Instant Genius - How parasites play a vital role as caretakers of Earth’s ecosystems

Episode Date: June 25, 2026

When most of us think of parasites, our minds will likely turn to thoughts of the various icky creatures that can invade our bodies, make their homes there and end up making us ill. But the truth is that parasites make up a hugely significant part of all life on Earth and bring many benefits to the organisms they live in or alongside and the wider ecosystems they are a part of. As part of the Nature’s Unsung Heroes miniseries, we’re joined by Timothy Brown, a researcher based at the University of Leeds and member of the IUCN Parasite Specialist Group who works on the conservation of parasite diversity, to talk about the many ways in which parasites influence life on Earth. He tells us how our own bodies are host to trillions of different beneficial organisms, the key role parasites play in managing the balance of the animal life in the ecosystems they are part of and talks us through the most recent ideas researchers are working on to preserve these overlooked, but ecologically vital creatures. Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hello and welcome to Instant Genius, a bi-size master class in podcast form. Every Monday and Friday, you'll hear world-leading scientists and experts talking about the most fascinating ideas in science and technology today. I'm Jason Goodyear, commissioning editor of BBC Science Focus. When most of us think of parasites, our minds will likely turn to thoughts of the various icky creatures that can invade our bodies, make their homes there, and end up making us ill. But the truth is that parasites make up a hugely significant part of all life on Earth and bring many benefits to the organisms they live in or alongside

and the wider ecosystems they are part of. In this episode, part of the Nature's Unsung Heroes miniseries, we're joined by Timothy Brown, a researcher based at the University of Leeds and member of the IUCN Parasites Specialist Group who works on the conservation of parasite diversity. We're talking about the many ways in which parasites influence all life on Earth.

He tells us how our own bodies are host to trillions of different beneficial organisms. The key roles parasites play in managing the balance of animal life in the ecosystems they are part of and talks us through the most recent ideas researchers are working on to preserve these overlooked but ecologically vital creatures. So welcome to the podcast.

Thanks so much for joining us. Yeah, thanks so much for having me. So today we're talking all about parasites, but not typically what people would think about parasites. We're talking about how they can actually be beneficial. But before we get into some of that detail, let's start with the basics. So what exactly do we mean by a parasite?

Yeah, well, we can start with quite a precise scientific definition of what a parasite is. So in biology, we tend to talk about a parasite as an organism that is dependent on living in or on a host organism for all a part of their life cycle and that derives resources at the expense of the host with the potential to decrease host fitness. Obviously that's quite kind of mealy and there's quite a lot of technical terms in there. But there's two kind of important bits. The first one is that parasites rely on their host as habitat. So they often interact with their hosts for quite long period of time. And the second one

is that parasites are kind of by definition detrimental to their hosts. So that can kind of vary in scale. So it can just be that they're taking energy away from the host. That's quite a minor impact. And it goes all the way up to kind of quite bad symptoms of disease and even mortality in some cases. So what are some common types? So I think most people will think of things like tape worms

and things that live in human stomachs. But there's a whole plethora of different types of parasites, aren't there? So can you tell us about some of those? Yeah, so there are two broad types of parasite. So there are micro parasites. Those are things like bacteria, viruses, fungi, and then there are macro parasites. And that's what I focus on. Within macro parasites, we have kind of three broad types.

So the first is protozoa. So these are single-celled organisms. A lot of people will be familiar with some that cause really nasty illnesses in humans. So blood parasites like malaria or sleeping sickness, also things like foodborne or waterborne illnesses, so things like Giardia or Cryptosporidium people might have heard of. And then we have parasitic worms, or to give them their scientific name, Helmimps, and these come in a variety of amazing different forms. So there are whale tape worms that grow up to 40 metres long,

and then they go all the way down to tiny filarial parasites that are so small that they're transmitted by mosquito bites. And then the third major group we have is parasitic arthropods. This covers things like ticks and mites, which are arachnids, also insects like fleas and lice, and then some of the other really kind of wonderful, gross and creepy parasites. So people might be familiar with things like botflies. There's also something called a batfly. Batflies are wingless and eyeless species of fly that livers ecter parasites on different bat species. and they basically look like the facehugger from alien. And outside of those three major groups, there's a range of other parasites.

So a lot of crustaceans are parasitic, and there's a lot of really funky-looking parasitic copepods that live in oceans. There are also some parasitic mollusks, so a lot of freshwater muscles are parasitic in their juvenile life stage. Even some species of fish can be parasitic. Yeah, so having said that, I think a lot of people don't realize, but parasitaph, Parasites are hugely abundant. They make up a huge proportion of animal diversity. What do we know about the balance of parasites, not necessarily in terms of biomass, but in terms of prevalence?

