Fish infected with piscine reovirus (PRV) . (Photo: alexandramorton/FIS)

Experts disagree on significance of reovirus in BC fish

CANADA
Friday, July 20, 2012, 23:30 (GMT + 9)

The piscine reovirus (PRV) has been identified in freshwater fish in British Columbia (BC). Simon Fraser University Professor Rick Routledge said he found the reovirus in 13 of 15 cutthroat trout taken from Cultus Lake east of Vancouver -- and he wants the province to pay attention.

The virus is pervasive in Norwegian salmon farms and can kill 20 per cent of infected fish, he explained, yet it was easy to find fish infected with it once he started testing with a biologist from the Watershed Watch Salmon Society.

Followup analyses identified their genetic sequencing as 99-per-cent identical to Norwegian strains, Vancouver Sun reports.

"We found it because we looked. It's as simple as that. I think it's really serious and sometimes I feel desperate that the province isn't taking this more seriously, and the federal government. They should be," Routledge stated.

He argued that a real concern exists about cross-contamination to many other freshwater fish species, which he has not tested yet, CBC News  reports.

"This was our very first set of tests on freshwater fish, and well, I am concerned that this could be happening anywhere in the north Pacific watershed," he said.

Gary Marty, BC Ministry of Agriculture fish pathologist, has dealt with such worries before. In 2010, he found 75 per cent of tested farmed salmon were positive for piscine reovirus — but assured that there is no reason to believe that it is causing disease to farm-raised fish because it can also be found in healthy fish.

"Turns out, this is fairly common,” Marty said last April. “The ‘O’ in reovirus, stands for ‘orphan.’ They're called orphans because they're viruses without a disease."

"If we have fish that aren't sick and have this virus that we don't know very much about, that tells me that virus is probably not a serious concern," he explained. "If it was, those fish wouldn't have survived to be sampled."

That same April, biologist and activist Alexandra Morton informed that her testing detected the virus in farmed salmon sold in supermarkets across BC. However, the government and the industry both dismissed the test results as unreliable.

The reovirus has been linked to the fish disease heart and skeletal muscle inflammation (HSMI), and Morton referred to this to posit that a weak heart could be the reason why some wild salmon never make it up stream.

In contrast, the aquaculture sector refutes that the evidence linking the virus with HSMI is feeble and have also dismissed claims that the virus poses a danger to farmed or wild fish stocks in the province.

The virus is not harmful to humans, according to experts.

Related article:

- Disease in fish claimed wrong by salmon farmers

By Natalia Real
editorial@fis.com
www.fis.com

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