photo of a pile of dried sausages

The Round Barn:
How does human behavior impact the spread of African Swine Fever (ASF)?

African Swine Fever is a borderless problem in the swine industry. Dr. Lowe explains the transmission, impact, and lifecycle of ASF
as the U.S. swine industry faces increased risk of exposure in this episode of the Round Barn.
Listen in as he answers Dr. Mitek’s questions regarding if humans can get ASF, how to eradicate the disease, and at what costs to a culture.

A transcript of this episode is available below.




released October 21, 2021

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Dr. Ashley Mitek: Do you know anybody in the College that may know anything about this thing called ASF? Because I keep getting emails every day about it.

Dr. Jim Lowe: A… S…F? Yeah, no, I know. Dan Rock, who's in Pathobiology, is probably one of the world's leading experts on ASF. He's probably infected more pigs with ASF than anybody. But I've dealt a little bit, maybe more than a little bit now, over the last few years, particularly in Eastern Europe, in some work I do. It's a fascinating disease, and certainly devastating both for the pigs and socially. So, we should chat about that. It sounds pretty interesting.

Welcome to The Round Barn.


Dr. Mitek: So, can you talk to us a little bit about, ASF, what does it stand for, and what the heck is it?

Dr. Lowe: ASF is African swine fever, and not surprisingly, it originated in Africa, Sub Saharan Africa in particular. And it is a really old disease. And it's cool, because it's the world's largest virus that we know of. It's this giant DNA virus, which means it's genetically very stable, it doesn't change very much. And it's endemic in Africa. And it has been-

Dr. Mitek: What does it mean when you say it's endemic in Africa?

Dr. Lowe: Pigs are infected in Africa all the time with African swine fever, but the herds tend to be - they're smallholders in Africa, so there's small herds, and so there's kind of low rates of transmission. And it is a concern, right? If you talk to people working in that space - and we've got some people here that that, you know, they're from Africa or spent a certain amount of time working in Africa, in those food systems - it is a significant drag on economies in southern Africa, because pork is a largely consumed meat there. Pigs can forage, they can eat stuff that humans can't eat, it's easy to keep them in close contact. So, pigs are an important part of the food chain in that part of the world.

Dr. Mitek: And you're saying they're raising pigs very differently than how we would raise pigs in the U.S. They're essentially eating trash or leftovers, or things like that?

Dr. Lowe: That's exactly right. They're eating scraps and foraging, roots and other stuff. And I guess, smallholders are, you know, a family has a sow. Very much a recycling mentality to maintain the food chain as opposed to here, right, where we raise things commercially.

Dr. Mitek: So, if there's one pig on a family farm in Africa, how many pigs would be on a family farm here in the U.S.?

Dr. Lowe: Well, the typical farm in the U.S. - and we're talking breeding females, so sows - I mean, we kind of think of a farm today as 5,000 sows. The U.S. and Western Europe are clearly industrialized. We're much larger in the U.S. here than they are in Western Europe. And then, Brazil would very much mimic the U.S. And then you're seeing the same thing in China. So, there's progression for pigs to large industrial complexes. It has a lot to do with efficiency. And believe it or not, these big complexes are much better for greenhouse gases, because we use less corn and they use less food, and so we raise them much more efficiently.

So, very different deals. And so, in Africa, we've got these subsistence farmers raising pigs basically for their own consumption most of the time. That's where most of the pigs are. Very few commercial farms in Africa. And then, we only care about it - or, it's made the news - because it was introduced to the Republic of Georgia - not the state of Georgia - in 2014. I may have the date quite wrong, now that I think about that. But, 10 years ago, ish, it was introduced to the Republic of Georgia. And it has spread across Eastern Europe from there.

Dr. Mitek: How did it spread?

Dr. Lowe: I'll talk about that in a second. It spread from Eastern Europe, then into China. So, the first question is, how the heck did from Africa to Georgia? The interesting part about ASF, and why we're so concerned about it in the United States, is that ASF survives in meat. So, most viruses die when the host dies. African swine fever is exactly the opposite. When the host dies, the viruses in a happy place.

Dr. Mitek: I thought I read something, that ASF can stay alive or transmissible in meat even after it's been cooked or cured.

