Minnesota's Swine & U

Sarah Schieck Boelke:
Hello and welcome to a Minnesota’s Swine and U podcast series, a University of Minnesota Extension Swine program. Today's podcast is a research update on Senecavirus A seroprevalence in U.S. pig farms and biosecurity procedures to prevent indirect transmission.

My name is Sarah Schieck Boelke, your host, and I'm a Swine Extension educator with the University of Minnesota. Joining me today is Guilherme Preis, who is a recent graduate of the University of Minnesota College of Veterinary Medicine with his PhD in veterinary medicine.
To get started today Guilherme, will you tell us a little bit about yourself, your background, how you got to where you are currently, and also include who you worked with on this research?

Guilherme Preis:
Hello, Sarah and thank you for having me here today so I could talk about the research that I did during my PhD work. So originally I am from Brazil. I was born in a family of hog producers. So my dad has been producing pigs since before I was born, and that's actually the reason why I decided that I wanted to be a swine veterinarian and work with pigs too. And that's what I did. And then in 2014, I got my veterinary degree in Brazil and then I joined a major swine producing company, where I did a lot of extension veterinary work and I also managed the health of the multiplying farms in the south of Brazil.

And then, in 2018, Dr. Fabio Vannucci from the University of Minnesota invited me to come to the U for a PhD program. And then he introduced me to Dr. Cesar Corzo because they would both co-advise me during my time in a PhD program. I graduated in November in 2022. Since December of 2022, I have been working with Topigs Norsvin USA which is a swine genetics company and I am working in the role of product performance manager.

Sarah Schieck Boelke:
Interesting. I always find it interesting: the individuals, and primarily the graduate students that I talked to on the podcast and getting to hear, you know, a little bit about their background, and where they came from, and how they got interested in the swine industry, and what led them to the University of Minnesota. So thank you for sharing that background.

Guilherme Preis:
I’m sure you have people from all over the world and all over the U.S. and all over the world, so it’s always nice to listen to where people came from, so yeah.

Sarah Schieck Boelke:
Yeah. So I alluded to it a little bit when I said what the research update for this podcast was going to be. But can you share a little bit more specifically what research topic that you will be talking about?

Guilherme Preis:
So today I'll be talking mainly about one research project from my PhD work. And this one in particular I conducted with Dr. Cesar Corzo between 2018 and 2019, in which we were interested in assessing the seroprevalence of Senecavirus A in U.S. pig farms.

So in other words, we wanted to have an estimate, or to know what was the proportion of sow or breeding and growing pig farms in the U.S. that were exposed to the virus right. And at the same time we wanted to perform some exploratory modeling analysis to see if we can find what are the risk factors that may be associated with this previous exposure to the virus? Right?

And so that's gonna be one. We're gonna be, probably spending most of our time with this research in particular. But since we're gonna also be, since we're gonna be talking about risk factors, I thought it would be very good to talk about another study that I conducted with Dr. Fabio Vannucci, and I think it would bring a lot of value to our discussion.

Because in this one, we were interested in evaluating different biosecurity procedures. So there are standard biosecurity procedures that pig farmers, and even farmers from animals of other species already do, right, to see what their effect would be to prevent the indirect transmission of Senecavirus A between pig populations.

Sarah Schieck Boelke:
Very interesting. But before we get further in our discussion as to exactly what you did for this research, are you able to share who the funding source was, or maybe it was a couple of sources for these research projects?

Guilherme Preis:
Yeah. So the first study, the seroprevalence and risk factor study, was funded by the National Pork Board. And then the second study was funded by the Minnesota Rapid Agricultural Response Fund.

Sarah Schieck Boelke:
Thank you.

Guilherme Preis:
Yeah, thank you. And thank you for the funding agencies, too. Otherwise we wouldn't be able to be talking about it right now.

Sarah Schieck Boelke:
Exactly. That's exactly what I was going to say. I was going to say. It's always important to give a shout out to the funding sources because they are able to make the research possible.

