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Salmon Industry Hits Back at Claims of New Virus

19 April 2012, at 1:00am

CANADA - The British Columbia (BC) Salmon Farmers Association has hit back at claims made by biologist Alexandra Morton that Heart and Skeletal Muscle Inflammation (HSMI) has been found in Atlantic Salmon purchased in the Vancouver area.

In her blog, Ms Morton claims that Piscine Reovirus (PRV) (which she links to HSMI) has been identified in 44 out of 45 farmed salmon, bought in Vancouver supermarkets.

Ms Morton has suggested that her findings show that the salmon has come from BC farms. If the salmon did not come from the farms, Ms Morton has stated that there is therefore a flaw in the BC Food Security Protocol.

Ms Morton's concern was also on how the disease could effect wild salmon populations in the Fraser river. Talking about infected fish, Ms Morton stated in her blog that; "People preparing to cook these may wash them, sending the virus into the water system."

However, the accuracy of Ms Morton's investigation has been questioned.

At present little is still known about the diseases and experts told TheFishSite that no conclusive link has been found between PRV and HSMI. The presence of PRV therefore does not mean a fish is infected with HSMI.

However, some industry experts believe there is correlation between HSMI and high PRV virus titer in farmed fish.

According to the Norwegian Veterinary Institute, PRV is thought to have a major role in the pathogenicity of HSMI. But, virus investigations in Norway (which has been suffering with the disease since 1999) have shown that PRV is 'endemic' and can be found in healthy farmed fish.

In terms of testing for HSMI, experts say the most accurate method would be to test heart tissue by Polymerase Chain Reaction (PCR) methods. As Ms Morton tested fish from a supermarket it will have most likely have been gutted.

The BC Salmon Farmers Association released a statement saying that HSMI has never been found in BC farmed salmon and that no clinical symptoms have been observed.

According to the Norwegian Veterinary Institute, HSMI is a contagious disease in Atlantic salmon. It has been associated with the newly described disease, Piscine reovirus (PRV).

HSMI mainly affects the heart, where changes can be detected some months before an HSMI outbreak. During a clinical outbreak changes can also be seen in skeletal muscles and the liver.

Prevention is centered around good biosecurity measures and management of fish stocks.

Research is currently underway to develop a vaccine against PRV.

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