The hoof and mouth disease of the salmon farming industry
Stephen Hume
Special to the Sun
Monday, April 07, 2008
It's been a bruising fortnight for fish farmers. First, a blockbuster story March 27 in the New York Times outlined the difficulties plaguing Chile's salmon farms.
Then provincial Agriculture and Fisheries Minister Pat Bell announced a moratorium on expansion of fish farms to the north coast "until we figure out how to move forward with a long-term vision for aquaculture."
Next, Scotland's Sunday Herald newspaper reported that the Scottish government's Fisheries Research Services found "strong evidence that sea lice from caged salmon contaminate wild fish -- and the problem seems to be getting worse."
And this week, word that research in Clayoquot Sound suggests an increased sea lice presence in proximity to salmon farms in a region that was previously considered a "zero lice" zone.
Michael Price, fish biologist for the Raincoast Conservation Foundation, insisted work was preliminary and samples small but confirmed that sea lice loads in plankton trawls near three fish farm sites were an average of 28 times those found at control sites.
This follows other research indicating elevated burdens of sea lice on immature wild salmon in the Broughton archipelago and in the Discovery Islands off Campbell River where fish farms are concentrated.
The big story, though, is the aftershock from mainstream American media paying attention to Chile, where a lethal, highly communicable and so far incurable virus has been raging through farmed salmon stocks since last July.
According to the Times story, infectious salmon anemia has killed millions of fish, resulted in more than a thousand layoffs by one major employer -- about one in four workers -- as infected sites closed, and is sending tremors through retail markets in Japan, Europe and the United States.
There's no evidence that ISA is transmissible from fish to mammals or that it affects humans in any way, but reassuring customers still twitchy in the aftermath of concerns about mad cow disease is likely to pose a significant marketing challenge.
Identified as an "emerging viral pathogen" by the United States department of agriculture's animal and plant health inspection service, ISA belongs to the orthomyxovirus family of viruses.
Like the "flu" virus, what's most alarming about ISA is what the U.S. government's veterinarian service says is its ability to mutate rapidly by recombining genetic elements within its hosts.
For example, researchers have found significant molecular differences between strains of the virus in Norway, Scotland and New Brunswick. These outbreaks in the 1990s caused more than $50 million in estimated damage.
So consider ISA the hoof and mouth disease of the global salmon farming industry.
According to an information leaflet from the U.S. government's National Fish Health Research Laboratory, infected blood, feces, urine and mucus, animal wastes, contaminated slaughter facilities, transport vessels and workers all easily transmit it from fish to fish and from site to site.
As with hoof and mouth, the standard treatment is to kill all infected or exposed stocks within designated containment zones, disinfect all equipment and facilities and then keep fingers crossed.
What does an outbreak of ISA in Chile have to do with salmon farmers on Canada's West Coast? Think bird flu in Indonesia.
Despite vigorous hygiene control, its virulence, transmissibility, rapid mutation and genetic recombination make it a continuing threat -- in the case of ISA not to people but to farmed and possibly also wild fish stocks.
Since ISA first emerged in Norway in 1984, it has marched halfway around the planet. Known outbreaks have occurred in New Brunswick, 1996, Nova Scotia and Scotland, 1998, Chile, 1999, Faroe Islands, 2000, U.S., 2001 and Chile again, 2007.
Thus far the disease has been limited to Atlantic salmon, but there are gloomy hints that it might be extending its reach. The U.S. government notes "other wild fish are also susceptible to infection" including both sea run and freshwater brown and rainbow trout, and herring, all of which are important B.C. species. It also says ISA has affected coho and Chinook salmon in some isolated cases.
Furthermore, it says sea lice, already the source of debate in B.C., may also play a role as vectors that can enhance contagion during epidemics. That promises to stoke the discussion. And so it should.
shume@islandnet.com
Author
Topic: The hoof and mouth disease of the salmon farming industry (Read 1821 times)