Minnesota's Swine & U

Sarah Schieck Boelke:
Hello, and welcome to Minnesota's Swine & U podcast series, a University of Minnesota Extension swine program. Today's podcast is another research update on the topic of PRRS virus variance infectivity.

My name is Sarah Schieck Boelke, your host, and I am a swine extension educator with the University of Minnesota. Joining me today is second year Ph. D. student, Marcelo Malini. And, like I mentioned, he is a Ph.D. Student in the Department of Veterinary Population Medicine.

To get us started today, Marcello, will you tell us a little bit about yourself, including who you are working with on this research project.

Marcello Melini:
Well, thank you for the invitation, Sarah. I'm currently working with Cesar Corso who is my Advisor on our own PRRS projects. I'm also helping part time with the Morrison Swine Health Monitoring Project Group. And they have also their own projects, which sometimes I get the chance to help.

A little bit more about me is, I was born and raised in Guatemala, so Central America Country. There I got my degree in veterinary medicine. I also got a Master's degree there and before I came to the University of Minnesota, I also work for several years in different swine related companies and farms to improve the health status or management and production of the pigs.

Sarah Schieck Boelke:
Thank you. So, what ultimately attracted you to a Ph. D. program here at the University of Minnesota.

Marcello Melini:
That's, I won't say like a funny story, but it's interesting story in I was just working at this company back home and there was this veterinarian that is a consultant for the company. And when I was driving him around and he told me you should apply to graduate student program in University of Minnesota.

Do I really qualify for this? You have the qualifications. Just apply. Then COVID hit and I had to pause that idea. And the following year I said, No, I'm gonna apply again because I really want to improve and help our industry. I do like this industry. The swine industry to me is extremely interesting. There's a lot of things to improve. So that's what I wanted to focus on. So, I came here to University of Minnesota on a master's program and after that work was discussing with Cesar. And he asked me, do you want to pursue a Ph.D. program?

And I said, yes. So, I switched recently around May we made the switch from the master's program to a Ph.D. program.

Sarah Schieck Boelke:
Yeah first question is always my favorite in asking graduate students. Because, yeah, everybody takes a slightly different path to their graduate program here at the University of Minnesota. So thank you for sharing that.

Marcello Melini:
My pleasure.

Sarah Schieck Boelke:
So now we'll get to yeah, what we plan to talk about here. And that's your research. So can you share a little bit about specifically, what topic will you be talking about today in terms of your research?

Marcello Melini:
I'm going to share information about one of the projects we concluded early this year. And this project addresses infectivity of 3 PRRS viruses. And this experiment and project include the recent 1C-4-4 variant. Most swine producers, I think, have heard about this. I hope if they have encountered it, they have control because it just behaves differently than the other viruses.

Sarah Schieck Boelke:
Yeah, So it'll be interesting to hear what you have to say. Because, yes, I've heard from folks in the industry that yes, that that variant does react and respond a little bit differently than other PRRS variants that we've had within the industry.

Marcello Melini:
Yes, that's a general consensus that PRRS is a nasty virus. It always behaves differently, but this variant just went over the limit. And just took everyone by surprise. So that's one of the reasons. We wanted to address this subject.

Sarah Schieck Boelke:
So before we get too far here on our conversation, I would like to give recognition to your funding source, because, after all, research that is done at the University of Minnesota, or any other location, whether it be within other universities, we rely heavily on that funding source. So, who funded or what entity funded your research project?

Marcello Melini:
We have the funding provided by the Rapid Agricultural Response Fund. And so this fund aims to help researchers from the University of Minnesota to respond to urgent issues and challenges that the State’s industries face regarding agriculture and natural resources. So this funding really helped us obtain the pigs for the project, pay for the housing, and the feeding of the animals, also to purchase the materials, to collect the samples, and also the money to test the samples. It really helped us.

The duration of the project overall was one and a half years. So we couldn't do this unless we had this support from the Rapid Agricultural Response Fund.

Sarah Schieck Boelke:
Yeah, thank you for sharing the fundings source, and then also sharing as well the specific components of the project that that funding was able to cover.

So now let's dive in to, further into your research. Can you give a brief introduction to your research study and explain why it was a valuable project to do?