Yeah, so I guess the big thing is we don't know of any great accuracy, because parasites are really among the most poorly described of any of the animal species. But quite a lot of work has been put into trying to produce estimates of parasite biodiversity. and our best estimate suggests that parasites make up a significant proportion, so at least kind of 30 to 40%, if not actually, a majority of animal diversity. And the way we kind of get to these numbers is we look at the mean number of parasites for a given host species, and then we also look at the mean number of hosts that each parasite uses, and then we can kind of use what we know about the numbers of vertebrate animals there are. So for the 45,000 species of vertebrate that we know to exist,

Best estimates suggest that there are as many as 75,000, up to maybe as many as 300,000 Helmymph parasites. So that's not even touching things like arthropods or protozoa. Another way you can kind of look at it is there's not a single animal host we know of that doesn't have at least one parasite. And a lot of hosts have a host-specific parasites, so parasites that only live on one specific kind of host species. And a lot of hosts have many, many more. One species I've been looking at recently is the European bison, and we know that hosts as many as 101 parasites, including three host-specific ectoparasites, two of which are mites that live on different parts of the host face. So yeah, the more we look, the more we find, basically.

So often when people mention parasites, they talk about something called a symbiotic relationship. So what exactly do we mean by that? And, you know, other subtle variations, within that terminology? Yeah, so a symbiotic relationship, I guess it describes the first part we had of our parasite definition about an animal that kind of has an intimate interaction with another species

and which it kind of depends upon to complete its life cycle. And we tend to define the different kinds of symbiotic relationship by the impact that the dependent species has on the host. So if it's negative, we call it a parasite. If it doesn't really have a positive

or a negative effect, we call that a commensal. So people might be familiar with remora. They're sometimes called like sucker fish. You'll see them in kind of nature documentaries on the sides of sharks. They don't really impact the sharks at all, but they benefit from increased mobility

and they tend to eat the scraps left from the meals that the sharks feed on. And then if the dependent species has positive effects for a host, we call that a mutualist species. And there are a lot of amazing mutualism. There's lots of classic ones. so plants and pollinators, and you also get like coral and algae.

One of my favorites, there's a group of parasitic wasps that have evolved this symbiosis with a virus, and so what they'll actually do is they'll inject the virus along with their eggs into an insect host. And what the virus kind of does is it suppresses the immune system of the host, which allows the wasp larvae to thrive and grow and basically take over the host. And so there's this symbiotic relationship where this wasp keeps on passing this virus onto its offspring and uses it as almost kind of like a venom in a way. Yeah, absolutely fascinating. So let's start with humans. So, you know, our bodies are host to all sorts of different organisms.

But so, you know, a lot of them really do benefit our health. You know, what can we say about some of those? Yeah. So our bodies are actually host, we think, a trillion. of microbial organisms, we actually think that in the average human, there might be more microbial cells than there are human cells, which is kind of mind-boggling to get your head around. I think before we kind of get into the benefits to humans, it's important to still say that hygiene is a really important thing. You know, hand-washing is probably one of the most important

inventions in human history in terms of the number of lives saved. So it's important to remember that there are still a lot of harmful microbes out there that we have to take precautions against. But yeah, kind of back to the positives, a lot of these microbes live in what we term the gut microbiome, which is probably a term a lot of people will be familiar with, particularly in kind of recent years. And a lot of the functions of the gut microbiome are things like it aids us to digest certain complex foods. And also a lot of these bacteria help us to produce certain molecules that we need and wouldn't otherwise be able to access. So I think vitamin K is one, one example of something these bacteria help us to produce. Some of your listeners might have

experienced if they've ever gone vegan for a period of time and then try to go back to eating dairy, they might have found that they have stomach problems. That actually happens because when you go vegan, you experience a short-term decline in certain backgrounds. that help you to digest lactose. And so when you go back to eating things with lactose in, you're kind of missing those bacteria from your gut microbiome. And that's one of the reasons that you can have some problems with digesting that. And there's a lot of interesting examples from the animal kingdom as well. So baby hippos are actually born with a really poor gut microbiome and they'll actually eat their mother's feces to gain the bacteria that they need to break down

certain complex plant fibers. And we've also applied this to animals as well. So quas are a good example where individual quas tend to only be able to eat certain species of eucalyptus tree. That's quite a negative for quite an endangered species because it means in a whole wide ecosystem there's only a couple of trees that you can eat from. But some studies and some tests have been done recently where they've transplanted feces from one quala into the other to introduce the bacteria to the quala's digestive system.

