The infectious salmon anemia (ISA) outbreak that has stymied Chile's farmed salmon industry for the past two years likely originated in Norway 13 years ago, according to a study published in the current issue of Virology Journal.
Researchers analyzed tissue samples collected from numerous ISA-afflicted fish in Chile and discovered that they related most closely to samples gathered from fish subject to the 1996 ISA outbreak in Norway. Researchers also looked at samples gathered from fish hit by ISA outbreaks in Scotland, Faeroe Islands, Canada and the United States.
"These findings suggest that the ISA outbreak was caused by a virus that was already present in Chile that mutated to new strains,” the researchers said. "This is the first comprehensive report tracing ISA from Europe to South America.”
The study was led by Fred Kibenge, professor of virology at the University of Prince Edward Island in Canada.
"The ongoing ISA outbreak in Chile was introduced from Norway several years before the first reported outbreak in June 2007 and probably circulated undetected for more than 10 years,” said Kibenge in an e-mail to the International Society for Infectious Diseases.
ISA has forced farmed salmon companies to curb production significantly this year. Marine Harvest, the world's largest farmed salmon producer, harvested 9,000 metric tons of fish in Chile in the second quarter of 2009, half of what it culled during the same three-month period in 2008.
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July 20, 2009