So now we'll get back to talking about this research that you did. Can you give us a brief introduction to the research study explaining why it was a valuable project to do for the industry.

Guilherme Preis:
Yeah. We should probably start talking about the disease itself, and why we actually care about it. So Senecavirus is a fairly new virus and a fairly new disease in the swine industry. Actually, let me step back. Maybe it's not a new virus, but only it's a new disease, right? We didn't know before that it could actually cause the disease in pigs.

So senecavirus, or we just call it SVA. It causes a vesicular disease in pigs and the clinical signs are very similar to other vesicular diseases, such as foot and mouth disease, which is probably the most famous one. Right? What you know, they are diseases that need to be reported to the World Organization of Animal Health, right?

FMD or foot and mouth disease can have a great impact for the food security of our country. Right. And SVA, it looks exactly like it, right? SVA itself is not reportable to the World Organization of Animal Health or OIE. You could just call it OIE. But other diseases, such as foot and mouth disease are. So that is actually the only reason that we care about SVA.

SVA can only affect pigs and not only others, and not other species right? While FMD can affect pigs and other species as well. So every time we see vesicular disease signs in any species of animals in this case, pigs, of course, we need to further investigate to rule out the reportable ones. And this is actually causing a lot of trouble for swine producers and swine producing companies and packing plants and even state and federal animal health agencies around the world because when a pig population is suspect to having this reportable disease, these pigs cannot be moved. And as you can imagine this causes a lot of logistic problems. Right?

It's kind of curious because the first documented case of the vesicular disease, where Senecavirus A was present, actually happened in a harvest facility here in the state of Minnesota in 2009 in pigs that came from the province of Manitoba in Canada. And then the large-scale SVA outbreaks were only reported starting in 2014, starting with Brazil and right after the U.S., China, and then other countries in the Americas, and also in Asia started reporting a large-scale SVA outbreak. So several farms breaking at the same time. And yeah, a lot of you can say it was a lot of chaos, you know, to solve all that issue and see what was going on. We didn't know that it was a new virus, let's call it, right, causing these problems, and it could be foot and mouth disease. So it took a while, but we finally figured it out.

But since this is all very new, there's very limited information about the epidemiology of the disease. The whole industry was seeing a lot of outbreak reports, and they were conducting these emergency investigations or foreign animal disease investigations to quickly rule out the reportable diseases, right? And and because of that, there was no estimate about the prevalence and the risk factors associated with Seneca. And all the processes involved the transmission of the virus were also not known. We didn't know how it works, right? So knowing these is actually a very important step. So we can start, think and start talking about developing plans to control the spread. And maybe even start thinking about disease elimination plans.

And then in the end, yeah, so both of these projects were done to serve as scholar foundation and studies for other studies, and also to provide information to develop science-based solutions for the producer and also for governmental agencies.

Sarah Schieck Boelke:
As, like you, mentioned Seneca virus A is very similar in its signs that it shows in the pigs right compared to foot and mouth disease. And so yeah, there's really no way to do differentiation between the two just looking at, right? You have to do that further diagnostics to be able to rule out foot and mouth disease. Is that correct?

Guilherme Preis:
Perfect. Yeah, yeah, you need somebody to go in there, collect sample, send it to the lab. You need to run the tests to rule out other diseases. Right? So yeah, it takes time. And that's why it creates a lot of logistic issues. Right? Because in the case, what if it really is foot and mouth disease? And you move these animals, and then you transmit the disease to other parts of your country, or your state, you know, that can create a lot of problems. So yeah. It's a caused a lot of headaches.

Sarah Schieck Boelke:
So right because those pigs are as they're going through that diagnostics, and while they're waiting for results, they have to be held right. They can't move. And if marketing is the destination or another barn. They have to remain in place right until the foot and mouth disease is ruled out.

Guilherme Preis:
Yeah, exactly. Because if you find it very close to marketing these animals, and the packing plant is counting on them. You cannot move them. So what is the packing plant going to do without these animals? Right? What if, in most cases the signs are actually seen in the packing plant. So what's the packing plant going to do with all these animals? Right? They may not be able to move these products out of the way.

