The wildlife trade may be speeding up the next pandemic | Science Quickly Podcast

0:13 For Scientific American Science Quickly, I'm Rachel Feltman.

0:22 What comes to mind when you think

0:24 about wildlife trade and diseases like COVID-19?

0:28 If you live in the US, you probably picture so-called wet markets in Asia where

0:33 people buy and sell animal meat in an open-air setting,

0:36 or perhaps foreign-sounding bushmeat.

0:40 But in reality, the wildlife trade is everywhere,

0:43 including at your local suburban shopping center.

0:46 And new research suggests that pathogens are spreading through

0:50 this global trade network far faster than anyone realized.

0:54 Here to tell us more about these findings and their implications

0:57 for the spread of zoonotic disease is Colin Carlson,

1:00 an assistant of epidemiology at Yale University School of Public [music] Health.

1:05 Thanks so much for coming on to chat today.

1:07 Thanks for having me.

1:08 To ask a very basic question,

1:12 why is it that contact with animals leads to new diseases emerging?

1:17 Pathogens have to have an opportunity to get to us,

1:20 and that usually means proximity.

1:22 We have to be close to another species.

1:25 We are close to animals in our day-to-day life all the time,

1:29 much more than we think we are, right?

1:30 We have our pets in our house, maybe we have that pigeon that, you know,

1:33 sits on the window outside of our office,

1:35 but we also have rats living in our buildings,

1:38 we have bats roosting in our attics.

1:41 I'm from Connecticut,

1:41 so we had flying squirrels living in our attic when I was growing up,

1:44 you know, who knows what viruses those guys have, right?

1:47 We are constantly in contact with wildlife,

1:49 but most of the time it is very indirect and it's very rare.

1:53 Wildlife trade changes that equation.

1:56 You are talking about people handling animals, butchering animals.

2:01 You're talking about moving animals thousands of miles sometimes,

2:06 and that means that people are shipping them,

2:08 they're storing them in these dense conditions

2:10 where the animals usually get pretty sick.

2:13 And in all of that, what we're also doing is we're

2:15 putting animals together in combinations that don't necessarily exist in nature.

2:21 And that means that viruses and other pathogens

2:23 are spreading not just from animals to people,

2:25 but between animals back and forth.

2:28 We're sort of turbocharging their evolution, right?

2:30 We're giving them all of these different opportunities

2:32 to just bounce between hosts until they get something right.

2:36 All of that makes it much easier for a pathogen

2:38 to get into humans in the long run.

2:40 So, you recently published a study

2:42 about the wildlife trade and zoonotic disease.

2:45 Can you tell me a little bit about how you

2:48 and your co-authors came to be curious about that question?

2:51 Sure.

2:52 We have been worried about the wildlife trade and public health for a long time.

2:56 COVID comes to mind, obviously,

2:58 with sort of this question of where did the SARS-CoV-2 come

3:01 from, but we've been thinking about

3:02 the wildlife trade for much longer than that.

3:05 You know, SARS started in the wildlife trade,

3:08 we had an outbreak of mpox in the United States back in 2003,

3:11 and of course, HIV probably started with rural hunting communities in Africa.

3:16 And so, there's always been this understanding that wildlife

3:20 trade is probably a risk to human health,

3:23 but what's been really hard is we don't know how to quantify that, right?

3:25 We have a lot of anecdotal evidence,

3:27 we have these individual outbreaks that matter a lot to us,

3:31 but we haven't had a big picture look

3:32 at what is the cumulative impact on our health.

3:35 So, that's sort of the jumping-off point for this.

3:38 And where did you go looking for that data?

3:40 So, we're doing a a very like global look here, right?

3:44 So, we're saying, "Okay,

3:45 here's every species that we know exists in the wildlife trade,

3:48 and here's every virus that we know those species

3:51 have." And we're putting those data together and we're saying,

3:53 "What does that tell us about how viruses are moving around?"

3:56 Those data are incredibly hard to get on both sides, it turns out.

3:59 We don't know a lot about the wildlife trade,

4:02 and we know even less about what viruses most animals have.

4:06 So, it's taken a long time to get enough

4:09 data to ask a question like this, but we're

4:12 finally at this point where we know enough about

4:14 some of these species that we can say, "Okay,

4:17 here are the viruses that are in animals,

4:20 and then as they spend time in the wildlife trade,

4:23 here are the viruses that are making the jump to humans,

4:26 and that's the red flag we're looking for." Yeah.

4:29 Well, one thing that I thought was interesting is the fact that, I

4:32 think you have something like a quarter of vertebrates are traded in some way,

4:37 and I think, you know, most of our listeners, you know,

4:39 will probably hear what this study is about and think like, "Oh, yeah,

4:42 bats." But can you tell me a little bit more about just how broad this issue is,

4:48 you know, what kinds of animals are we talking about, what kinds of diseases?

