Instant Genius - Bird flu, with Dr Alastair Ward

Episode Date: December 9, 2022

This year around the globe, an estimated 160 million domestic birds have died as a result of avian flu. But why has the virus spread so widely? And could humans be at risk? Dr Alastair Ward, associate professor of biodiversity and ecosystem management at the University of Leeds, explains all. Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Music just as the artist intended. Visit name audio.com to learn more. Oh, and welcome to Instant Genius, the bite-sized masterclass in podcast form. I'm Thomas Ling, digital editor at BBC Science Focus magazine. Currently, the world is going through its worst ever outbreak of bird flu. An estimated 160 million domestic birds have died as a result of the virus around the globe. But why exactly has the disease spread so far? What happens when a bird gets the flu?

and are humans at risk? To discuss all this, I'm joined by Dr. Alistair Ward. He's not only a member of the government Birdflew Task Force, but Associate Professor of Biodiversity and Ecosystem Management at the University of Leeds. Hello, Alistair, thank you very much for joining us. Morning. So, in the UK, 600,000 free-range turkeys, that's half of them, have died or been cold because of bird flu,

also known as avian flu. If you were a healthy turkey right now, how worried would you be? Well, as we've said in last year, this is unlike any other year we've seen before, and we're seeing it again this year. More outbreaks that we've seen before, and every time we have an outbreak, the entire flock is depopulated. So it is a worrying time. It's a huge worrying time for the industry,

especially at this time of year when we're all looking forward to getting a bird on the plate, on the Christmas table. So yeah, it's a continuing concern. But particularly bad, again, this year, worse than it was the year before. So why is it particularly bad this year? Well, the strain of virus, which does change regularly, seems to be particularly good at surviving. It seems to be more infectious, and it also seems to be more deadly than it has been before. So the current strain of H5N1 just seems to be, when it gets into a flock, it just decimates the flock. and whether that's a flock of poultry or a flock of wild birds as well, or some wild birds, not all wild birds, just some of them.

So how is it exactly that bird flu spreads? Typically we thought of it as being, or traditionally thought of it as being almost like an aerosol transmitted virus, but it doesn't seem to be as effectively transmitted in that way as other influenza viruses are. So it seems to be that there is some contact with contaminated material, whether that is a contaminated bird, so physical contact, or whether it's physical contact with contaminating material. So they may be additional ways, and they're probably the more likely ways, that the virus is spread between individuals and between species. So that physical contact does seem to be an important element of transmission. So this particular strain, the H5M1,

how long has it been around for? It was first discovered in the 1990s on poultry farm in China. So that's where it first emerged. But I mean, the disease goes back well over a century. It was first identified on a poultry farm in Italy in the late 1800s. But the H5N1 strain that is given rise to all the problems we're seeing today was a poultry farm in China in the 1990s. There are lots of headlines concerning domestic birds at the moment, birds and farms being under threat. But how much are other birds? What about wild birds?

Are they under threat at the moment? Absolutely, yes. again, in an unprecedented way. Normally when we've seen significant outbreaks of avian influenza, H5N1 strain, you typically see it in anceriform, so the ducks, geese and swans. But they seem to be relatively resistant to it. You haven't seen the huge die-offs of those populations in the past. But what we saw over the previous winter was significant die-offs in some species of sea bird, which we'd never seen before. So it's been a bit of a shock to see in some of these large colonies on Bass Rock, for example, in Scotland, many of the other colonies around Scotland and Northern England. We've seen substantial die-offs of species such as Gannets, Great Skewers, that we've never seen this virus in before. So it seems to be not only more infectious and more lethal, but it also seems to be infecting more species of the birds than it has done in the past. Could this virus be an extinction threat to some of these species?

It certainly will likely drive populations down. I am clinging to the hope that many of these species will end up developing a herd immunity. Once the virus has spread through the population and unfortunately may well kill off a large number of birds, then those that are naturally resistant to the infection should hopefully survive and give rise to the future populations or future generations of those birds. And so, yeah, unfortunately, I think it will be a very tough period, but I'm hopeful that no species will go extinct. That is less likely to happen if we can alleviate some of the other pressures that we're causing on wild bird populations such as the impacts of climate change, the impacts of habitat loss,

habitat fragmentation, because they're causing additional pressures on these birds. So they're already under pressure. So then facing this disease now is one other pressure that the could well push them over the brink. So if you can perhaps reduce some of those other pressures, then maybe the effects of bird flu might be lessened. What happens if you're an adult bird and you get this flu? Is it like when a healthy adult gets a flu and generally have to spend a few days under duvet watching homes under the hammer?