And that's had really positive effects. So after a couple of weeks, it seems to be that these individual qualets can kind of broaden their dietary niche and eat a couple of species of eucalyptus instead of just the one or two that they had originally. Yeah, so it might be a bit icky, but let's have some worms that we might have living inside us. So, you know, people will think of tapeworms, etc. I find it really funny that, yeah, I'm sure you've heard of this, like Victorian women. we're like eating tapeworm cysts and I hope that it would make them slimmer so they could fit into the courses, etc. There's a theory called the hygiene hypothesis, like when you're talking about hand washing etc. That some of these things might actually help protect us from allergic reactions and immune responses.

You know, is there really a truth to that? Yeah, yeah. So I'll get to the hygiene hypothesis in a second. I guess I should say I feel I have a slight jeet of care as a parasitologist to say, don't ever infect yourself with a tapeworm for weight loss. Yes, I think that's sensible. It won't work because you might end up with quite nasty repercussions, not least in how they often have to come out. So yeah, the idea of the hygiene hypothesis,

it kind of came about from some big statistical studies. And what these showed is that in the 20th century, particularly in a lot of rich nations, you see a real increase in allergies and certain autoimmune disorders, at the same time that you see a real decrease in certain infections, particularly of helmimps. And so there was some hypothesizing that maybe these worms have some sort of role in stimulating our immune systems, and that goes on to prevent autoimmune diseases in later life. And there seems to be some evidence of it. So there have been some observations

in tests with mice in kind of laboratory conditions, where helmets do seem to stimulate certain immune responses that are kind of involved with mediating autoimmune diseases and allergies. It kind of comes along with this other hypothesis, which is the old friends or the microbiome depletion hypothesis. And this kind of suggests that the issue might be more that we're not being exposed to certain benign microbes that we've co-evolved with over a long period of time and that that's actually what's impacting these kind of immunoregulatory disorders. I guess I'm not the best place to answer this in terms of I don't really have a medical background. And it's kind of one, it's really a massive debate within medical sciences about which of these hypothesis is kind of the

more important one. There's a lot of tests being done to see if we can develop kind of therapeutic treatments using helmet worms or things like probiotics. I think what's clear is that parasites, including helmets, but particularly the microbiome, do have kind of really, really fundamental impacts on a lot of our functioning, including the immune system and including digestive health. And we're only really at the tip of the iceberg of understanding all that. So hopefully as kind of research develops, we'll get a better sense. And then we might be able to use this in the treatment of some human diseases. On July 3rd, our neighbors are coming over. Accept the invite.

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Yeah, how would this shake down? The invite in Cinemas, July 3rd. Let's shift gears then and go into the wider animal kingdom. So a lot of parasites play, you know, really important roles in the ecosystems that they live in. I thought that maybe the first place to go to is they can sort of weaken some of the populations of animals that they infest and sort of thin out like the weaker animals to sort of manage the ecosystem, you know, in the same way that, you know, I don't know,

like a game warden ward or something. Yeah, so parasites can definitely be a really important kind of evolutionary pressure. and that definitely involves kind of, particularly they select against inbreeding is one thing, so they can kind of boost genetic variation and that can really boost the health of host populations. We might return to some of that later on, I think, but they also just have a really important role

in regulating host populations. So parasites are often involved with host declines once hosts reach a certain kind of population threshold. And the reason this happens is that a lot of parasites depend on something called density dependent transmission. And what that means is the transmission rate, so how much

the parasite is being spread between hosts, depends on the kind of the rate of contact between susceptible and infected individuals. So the greater density of hosts you have in an area, the more transmission is occurring. People will be familiar over COVID, certain rules about kind of maximum group size

and social distancing. All of that is trying to control the density of people to try and reduce the transmission rate. But in nature, that has the effect of when certain hosts reach certain abundance levels, parasites will basically take over and bring those population levels down. A classic example is red grouse on grousemores in the UK.

