Scientists seek to study eDNA to identify how MSX creeps up on oysters

Winnipeg Free Press

05-06-2025

Scientists are pursuing a new line of research to predict the times and locations of parasitic outbreaks that are wiping out oysters off the Atlantic coast.
It's all part of the latest efforts to examine multinucleate sphere unknown, a parasite commonly referred to as MSX.
The new research would examine the genetic material, or environmental DNA, left behind by the parasite and any other intermediate hosts. Scientists believe this can help them understand more about how MSX behaves in the water and where it goes.
'It'll give us a whole lot more information about the parasite, what the parasite is doing, how long parasites last,' said Rod Beresford, an associate professor at Cape Breton University's biology department.
Beresford is among a group of scientists in Nova Scotia, New Brunswick and P.E.I. who have obtained $800,000 from various sources including Genome Atlantic, Genome Canada and provincial governments for two years, starting this summer, to study MSX using eDNA.
While their research is likely years away from practical applications, scientists say it could make it easier to protect oysters from deadly outbreaks that have left farmers in the lurch.
The single-celled MSX has been wreaking havoc on oysters for about 60 years. It was first found in Delaware Bay, near New Jersey, in 1957 and was detected in Bras d'Or Lake, Nova Scotia, in 2002. It has since been found in Prince Edward Island, New Brunswick and southern British Columbia.
The parasite targets cultured and wild oysters, and kills about 95 per cent of affected mollusks within two to three years of infection, and prevents them from reaching their full size. However, it poses no risk to human health or food safety.
In most cases, the fishing industry will often observe the parasite after oysters have started dying, Beresford said.
But scientists say the new research may identify how to get earlier warnings about potential outbreaks.
By learning more about the parasite's eDNA, scientists believe it could solve a mystery about its life cycle, said Ryan Carnegie, a shellfish pathologist at Virginia Institute of Marine Science.
'That's the primary application to addressing this mystery of the life cycle,' he said.
Environmental DNA can be detected in an environment sample such as sea water, Carnegie explained. But he said it cannot be detected in individual organisms such as shellfish.
The widespread use of eDNA began in the early aughts and an article in the journal, Bioscience in 2021, said this tool is becoming more widespread because it requires tiny amounts of genetic samples, is reliable and non-invasive.
Beresford said scientists could use eDNA to identify intermediate hosts of the MSX before it infects oysters. Intermediate hosts could be anything from tiny plankton, snails, worms, fish or other organisms on the sea floor.
Although he said it would likely be impossible to remove those intermediate hosts, he explained scientists might be able to collect information about them in order to predict when an outbreak might occur or assess whether any oysters are resistant to the parasite.
'We don't know if it takes a lot of MSX particles for an infection to take place, or if it only takes a little bit,' Beresford said.
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The research could be particularly welcomed by farmers in an industry that is worth millions of dollars. Overall, Statistics Canada data from 2023 shows the oyster aquaculture industry was valued at $17.8 million in Prince Edward Island, $3.7 million in Nova Scotia, $25.9 million in New Brunswick and $16 million in British Columbia.
While the parasite threatens to wipe out some of that value, the new research could be a lifeline for some farmers.
Bob MacLeod, president of the P.E.I. Shellfish Association, said he hopes the research is successful.
'If they ever figure out the intermediate host or a way to kind of get around the host … it would be a real plus for us. Because right now, this many years later from when it hit the States, they haven't figured it out.'
This report by The Canadian Press was first published June 5, 2025.