So you know, it gets in the way of getting the job done. And you know, harvesting other animals, too. So yeah, it is a big logistical problem.

Sarah Schieck Boelke:
Yeah, I'm sure. So before, I guess we get a little bit too far, tell us how did you go about completing this research project?

Guilherme Preis:
So for the seroprevalence and the risk factor project, we designed it as a cross-sectional study. So participation in that study was totally voluntary. We called or emailed major veterinary clinics in the U.S. and also production systems throughout the country. We invited them to participate. And, if they agreed, each production system or a veterinary clinic was asked to randomly select breeding herds or growing pigs herds for sample collection. And then both participating in veterinarians, and in some cases we ourselves, as investigators, collected the study samples in the farms, but for most of them it was the companies or their veterinarians that were collecting it for us.

Yeah. After, I mean sample size calculation, we determined that we would need a lot of samples to be able to pull the study off right? So we needed 97 breeding farms and 97 growing pig farms to participate so we can estimate the prevalence of Senecavirus A in the U.S. And then, in order to tell if the farm was positive or negative we did determine that we would need at least 29 blood samples, so we could have good confidence that the that the farm was free of the disease, or if the farm had the disease in it right, or at least I mean the antibodies, right?

So in all the samples they were tested at the UMN Veterinary Diagnostic Lab for the presence of Ig antibodies with a immunofluorescent antibody test, or we could just call it IFA.

So that was, I mean, what we needed to do in order to be able to estimate the seroprevalence. But then talking about the risk factors then, since we were, we would be, you know, determining if the farm was positive or negative. All we needed to do was to develop two questionnaires one for breeding farms and another one for growing pig farms

They were designed to capture general information from the farm, such as farm type. Is it a breeding herd or is it a finishing farm, right? What's the farm size? How many animals are in there? Information about the person out of flow? I mean, what kind of, I mean, how many people do you have walking in and out of this farm right? How many workers do you have? Where are these animals sourced? You know, and other details about biosecurity measures.

And then we just ran univariable and multivariable logistic regressions. So basically modeling, just to see if we could determine what were the associations between all of these farm characteristics that were recorded with the farm being either positive or negative to the virus.

Sarah Schieck Boelke:
So now that you explained how you went about completing this project, what were the results?

Guilherme Preis:
So yeah, as you can imagine, as we, we did have a lot of blood samples and a lot of farms participating. In the end we were able to get 193 farms to participate. We had 98 breeding farms and 95 growing farms participating from 17 different States in the United States. And then the whole study was conducted between October 2018 and October of 2019. So within a one-year timeframe.

After testing all those samples, we could see that 17 out of 98, so 17% roughly, of the breeding farms had at least one positive sample. So 17% of the farms were seropositive meaning that they were exposed to the virus before. And these farms were located in different States, such as Illinois, Indiana, Kansas, Minnesota, also had positive cases but we also saw in North Carolina and in Texas.

Now for the growing pig farms 7 out of 95, so 7.4%, of the growing pig farms had previous exposure to Senecavirus A. And then in the states of Illinois, Indiana, Minnesota again North Carolina and Oklahoma.

For the survey, our response rate was actually pretty good, which was actually very exciting, because we would need a lot of information to be able to do the analysis right. So 80% of the farms responded to the survey, and sent it back to us. And it was a very lengthy one. So thank you to all the producers and veterinarians and partners that, you know, pulled that one off because I honestly wasn't expecting such a high response rate. So that was actually pretty awesome.

And for all the farmers that did respond, we got all of the positive breeding farms responding to the survey but only 6 out of 7 positive growing pig farms were able to respond to this questionnaire for us. And then, after the analysis, we found that for the breeding farms. So the farmers might have you know, sows. The carcass disposal method was actually highly associated with the farm being positive or with the farm having a previous exposure to the virus. So when I'm talking about carcass disposal method, I'm asking if the farm either composts dead animals on site, if they bury the animals on site, if they incinerate the animals on site or if they practice the rendering of these animals, and that is the one that we are interested in right now.