They have quite distinctive population cycles, and it's been kind of proven that one of the reasons for that is a certain species of parasitic worm that infects the grouse and, yeah, controls population. numbers when they get too high. But you might think, well, isn't that a terrible thing, right? Like, we tend to prefer all the cute and the cuddly and the feathered hosts to parasites, which tend to be pretty gross. We don't really get to look at, we don't really interact with,

or when we do it's negative. But it's really when you take a step back from looking at individual hosts and look at kind of the wider system, then you really begin to appreciate the value that parasites have, including in regulating host populations. One example of this is something called parasite-mediated apparent competition. So imagine we have two host species, we've got host species A and host species B that live on a little island ecosystem. Now, ordinarily, host species A is kind of a super competitor, so it's faster, it's stronger than host species B. All else aside, it will probably wipe out host species B. But these two host species happen to share a parasite, and it just so happens that the weaker host species, so the less competitive one, is actually

quite immune to it. But the more competitive one actually suffers quite badly from the effects. And the effect that this will have is that it will kind of keep the population of host species B at a low level, because it can always survive in host species A. That's what we call kind of a reservoir our host where the parasite is living in a host that doesn't have really negative impacts on it. And so the effect of parasite mediated apparent competition is that we now have two species in an ecosystem because of this parasite driving down the population levels of one where before we might have just had the one. And then when you scale that up to the level of ecosystems, communities and ecosystems where you've got, you know, hundreds of host species competing,

thousands of parasites within those species, you get a sense that parasites can actually have a really pivotal role in determining community and ecosystem structure. I guess just one final thing in this. We can link it to something called the Janssen-Connell hypothesis. These were two ecologists who worked in forest ecosystems and they basically hypothesized that natural enemies, particularly things like host-specific parasites, will kill offspring when they're living closer to a host. So they were particularly looking at seedlings of trees. So they'll kill tree seedlings when they're close to their parent organism, although the parent organism can kind of sustain some population of the parasite and be healthy because it's fully grown. Host specific parasites will control the abundance of

certain species when they reach certain high abundance thresholds. So working in tandem, what this means is parasites basically open up ecological niches for things to move into. And so over evolutionary time, parasites are kind of driving a more diverse community, a more diverse ecosystem, and all of the benefits that we get from that. Yeah, so how about the effect on food chains that parasites might have? You know, you can see if they're picking off some sort of weaker animals, maybe making them, you know, run more slowly or altering their behavior in different ways, so that they can be predated on by other animals.

Is that a big effect? Yeah, so at a very basic level, We know that parasites make up a majority of the links in food webs, and often the links that parasites are involved with have quite different characteristics to those of free living diversity, so species with non-parasitic life cycles. Parasites can also make up quite a substantial proportion of biomass and a lot of food webs, so they can be quite an important source of kind of energy and nutrients. One way to kind of imagine the impact of that is instead of a food web, if we imagine kind of a social network,

So if you imagine your kind of network of like friends, family, colleagues, if you imagine if you took out half the links of that network, we'd expect that to have quite a profound effect on the behaviour of that network, particularly if all of the links that we took out shared one common feature. So imagine if you took out kind of all of the links of people you know in your hometown, suddenly your social network is going to interact in a very different way that it did before. So that's one way that we can kind of imagine the impact. that parasites have on food links. If you take out half the links of a food web, you're going to see kind of quite profound changes. Another way is to give quite specific examples that we know of where parasites have profound impacts on food webs. And the key parasites in this regard are a lot of parasites have something called an indirect life cycle. So there are two main kinds of parasites. There are those that have direct life cycles where they're passed straight from one host to another. again, something like COVID's quite a good example of that, passed between human-to-human contact.

But there's another suite of parasites that have indirect life cycles, and these parasites have to pass through another species on their way to the host species. It could be something like a vector, so it could be like a mosquito transmitting malaria between two humans. So a lot of these parasites with indirect life cycles have evolved these incredible life history strategies where they manipulate hosts into performing some sort of behavior

that makes it more likely that they'll be preyed upon by the final host of the parasite, and then the parasite will get passed on. And these are the ones that tend to have really profound impacts on food webs in some cases. So a great example of this, there's a kind of trematode or flat worm called Locochloridium paradoxum. And this trematode lives in land snails.