Marcello Melini:
Sure. Well, since this virus that causes the causes PRRS was first described in the early nineties. The swine industry over the world, and also in the United States has seen the emergence of different type of variants that depending of the source say that it can cause severe disease, severe lesions, or can be easily transmitted, depending on the type of strain or variant. But in the fall of 2020 there was an increase in wean to market mortality that was associated with this new virus that was classified as an LC 1-4-4 variant. And in the cases that were studied, 91% of them were positive to this variant. And producers, and again, veterinarians in the swine industry were describing it is behaving similar between farms, even though these farms are not close, and between them there's no relation, but the signs, lesions. Everything is quite similar, and it's hitting us hard, even though we have strict biosecurity measures. It’s just going past them and we don't really understand why. So from this we try to address the situation and to see, okay, if this really is this virus really behaving the way it's being described in the field?

So from this we said, Okay, let's compare this variant to other two known viruses, especially one that was in the past. Also a concern by itself. I'm talking about the L 1A 1-7-4, around 2014, 2015. It was also
high concern about this virus. Still a concern to the producers, of course, but the 1C. 4-4 variant has taken over that. But we expect that with this information of this comparison of if it's more infectious, or if it has more effectivity, and can we really assess or say every time a new variant emerges, that is of concern to the industry, is really worse. And also with this information I hope we can improve biosecurity protocols in farms. Cause ,that's the first thing we need to assess, I believe.

Sarah Schieck Boelke:
So now, can you explain? How did you complete this research project?

Marcello Melini:
As I mentioned before, this study took around one and a half years, a little bit more, but just experimental part took us around 6 months to be completed. So we, in during this 6 months we divided the experiment in 3 stages or 3 main groups. Each one of these groups corresponded to a specific PRRS virus for example, the first group correspondent to the L 1A 1-7-4. The second group to the lineage 9, 1-4- 2, that is also known as the Minnesota, 3,100. This was used as a reference virus. And the third group was the L 1c. 1-4-4 variant.

So for each group we allocated 36 pigs. They were purchase for a local vendor in Minnesota and pigs were ELISA and PCR Negative to PRRS. They were the same age, and this 36 pigs were divided into 6 groups. But 5 of these groups were to be intranasally infected with a specific dose of the virus. And so we have a group that were that came infected with more viral particles and then diluted until the final group have fewer particles. Then for the last group. It was just a control group that we sham manipulated.

Also, I would like to mention that each one of these subgroups was in their own room. They didn't have contact between groups. And also inside their room each one of the pigs was allocated in their own individual pen. So, even though they were in the same room. They didn't have contact with their neighbors And this was because we didn't want to the pigs being infecting other pigs. We wanted to a. If there was an infection present, it was because we caused it, and not because other pigs caused it. So we have a better evaluation for them.

So this experiment for each group lasted 35 days approximately. During that time, we collected different samples, such as blood, nasal and rectal swabs. And again we follow very strict biosecurity protocols inside of the rooms. We had to change gloves, bonnets, the face mask. Everything was changed between animals. To ensure that we weren't contaminating and reinfecting or infecting negative pigs. And day 11 post-infection we randomly selected 2 pigs from each of the subgroups to be euthanized. So we can collect a specific organs and tissues to assess if there were pathological lesions.
and the euthanasia process was repeated the final day just to end as an end point to this group.
Then their rooms were washed and disinfected. For a whole week there was a downtime. After that the next group came, and everything was repeated again, washing and disinfecting, and the last group came into the facility. And after that it was just testing the samples.

Sarah Schieck Boelke:
So how many times did you replicate? Was it just those 2 groups that you had?

Marcello Melini:
In total there were the 3 groups, including the one that is including the control group. That is the Minnesota 3,100. So 3 groups in total.

Sarah Schieck Boelke:
Thanks for clarifying.

So what were the results of your research?

Marcello Melini:
They are interesting results. We found that comparing this variant with the reference strain, the L 1c 1-4-4, needs fewer virus particles to successfully infect at least half of the pigs by day 4. Even at day, one after exposure, But we're now analyze at day 4, and we can see this, I won't say huge difference, but a significant difference in the amount of virus that is needed to infect the pigs. So from this we can say, yes, it's more effective. Also between the reference group and the L 1A 1-7-4 there is no difference in the amount of virus particles that are needed. It is basically the same amount that has been described before by other projects. There's no change there.

But when assessing the nasal swabs and the rectal swabs to assess vital sharing through 30 days. We found that even between subgroups, I mean the ones that had higher virus particles and lower virus particles, the behavioral was similar. They shed continuously or intermittent during the 30 day period. Some pigs may last a couple of weeks. Some pigs may shed through the 30 days. So that was not unexpected. But it was unexpected that the 3 groups the behavior was similar.