Dr. Lowe: Correct. And that's the risk. It'll live in dry sausages - pepperoni is a dried sausage, salami - for years. In the freezer, we think it's basically stable for a really, really long... I mean, years, it's stable at freezer temperature.

Dr. Mitek: How does the virus do that?

Dr. Lowe: Well, it's big. Big viruses tend to be a bit more, you know, it's more protected. It's also how it's evolved to be... it's fitness factor. So, if we think about where it came out of, you've got small herds in Africa. The chance of contact between one herd and the next herd isn't very great. And so, the virus evolved to be a virus that, if it lived outside the host, it increased its chance of contacting another susceptible host. So, the virus itself doesn't spread between live pigs very easily. In fact, it spreads quite slowly. But in an animal that dies, that carcass is infectious, particularly in the winter, for a really long period of time.

Dr. Mitek: So, how do you kill it if you can't kill it by cooking meat? That seems like the way we kill all viruses, is you just light it on fire, and then it's dead.

Dr. Lowe: You can kill it in meat if you cook it at almost twice the boiling temperature of water. So, you've got to nuke it. And so, that's one of the challenges. So, the strategy is, we don't want to consume, we don't want contaminated meat in the food supply chain. Because if we have meat in the food supply chain, if we butcher and process infected pigs, the meat out of those pigs is infectious. And if you think about what goes on, if I'm feeding pigs scraps, then the scraps that are left over from the meat gets fed back to the pigs, and I infect a new population.

Dr. Mitek: Can a human get sick from ASF if they eat-

Dr. Lowe: Absolutely not. No other species we know of can be infected with ASF. Now, if you eat infected pork, you will shed it, the virus, because not all of it dies in our digestive tract, either. So, if I feed infected meat to a dog, and that dog goes to the next village and defecates, the pigs that interact with that stool could be infected.

Dr. Mitek: Oh, wow.

Dr. Lowe: This stuff is tough. I mean, it really lives in the environment a long time. And that's its key survival tactic, is surviving outside the host. So, it's an interesting bit about the virus. And I've spent a fair amount of time in Eastern Europe, and certainly I've got friends and colleagues and clients there-

Dr. Mitek: You have friends?

Dr. Lowe: Don't tell anyone, it's a secret.

Dr. Mitek: [laughs] I'll be one of your friends, Jim.

Dr. Lowe: You’ve got to go to a foreign country. But, as you look at, you know, what's happening there, Eastern Europe is different than Western Europe culturally.

Dr. Mitek: What do you mean by "they're different culturally"?

Dr. Lowe: Pig farming in Western Europe is almost all commercial. So, the pigs are in not nearly as large of holdings as we would have here in the United States or Brazil. They're not raising pigs for their own food, they're raising pigs to sell meat to other people, for other people's food. If you think about food chains that way - am I raising food for myself, or am I raising food for other people? So, Western Europe, the United States, you know, most of Brazil's production, and Chinese production today, is making food for others. We've industrialized agriculture. That's how people can move to cities, because 2% of the population feeds 98% of the population. That's what happens in the U.S., right? There's less than 2% of the people working in agriculture today that feed the rest of this country and big chunks of the rest of the other countries. That's what goes on in Western Europe. The percentages aren't the same, but basically, where you've got urban areas, that's what goes on.

In large parts of eastern Europe, you still have people raising pigs in particular for their own food. And part of that is just sustenance, like, they need that food. But a bigger part of that in Eastern Europe - because there's plenty of food available. I mean, as the Wall came down in '89, there's plenty of food available in Eastern Europe. Plenty of pork available. And pork is a huge part of their diet. And pork is the most commonly consumed protein around the globe. It's an important part of our global protein chain. In Eastern Europe, there's really a cultural aspect of that pig.

In Romania, and the farther south you get in Eastern Europe - you see some of it in Poland, almost none in Germany, but I've spent a lot of time Romania, Moldova, Hungary - there are still small villages. And those small villages typically have pigs. And they raise those pigs to eat, but it's very much tied into the winter/Christmas tradition. So, they raise these pigs, in early December they'll butcher these pigs, in very much a community thing. It's very much a community event, all the wonderful products that they make in that part of the world. Head cheeses, different sausages, blood sausage, etc, etc. And then, that becomes part of the Christmas celebration, but that also becomes gifts that they share between villages, or gifts they share with friends, or gifts that they send to others in other parts of the country.

