Endangered wild salmon infected by newly discovered viruses

[GLG]

I would advise caution not to add 1+1 and make 5 out of this. With that said there will be plenty to watch as scientist mull this over and discuss what implications these new results means to our beloved salmon.

https://elifesciences.org/articles/47615

Abstract
The collapse of iconic, keystone populations of sockeye (Oncorhynchus nerka) and Chinook (Oncorhynchus tshawytscha) salmon in the Northeast Pacific is of great concern. It is thought that infectious disease may contribute to declines, but little is known about viruses endemic to Pacific salmon. Metatranscriptomic sequencing and surveillance of dead and moribund cultured Chinook salmon revealed a novel arenavirus, reovirus and nidovirus. Sequencing revealed two different arenavirus variants which each infect wild Chinook and sockeye salmon. In situ hybridisation localised arenavirus mostly to blood cells. Population surveys of >6000 wild juvenile Chinook and sockeye salmon showed divergent distributions of viruses, implying different epidemiological processes. The discovery in dead and dying farmed salmon of previously unrecognised viruses that are also widely distributed in wild salmon, emphasizes the potential role that viral disease may play in the population dynamics of wild fish stocks, and the threat that these viruses may pose to aquaculture.

Epidemiological maps of Salmon pescarenavirus 1 and 2 (SPAV-1 and SPAV-2), Chinook aquareovirus (CAV) and Pacific salmon nidovirus (PsNV) around the coast of Vancouver Island.
Individual samples are shown at the location collected, negative samples are black, and positive samples are coloured and sized according to the virus copy number.

Viral disease is a potential threat to wild fish stocks; yet little is known about viruses circulating in wild, farmed, or hatchery salmon. Here, through metatranscriptomic surveys, we reveal several previously unknown viruses that were discovered in dead and dying aquaculture fish, and show them to also occur in wild and hatchery-reared fish. Depending on the viral and host species, the viruses range from being localised to widespread, from infecting <1% to >20% of fish, and being from within the limits of detection to very high loads. Our results are consistent with some of these viruses being causative agents of disease, making it critical to understand their possible roles in salmon mortality and the decline of wild salmon populations, and their potential interactions with net-pen fish farming and hatchery rearing. Viral discovery in moribund individuals followed by extensive surveillance and histopathological localisation are powerful tools towards the ultimate goals of identifying causative agents of disease and understanding the impact of infectious agents in wild populations. These insights are crucial as juvenile salmon that are in less than optimal health are expected to have lower rates of survival in the wild. Continued surveillance and knowledge of endemic and emerging virus infections in these iconic salmon species is beneficial for their conservation.

 

[cuttlefish]

Just one observation; Clayoquot Sound sure lights up for CAV in Figure 2...

 

[GLG]

New viruses discovered in endangered wild Pacific salmon populations
September 4, 2019

Three new viruses—including one from a group of viruses never before shown to infect fish—have been discovered in endangered Chinook and sockeye salmon populations.

While the impact of the viruses on salmon health isn’t yet known, all three are related to viruses that cause serious disease in other species.

“We were surprised to find viruses which had never before been shown to infect fish,” said Gideon Mordecai, researcher at UBC’s department of earth, ocean and atmospheric sciences. “Although there’s no risk to humans, one of the viruses is evolutionarily related to respiratory coronaviruses, and is localized to the gills. That suggests it has a similar infection strategy to its distant relatives that infect mammals.”

UBC and Fisheries and Oceans Canada researchers used DNA sequencing followed by tests specific to each virus to screen more than 6,000 salmon from along the B.C. coast, including wild, hatchery and aquaculture fish.

“We found the new viruses widely distributed in dead and dying farmed salmon and in wild salmon,” said UBC virologist Curtis Suttle. “It emphasizes the potential role that viral disease may play in the population dynamics of wild fish stocks, and the threat that these viruses may pose to aquaculture.”

One new virus, detected more commonly in salmon hatcheries, infected more than 15 percent of all hatchery Chinook tested.

Another new virus was detected in 20 percent of Chinook from fish farms —but was only found in adult or sub-adult salmon. In general, the new viruses were more commonly found in cultured fish populations than in wild.

“It’s essential that we determine whether these viruses are important factors in the decline of Chinook and sockeye salmon stocks,” said Suttle. “The research highlights the need for robust surveillance to improve our understanding of how viruses might impact the health of wild Pacific salmon populations.”

Over the past 30 years, steady declines in Chinook and sockeye salmon populations have been of great concern to Indigenous peoples, commercial and recreational fishers, and the general public. While much of the focus has been on the impact of piscine orthoreovirus (PRV), the new findings highlight how little is known about other viruses endemic to salmon populations.

“Being able to screen so many fish for these viruses was an exciting breakthrough, and meant we were able to identify hotspots of infection,” adds Mordecai.

“One of the viruses was relatively common in juvenile migratory salmon as they enter the ocean—a period thought to be critical to their survival into adulthood.”

The work was funded as part of the Strategic Salmon Health Initiative, a partnership of Genome BC, Fisheries and Oceans Canada, and the Pacific Salmon Foundation.

https://science.ubc.ca/news/new-viruses-discovered-endangered-wild-pacific-salmon-populations