July 15, 2010

US researchers identify European salmon killer virus

The virus causing a mysterious disease that raged through European salmon farms, wasting the hearts and muscles of infected fish, has been revealed by researchers at Columbia University.

"It's a new virus. And with this information now in hand, we can make vaccines," said Ian Lipkin, director of Columbia University's Centre for Infection and Immunity, a World Health Organisation-sponsored disease detective lab.

Two years ago, Norweigan fisheries scientists approached Lipkin and asked for help in identifying the cause of Heart and Skeletal Muscle Inflammation, or HSMI, the official name for a disease first identified in 1999 on a Norweigan salmon farm.

The disease is often fatal, and the original outbreak has been followed by 417 others in Norway and the UK. Every year there is more of the disease, and it is now been seen in wild fish, suggesting that farm escapees are infecting already-dwindling wild stocks.

Lipkin's team combed through genetic material sampled from infection salmon pens, looking for DNA sequences resembling what was seen in other viruses, and inferring from those what the HSMI-causing sequence should look like. The researchers eventually arrived at the 10-gene virus they called piscine reovirus, or PRV.

Related reoviruses have been found on poultry farms and cause muscle and heart disease in chickens. "Analogies between commercial poultry production and Atlantic salmon aquaculture may be informative," researchers said. "Both poultry production and aquaculture confine animals at high density in conditions that are conducive to transmission of infectious agents."

Such findings may be useful as the Obama administration develops a national policy for regulating aquaculture.