Is there a bird equivalent to that? I don't think there's an equivalent of birds homes under the hammer, but yeah, the symptoms are actually remarked. remarkably similar. So there will be nasal discharge of some birds that are inflected with highly pathogenic avianine into Valenza, such as the H5N1 strain. And then they can go through a period of lethargy that we're all familiar with. But in those extreme cases, then the birds can decline quite rapidly. You tend to see a lot of malaise within the birds, a disinterest in food and drink, not wanting to move around very much. And you sometimes see a bit of a discolouration.

of the comb and also of the wattles on the head, they can go a sort of funny blueish colour. But generally speaking, the symptoms seem quite similar to what you would see in a human. So, were you saying that there's a way you could just tell if a bird has flu just by staring at it? No, sorry, it's not quite that simple. So these are some of the classic symptoms. And some of these symptoms are shared with other diseases as well. So just looking at a bird and seeing these symptoms does not guarantee that it has bird flu. There are many strains of bird flu that go undetected. So these are low pathogenic avian influenza.

So they're the same virus. They're just different strains. They don't cause mass mortality amongst poultry and often go undetected. So, I mean, what the government asks is that if you see signs that you think might be bird flu as a poultry farmer, that you get in touch with them so they can come and test the birds for you, to confirm where the tree is, because you cannot be 100% sure that it is bird flu just by looking at the symptoms alone. What about humans? So I guess a big question a lot of people have is can bird flu spread to humans? In some extreme circumstances it has in the past, and the strains

that have passed to humans have typically been the H5N1 strain, but there are genetic reassortments that have to happen for it to be able to pass easily to humans. So the current strain doesn't seem to be posing a huge threat to humans. There has been a case in the UK of someone that lived very close to an infected population of ducks, but that was very, very rare, and that individual was almost asymptomatic. So the symptoms were very, very low indeed. Now, in the past, there has been significant outbreaks among people, particularly those working very closely with poultry in Asia, and people have died from it.

There was a mortality rate of around about 60% amongst human beings who contracted H5N1 in China several decades ago. But as I say, it requires certain genetic changes to happen before it can make that leap from birds to human beings, and those changes seem to happen very infrequently. So the current belief is that risks to humans are low, but we say that with a high degree of uncertainty. And I guess the big figure that's going to stand out from what you just heard is the 60% fatality figure. And obviously with coronavirus, it was what's sitting around 1, 1, 2%. So do you think overall that humans should be scared at this point?

No, I don't think it's anything to be scared on a human health basis, because that 60% that was amongst poultry. workers. So people that were working in abattoirs and so, you know, and levels of PPE weren't exactly great. So personal protective equipment. So biosecurity measures weren't exactly great. So it was perhaps no surprise that those individuals were coming into contact with very high infectious loads of material, which you just don't get in the United Kingdom. So our biosecurity practices are of a very high standard. So, and as long as people follow advice with regards to, you know, the way that they handle birds or avoid handling found dead birds, for example, then the risks to humans are very low. But again, I'm going to say that with a high degree of uncertainty, because, you know,

we are just one year in to the current outbreak of H5N1. If a human contracts bird blue, could they potentially pass it on to another human, or is that quite difficult to do? Yeah, I mean, that seems to be a very rare occurrence. Again, there is some evidence for. or having happened in previous outbreaks in Southeast Asia, but it just does not seem to transmit very effectively from one person to another. So if there was an outbreak within a human population, which is highly unlikely, then theoretically it should be very easy to contain.

