S3 Ep 47: When Oysters Get Sick: A Story of Disease, Science, and Resilience

When people hear the word disease, it's easy to jump to the wrong conclusion. But MSX (Haplosporidium nelsoni) and Dermo (Perkinsus marinus) aren't diseases that affect people—they're diseases that affect oysters and the communities that depend on them. 

In this episode of OYSTER-ology, host Kevin Cox sits down with three scientists from the Virginia Institute of Marine Science (VIMS) to explore what these oyster diseases are, how they affect both wild and farmed oysters, and why they're shaping oyster farming from the Chesapeake Bay to the current MSX outbreak in Prince Edward Island, Canada. Along the way, the conversation expands beyond biology to examine how growers, researchers, public agencies and coastal communities respond to uncertainty, adapt to changing conditions, and build resilience for the future. From oyster farmers and researchers to seafood professionals, policymakers, and oyster lovers alike, this conversation reminds us that behind every oyster is a remarkable story of science, adaptation, and resilience.

Guests

Dr. Bill Walton is the Acuff Professor of Marine Science at VIMS and works closely with shellfish growers to apply science to the practical challenges of oyster aquaculture.

Dr. Ryan Carnegie is a Professor at VIMS and one of North America's leading experts on oyster diseases, with research focused on shellfish pathogens, including MSX and Dermo.

Dr. Adriane Michaelis is an Assistant Professor at VIMS whose research explores the relationship between oysters, people, and place, with a particular focus on the resilience of coastal communities.

00:00 Crisis Stakes

00:27 Show Intro And Guests

03:29 What Is MSX

05:51 What Is Dermo

06:28 Water Quality Myths

07:46 Outbreak Signs On Farms

08:58 How Transmission Works

10:34 Diagnosis And Testing

12:14 What Farmers Can Do

14:27 Community Impacts And Pivots

17:03 Chesapeake MSX Resurgence

20:44 Public Perception And Marketing

23:11 Long Term Business Pressure

26:01 History Lessons And Tools

27:55 PEI Outbreak And Response

31:43 Resilience Beyond Disease

36:59 Big Picture Funding And Alliances

40:19 Industry Wide Risk Outlook

43:04 Final Advice And Key Takeaway

46:23 Closing And Thanks

Links:

•   Bill Walton | Virginia Institute of Marine Science - Acuff Professor and Shellfish Aquaculture Program Coordinator at VIMS.
• Adriane Michaelis | Virginia Institute of Marine Science - Assistant Professor and Social scientist whose work explores the relationship between oysters, people, and place.
• Ryan B. Carnegie | Virginia Institute of Marine Science - Professor and Chair, Ecosystem Health at VIMS and internationally recognized expert in shellfish pathology.
• Virginia Institute of Marine Science (VIMS)
• Batten School of Coastal & Marine Sciences 
• Canadian Atlantic Shellfish Health Network - For more information about MSX in Prince Edward Island, Canada.

Credits:

Guest: Dr. Adriane Michaelis, PhD; Dr. Bill Walton, PhD; Dr. Ryan Carnegie, PhD

Host: Kevin Cox

Digital Deckhand: Chet Jipty

Special Thanks To: Virginia Institute of Marine Science (VIMS)  and Willian & Mary - Batten School of Marine Sciences

Production: OYSTER-ology Podcast

Please be sure to Like and Follow OYSTER-ology wherever you listen to podcasts, and tell others about it. Every positive mention of it helps more people find the podcast!

Transcript

Transcript: When Oysters Get Sick: A Story of Disease, Science, and Resilience (prepared by Chet Jipty)

[bubbles] 

Bill Walton: The problem is so massive, and affects so many people.

Ryan Carnegie: They can be, killed in, in very large numbers.

Adriane Michaelis: It's hard for the community to look ahead. And in some cases it was, devastating for the commercial fishermen.

Bill Walton: If you're one of those growers that's being affected by this, it's an existential threat.

Bill Walton: This is going to happen at some point. You need to be prepared for it.

 [bubbles] 

Kevin: Welcome to OYSTER-ology, a podcast about oysters, aquaculture, and everything from spat to shuck. I'm your host and the Foodwalker, Kevin Cox. When people hear the word disease, it's easy to jump to the wrong conclusion. But today's episode isn't about a disease that affects people. It's about diseases that affect oysters and what happens when those diseases threaten the communities, businesses, and families that depend on them.

For decades, two oyster diseases, MSX and Dermo, have challenged oyster growers across the East Coast of North America. Most consumers have never heard of them, yet they've shaped the history of oyster farming in places like the Gulf of Mexico, Chesapeake Bay, and now more recently, Prince Edward Island, Canada.

 To better understand what's happening and what it means for the future, I sat down with three scientists from the Virginia Institute of Marine Science at their VIMS facility at the William & Mary Batten School of Coastal and Marine Sciences. 

Dr. Ryan Carnegie is one of North America's leading experts on oyster diseases; Dr. Bill Walton works directly with shellfish growers, helping them apply science to the everyday challenges of aquaculture; and Dr. Adriene Michaelis studies the relationship between oysters, people, and place, exploring how coastal communities respond to change

What began as a conversation about oyster diseases quickly became something much larger. We talked about science, uncertainty, adaptation, and resilience, about how growers respond when a disease appears, how communities weather those moments, and why every outbreak leaves behind lessons that makes the next generation better prepared for the next one.

This is a conversation about oysters, but it's also a conversation about the people who depend on them and what it takes for an industry and its communities to endure. So pop on your thinking cap and slip into your lab coats to hear about diseases, parasites, hosts, and infectives, outbreaks that have killed countless oysters, growers in their communities and how they fight back, and the fact that none of this will cause any harm or illness to people. With my esteemed panel of some of the smartest, most well-informed oyster experts on the planet, Doctors Bill Walton, Adrienne Michaelis, and Ryan Carnegie.