Dr. Mitek: Gifts with a little gift inside, it has a gift of ASF in it!

Dr. Lowe: That's right. And so, that's the concern. And so, as we look at that, that's why they've spread - well, we believe that there's two things. One, we've spread virus around within the domestic pigs. Let’s talk about Europe having three pig populations - commercial pigs, which are housed and reared like we do here, we're making food for others; domestic pigs, where they're raising food for themselves, or, in this case, cultural things for themselves; and then, the third big bucket is wild pigs or wild boar. So, the European wild boar is all over in Europe. We have feral pigs here, we don't really have wild pigs. We have domestic pigs that have gone wild. The European wild boar is actually a separate species. It's not a commercial pig we raise. But, he's susceptible to ASF, just like domestic pigs are.

So, what we know is happening in Eastern Europe is, the virus is spreading amongst these backyard pigs, these village pigs. And it spreads with meat. And then we throw out the infected scraps, and now we get wild boars infected, the wild boar population. And it's not just males, it's the European wild boar, there are obviously females of those because they make more. But, the wild boar population gets infected. So, if you look at the maps in Poland, it's pretty interesting, and we've done a little bit of that mapping here, you see the virus moving, or new cases of the virus moving, in domestic pigs along a kind of a steady path, but then it jumps to the next village.

Dr. Mitek: And that's from the wild pigs?

Dr. Lowe: No, it's from food.

Dr. Mitek: Oh, from food, from somebody sharing.

Dr. Lowe: It jumps hundreds of kilometers. And then, from that point, you start to see the wild pigs reinfected.

Dr. Mitek: Oh, and then the cycle just probably keeps propagating itself and spreading further.

Dr. Lowe: Right. The cycle propagates itself. And so, the wild pigs, the wild boars, and the domestic pigs have a lot of interaction. And then, we've seen commercial pigs infected, particularly in southern Europe, particularly in Romania, where the outbreak is basically not under control at all, we see these commercial pigs being infected because you have food, again, coming into those farms, and we get contact that we don't understand, the virus is transmitted by ticks, it's transmitted, they think, by mosquitoes. As we put enough pressure, we don't have good enough biosecurity to keep virus out of commercial farms. So then, we start impacting commercial farms. Which, remember, they feed other people. So now, we're starting to put the food chain in some of those countries at risk, and we're forcing them to import meat. So, Romania would have been self-sustaining on pork, but they have to import a lot of pork now, because they've continued to depopulate their commercial farms in the face of ASF outbreaks.

Dr. Mitek: So, as an infectious disease person, I'm sure you look at this as a black-and-white type situation, right? Like, you want to control the disease, you want to stop the spread of it. But then, there's this really interesting cultural aspect to it. We ran into this with COVID, right? When people we were told, "Don't socialize, don't get together for Christmas," that goes against our culture as Americans, and I guess as humans, maybe. Depending on where you live, there's certain things we want to do. I guess my question for you is, how do we stop this, if part of the spread is people doing what's normal in their culture? They don't want to stop doing that. I don't want to stop people from sharing their pork products at Christmas, right?!

Dr. Lowe: I was told a long time ago, probably in vet school, that public health or population disease management - public health is with people, and we do it with... it's all the same, scientifically. It's all the same. But, it was the intersection of science and politics. And I think that's wrong. I think it's the intersection of science and sociology. How do societies function? And any of these decisions we make with respect to disease control - two-legged disease or four-legged disease - there has to be societal acceptance of what's going on, and the consequences of controlled or not controlled.

So, yeah, let's just take Romania, which I have probably enough knowledge about to understand what's going on. It would be very simple to say we should go depopulate all village pigs. We know where they're all at. It's Europe, they're reasonably tracked. We know where they are, we should just go depopulate all those village pigs. There aren't that many wild boars in Romania, it would be fairly easy to clean it up after that, and the country would be absolutely free of ASF. Could it be done? Absolutely.

Dr. Mitek: To wipe out the entire swine population of one country is a possibility?

Dr. Lowe: Except for the commercial pigs, because we know how to protect them.