Vaccines have been developed against bird flu, and there is prophylactic medicine available to take care of if there are any small outbreaks. and that combined with the fact that it doesn't transmit particularly well between people means it should be very easy to control if it does affect human populations. So is it basically unless you are working, say, on a chicken farm, when you're working with close proximity to these birds, is it only them that you might need to be worried? I think if you work very closely with poultry,

so whether in the raising of poultry or ducks geese and swans within a farm setting or on a unit where they are slaughtered, then you just need to adopt the standard biosecurity practices that most people who work in those instances are already taking because they should be enough to mitigate your risk. Do you think there's a lot of unwarranted panic around Burfle at the moment? There's a lot of people already asking, could this be the next pandemic,

especially with headlines saying that government scientists, on standby to produce modelling for a human outbreak of this disease? Yeah, I mean, it's good to plan, isn't it? So the thing is, with avian influenza, it's a fairly simple RNA virus. So they mutate very, very rapidly, but they undergo genetic reassortment. So they can combine elements of other influenza viruses into their own genomes, which means that they can form these different strains very, very quick. quickly. And sometimes those genetic reassortments do give rise to strains that can be more

infectious, more deadly, as we're seeing right now. So I think it's sensible to plan, but, and it's, I can understand why people are so worried at the moment with regards to the poultry industry and also with regards to wild birds. I mean, it's, it's hitting more domestic flocks than we've ever seen before at the moment, and it's hitting wild birds in a way that we've never seen before. So conservationists and poultry farmers, it's entirely understandable why they are so worried. From a human health perspective, I think at the moment we've got less to worry about, but it's certainly very sensible to plan for all eventualities. Thinking a bit ahead to Christmas, a question that some people might have is, if you eat a turkey

that has been previously infected with bird flu, what are the health risks there? You shouldn't be able to eat a turkey that is infected with bird flu because that disease should have been identified before the animal was killed and prepared. So it's highly unlikely that any birds will be getting through to the human food chain that are affected by avian influenza. Having said that, again, as long as the really good standards of hygiene are maintained, then the risks can be mitigated. I don't know anybody that eats undercooked chickens or turkeys. For example, and yet, you know, heating to a high degree or high temperature, so the internal temperature is well above 70 degrees centigrade is enough to kill off any virus. So the risks to people from eating poultry right now are minimal.

But again, I'm going to say that with a degree of uncertainty. When you spoke about a possible middling species between birds that allows the virus to spread, is there going to be any way of identifying that species? Is it a case of just simply getting out of the binoculars each morning and studying really hard? Or is there a proper scientific way to identify this? Yes, well, we have work ongoing at the moment in collaboration with a range of universities and other research institutes around the country where we look. more intently at the diversity of birds that may be affected by avian influenza.

So we're sampling, well, colleagues at the Rosalind Institute up in Edinburgh are sampling a wide diversity of environments to see if they can detect virus in different environments that different species live in. I very much doubt that there is a single species that we can point the finger at. I suspect it's a large, complicated ecological network of species that are involved in both transmission of the virus as an infection, but also the movement of virus in contaminated material, such as sediments, feces that may be picked up. You know, say, for example, if a bird was in a reed bed or in a mud flat where infected ducks, geese or swans would be.

If they picked up that mud, picked up feces on their feet, then they may just simply carry that contamination. So I think it's quite a complicated process that we haven't yet identified. So it's not as simple as just sitting out with your binoculars. We've got a number of dots to join up before we can really work out how this disease is moving around from immigrant ducks, geese and swans, and then spreading around the wild population of birds. Is there a vaccine for this strain of bird blue? So there are, or vaccines have been developed in the past against avian influenza.

But as we've seen with the COVID outbreak, you know, these viruses change rapidly. and unpredictably. So you really need to be developing new vaccines regularly to keep on top of it. And this is one of the many challenges that we would face in developing any approach to vaccination of domestic birds, for example, which is not currently part of the strategy in the UK. It's being looked at in the EU. So there are plans to explore the development of vaccines for the vaccination of poultry flocks across the EU. But we're not intending to do that in the UK at the moment because of the many challenges of developing the right sort of vaccine in time to combat the prevalent strain. The prevalent strain of H5N1 is not the same strain of H5N1 that emerged in China

in the 1990s. It's a very different organism. It's not the same as the strains of H5N1 that were here just a couple of decades ago. So they do change. They reassort their genetics. They mutate very, very frequently. So it's a real challenge to develop those vaccines. So you're saying that bird flu is mutating a lot faster than COVID ever did? I don't have any metrics to be able to give you an estimate of how rapidly it has changed. But what we do know is that we encounter different strains at different times throughout the year. And the strain we get in one year is different to the strain or the dominant strain we detect in one year is often different to the strain we detect in a following year.