[bubbles] 

Kevin Cox: Today, we're taking a deep dive into MSX and into Dermo with, probably the three people who are better positioned to talk about it than anybody, and we're gonna talk about, the oyster disease, the impact that it's having on aquaculture overall, and the impact that it's having on the human dimensions of oyster-growing communities.

So, we have Ryan Carnegie Bill Walton and Adriane Michaelis. And, welcome so much to OYSTER-ology. I really appreciate letting me come down in the gorgeous, VIMS Batten School facility in this awesome lab, to do this recording live. So thanks so much for being here.

Bill Walton: Thanks for coming.

Adriane Michaelis: Thank you.

Kevin Cox: Okay, so, Ryan, I wanna go to you first you've spent a great deal of time studying MSX and Dermo and other oyster-related... is diseases the right word to call them?

Ryan Carnegie: Right. Right

Kevin Cox: What is MSX?

Ryan Carnegie: MSX is a, a protozoan parasite, so it's a single-celled marine organism that will attack and infect oysters in wild and aquaculture contexts. Um, MSX has been a, a cause of very significant disease and mortality since it first emerged in 1957, and it continues to be regarded as one of the major oyster pathogens of the US and Canadian East Coast. And because the oysters have not, co-evolved with this protist, for their, evolutionary history, they are naive to this parasite. They can be, killed in very large numbers.

Kevin Cox: Is it limited geographically to the US and Canadian East Coast?

Ryan Carnegie: That's where its impacts are greatest, in Crassostrea virginica, in our eastern oyster populations. We believe that MSX is an import from Asia that came over some time prior to 1957, when it first emerged in Delaware Bay. Maybe it arrived, with early commercial or scientific imports of Pacific oysters. Maybe it came over with ballast water of ships returning from the Pacific Theater after World War II or the Korean conflict. Mm,

Ryan Carnegie: We'll never have an answer to that, but, it is known to occur naturally in Pacific oyster populations wherever they occur,

Bill Walton: And Kevin, I would just jump in to emphasize that these are diseases of oysters, and these are not parasites that affect people. So from a consumer's point of view, this is something that affects the supply of oysters into the market. It's not affecting the safety of the oysters that anyone is eating.

Kevin Cox: Yeah, I'm really glad you, you brought that point up. I think it's very, very important to emphasize that, that this is an oyster disease-not a people disease.

Bill Walton: "Think of this like spots on apples." Like, this is something that's not really affecting your experience as a consumer.

Kevin Cox: I would imagine that by the time an oyster gets to a consumer, it's already been culled through, it's already been identified, and they're certainly not gonna sell it and serve it, right?

Ryan Carnegie: Exactly.

Kevin Cox: All right, so that's in essence what MSX is. Mm-hmm. What is dermo? Because I often hear people talking about MSX and dermo almost together.

Ryan Carnegie: Well, they're, they're often talked about together because they co-occur along, so much of the oyster's distribution in Eastern North America. Dermo is another protozoan parasite. it, is directly transmissible from oyster to oyster in a reef or in a bag or in a cage, which is a contrast with MSX. MSX is infecting oysters from some intermediate hosts that have never been identified, so the two diseases work a bit differently, but they occur in really all the same places. 

Kevin Cox: Is water quality, an issue a-associated with this as far as you know?

Ryan Carnegie: Well, that's a good question. Um, I think we would struggle to come up with any direct, evidence of, aspects of water quality that are especially meaningful with regard to MSX and, and Dermo dynamics.

But then I think on the other hand, you know, water quality is profoundly important with regard to sort of general health and general performance, and, and so I think that, even if we don't see direct effects on th- these two diseases. You know, water quality is a very big issue for shellfish aquaculture production. We just don't really understand all of what water quality means -

Bill Walton: And, and Ryan, I think the general public, when you say water quality, they're thinking about pollution. Yes. Yeah, right. And particularly human sewage. And I, I just wanna be clear that, like, one of the things we've struggled with, um, these diseases aren't associated with human sewage. Um-

Kevin Cox: Right. No. Yeah.

Bill Walton: because we've handled problems of human pollution- with shellfish, uh, harvesting by having very clear zones with consistent testing of where you can harvest from and where you can't- Yeah ... and under what conditions. Yeah. So is continues to be a problem because it's not associated with human sewage. Mm-hmm ... dermo or MSX are in the water. They're a part of the marine environment.

Ryan Carnegie: So it's, it's clear that I don't work with the marketing department…

Kevin Cox: Understanding the disease is only the beginning. The next questions are much more practical, including what does an outbreak actually look like on a working oyster farm, and how can an oyster farmer tell if their farm is being affected? These are the very real, very simple questions that keep growers up at night

 How does a grower identify whether their oysters are suffering from either MSX or dermo? How do you tell?

Ryan Carnegie: Um, oysters that are infected with dermo or MSX, may be smaller than other oysters in the bag, from the same cohort, for example. Um, so there could be a reduction in growth. Um, but certainly mortality. dermo-caused mortality typically is occurring in the late summer and fall, and growers, throughout the Atlantic and Gulf Coasts of the US know to expect a certain level of mortality caused by dermo in the warmer summer months. MSX mortality, can occur almost any time of the year, not just in the, the warmer summer months. and it can be a very high level of mortality. not the 15 or 20% that might be caused by dermo, but it might be, you know, 60 or 70 or 80%- 

Kevin Cox: Wow

Kevin: Okay, something these scientists had to explain to me was that while both MSX and dermo can kill oysters, they don't play by the same rules. Dermo slowly spreads from one oyster to another, like a cold in kindergarten that gets passed around to all the kids who are in the room.