Dr. Mitek: Okay.

Dr. Lowe: So, we go take all the backyard pigs, village pigs. Their wild boars are not that big a deal.

Dr. Mitek: How do you confine a wild boar?

Dr. Lowe: They trap them. There are wildlife people that do it. I don't understand. But, they could cull that population. We’ve seen that done in Germany, although it failed a bit. But, is there a scientific path forward? Absolutely, there's a scientific path forward. The challenge is is that, that's not going to be very well accepted by society. Because it's so deeply ingrained in their culture, right? And so, to come in and say, "We're just going to wipe all these things out," without a plan B, is not going to be accepted. So, if it's not accepted, guess what? They're going to go hide pigs. They're going to avoid-they'll move pigs around, right? I mean, humans are much more creative than we... you try to control them, right, it's like, even the dog will outsmart you most days. And so, it's a pitch that we probably can't force it down their throat. And so, it has to say, how do we have a plan, how do we have an alternative strategy, how do we work within the social structure? Because it's a short-term pain versus a long-term gain strategy.

If you look at the consequences, just maybe in Romania, you could easily see, we're gonna protect this short-term sociological normality that we butcher these pigs at Christmas, and we damage the country's long-term. Conversely, I could reverse that and say, well, we have to protect the long-term feeding of the country, but I'd deeply damage the cohesion of the society. The societal bonds, the common story of Romania.

And so, both of them have a real crappy long-term outview. And so, it's figuring out, how do you balance those things? And I think those are the discussions we're not very good as professionals and sociologists to have. And if I just had a wild dream in life, it would be, how do we engage sociologists more in medicine, both veterinary and human, to say, how do we understand those cultural norms and traditions better and balance that? It doesn't mean we just roll over. But, how do we pitch our message in a way that helps people understand and balance those two bits of science betterness versus sociology betterness?

Dr. Mitek: Right. Yeah, I think that as a young clinician, I was all about the science, and the black-and-white, and the facts, and what's the disease, and what's the treatment? And now, I realize, I think most veterinarians realize, there's an art to it, and there's a sociology aspect to it. We really can't accomplish our mission without at least acknowledging it exists.

When we talk about ASF, and then monitoring it, there's been, at least I keep getting email notifications about, everybody's worried about it coming into the U.S. Why is everybody so worried that what's going on in Romania, what's going on in another part of the world, is now going to have such a significant impact on the U.S.?

Dr. Lowe: It's purely economic.

Dr. Mitek: It's money, as it always is!

Dr. Lowe: It always is. It's always the dinero. Well, I think there's a couple of things. One, so the World Organization for Animal Health, OIE, which is the animal equivalent of the WHO, we've all signed on to those treaties. And so, we've agreed that there's a certain set of diseases that are called reportable, meaning if you have those diseases, you basically cannot export meat. So, in the case of the U.S. with African swine fever, foot-and-mouth disease, or classical swine fever, we don't have any trade restrictions today in the U.S. because we're free of these reportable diseases.

Dr. Mitek: And we export a fair amount of the pork produced in the U.S.?

Dr. Lowe: Yeah, a lot.

Dr. Mitek: Where are we sending it to most of the time?

Dr. Lowe: All over the globe. Mexico's our biggest partner. Mexico, as you would expect, they're close, they'd be our biggest trading partner. But, bits of the globe take different bits of the pig. We send a lot of stuff to Asia that we wouldn't eat here in the United States. We send pig tongues to Asia.

Dr. Mitek: Have you ever had a pig tongue before?

Dr. Lowe: No. They put it in soup. I don't know.

Dr. Mitek: You don't lick it?

Dr. Lowe: No, you don't lick it. Because, again, it's sociology. There's demand for these parts. And so, if I'm going to make this one tongue, and if they kill X number of pigs in Vietnam, and there's demand for more pig tongues than what they can make in Vietnam, we can export those tongues to Vietnam to fill that market need. So, that's a great part about global trade. There's a lot of drawbacks to global trade, but one of the great parts of global trade is that we can meet market needs and create value out of things that, in our market, aren't worth anything, and there are worth a ton. By the same token, they're not buying bacon. That's not part of their... So, we need the belly. That's great. We'll eat our belly and ship parts and pieces to them that we don't need, and we create value. We don't pull meat back from Asia because of their ASF and CSF and all these reportable diseases positive, so we don't import pigs in the United States. Or meat in the United States.