And finally, in histopathology what we all know PRRS will affect the lung. But in in this case all of the pigs that were infected with the 1-4-4 variant had lung lesions that were severe. And most of these pigs also had brain lesions and heart lesions. Even though clinically, the pigs seemed fine during the first week of the infection. Yes, they were depressed, there was fever, anorexia but other than that you couldn't see a huge change in the pigs.

And to find lesions in the brain was, although it has been described but most of the pigs with this variant had presence of these lesions compared to the other 2 groups which may be one pig overall have these lesions. So I think this is also an important finding, just to assess furthering in histopathology.

Sarah Schieck Boelke:
So based off of these results that you shared, what conclusions can be made from your research?

Marcello Melini:
Well, I think special attention needs to be paid to merging viruses, especially PRRS viruses that are being perceived as more infective, more virulent, more pathogenic.

For this study. Again, we found that the latest variant of concern to the swine industry. Again, the L1c 1-4-4 variant does really need fewer viral particles to infect the pigs.

But the sharing of each one of these evaluated viruses, either through the nasal or fecal route, is similar, and it can be either continuous or intermittent. And even though it has been described before, in other projects from even the nineties, leasions in the brain, heart, and lung were present in all of the pigs that were infected with the variant compared to the other two compared viruses.

We can pinpoint that this variant is something else. It is really causing something different to the industry.

Sarah Schieck Boelke:
So to go along with that, can you explain why these results that you shared are important takeaways for the industry?

Marcello Melini:
I think the results from this study help us understand more about the dynamics that a new variant has under experimental conditions. But we also need to find a relation to what producers and veterinarians keep seeing on farms, because, again, under experimental conditions these pigs were just PRRS positive. But we know that in farms there's also help from other pathogens. Maybe there's influenza maybe there's another bacterial that is grabbing its opportunity to do more damage. That's maybe why it's seen. Farms are seeing it worse. But knowing that it takes fewer amount of bioparticles to have positive peaks means that we need to reevaluate some of the by security practices we have in place in the industry. So in order to improve them and minimize the risk of introducing these types of viruses in the farms. We need to look again at what we're doing. Just combine what we're seeing in these type of experiments to what we have in biosecurity terms.

Sarah Schieck Boelke:
So lots of important takeaways for the industry. So to wrap up our discussion today is there anything else that you would like to comment about whether it's something you forgot to say earlier, or if there's just, yeah, an important takeaway that you found from this research that you would just like to to stress to producers.

Marcello Melini:
Yes, thank you. I believe, as PRRS viruses are adapting an overcoming host biosecurity barriers. I think we, as members of the industry and academia also need to adapt and challenge the place protocols and the place knowledge that we have. Having more understanding of this virus can mean having better tools, and not only to prevent the introduction, but also the dissemination and the increasing cost of elimination. So, This means not taking everything for granted, and just don't accept everything that we have in place. We need to test better solutions or just challenge what we know in order to improve the interest, the overall industry.

Sarah Schieck Boelke:
And, as you mentioned about biosecurity, I'm assuming, as well, you know, not to become complacent on those biosecurity protocols that you know, making sure as we're entering those barns and interacting within those barns that we're following those biosecurity practices that are in place in the barn because they are there for a reason, they have been shown and proven to help with disease transmission. Correct?

Marcello Melini:
Yeah, exactly as maybe the practices we have in place now worked for viruses 5, 10 years ago. But we're seeing that these viruses are adapting to the environment are adapting to the host, to our practices, and they are how we say, updating themselves continuously. And we are just, I wouldn't say, all of us, but if we are stuck with the same practices that we have had for several years, and just as you mentioned, just complacent. And say, no, I have biosecurity measures. But maybe they're outdated. We need to review them constantly and say, maybe this way of doing this thing or this particular thing, is not the best way to go to prevent the introduction of this virus. Update is what we need at the moment, I think.

Sarah Schieck Boelke:
Very good. Thank you for sharing all of that. And thank you for sharing your research on PRRS virus variance infectivity.

And I'd like to thank everyone listening to the University of Minnesota Swine & U Podcast. Again, this has been Sarah Schieck Boelke, swine Extension Educator along with Marcelo Malini, Veterinary Medicine Graduate student.

To further connect with the University of Minnesota Swine Extension. Please visit the swine specific webpages on University of Minnesota Extension’s website at www.extension.umn.edu/swine. On those swine 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 at Www.umnswinenews.com.