While MSX comes from something else in the water, a third-party invader that scientists still haven't identified and which can trigger sudden severe outbreaks and much faster die-offs

Bill Walton: For dermo, dermo is directly infective. One oyster gets sick, and when it releases, the spores, those are brought into another oyster, and it gets sick. It's more comp- 

Kevin Cox: It's like, it's like contagious. 

Ryan Carnegie: Right. Dermo is directly contagious from one oyster to another, and the higher the density of the oysters, the more transmission that's gonna be happening, 'cause that one infected oyster is gonna spread the parasite to a whole bunch of its neighbors and establish that next generation of infections that's gonna be passed, again, directly from oyster to oyster.

And MSX, you know, there may be a lot of mortality from MSX. There's, you know, a lot of infections and a lot of release of that material to the environment, but we have no idea if all of that release from the oysters actually means anything. it's possible that the parasite is just cycling from, you know, one worm to another worm, or whatever the life cycle is, I mean, the oyster's acquiring the infections from somewhere. We know that's happening, but we don't know what's happening when the oyster releases the infected material. So we have very limited perspective on the epidemiology of this most important oyster disease. Yeah. you know, we don't know where it's coming from. We just know that we could see oysters get sick and die. Um-

Kevin Cox: So Bill, as a, farmer, how do you determine if you have a problem that's either emerging or already there, and what do you do?

Bill Walton: Well, like Ryan said, I think, you know, typically the alarm bells go off when you see a lot of dead oysters. Like, you go out and, and this happens in the wild too, but growers, people who are doing aquaculture, are looking at their bags. They know pretty much the number that they put in, and, they can count the live, and you often see what we call boxes, the em- the empty shells. Right. And so you have a very clear, quantitative sense of mortality. It sounds terrible. Anybody that's dumped out a bag of oysters, there really only has to be one or two dead oysters in there, and you think the whole bag is dead.

Kevin Cox: That sickening hollow sound.

Bill Walton: Yeah, we call it the death rattle. And you dump it out, and you can count those, and you can suddenly find that you've got, you know, 15% 20% mortality, 'cause you can actually count it.

Kevin Cox: Right.

Bill Walton: But the most common way I think we see, at VIMS is a grower has experienced heavy mortality and wants to know why, and the first thing we always say is, "We have to, we have to see if it's a pathogen, a known pathogen." And so I'll encourage them to contact Ryan or so- another shellfish pathologist in their area to send samples, and that's often where we'll get the, "Oh yeah, you have a lot of dermo, you have a lot of MSX.

Um, a lot of them have it, and they have very bad cases of it. That's probably causing your mortality." Right. But as Ryan said, if you're starting to see slower growth, um, growers have a lot of things that they're looking at in terms of the way the edges of the oyster grow. Um, s- that's, I think, a little bit harder for us sometimes to put into a quantitative sense, but there are lots of clues they're looking for, including the... Sometimes the meats get a little watery. Um, so there, there are clues that growers will look at 

Kevin: So far we've talked about the disease itself, but the diagnosis is only the beginning. For the people whose livelihoods depend on oysters, the more important question is this: Once you know MSX or DermA has arrived, what can you actually do about it?

Bill Walton: Unfortunately, you know, because it's shellfish aquaculture, we don't feed these animals. We don't have a way to give them medication, if you've got a crop that has it. you can move up your harvest and try to get as much stuff to market before it dies as possible. Um, you might have another area that you could relay them to, but You'd certainly not wanna be spreading the disease, but there are some farms that are big enough that they have low salinity areas and higher salinity areas, and they can move, stuff to the low salinity where disease is less of a problem. Um, but, you know, really you have to usually look to longer term solutions, and that's s-some type of selective breeding and thinking about different types of seed. In terms of stocking density. Dermo is directly effective, but, I don't think we have proof that if you grow 200 oysters in a bag versus 100 oysters in a bag, that it's gonna affect spread. 

Ryan Carnegie: For intensive aquaculture where the animals are harvested in the mid-Atlantic within about a year and a half or thereabouts, the aquaculture's basically doing more good than harm. It's actually a net sink for, for infective material because the animals are filtering. They're removing dermo- Right ... from the water, and then they're removed from the water before they develop serious lethal infections and release that infective material to infect other oysters.

Kevin Cox: So you're almost, by having the oysters there, it's almost a form of Extraction. Yeah, yeah, yeah.

Bill Walton: By the way, it is a cliche, but in terms of what a grower can do, it is that prevention is the best option. Um, and so I mentioned selective breeding, but then there are lots of rules and considerations for biosecurity. And, that's another way that you'll know you have disease, is that you're trying to transfer seed somewhere, and you have to get it tested. And you find out, "Oh, I, I can't transfer that seed because it has disease." And so one is just making sure that you're getting seed that's not bringing disease into an area. That's a proactive step before you have it.

Kevin Cox: But it sounds like nevertheless there are situations where a farmer or a whole farming area can be pretty uncertain about what's the future of this year's crop or next year's crop or that sort of thing. What does a community do, Adriane, a whole oyster region that is having this problem? What do they do to address it on kind of a broader basis?

Adriane Michaelis: So I think at the community level, it's a challenge. If they're losing, both wild or farmed, that, you know, is loss of crop, loss of wild reefs, that isn't just that one year, 'cause oysters don't grow to adulthood within a month or two. You know?

Kevin Cox: Right.