Dr. Mitek: We don't import any meat?

Dr. Lowe: No, we import, but not from Asia. We don't import from Asia. We import from Brazil and other spots across the globe that are free. We import from Europe, Danish hams, etc. But we have equivalent disease data. So, there's no sanitary requirements that we can't import. So, the problem with ASF is is that it would immediately cut off our exports.

Dr. Mitek: So, if we had a positive pig anywhere in the U.S., whether it's a potbelly pig or it's a commercial pig, it's essentially going to...

Dr. Lowe: Kibosh exports. Until we can prove we've eradicated it. Or, we could zone the country and say we have supply chains that are certified free, regions that are certified free. There's a lot of work going on in the background, we've been very actively involved with that, saying, how do we get to a position, if it shows up here, that we can maintain exports, if it's in one small part of the country? It's a big country, how could we divide the country up and make that happen? So, how that works, that's still up in the air. But there's a lot of work going down that path.

The concern is - I presume why you're getting emails - that ASF has been introduced into Hispaniola, the DR, the Dominican Republic. And so, ASF is in the Western Hemisphere now, which is a big deal. And if you've seen the stories, right, there's a lot of movement from those islands into Central and South America. And there's movement into the U.S. COVID's obviously cut a lot of that off. But we're pretty comfortable with our Customs Border Protection, that everybody's got their arm up - again, it's a meat problem, that we're not letting meat into the country.

Dr. Mitek: So, don't bring your ham sandwich from the Dominican Republic into the U.S.

Dr. Lowe: Do not bring your Dominican ham sandwich. I don't care good it is, do not bring it with you. But, Puerto Rico's right there, right? And that's part of the U.S. And so, the USDA has already moved to segregate Puerto Rico as a separation zone. So, if it would show up there, we've got protection from the U.S., we've already put all the buffers in to say that we're treating Puerto Rico as a foreign spot, that it's contaminated. It's not, it's not infected, but we've got all the barriers in place ahead of time so that we can prevent it from getting to the mainland.

I think everyone's concern is not, does it come straight from the DR into the mainland U.S. - although that could happen. I think the concern is, does it move from the DR to a country without as good of border control? And I don't mean who gets in the border, but, when you come in and those little beagles are at the airport?

Dr. Mitek: Yep.

Dr. Lowe: They're good. It’s pretty hard to get in here, except for a few borders across Mexico and Canada. Everything else comes in by plane or ship. And so, at those spots, right, we've got dogs, we've got searching, we've got x-rays on bags coming in. We do a reasonably good job of looking for all that stuff, i.e. meat. CBP has cranked it up, and we're grateful that Customs and Border Protection is really aware and work closely with USDA to protect us. But the fear becomes, what happens if it gets into the rest of the Americas? What if it gets on the mainland? What if it ends up in Brazil? What if it ends up in Argentina? What if it ends up in Mexico or Costa Rica? Once it gets on the mainland, that's a much more difficult conversation of saying, how do we stop it?

Dr. Mitek: Are the pig farms - can I call them pig farms? Is that what you call them? There's no fancy word for it?

Dr. Lowe: Yeah, yeah.

Dr. Mitek: Are the pig farms routinely doing surveillance in the pig populations in the U.S. right now? Every week, they're testing a sample of pigs, making sure they don't find ASF? How do you even look for it?

Dr. Lowe: We test routinely today, but it's all at harvest. At the time of slaughter, we pull samples, and that goes to our diagnostic lab here. We test for African swine fever and classical swine fever.

Dr. Mitek: Downstairs?