4:51 Wildlife trade is everywhere, right?

4:53 I think we have this idea in our head

4:55 of sort of this wet market with exotic animals, and it feels very, you know,

5:00 foreign to us, but anytime you go to PetSmart and there are geckos there,

5:05 there are tetras that come from the Amazon rainforest, right?

5:10 All of those species are that's wildlife trade.

5:12 We do wildlife trade in our day-to-day lives.

5:15 If you've ever worked at a PetSmart,

5:16 if you have watched the Joe Exotic documentary, right?

5:21 All of those tigers, that's wildlife trade.

5:23 And, you know, maybe we don't all have tigers, but, you know,

5:26 I guess more of us do than we thought, right?

5:28 But I think that idea that like a quarter of species are in the wildlife trade,

5:32 humans just interact with wildlife constantly, right?

5:36 We eat them, we turn them into products, we keep them as pets.

5:39 There are so many different ways that we are interacting with animals,

5:42 and there's sort of no limit to how [snorts] many species get pulled.

5:48 Yeah, so what other misconceptions do you think the public

5:51 has about the relationship between wildlife trade and disease?

5:54 I think that there is this common idea that all

5:58 we have to do is just ban the wildlife trade, right?

6:01 That this is a simple problem that exists somewhere else, when in reality,

6:05 it's a here problem and it's an everyone problem,

6:07 and it's probably not going away.

6:09 One of the things that I think a lot of people

6:11 don't know about wildlife trade is at the international scale,

6:14 it actually looks a lot like climate change or deforestation,

6:19 where a lot of the impact is falling

6:20 on biodiversity in tropical countries in lower-resource communities,

6:26 but it's driven by economic demand from [snorts] the US and Europe and China.

6:32 And that means that, first of all,

6:34 we have a role to play in reducing demand, right?

6:37 It's not just another people problem,

6:38 it's an us problem, it's an everyone problem.

6:40 But it also means that we are probably

6:42 not able to just ban wildlife trade, right?

6:46 What happens when we do that is we push trade underground,

6:49 and this has been seen again and again over the last few decades.

6:52 Every time we get really worried about wildlife trade,

6:54 we go and we scramble and we try to shut it down, and it just doesn't work.

6:59 Can you give me a sense of the scope

7:00 of the data that you guys were working with?

7:03 Sure.

7:04 So, what's really special about this study is that we

7:07 have more data than we've ever had on animal pathogens.

7:11 So, not just viruses, but also bacteria, fungi, parasites,

7:14 there are worms that come from animals to humans.

7:18 And we have more data than we've ever had in one place on wildlife trade.

7:21 So, we're looking over about 40 years of trade.

7:25 The wildlife trade has changed dramatically in that time.

7:28 If you think about 100 years ago,

7:30 we're talking about rural communities living off of wild animal hunting.

7:35 But wildlife trade has become not just international, but industrialized, right?

7:41 We have wildlife farms at a scale that we've never had,

7:44 and that's the mink farms in the US and it's fur farms in China, right?

7:48 All of that is a relatively recent thing

7:51 on the time scale of humans sharing viruses with animals.

7:56 Hm.

7:56 So, let's get into your results.

7:58 What did you actually find when you looked at this data?

8:00 Turns out that diseases are spreading

8:03 in the wildlife trade much faster than we thought.

8:06 Wildlife trade is this incredibly intense process,

8:11 diseases are moving very quickly,

8:12 and so what we found is that just being in the wildlife trade makes it about

8:17 50% more likely that an animal hosts

8:20 a pathogen that poses some risk to human health.

8:22 Wow.

8:23 You know, again, wildlife trade is sort of ubiquitous within mammals, right?

8:26 So, it's actually quite striking we get that strong a result.

8:29 And then the part of the study that I just think is so cool,

8:32 there's always a possibility, right, that this is just correlation.

8:36 So, if you think about some of the species we trade a lot,

8:39 there are a lot of primates in the wildlife trade.

8:42 We also share a lot of pathogens

8:44 with primates not because of the wildlife trade,

8:47 but just because their immune systems look like ours.

8:50 It's very easy for diseases to move back and forth.

8:53 That's not necessarily causal, right?

8:55 So, how do we disentangle those things?

8:57 Well, the trick here is for most of these species,

9:00 we know how long they've been in the wildlife trade,

9:03 and that gives us the smoking gun.

9:05 So, for every 10 years that a species is traded,

9:08 on average, about one more pathogen makes the jump.

9:12 Think about that versus like 10,000 years of livestock disease, right?