Adriane Michaelis: They're thinking sort of generationally, so that business is impacted for several years at least, depending on the scale of disease. and you can see it impact, you know, the supply chain, so whoever's buying the oysters, the seed suppliers, if they're also struggling. And larger farms maybe have opportunities to move seed to lower salinity if they have it. And larger farms may have other opportunities to sort of weather the storm a little bit easier- Right ... than small scale. but it's still, because of that uncertainty, it's sort of hard for the farmer to predict, hard for the community to look ahead. And in some cases, like where we've had here in the Bay with Dermo and MSX, it wasn't great. It was, devastating for the commercial fishermen, but many of them are accustomed to adapting and more diversified and working in other fisheries. Some took the land-based jobs, and so there's sort of that, whether it's welcomed or not, most likely not- Yeah ... but the opportunity to diversify and lean into maybe other products that they're growing or other trades that they were doing in addition to the farm, um- could be one way.

Kevin Cox: Right. Kind of being forced to pivot almost because of the circumstances.

Adriane Michaelis: Right, and some farms are better equipped to do that than others. some- Right ... fishermen are better equipped to do that than others.

Bill Walton: If the, wild fishery was being devastated by disease, as it was here in Chesapeake Bay ... that actually spurred some people, I mean, went into other businesses, but others said, "I'm gonna do aquaculture" and started growing oysters that way and thinking about how can I get an aquacultured oyster, to weather this disease, whether it's resistance or harvesting before they die from it. But there are a number of strategies because, for example, shucking houses, um, You know, their entire business depends on supply, and so here in Chesapeake Bay, we had a number of growers turn to bottom culture as a way to replace the quantity of oysters that they'd been getting from the wild, which was in decline due to disease.

Kevin: No oyster farmer wants to hear the words MSX or Dermo, but these diseases have been part of our oyster history for decades. And while every outbreak is different wherever they've happened, the challenges often feel familiar. From the Chesapeake Bay to Prince Edward Island, oyster communities have been forced to adapt, and each one before it has something to teach to the next.

Kevin Cox: You mentioned the Chesapeake Bay and that there was a problem. Tell me a little bit about what happened in the Chesapeake.

Ryan Carnegie: There was this event we had in, late '23 into '24, which was extraordinary in that it was an MSX event, outbreak, some years, after we'd had the previous one we'd had, I mean, 15 or so years of relatively light MSX infection pressure, relatively light impacts on aquaculture businesses and, and so on. And then we, we started getting reports in the fall of 2023 from growers that they were seeing, you know, very high levels of mortality. so we looked at a number of samples from a number of farms and found that there were very high levels of MSX infecting those oysters. And there were probably a few different things going on there. one being that, you know, we hadn't had MSX infection pressure in a long time. Right. So, you know, in the wild, there had been so little MSX for so long that, the populations probably increased in susceptibility and when the infection pressure is low, those susceptible genotypes from those upriver areas have a chance to sort of spread into the lower parts of the estuary, without any cost-

Kevin Cox: Mm

Ryan Carnegie: because the parasite's not there. It's not active.

Kevin: Here's the part that really caught me off guard: You'd think that never having MSX would be a good thing, but Ryan explained that oyster populations exposed to the disease over generations can gradually become more resistant. In areas where MSX has never been present, that resistance may never have had a chance to develop. So ironically, when the disease finally shows up, the losses can be even greater. I'll admit that it took me a minute for my brain to wrap around that

Ryan Carnegie: So probably what happened was there was a general increase in susceptibility in the oyster populations, and they were hammered by MSX when it increased in sort of abundance in the system because the salinities were appropriate. Now, in aquaculture, we're not 100% certain about what happened, but we were probably making assumptions about the disease resistance of these animals in aquaculture and, and in breeding. that it- everything that we're growing and providing to growers is gonna be resistant to both of those diseases. But if the reality was that MSX pressure had fallen away, the breeding population's probably eroded a bit in their resistance to that disease in particular, which probably explains why even in aquaculture, with oyster strains resistant to MSX, that we were seeing fairly high MSX impact. So, so we're working really hard now to really think about how we can properly have MSX and dermo on the radar, to sort of sharpen and strengthen how we approach these diseases to make sure that, um, we sort of know what we're getting- with the performance of these lines.

Bill Walton: I think the other thing is, uh, you know, the very human, aspect of, our growers, if there isn't a disease around, do you focus on making sure that you have seed that's resistant to it, I mean, I'm sure this happens in other industries, but, you know, we see this in the Northeast with ice, that, growers who go a number of years without ice, uh, and then you sort of get used to running your farm without ice or down south without hurricanes. uh, you know, It, it worked the last three years, so I'll get it this year, but this year turns out to be a bad MSX year. Yeah. And you weren't getting stuff that's resistant to MSX. And so this is where cranky old-timers look back and have the advantage of no, like, this is going to happen at some point. You need to be prepared for it. Mm-hmm. And so a newer grower, even if somebody who's been growing five years, you haven't seen those things that have happened across a decade or two.

Kevin Cox: We hear about MSX from a scientific perspective, and what we know and what we don't know, like you've been describing, but how does it fall upon growers and communities that aren't thinking about the science of it, but rather like, what the hell do we do?

Adriane Michaelis: Right. So I think from the growers, like they're thinking about it, and many of them do know the different diseases or parasites that they're concerned about, and, they just wanna make sure that they're able to successfully grow and sell that oyster.

Kevin Cox: Right.

Adriane Michaelis: From the community level, like Bill had mentioned at the start here, making sure people know this isn't something that affects humans. It's a disease of oysters, not something that's transmissible.

Kevin Cox: Yeah.

