‘Minimize the damage’: Race to study MSX heats up as deadly disease hits Maritime oysters

Scientists at Research and Productivity Council lab in Fredericton examine an oyster. (CTV News)

Researchers in Atlantic Canada are racing to try to solve a pressing problem — how to tackle a parasite that’s killing oysters and threatening the region’s multimillion-dollar industry.

“What we’re trying to do is minimize the damage as much as possible,” said Martin Mallet, an evolutionary biologist and co-owner of Mallet Oysters in Shippagan, N.B., where he manages his family’s oyster hatchery.

The disease multinucleate sphere unknown, known as MSX, is caused by a parasite that is harmless to people but is deadly to oysters and has already had a devastating impact to oysters in some areas of P.E.I. after first being detected in Bedeque Bay in July 2024.

MSX has now been confirmed across P.E.I. and multiple locations in New Brunswick.

As uncertainty grips the industry, researchers are trying to tackle the problem from multiple angles.

Environment detection

MSX was discovered in 1957 in the U.S. but there is a still a lot that remains unknown about the disease and the parasite that causes it, including how it’s transmitted.

Mallet‘s team is part of several projects involving governments, industry and academia aiming to solve key questions — can MSX be detected within the environment? What is its genetic sequence? How quickly can researchers create disease-resistant oysters?

One project, funded by Genome Atlantic, will try to detect MSX and Dermo — another deadly oyster disease caused by a parasite — in the environment.

“So in some cases we might be able to detect before we see oyster infections. That’s a really important piece of information,” said Mallet.

While major gaps in knowledge surround MSX, it’s suspected to be transmitted through an intermediate host.

“Much like malaria infects humans via mosquitoes, we think that oysters are infected via some unknown critter,” said Mallet.

Missing genetic data

Multiple teams are trying to solve a key piece of the MSX puzzle — figuring out its genetic sequence.

Mallet‘s team is collaborating with Université Laval on a project to sequence the genome for Haplosporidium Nelsoni, the parasite that causes MSX. The project received more than $110,000 from the Department of Fisheries and Oceans (DFO). Mallet thinks cracking this scientific problem would open up a host of questions, such as where it comes from and how it got here.

“That requires an understanding of the genetic diversity that exists within the parasite population,” he said. “And with the available small fragments of DNA that we have, we can’t do that kind of work.”

New Brunswick’s Research and Productivity Council (RPC) lab also received more than $250,000 from DFO.

Attiq Rehman, Director of Bioscience at the Fredericton RPC lab, is working to map out the DNA of MSX by doing single-cell whole genome sequence analysis.

“This will definitely increase our understanding of the infection dynamics,” said Rehman. “The scientific community would be thrilled to have that information for infection models and for developing resistant seeds as well as understanding the intermediate host which is currently unknown.”

Scientists at RPC have been monitoring for MSX through a provincial program in New Brunswick since 2002, when it was first detected in the Bras d’Or Lakes in Nova Scotia. Since the disease was found in P.E.I. last summer, the lab has received thousands of oysters from across Atlantic Canada to shuck and test.

Initially, the team relied on a conventional PCR test, which took more time and was more costly.

To keep up with demand, they developed a faster and more sensitive process by using a rapid multiplex PCR test that can detect for three diseases — MSX, Dermo and seaside organism — at once.

“We’ll get three hits in one test in a lot quicker turnaround time and sensitivity in results,” said Rebecca Liston, Supervisor of Fish Health Diagnostic Services at RPC.

To Liston, her team‘s role is to provide industry support.

“It’s a concern for all producers and they work hard to provide these beauty gems from our waters,” she said. “We’re here to help them in their time of crisis.”

Aiming for disease resistance

Mallet, who’s been breeding oysters for about a decade, called a disease-resistant strain the “holy grail”.

“We’re throwing sort of all the tools in the toolbox, at this,” he said.

One traditional method involves moving oysters into areas that have been affected by MSX and seeing what oysters get infected what oysters survive, and who their relatives are.

Mallet notes his team is looking to augment that process with genomic tools.

Disease-resistant breeding has helped the industry adapt in the U.S. east coast. Mallet explained the industry in the U.S. relied on oysters that survived MSX outbreaks to breed but it took a few generations to develop an appreciable level of resistance.

Most experts, he said, are comfortable saying it takes two generations to develop 50 per cent resistance.

“That’s kind of like our baseline target. And what we’re trying to do is improve on that, with genomic tools,” Mallet says, “We’re hopeful some amount of resistance within a year or two, an appreciable amount of resistance within probably four years. And that’s being kind of like hopeful but reasonable.”