9:16 It's so fast, and we wouldn't see that pattern if there weren't something

9:21 dramatically different happening in the wildlife

9:23 trade than in any other setting, really.

9:27 So, do you have any thoughts on what we should be doing about this?

9:31 Wildlife trade is a hard problem to solve.

9:32 I've worked on it for a long time.

9:34 I have for a long time been one of the sort of dissenting voices on, you know,

9:38 we shouldn't just be rushing to ban everything,

9:40 and that's because I don't want to see trade get driven underground.

9:44 One thing that we find in this study is that black

9:46 markets actually probably make all of these problems even worse.

9:50 So, species that are illegally traded are

9:53 actually sharing even more pathogens with us.

9:56 Criminalizing doesn't seem to work.

9:58 There's also like human rights issues here, right?

10:01 We can't just solve everything with criminalization

10:04 and among other things, you know, think about if we know that the next pandemic

10:08 is going to start with someone who handles wildlife,

10:10 someone who works in a market or works in a supply chain,

10:15 when that person gets sick, we need them to be able to go to the doctor

10:19 without being afraid that they're going to go to jail.

10:22 So, we can't just ban the wildlife trade.

10:26 There are a couple things that we can do though.

10:29 One is we can try to reduce demand,

10:32 particularly in the US, a lot of wildlife trade is our fault.

10:37 Next time you're at Petco, think about whether you really need that gecko.

10:41 Another thing that we can do is we can invest in alternative careers

10:48 in communities that rely on particularly things

10:51 like wildlife farms that we really don't need.

10:54 I think it's going to be very hard to shift people

10:56 off of wild animal protein and there's actually studies that show

11:00 that the task of doing that would actually lead to so much

11:04 more agriculture in some places that it

11:05 would actually be worse for biodiversity.

11:08 So, you know, some people are always going to be living

11:11 off of wild animal protein and that's not just in faraway places.

11:14 There are certain industries, especially fur farming,

11:17 that we just really don't need and I think

11:19 it is very reasonable to think about eliminating them.

11:23 The last piece of this though and and to me

11:25 what the public health answer is, you know,

11:28 there's always going to be some wildlife trade

11:30 and like with climate change or biodiversity loss,

11:35 it's going to take us decades to solve this.

11:38 We can't wait to solve wildlife trade to be ready for the next pandemic.

11:43 So, what that means is we need to start looking for viruses in markets,

11:51 on farms, in the people who work in these settings.

11:55 We have really poor disease surveillance in most wildlife trade communities.

12:02 And statistically, the next person to get a SARS-like virus

12:06 is probably going to be one of those workers, right?

12:08 And we want to be able to day one when we see that first case of SARS-CoV-3,

12:13 we want to be there, we want to be ready to quarantine people and we

12:16 have to be able to do that transparently and with trust

12:19 with communities and all of that is just it's

12:22 a huge state shift in how we think about these problems,

12:25 but I think public health has to tackle it

12:27 or we're just going to keep having more COVIDs.

12:29 As somebody who's working in this field and looking at this data,

12:33 what are some things we need to be doing to prepare for the next pandemic?

12:38 We need a lot more basic science about

12:40 viruses and animals and the connections between them.

12:44 There are a lot of just foundational things

12:45 we take for granted about how ecosystems are

12:48 changing or how people are affecting disease patterns

12:51 in nature and we just don't know for sure.

12:55 We don't know how many people die from climate change every year.

12:59 We don't know where wildlife trade is actually accelerating the fastest.

13:05 There are things we can measure from space,

13:07 so maybe we have a sense of where deforestation is happening,

13:10 but for the most part, we don't have eyes and ears in most of the places where

13:14 the next pandemic will start or the next planetary crisis is happening.

13:18 So, I think just we need so much more

13:20 basic investment in science and in data collection, right?

13:24 There's a lot that we can do with the data that's already out there,

13:27 but we need a lot more data before we

13:29 can actually start to tackle some of these problems.

13:31 I think that this project is a really great poster child for basic science,

13:38 all the boots on the ground tracking of wildlife trade, but 5 years ago,

13:42 we wouldn't have been able to do this study because we didn't have a list

13:46 of here are all of the animals and here are all of the viruses they have.

13:50 You know, 5 years ago,

13:51 we couldn't ask that question with the data we had and 5 years from now,

13:55 we might not be able to because those data might not be supported anymore.

14:00 So, you know, a general plea here of we're doing what we can,

14:04 but I hope that this is a wake-up call

14:07 that we have to keep investing in this kind of work.

14:09 Well, Colin, thanks so much for coming on to talk to us about this study.

14:12 I really appreciate it.

14:14 Thank you.

14:16 That's all for this week on Science Quickly.

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14:40 For Scientific American, this is Rachel Feltman.

14:43 Have a great weekend.