Adriane Michaelis: That's where I think the recognition starts to get a little fuzzy because people will just hear disease- Yeah ... and think that it's something scary for them also. And so when we think about the general public, it gets lumped into other things that could be you know, a foodborne, risk for humans, which it's not. But they just might hear that, and it may affect the, you know, public opinion and social acceptability of the industry, or they might hear that there's disease in these waters, and so they may choose to not buy oysters from that region if they're out to eat.

Kevin Cox: I hear so many people who don't eat a lot of oysters, and, you know, they're afraid of them. This compounds on that fear, I guess. how does a community fix that? What do you do? Is it a marketing issue? Is it an advertising thing? How do you educate people in an area that is being affected by this, that it's okay to continue to eat oysters?

Adriane Michaelis: I think probably a-a combination, 'cause people learn in different ways and retain information in different ways. And so part of it might be at the restaurants, at the seafood shop where they're buying their oysters to, to educate and make sure people know-what's coming out and that what's being sold is still safe. And that if they can support the oysters that have survived, whatever disease is, affecting that area, then they're supporting those farms and supporting those fishermen.

Kevin: By now, it's clear that MSX isn't just an oyster story. Its effects ripple far beyond the water. Behind every oyster farm is a family, and behind many of those families are generations of hard work, parents and grandparents who built a business hoping one day to pass it on to their children. Entire coastal communities have grown up around those working waterfronts. So when something like MSX threatens not just a crop, but a way of life, how does both a grower and an entire community respond?

Adriane Michaelis: Whether it's accurate or not, the rumors associated or what people start to fear lasts for years. Even 10 years after the oil spill, people were still questioning about eating oysters from the Gulf, even though the oysters were safe to eat. Um, I think it does start to wear on people when they're thinking about if they're, gonna stay in the industry because again, those businesses that are able to weather the storm, do they want to? How many times do they wanna, to deal with this in the years ahead, and is this something that they wanna pass on to children? Are there children there to pass it on to? Um, we're seeing more broadly, separate from disease, with challenges of passing along a business and finding successors and heirs. And so I think that certainly weighs in to, you know, just one more factor that could be something that steers someone away- Mm-hmm ... and thinking about it, if there's an insurance program that can support the losses that they face reliably, um, so- it sort of just in- introduces more risk to wanting to stay in the business and for the community to be relying on that as a broader economic input for the community.

Kevin Cox: Have you found that the growth of aquaculture in communities hard hit has slowed down? Has it really driven people away, or they're just, you know, old people getting out and new people getting in? What kind of long-term growth impact does this have on communities?

Adriane Michaelis: I think there's certainly been patterns where we've seen growth slow down a little bit in areas after sort of initial surge and, like, innovation period.

Kevin Cox: Right.

Bill Walton: It's one of those challenges to your sustainability of your business, and anybody that's on the edge. It has, uh, the potential to knock out of the business, for sure. We've seen this with some of the other things, like the sudden unusual mortalities, where people have to ask, "Is that worth doing?" And generally, it's the ones who are closer to the edge already that say, "This is not worth doing."

. It does spur some innovation, too. there are people who are invested enough that they're looking at, "How do I survive this? How do I come out of this?"

Kevin Cox: Uh, when you consider the investment that's necessary, especially with modern technology. Once you make that investment, do farmers tend to feel kind of stuck between a rock and a hard place. It's like, "Well, I made this big investment, but I'm losing all my oysters, so what do I do?"

Bill Walton: I think there's something to that. I think we see that with any of the big companies, that once you've expanded, that you have... You must, keep succeeding, and so there is something to that. But I think uh, there's something about shellfish aquaculture. I think it's one of those things where you're producing something, and I think that one of the sort of the nature of the people who do this is sort of problem-solving and- Mm ... how do I make this better? Um, and so I think you see that sometimes come out with, uh, with challenges like disease.

Kevin: History tells us that diseases like MSX don't simply come and go and are forgotten. They become part of the story of oyster farming. Communities have faced these challenges before, and each time they've found new ways to adapt. The science has improved, the technology has improved, and with every outbreak, we've learned a little more about how to protect both oysters and the people who depend on them

Ryan Carnegie: I think it's helpful to sorta step a bit further back and think about some of the historical stuff. You know, the, the early MSX disease outbreak in the '50s, you know, '57 in Delaware Bay, '59 in Chesapeake Bay, you know, there were wild fisheries that were impacted by that. There was a planting industry that was tremendous in the Virginia part of Chesapeake Bay. I mean, it was worth, you know, many, many millions of dollars, and it supported thriving communities, all around the shores of the lower part of the bay region. And when MSX hit in '59 and '60, it basically ended that planting industry- Right ... with only vestiges remaining in the upper parts of the big rivers, beyond where MSX could reach. and we still have some big players in the industry that are representing businesses that hung on in those areas,  but others were forced to pivot. You know, Cherrystone Aquafarms was the old Ballard Fish and Oyster Company- Right ... you know, that was doing a lot of wild harvesting and extensive planting. And, you know, they and some of the other businesses, H.M. Terry and Walker Brothers, pivoted to, pivoted to clams. But the upheaval caused by those early outbreaks affecting early aquaculture in the region lasted, half a century or more. And, where we are now, you know, we had an MSX outbreak in Maine in 2006 or '7 or something it was, devastating in the Damariscotta, but it was over in about a yea because we had different, just different tools now to deal with this stuff. We, we do have selective breeding that we can rely on to, you know, get resistant seed into the hands of growers to, navigate this crisis as quickly as possible. if we have a new pathogen emerging, we have genetic tools to respond to that. So, it's not that it's not, stressful to the growers and the communities and so on, but, relative to where we were historically in being able to deal with this stuff, we're in much better shape now.

