Sunday, 5 February 2012

HSMI - A New Viral Infection of Farmed Salmon

HSMI (Heart and Skeletal Muscle Inflrammation) is a 'new' virus affecting farmed Atlantic salmon, killing 20% during infection. It was first noted in Norway in 1999, and is in 417 farms.

HSMI gets started in farmed salmon because their density in pens stresses the animals allowing them to become more susceptible to HSMI.

Kristi Miller found HSMI in Clayoquot Sound and reported it during Cohen Commission testimony in Dec 2011.

See this article: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011487.

Here is the abstract: Fish are an increasingly important source of food and income; global annual consumption is projected to rise from 110 million tons in 2010 to more than 200 million tons in 2030. With depletion of wild stocks, suppliers are shifting from capture fishing to aquaculture. However, the emergence of infectious diseases in aquaculture threatens production and may also impact wild fish populations. Heart and skeletal muscle inflammation (HSMI), first detected in farmed Atlantic salmon (Salmo salar L.) in a single farm in Norway in 1999[1], has now been reported in 417 farms in Norway, as well as in the United Kingdom[2]. HSMI appears 5 to 9 months after fish are transferred from fresh water to ocean pens[1], is characterized by epi-, endo- and myocarditis, myocardial necrosis, myositis and necrosis of red skeletal muscle, and up to 20% mortality[3]. Disease can be induced in naïve fish by experimental injection with tissue homogenate from HSMI diseased fish or by cohabitation with fish with HSMI[1]. Virus-like particles have been observed[4]; however, efforts to implicate an infectious agent by using culture, subtractive cloning and consensus polymerase chain reaction for detection of other viruses found in salmon aquaculture including infectious pancreatic necrosis virus, salmonid alphavirus, infectious salmon anemia virus have been unsuccessful.

The article concludes: Unlike terrestrial animal farming, where contact between domestic and free ranging wild animals of the same or closely related species is easily monitored and controlled, ocean based aquaculture is an open system wherein farmed fish may incubate and transmit infectious agents to already diminishing stocks of wild fish. Formal implication of PRV in HSMI will require isolation in cell culture and fulfillment of Koch's postulates, or prevention or modification of disease through use of specific drugs or vaccines. Nonetheless, as our data indicate that a causal relationship is plausible, it is urgent that measures be taken to control PRV not only because it threatens domestic salmon production but also due to the potential for transmission to wild salmon populations.

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