Because when you render your animals, you basically have trucks going into different farms and picking up these dead animals and bringing it back to a rendering facility. So this rendering truck is one very big risk factor to bring pathogens into your farm because they're they're just driving around over different farms that you don't know their health status, and they can be exposed to different pathogens and then bring it to your own farm just because of how they operate right?

So sow farms that practiced rendering had 9 times the odds of being positive or of being seropositive to Senecavirus A. And that's quite a lot right?

And then for the biosecurity measures that when we ask them, so farms that reported having at least 5 or 6 biosecurity measures in place, and then we asked questions regarding do you have a downtime? Do you need a downtime to visit your farm? Right? Do you have a shower in, shower out a procedure in place? Do people have to change their clothes or their boots to go in right? Do you have a visitor login, right, to be able to enter the farm? So farms that had 5 or 6 seem to be protected. They had 20% of the odds of being seropositive when compared to farms that reported only doing 4 or last of these biosecurity measures. So this is just basically saying that you know more biosecurity measures in place, and the farms seem to be protected against the virus.

And then for the growing pig farms, we had less information about them, and the very few farmers were positive. But one interesting association that we found is that growing pig farms that hired external pig loading crews so different people that don't work in the farm. They would come in just to help market the pigs they were 9 times they had 9 times the odds of being seropositive. So which you know, if you think about it, the possibility is that these external pig loading crews, as they are rotating between farms, they get in contact with the virus, and then they are able to spread the virus around.

Sarah Schieck Boelke:
That was great that you had a good response rate to your survey, because I know, like you mentioned, that is not always the case when we send out those surveys. So that's great that you had that high response.

GuilhermePreis:
Yeah. Yeah. And and like, I said, for a few of the farms, we were the ones collecting the sample. So we helped them respond to the questionnaire. And then I saw, I mean the time they took to actually respond so well, yeah. Thank you again for everybody who participated and that took the time to respond to the survey.

Sarah Schieck Boelke:
Yeah, it sounds like from the responses. You got a lot of great data.

Guilherme Preis:
Yes

Sarah Schieck Boelke:
So based off of the results that you did share what conclusions can be made from this research project.

Guilherme Preis:
So I would say that seroprevalence, it seems to be higher in breeding farms than in growing pig farms, and this makes sense. If we think about the way that this one industry organizes the production right? So breeding farms are in a continuous flow production style meaning that you always have animals present in the barn. Right?

So older animals are going to leave the farm, and younger animals are going to be brought in to replace the older ones. Right? So you kind of have, like the perfect scenario of infected animals being at the farm at any given time. Then they're able to shed the virus and transmit the virus or the disease to the incoming young animals that are usually naive to the bug. Right? So in theory, this can be a let's call a perpetual system right where exposed and infected animals are always transmitting to susceptible animals that are constantly being introduced into the herd.

And then, growing pig farms on the other hand, they are most often not an all in all out system, where all pigs are brought into the barn at the same time. But they're also removed from the barn and sent to harvest at the same time. So this way we are emptying the barns, washing them, and disinfecting and breaking this disease cycle and this prevents the next young incoming animals from being infected with the bug that was inside the barn before.

And then other key conclusions here would be that, you know, key risk factors associated with the previous SVA exposure were the rendering of dead animals in breeding farms, and also the access of external working crews to the growing pig farms.

So at the same time, the implementation of biosecurity measures seem to have a a protective effect against SVA exposure. So really makes us think that there, there are some things that we can do to protect our farms right, some things that we have to keep in mind. and then we know that by security can help us.

Sarah Schieck Boelke:
So you alluded to it a little bit already. But why are these results that you shared? Why are they important takeaways like, what? What can the industry learn from them?

