Karmactive Team
UBC scientists have found a new virus that could explain why thousands of farmed Pacific oysters have been dying in British Columbia. This discovery might help protect B.C.’s $16 million oyster industry.
Researchers detected the virus known as Pacific Oyster Nidovirus 1 (PONV1) in a significant number of deceased and dying cultivated oysters collected during a mass mortality event in 2020. Healthy wild oysters from nearby areas showed no signs of the virus, suggesting a connection to the deaths.
“We’ve recently seen annual mass die-offs in B.C. and elsewhere of Pacific oysters, the most widely farmed shellfish worldwide,” said Dr. Kevin Zhong, who led the study. “Often, we don’t know the cause.”
What makes this virus special is its size. Its genetic material is enormous for an RNA virus – about 64kb pairs long. That’s so unusual that scientists have proposed creating an entirely new virus family called Megarnaviridae, meaning “large RNA viruses,” to classify it.
“The extraordinarily large genome of this virus makes it particularly fascinating as it pushes the known boundaries of how big RNA virus genomes can get,” explained Dr. Zhong. This large genome might give the virus extra tools to infect oysters and cause disease.
While this virus belongs to the same broad group as the COVID-19 virus, researchers stress that it cannot infect humans. It appears to only affect oysters.
The scientists’ database analysis revealed related viral sequences in oysters from multiple countries across Europe and Asia, indicating these viruses exist globally, although previous discoveries weren’t linked to oyster mortality.
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Dr. Curtis Suttle, senior researcher on the study, cautions that while they’ve found a strong connection, they can’t yet prove the virus directly causes the die-offs. “This discovery highlights how little we know about viruses infecting invertebrates in general and oysters in particular,” he said. “Similar to humans, disease and death is not caused by a single factor.”
The discovery has important implications for oyster farming. Oyster growers commonly bring in juvenile shellfish (spat) from various locations, a practice that could potentially spread pathogens if not properly managed.
“The discovery of the virus is a reminder that growers should use an abundance of caution when moving oyster spat internationally and nationally,” said Dr. Suttle. “New pathogens may be introduced when spat are imported.”
The researchers now want to develop quick tests to check oyster seed before it’s moved to new locations. They also plan more monitoring to better understand the virus’s role in oyster deaths.
“This research is not a cause for alarm,” Dr. Suttle emphasized. “Rather, this is a meaningful step forward in advancing our understanding of oyster health and supporting the long-term sustainability of shellfish aquaculture.”
The team is now working to determine whether PONV1 directly causes oyster deaths and what environmental factors might make oysters more vulnerable to infection.