Kevin: The lessons of the past are being put to the test once again. Today, Prince Edward Island is confronting one of the most significant MSX outbreaks in its history. It's a challenge that's testing one of the world's great oyster-producing regions, with consequences felt far beyond oyster beds. And this isn't a problem that farmers can solve alone. It takes scientists, hatcheries, processors, government agencies, and entire communities working together, each playing a role in protecting an industry that's woven into the very fabric of Prince Edward Island

Kevin Cox: Let's talk a little bit about PEI, right now, they're really embroiled in a, crisis situation with MSX. How long has that been going on up there?

Ryan Carnegie: It was about two years ago that MSX first was discovered in the context of unusual mortality, um, in Prince Edward Island.

Kevin Cox: Do the oysters die immediately, or is there a progression where they get unhealthier and unhealthier and then ultimately die? And can a farmer or a community do something to backfill or buttress that inevitability?

Ryan Carnegie: That's a good question. You know, MSX is, is a very acute disease, so it tends to kill very quickly. Um, it, it doesn't take, years Um, MSX can kill within weeks, and it can kill oysters of any size. I'm, talking a lot to, to PEI interests, you know, growers, to regulators and so on, and, it seems like there are areas where they're discovering they're being heavily impacted by mortality. There are other areas where the parasite is detected at lower prevalence and, not yet causing any mortality, suggesting that, you know, there may be a crisis sort of on the horizon within a, month or two or three or so  these are very short timelines- Right ... within an MSX outbreak- from discovery to, to devastation really. And we know that ... that there will be a light at the end of the tunnel for the wild resource, based on, evolutionary processes. Eventually, the oysters will become resistant to these diseases, and many more of them will grow to market size and survive. But the whole other part regarding aquaculture is getting fast-growing, disease-resistant seed into the hands of the growers so they can get that onto their farms and sort of get through the crisis as quickly as possible, by k- you know, getting something surviving to market. And that's where the engagement with the US, has been focused. You know, we have disease-resistant animals that, grow very quickly, and that's part of the secret of their success is not just that they can-fight off the parasites, but they can sprint to market size- and get to the, raw bar or, the supermarkets before the parasites catch up to them. So getting that seed into the hands of the PEI growers is critical. The question has been for PEI, how do you do that? Um, is it importing US animals? Is it developing it completely sort of de novo within the Canadian setting where they're experiencing this outbreak,

Kevin Cox: it sounds like it requires a large scale community-wide or even governmentally sponsored kind of mobilization to take these precautions and safeguards for the future. Have you seen communities that have been able to mobilize and really address the issue and get through it together? Because I would think this is almost an existential issue for PEI or other communities.

Adriane Michaelis: In some cases I've seen where communities have leaned into aquaculture as a way to support s- a struggling wild fishery. Whether it's providing resources or seeking funding to do so, to support a larger initiative that's more than just an individual.

Kevin: Somewhere along the way, I realized this conversation had stopped being just about oyster diseases. It had become a conversation about how people respond. Scientists adapt, growers adapt, communities adapt, and each challenge leaves behind new knowledge, and every crisis teaches new lessons. But the response of a community is rarely simple. It requires difficult decisions, competing priorities, and people from across an industry working together to protect not just oysters, but the families, businesses, and very way of life that depend on them. And that's when I realized that we had been talking about resilience all along

Kevin Cox: What does it take for one community to be resilient in the face of either disease or other conditions, so that they survive compared to communities that don't?

Adriane Michaelis: When I think about resilience, it's sort of complex big picture where, some of the challenges that we'll see are if they, are limited by labor, they don't, can't find employees, but they also don't have housing because housing has become unaffordable. So when we're thinking about these coastal areas, even some of the rural ones, it's, it's becoming tougher to eke out a living there. And so employees are being sought from farther away, and then that makes it less ideal if they're making that commute to get to a farm. Um-

Ryan Carnegie: Is there access to the waterfront? Or, you know, are there areas to work on the waterfront?

Kevin Cox: Yeah.

Ryan Carnegie: if the industry has been gone for, 30 years, and there's no living memory of when there was an industry, you know?

Adriane Michaelis: And I think that's a challenge with the uncertainty of a disease outbreak. If it is something that lasts for a while, what happens during that while if these businesses have to shut down and, and shutter. And then someone buys them and develops something else there that may not suit a future return?

Kevin Cox: The more practical realities of the thing is very interesting that you mentioned, Adriane, and that is labor force, housing, all of the, what maybe I would call the ancillary aspects of supporting an aquaculture community. You're not gonna bring in a new labor force, or I'm not gonna move to a small town because I wanna be an oyster farmer if I hear that the oysters are diseased or dying or that there's not gonna be any money or long-term employment in it, right?

Bill Walton: Uh, you know, I would say you are vulnerable to, lots of changes, external forces that can, um, push you to the edge and potentially out. And you know, aquaculture is a way that we've seen, coastal communities around, uh, the US and the world, that that's one way that they have kept their communities going. You, you have industries there that rely on the water, rely on clean water, um, that have people out working on the water- Then it becomes a matter of whether the community embraces that or decides, "I don't like the look of that." You know, if, if you grew up with the idea that oysters are all harvested from reefs, and so it's those beautiful boats going out with these hardworking people that are, like, pulling oysters off the bottom, I love that. I want that to exist. But I also just want the coastal communities to have working waterfronts, and we know that shellfish aquaculture works. 

And so when I look at a community, uh, Cedar Key, Florida, has embraced clam farming as one of the things that defines it. And so I feel like every third pier in Cedar Key is a clam nursery, and there are clam farmers everywhere. Like at Christmas, they have a clam in lights on the streets. Um, you know, It's part of their identity.