Guilherme Preis:
I would say that the results show that there are there are a lot more susceptible farms than infected farms in the industry

meaning that there are many more farms that are currently at risk of being infected with Seneca and they could potentially increase our current pro problem right? And having more for an animal disease, investigation is being conducted to rule out the important diseases that we truly care about right? So that we are really concerned about their consequences. Right?

So if the prevalence in the growing pig farms is truly lower than in the breeding farms, perhaps focusing on protecting the breeding farms or eliminating the disease from them, will greatly benefit the industry as a whole.

The risk factor analysis. It also shows that it may be a good idea to rethink our current methods for carcass disposal. Because these rendering trucks they may be acting as mechanical vectors and transmitting the virus from infected to susceptible farms.

External working crews same way. They may, you know, just be visiting several sites, big sites, in a short period of time. They may also act as mechanical vectors. And those are all factors that the pig farmers and the producer companies are able to control, so they may be able to use this information to protect their herds.

More studies are, of course, they are needed. to further understand the mechanisms behind these factors, right? And also, perhaps we even have better estimates about the risks involved with with these factors. But the very same findings from this study were also detected in other studies for that, we're investigating the risk factors associated with other swine diseases, such as the porcine reproductive and respiratory syndrome or PRRS for swine, epidemic diarrhea, or PED, right and influenza, and there's a influenza has also been a reported for studies in other species, such as in poultry. You know that rendering trucks may make it seem like, no, the farms that do rendering are more likely to be infected with these viruses. Right?
So And then again in the breeding herd model that we ran in the study. The farmers are responding to having more biosecurity measures in place, they seem to be less likely to be positive to Seneca. So biosecurity seems to have to be a real, a protective agent here. Right? So standard biosecurity measures really protect us from disease exposure.

Sarah Schieck Boelke:
Thank you. As you were talking about those takeaways, and you know what the industry can learn. Here I was you know, kind of thinking and relating that to my work as an extension educator. Not only does your results help me in my job. but also make kind of gives me a little bit of a to do list as well. So one of the to do list is, I have had at least one opportunity to speak to those in the Renderers Association about biosecurity. So whenever I have data, such as like what you have gotten from your research here it's always good to add that data when I'm speaking to various groups.

so, yeah, this is really good that you're able to, like You said at the beginning to learn more information about Seneca virus A, and how the biosecurity relates in terms of its spread throughout the industry. So this is this is really valuable research.

Guilherme Preis:
Yeah, I think so, too. And then, I wouldn't say that, you know you don't. I mean what you're gonna do with this information right? I'm not saying you should stop rendering, or, you know, do one practice versus the other? It's just important to know the risks there are associated with doing that right. So I mean, if you need to do to practice rendering. There are several reasons to do so. Right? Perhaps we need to be really extra careful, with how I mean the truck is entering the farm. Where our dead box is right so To help us mitigate the risk, and you know, not having these unwanted pathogens entering our farms right?

Sarah Schieck Boelke:
Right, Exactly. And now the renderers, they can kind of create their biosecurity measures so as they do visit these farms. They are also able to help the industry in mitigating these risks.

Guilherme Preis:
Absolutely.

Sarah Schieck Boelke:
So I know you've kind of alluded to it already that you have done some other research, that's looked more at biosecurity procedures to prevent the indirect transmission of Seneca virus A. Can you briefly explain a little bit more about what you did in that research and a little bit more about the results that you got from that research?

Guilherme Preis:
Yeah. So for this one. we can talk to us briefly about it. But The objective of the study was to evaluate the role of Fomites in the indirect transmission of Seneca between pig populations.

And then for the study, we had a room of experimentally infected animals, so there were animals that we infected with Seneca, and we were 100% certain that they were shedding the virus.

We then had 3 other treatment groups with 3 replicates each. So we had a low Biosecurity group in 3 different rooms. So we had low by security room number one, low by security room number 2 and low by security room number 3.