Dr. Lowe: Downstairs, yep, on slaughter samples, every week. And that happens across the globe. And the same thing goes on for foot-and-mouth disease and etc on the cattle side. The USDA APHIS has a very nice surveillance plan to pick it up. The problem is, if we pick it up there, it's probably late. So, we know we're free. And that's how we report we're free. But, we spend a lot of time, there’s been a lot of preparedness of getting posters out of, what are these diseases look like? Because classical swine fever, formerly called hog cholera, African swine fever is vesicular stomatitis, they look the same. So, "I don't know, we've got dead pigs with blisters, what are we doing," you know, etc, etc. It's hard to differentiate between those. Even foot-and-mouth disease, there are hemorrhagic fever diseases, and theoretically, could I tell them apart? Sure. But it's really raising this awareness that we could have a disease in the U.S., and it's probably gonna take some individual on a farm taking care of pigs every day to say, "Wait a minute, these pigs are dying of something I don't understand." And how do we raise that flag and get the veterinary authorities involved?

Dr. Mitek: And this isn't just a pig problem, right? It is now impacting dogs coming into the U.S. I saw that the USDA put out some restrictions about dogs, I think it was effective the middle of August - dogs being imported into the U.S. from known countries with ASF now have to follow various restrictions. Can you help me understand why that's related to ASF?

Dr. Lowe: It's all risk of them eating contaminated meat.

Dr. Mitek: So, a dog in Romania that eats a ham sandwich, and then that dog is coming into the U.S., that dog may have ASF?

Dr. Lowe: Well, the dog itself wouldn't, but again, if it ate the ham sandwich, the virus will pass through the intestinal tract. We worry about dogs eating infected carcass or meat scraps in Romania, and going to the next village and infecting those pigs when they defecate. So, that's the same concern here, that the dog itself will not be infected, they're not infectious, but they serve as a fomite, which is a fancy word for a physical carrier. And so, they physically could carry that virus. And the concern is, because dogs may eat either meat scraps - which would be very, very common, to feed meat scraps to dogs in other countries - or dead birds.

Dr. Mitek: We do that here, too, right? Probably everybody who has a dog gives them a little bit of hamburger, or pork, or whatever.

Dr. Lowe: Yeah. Meat scrap feeding back to dogs is a big concern, or if they're eating carcasses, which is less likely. But if you think about it, if you're in a country that has a bunch of dead pigs that they don't know what to do with, it might be handy to grind those up and feed them to dogs as dog food, or chop those up and feed them to dogs. So, the risk of feeding ASF-contaminated carcasses to dogs is quite high. They may not put them in the human food supply chain, but they wouldn't think two seconds about putting it in the dog food supply chain.

And so, the challenge is, remember I said you've got to cook it to 180. Even if I render it, which is what we do to scrap meat here in this country - rendering means you cook it to a really high temperature, you boil the fat off, you separate the fat from the protein that's left, the meat meal that's left. Even if you do that, that process has to be super effective. I mean, it has to get to temperature, and you can't have any cross-contamination between uncooked and cooked material. And if you look at bovine spongiform encephalopathy, BSE, mad cow disease, in the U.K., that's what happened. They were rendering cattle parts from deadstock, and some of that ended up in the cattle feed, and the rendering didn't kill the prions because it didn't get hot enough, and there was some cross-contamination. So, it's been a ban, right? We don't feed ruminant byproducts back to ruminants because of the risk of BSE. But here, I'm feeding porcine byproducts back to dogs, and I could still have ASF if I get cross-contamination in there. So, now I'm worried about the dog being infectious, coming into the country. So, that's where that risk is coming from.

And I was shocked - I've had discussions with Mark Ernst, our state veterinarian. It's not like two dogs coming in. It's lots and lots and lots of dogs coming in.

Dr. Mitek: Sure. And I know that there's a fair amount that come in through here on a daily basis that are going to be impacted by these new regulations. Do you have any other parting words of wisdom for folks that are interested in following this ASF problem?

Dr. Lowe: I would stay abreast of it. The news is a little behind once in a while. Hopefully nothing comes into the U.S. But I think this is just one more example about how we as a society have to engage in these conversations more deeply and not just argue. If COVID hasn't taught us that, maybe ASF or other diseases like this can have these discussions. Because there will be a next one. Short-term benefits and losses with long-term benefits and losses. Communicate that in an effective way that pulls society together instead of pushing it apart.

Dr. Mitek: I like that. That's a good way to end this. We all have to come together. We're all in it together, and we'll get through it all together. Well, thank you Dr. Lowe!

Dr. Lowe: Thank you, Dr. Mitek.

Dr. Mitek: All right, everybody, have a great day.

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