Adriane Michaelis: So Cedar Key, for example has, has boat ramps that are exclusively for commercial industry so that they can't be overtaken by, you know, weekend boaters, recreational boaters.

Kevin Cox: Right.

Adriane Michaelis: Um, and so there's certainly things in place in other areas. um, up in Cambridge, Maryland, there's marinas that have commercial slips that there's a, uh, a required minimum number of commercial slips that will be there. Um, and so there, there's approaches like that to help ensure that that waterfront can stay working despite efforts to redevelop. Um,

Kevin Cox: So someone's not gonna be able to build their million-dollar house on that shoreline because of that priority for the commercial, aquaculturists?

Adriane Michaelis: Right. And there's always the question of that could change. So how many years if there's not oysters being produced-

Kevin Cox: Mm ...

Adriane Michaelis: Can they sort of maintain that, that claim? And so that's where, having that broader community support to show that this is something that's important to us, this is something we value, and, you know, we're waiting for this to come back, or to help ensure that it does come back.

Bill Walton: I think of places- right ... in Maine where they've said, "This is something that we do." So you do need a community to say, um, "This is something that we wanna do." When we think about the Canadian Maritimes, aquaculture is something that they do.  Um, PEI, they're doing it. They're in a position, though, that their aquaculture has depended on harvest of wild seed. Um, and so they've had this, uh, tremendous bounty of seed from nature, and that is now in jeopardy. And so that's why you have to then turn to this idea of hatcheries Hatcheries can be limiting in communities because they're expensive. Um, they take a certain set of skills, to run, and those set of skills aren't everywhere. You have to find the people that can do it. And so I think one of the questions logistically for, that area will be, can they build those hatcheries? Can they staff those hatcheries? Will they support them? And then the question will be, how many growers can those hatcheries supply?

Kevin: One of the things I found really interesting was how the response to oyster diseases grows in proportion to the challenge it presents. A farmer can respond to problems on his farm. A community can respond to challenges facing its local industry. But when an entire oyster-producing region is threatened, the response has to expand even further. That's where universities, industry associations, public agencies, and governments become part of the story, investing in research, coordinating resources, and helping oyster communities respond to challenges that no one can solve alone.

Bill Walton: The problem is so massive, um, and affects so many people, the growers, the people who are trying to transport those oysters, that certainly in Virginia, state and then federal funds were brought in to try to tackle the problem, the public made investments here.

Ryan Carnegie: Well, there were, myriad public investments. And, I mean, notably, there was the creation of an oyster disease research program, in the 1980s that was administered by Sea Grant that supported, literally decades of really important science, a lot of it behind the breeding and disease management that helped provide the scientific foundations for the growth and recovery of these aquaculture industries. Um, and then a lot of investments at different scales in, shellfish restoration, you know, planting shell, creating new reefs and so on to help on sort of the wild, the conservation and restoration, uh, angles. But all of that was very, very important, you know, in coming together to, to support the communities that were dependent on these resources.

Bill Walton: Here in the Chesapeake, we've got something called the Chesapeake Oyster Alliance, and that brings together restoration and growers and managers and fisheries with the goal really of the bay... the premise is the bay is better off with more oysters in it. And so the way we get to the most oysters in the bay is by having that mix. I think they're sort of swimming in the same direction.

Adriane Michaelis: But certainly where, like, one, one region's loss could be another one's gain, and we're already seeing where, folks are filling the gaps that those, the, you know, Canadian oysters previously filled.

Bill Walton: Right.

Adriane Michaelis: And so that comes that uncertainty again with when they start producing again, will their buyers want those oysters back, or will they be happy with what they're now getting consistently from somewhere else?

Bill Walton: Right.

Adriane Michaelis: Um, will the consumers want those back?

Kevin: One of the things I found myself thinking about as the conversation unfolded was the importance of keeping all of this in perspective. For the people living through an outbreak like the one in Prince Edward Island, this is a very real crisis with serious consequences for families, businesses, and entire communities. It deserves attention, investment, and a thoughtful response. But MSX isn't unique to PEI, and it's important to remember that oyster farming has faced diseases like this before. Across North America, different oyster-growing regions have confronted different diseases, environmental pressures, and other crises over the years.

None of that minimizes what's happening on PEI, but instead, it reminds us that responding to these realities has always been part of oyster farming. The locations change, the diseases change, the response evolves, and together, it reminds us of something important. These are only moments in the continuing story of oyster farming, not the end of it, but just another step in its evolution.

Kevin Cox: How big a problem is this in the overall world of oysters and oyster aquaculture? Is this something that is really damaging the whole industry, or is it, is it localized enough that it's a problem if you're one of the farmers or if you're living in the community where that grows, but it sort of doesn't go beyond that?

Ryan Carnegie: Well, that's a good question. Um, I mean, dis- disease generally, you know, it, it's a problem. It, um, it, it could cause unacceptably high losses. um- It, yeah, it's, it's just, it's just one of these things that, you know, we need to constantly, one, be vigilant against the possible introduction or emergence of new diseases. We constantly need to be working to try to find the answers to better managing the diseases we have. Um, you know, there's a lot of news about MSX right now, and that's, you know, mostly localized, you know, Atlantic Canadian-

Kevin Cox: Right ...

