New viruses found in endangered populations of wild Pacific salmon

Three new viruses – one belonging to a group of viruses never previously infected by fish – have been found in endangered populations of chinook salmon and sockeye salmon.

Although the impact of viruses on salmon health is not yet known, they are all linked to viruses that cause serious diseases in other species.

"We were surprised to find viruses that had never been infected by fish," said Gideon Mordecai, a researcher at the Department of Earth, Ocean and Atmospheric Sciences. of UBC. "Although there is no risk to humans, one of the viruses is evolutionarily linked to respiratory coronaviruses and is localized to the gills." has an infection strategy similar to that of his distant relatives who infect mammals. "

Researchers from the University of British Columbia and Fisheries and Oceans Canada have used DNA sequencing followed by virus-specific tests to detect more than 6,000 salmon along British Columbia . coasts, including wild, farmed and aquaculture fish.

"We found that the new viruses were widespread in dead and dying farm salmon and in wild salmon," said Virginia virologist Curtis Suttle of the University of British Columbia. "It highlights the potential role that viral diseases could play in the population dynamics of wild fish stocks and the threat that these viruses could pose to aquaculture."

A new virus, more commonly found in salmon hatcheries, infected more than 15% of all hatchery-tested chinooks.

Another new virus was detected in 20% of Chinooks from fish farms, but was only detected in adult or sub-adult salmon. In general, new viruses have been found more frequently in farmed fish populations than in wild populations.

"It is essential to determine whether these viruses are important factors in the decline of chinook and sockeye salmon stocks," said Suttle. "The research highlights the need for strong surveillance to improve our understanding of the impact of viruses on the health of wild populations of Pacific salmon."

Over the past 30 years, the steady decline in chinook and sockeye salmon populations has been a source of great concern to Aboriginal peoples, commercial and recreational fishers, and the general public. Although the focus has been on the impact of the orthoreovirus pool (GRP), the new findings show how little is known about the other endemic viruses in salmon populations.

"Being able to track as many fish to detect the presence of these viruses was an exciting step forward, which meant we were able to identify hot spots of infection," adds Mordecai.

"One of the viruses was relatively common in juvenile migrating salmon when they entered the ocean – a period considered essential for their survival in adulthood."

The work was funded under the Strategic Salmon Health Initiative, a partnership between Genome British Columbia, Fisheries and Oceans Canada and the Pacific Salmon Foundation.

The results were published today in the journal eLife.