So it just seems to, as I say, both mutate and genetically reassort very, very frequently, very rapidly, and hence give rise to these new strains. What are still the biggest unknowns about this strain of bird flu? At the moment, I mean, we still don't really know why it is so infectious. We don't know why it is so deadly. So we need to understand a lot more about the virus and its genetic makeup. And that will be helpful not only to work out. why it is the way it is right now, but that will also give us a much better idea about what we might expect from this strain of the virus in the near future. So how it might continue to mutate,

how many steps of mutation or genetic reassortment it might be needed for it to make, for example, the jump to human beings, we can start predicting that. So that's a big unknown. We also have no idea why it is affecting so many different species of wild birds in ways that it hasn't done before. So it'd be really helpful to understand why. So we can at least try and think about new ways of trying to reduce potential consequences or mitigate consequences for wild bird populations because it does seem to be having quite a devastating impact on many of those populations. The other big unknowns is we really don't know how it spreads among wild bird communities and therefore from wild bird communities to the poultry shed.

So as I said earlier, we need to join up all of those dots to be able to work out how the virus flows from both immigrant wild birds but also now birds that stay within the country over the summer. How does it get from them into other bird species and then into the poultry shed? We need to understand that a great deal more as well. So there's lots and lots of questions that still need to be answered on this. So you were saying earlier about how,

this virus is not so much seasonal anymore that it's happening pretty much the entire year. Is that quite a big problem in terms of sort of the bird population then? If there isn't any sort of rest for them, will a lot more be dying off, essentially? I mean, many of our birds are migratory. We see huge influxes of birds in the autumn and then they'll disappear off to their breeding grounds again in the spring. and they will be taking variants now that have probably developed in the UK back to their Central European and Northern Asian breeding grounds. So will it be more of a problem?

I mean, yes, inevitably it will because for those birds that stay present in the UK over the summer, it will continue to be an issue for them. But it's also going to continue being a problem for poultry farmers. Because in the past, it was a case that it seemed to just die out with the spring, migration as birds return to wild birds return to their breeding grounds. The disease seemed to just die out of the wild populations and hence the risk was not posed to domestic poultry. But with it now spending the summer here, we can expect to see continuing outbreaks. If this strain of the virus continues in the way that it has done for the past 12 plus months, then we can

expect to see continuing outbreaks on poultry farms throughout the next summer, next spring and summer as So overall, humans seem to be fairly safe, but for birds, it's pretty much almost like the early stages of 2020 with COVID in humans. It's a devastating disease, yes. The highly pathogenic strains of avian influenza, by definition, have a very, very high mortality rate amongst paltry. And they seem to be having this very high mortality rate amongst certain seabirds as well now. So yes, it is a very devastating disease for populations of birds. Is there anything else you'd like to say about bird flu that we haven't covered already? Just I think really a message to remain vigilant and to keep reporting observations of birds that are found dead out in the wild. So there is a reporting mechanism via defra whereby those wild birds can be reported.

And in doing that, we should be able to get a better picture on what strains are going around wild bird populations. So if you find a cluster of birds dead in a field, for example, or you know, you're out for a weekend walk or something, and you find a few birds just dead in a rather unusual circumstance so that you can't explain in any other way, then that would be good reason to alert DEFRA to come out and collect samples from those birds and test them for bird flu. Dr. Ward, thank you very much for your time.

You're very welcome. That was Dr. Alist Award, Associate Professor of Biodiversity and Ecosystem Management at the University of Leeds. Thank you for listening to this episode of Instant Genius, brought to you by the team behind BBC Science Focus magazine, which you can find on sale now in supermarkets and newsagents, as well as your preferred app store. You can, of course, also find us online at sciencefocus.com. This podcast is sponsored by name, audio and focal. The texture and emotional depth of music can be lost through digital sources or poor signal.

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