Ryan Carnegie: effects. But, you know- We have plenty of farmers that are growing, in the Mid-Atlantic and, the Southeast, the Gulf Coast, that are experiencing problems that are, just as challenging, just with other disease problems. So, um, you know, I'm not sure that's the best answer to your question. But, MSX, you know, it's a local issue that flares up, here and there across the vast oyster geography. Disease generally is a problem that, that everybody is challenged with everywhere, on an almost daily basis. How am I gonna beat one or another of these pathogens and get enough of this stuff to market that I'm running a profitable business? And, um, if you don't have a problem now, that's not to say that you're not gonna have a problem tomorrow, which is why we need to you know, uh, keep our eyes on the ball and focused on, alertness, passive surveillance, what's going on. Are there changes that we need to get on top of, something new emerging, and what are we doing to manage these, chronic, endemic diseases now? Right.

Bill Walton: You know, from my point of view, I would say, like, um, if you're one of those growers in the Canadian Maritimes that's being affected by this, or the people that, that work with them, it's an existential threat. I mean, this, I truly hope that the provincial governments and the federal government of Canada, address this as the crisis that it is. 

From the big picture of sort of the oyster industry and the oyster aquaculture industry, as, as Ryan s- like, there, there are going to be these problems in, uh, there and other places, but the industry is strong enough and resilient enough that, consumers will still have oysters. There'll still be an oyster industry. There'll still be farmers growing oysters.

Kevin: As our conversation began to wind down, I wanted to hear one final thought from my scientist guests, each reflecting the unique perspective they bring to the oyster world. Bill through aquaculture and applied biology, Ryan through oyster disease research, and Adrian through relationships between oysters, people, and place.

Kevin Cox: If you were advising, a new person wanting to get into aquaculture today, what would the number one piece of advice that you would give them be?

Other than run far, run fast… 

Bill Walton: Well, no, I think, you know, probably all of us, uh, we've all been asked, like, about, you know, I think one thing we do is, uh, do a gut check and go see what it's actually like, 'cause make sure that you're not doing it because of the romance of it. Mm. But if I had somebody that really wanted to do it, my first, and I know this isn't disease-related explicitly, but is site selection, that making sure that you have a site that the environment supports good, growth, that logistically works, it has access to markets, that you have the community supporting it, that is feasible and that you could get permitted. So I, I would start with the site, is always my first one, because sometimes I have people that have fallen in love with the idea of oyster farming, and they wanna use the latest and greatest gear, uh, and so they've fallen in love with that, or they've fallen- Right ... in love with the idea of, of growing an oyster that they think they're gonna get $2 for or whatever when they sell it. And I think you have to start with the site, because that will tell you how fast it grows, how well it grows, how well it survives, and what it's gonna taste like. So I start with site.

Kevin Cox: If there was one scientific question, Ryan, about MSX that we don't currently know that you wish could be answered, the top question, what would that be?

Ryan Carnegie: Well, I think the, the top question for MSX is where is it when it's not infecting the oysters? Oh, you know, what is the intermediate host? Um, it's something, in our marine systems, it's something that's intimate with oyster reefs, oyster bags, and cages. Probably some small invertebrate that we've seen, 1,000 times, but we just haven't figured out what that host is, or hosts. There could be more than one. Um, but having that information It would provide levers for management that we don't currently have now because we just ... You know, this whole area of the parasite's life cycle is just a, just a, a huge gap in our knowledge. So that's the big question.

Bill Walton: I think it's critical to note that the industry relies on the wild set, and so that's, I think that's why they're gonna be challenged by responding to this, that there's no quick fix because, because it's in- requiring them to do a complete shift in how they've done their stocking of their farms.

Kevin Cox: What do you wish an oyster community or oyster aficionados, what's the one most important thing you would want them to know about MSX

Adriane Michaelis: I think it is the knowledge that it's not a disease that affects the consumer, but also make an effort to support those industries if they're struggling. And, you know, maybe there are other ways you can support the industry if you can't buy their oysters.

Kevin Cox: Not to mention, eat more oysters, right?

Adriane Michaelis: Right, keep eating oysters. Try some new ones.

Kevin Cox: Well, I want to thank all three of you for  coming here, giving me your time. Very generous to prepare for this and to talk to me about this,

Ryan Carnegie: Right.

Bill Walton:  Cool, yeah ... 

Kevin Cox: I really appreciate it. Thank you.

Kevin Cox:  Well, that's it for this episode of OYSTER-ology. My great thanks to Drs. Ryan Carnegie, Adriene Michaelis, and Bill Walton for sharing their expertise and their perspectives on the relationship between oysters, disease, people, and place. 

As I listened to this conversation, I realized that while we spent a lot of time talking about MSX and Dermo, this story was never really just about oyster diseases. It's about scientists working to better understand these parasites, growers adapting to changing conditions, and communities finding new ways to respond to challenges that no one can solve alone. Just like so many other chapters in the history of oyster farming, this one is ultimately about adaptation, innovation, and perseverance.

Links to the VIMS website and the detailed bios of our esteemed scientists are included in the show notes, along with a transcript of this episode. And please follow OYSTER-ology wherever you listen to podcasts. The more followers we get, the more others will discover us, too. And if you liked this episode, have questions for my guests, or would like to say something about your own experience with MSX or Dermo, please leave a comment to let me know.

In the meantime, keep enjoying oysters. Support your local oyster farmers, your seafood markets, and restaurants. Every oyster you enjoy helps support the people and communities who work so hard to produce them. And the most important takeaway from this episode is that MSX and Dermo are diseases of oysters, not diseases of people.

They do not make oysters unsafe to eat. They are not harmful to humans, and they should never be confused with foodborne illnesses. The diseases affect oyster production, not consumer safety, or in the words of Bill Walton:

Bill Walton: Like spots on apples. It's not affecting the safety of the oysters that anyone is eating. ."

Kevin Cox: Thanks so much for listening, and be sure to join us again next time when we pry open the shell of another interesting OYSTER-ology topic.

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