islands, the aquaculture was nearly wiped out by ISA outbreaks from 2001 to 2003, resulting in losses to the industry of DKK 250 Million

In 1996,ISA severely crippled the aquaculture industry in southwest New Brunswick, requiring the slaughter and industrial disposal of millions of farmed salmon that were dead, or needed to be slaughtered
By 1997, there were 21 farm sites testing positive for ISA, and more than 35 farm sites in 1998, and even in 2000 there were 17 sites infected
ISA caused the first eradication order for the Canadian sea cage industry.
$20 Million (CDN) was paid to growers to compensate for losses, but the uncompensated losses were as much as $40 Million (CDN)
In 2001,Maine’s Cobscook Bay was infected and more than 2.5 million fish were killed, to be followed by other outbreaks in 2002 and 2003 that killed at least another 150,000 salmon
In southwest New Brunswick in 2003, 2.7 million fish were wiped out as a result of the ISA epidemics sweeping through the waters
The last case in NB requiring “depopulation” was 2007 (528,000 fish destroyed).

Chile’s aquaculture industry was partly destroyed by widespread outbreaks of ISA in the past several years, resulting in the deaths of 10′s of millions of fish, and the loss of thousands of jobs in the industry.
Chile is now trying to rebuild on a healthier model, but outbreaks continue to occur.
In British Columbia, there were reports of ISA showing up in wild and aquaculture salmon, but the tests have proven inconclusive at this point.

ISA being highly contagious, it is necessary to slaughter immediately all the fish in any site suspected of having the disease
It requires two positives within a cage of salmon for the cage depopulation to be ordered.
Bay-wide management with single year classes has been implemented to attempt to control the outbreak of ISA. Overall it is successful, but there are still outbreaks, and those will result in widespread death of farmed salmon
ISA require the expenditure of many millions of dollars to control and deal with the disease. The costs begin with disinfection, and may include use of vaccine

ASF was the first to find ISA in wild Atlantic salmon in North America, when several individuals were tested on entering the Magaguadavic River fish ladder.
The impact on wild Atlantic salmon remains an uncertain area, but there is great concern for individual salmon swimming through areas where farmed salmon are infected.
On the Pacific Coast, there is continued concern that, if ISA is confirmed, it could have massive implications there for wild salmon populations

Aquaculture DIGEST