So for this group, it basically meant that we would be going into. First we would go into the infected room with infected animals. We would spend 20 min with them, and then we would just walk straight into one of the low biosecurity rooms without changing any clothes, you know, changing gloves, our boots, without washing our hands, without doing anything. We're just walking straight to them. And then we would handle the animals, and then with that we, could evaluate. If the animals in the low biosecurity rooms would be infected with the virus or not. Right

And a difference between a low by security and the other treatments was that for the medium, biosecurity treatment, for instance, we would change our clothes and our boots and also our gloves going into the medium biosecurity rooms.

In the high biosecurity group. we would have to leave the infected room. Shower completely, change everything that we were wearing, right? Then wear a new overalls, new boots and new gloves, everything, and then going to the high biosecurity rooms, right? And we would also be able to evaluate if these animals got infected or not. And then, before we would enter any of the biosecurity rooms, we would swab our boots, our coveralls, and our gloves. For instance, this to see if they were still positive with Seneca

The infected group. Then, as I said they were. They were infected at day 0, and then we had 9 movement events that happened from days to today's 10 post inoculation of the infected group. And then we started doing this, moving between the infected and the low, medium, and high biosecurity groups.

And then we found that the virus it was was successfully transmitted to pigs in all of the low biosecurity room so low biosecurity, 1, 2, and 3 pigs from all of these rooms were infected. While all the pigs, from all the medium and all of the high biosecurity rooms they remain negative for the entire study.

So it really show that Seneca can be directly transmitted, indirectly transmitted, sorry between pig populations through Fomites, the fomites being, you know, the people carrying it through their boots, gloves, overalls, for instance, right.

And when I completed the study I immediately thought of the risk, analysis, portion of the prevalence study that I talked about before, where you know the sow farms that reported having more biosecurity measures in place, had lower odds of previous exposure. So that model that study with this study now showing that the only the pigs in the Low biosecurity group, so pigs that were exposed to the clothes and boots and gloves that were, you know, that were used in the same room of the infected animals, right? These animals got infected. So this shows that this standard biosecurity works, and then we need to keep working hard, to improve the biosecurity on all of our farms to keep all these bugs out.

Sarah Schieck Boelke:
Thank you for further explaining that, because it sounds like that was another great project as well, that you were able to learn a lot of valuable information to share with the industry.

So to wrap up our discussion here. are there any closing remarks that you would like to make at all. I don't know. Maybe there's something you forgot to say, or you wish I would have asked you.

Guilherme Preis:
I'm only gonna be repeating myself right now, but I mean, it looks like we have a lot of susceptible farms, so more susceptible farms and infected farms.

This can be true, maybe for the case of Seneca virus. But it's also likely true for many other diseases. Right? So I don't think that anybody would argue that we have to, you know, keep pushing and working to keep this pathogens or these diseases from entering our farms. Of enemies, any animal species that you we're working with. Right? So for the sake of animal welfare, even food security, or even for economic reasons, right? It's important to keep diseases out.

So we already have a lot of information about different ways to protect our farms. So again biosecurity again. Right? So let's keep pushing biosecurity and protective our herds from diseases.

Sarah Schieck Boelke:
Well, thank you, Guilherme, for sharing your research on Senecavirus A seroprevalence in U.S. pig farms and biosecurity procedures to prevent indirect transmission.

And I know for those folks that are listening if they are interested in reading Guilherme’s paper that he has published on the seroprevalence work. That was published in the Frontiers and Veterinary science. I will give that citation in the show notes, so folks can find that there.

But lastly, I'd like to thank everyone for listening to the University and Minnesota, Swine and U podcast. Once again, this has been Sarah Schieck Boelke, Swine Extension Educator with Guilherme Preis. who is a recent graduate of the University of Minnesota's College of Veterinary Medicine

To further connect with University of Minnesota Swine Extension, please visit the swine-specific webpages on University of Minnesota Extension’s website at www.extension.umn.edu/swine, and on those pages you will find connections to our blog as well as our Facebook page.

To learn about research being done by our swine faculty in veterinary medicine please visit their Swine in Minnesota blog, which can be found at www.umnswinenews.com.