And after it's finished developing in the snail, the worm does two incredible things. So firstly, it manipulates the snail's behavior and encourages it to climb to kind of better lit places, so it will encourage it to move up vegetation, up stalks, onto the kind of top of plants, where it will be more visible to birds. And the second thing the parasite does

is it develops something called a brood sack, which is kind of like a sack full of loads of parasitic larvae. And where it develops its sack is in the eye stem of the snail. So if you imagine your snail, those kind of two bits that poke up off the top of the snail's head. And this Brutac is really brightly coloured and it also pulsates. It kind of frobs like a heartbeat. And what this means is that when a bird looks at the snail, it doesn't actually see a

snail. What it sees is kind of two caterpillars that are really juicy and colourful, kind of wiggling their bodies in the placer where the snail's eye should be. So the bird kind of swoops down, either eats the snail hole or, pecks out the eyes. And the effect that this has on the food web is that it strengthens that link between the bird and the snail. So it makes predation more likely. But obviously the bird and the snail are involved in a lot of other food web links. And so we see examples where these kind of one effect that a parasite has on one host can kind of ripple out of ecosystems. So another example

we can draw upon is in Japanese stream and forest ecosystems. And the parasite we're in interested in here is something called a nomathomorph worm or a horsehair worm. If you see them, they kind of look like a tangled mass of quite thick black thread. This parasite spends most of its life inside a bush cricket. Once it's matured, it manipulates the bush cricket and encourages it to basically jump into water, which is something the cricket otherwise wouldn't ever do really. Now, as far as the parasite's concerned, once it's in the water, it burrows out of the cricket's exoskeleton, it finds a mate, it mates, it lays its eggs, they pass on into the next host and the whole cycle repeats. But that's not where the story ends as far as the food web is concerned.

So with all these crickets passing from the land into the stream, these then provide a really important food source for an endangered population of stream trout. These stream trout are now fill up on crickets, which means that they're not eating as many of the invertebrates that already lived in the stream. And so those invertebrates can kind of flourish. And later in the year, a lot of them will emerge as various flying insects. And eventually they will end up as an important food source for a lizard in the forest ecosystem. So what starts from kind of just one stage in the life cycle of one parasite driving this cricket to jump into the water, ends up rippling all throughout the ecosystem. And I think this is where we really see kind of the beauty of parasites in

systems, and it's why a lot of ecologists or parasitologists refer to them as ecological dark matter. We kind of don't see them, and we don't often know what they're doing, but they have these really important effects in driving energy and nutrients for our ecosystems, determining different food web links, and affecting, yeah, community and ecosystem, structure and functioning at broader scales. Yeah, so sticking with that idea, but slightly shifting gears, parasites could also have an effect on the health of different environments that they live in. So one example is I've heard of a snail parasite that due to its action on the snail

makes certain environments become more resistant to drought. Yeah, I guess there are two ways of answering the question of kind of how do parasites impact the environments and ecosystems of which they're part. There's kind of an abstract view that we can give. and then, yeah, there's more specific examples. I can start with a specific example that you just highlighted. So, because, yeah, it's an amazing story, really. It starts on kind of the salt marshes on the coast of the USA in North Carolina.

And scientists were noticing that intense droughts were causing quite intense die-offs of marsh plants, but also that these droughts were interacting with the grazing of a particular snail species. I think they're called Litterina is the genus name. So between these droughts and between the snail species grazing, they were witnessing these kind of mass die-off events of marshland plantation. Now, what scientists noticed is that along the borders of these patches, where these plants were dying off, a lot of the snails, so by the border I mean kind of

the bit where you go from where all the vegetation has died off to the bit where there's still some vegetation intact. What scientists noticed along these border zones was that a lot of the snails were affected with a specific snail trematode. The Latin name is parochus acampus, and that seemed to be associated with lower grazing in snails. And so they kind of hypothesized that because these parasites were causing snails to graze less, that might have been bolstering the ability of vegetation to resist the drought. And so what they did is they basically carried out some field tests and they manipulated parasite prevalence along these die-off borders. And what they saw is that reducing the prevalence of parasites had a market effect on the rate at which plants were dying off at the rate of which they were getting eaten by snails.

And so parasite presence was basically having a really important effect on the resistance of the ecosystem to resist overgrazing, which allows it to resist drought. And that's kind of just one example. So like we said before, there are hundreds of thousands of parasites out there. And there are probably thousands more examples like this, all of which will probably kind of be quite ecosystem-specific. Going back to what I said earlier about the other way of answering this question. So yeah, we can also answer the value of parasites to ecosystems in a more abstract way. So a really famous evolutionary biologist you might have heard of Paul Ehrlich.

he had various, some ideas which were quite controversial, but he came up with this metaphor that a lot of ecologists still turn to. And the idea is that imagine if instead of an ecosystem we had a plane and instead of the species in the ecosystem, we have the screws of the plane. If you kind of remove one of the screws, the plane's probably going to be able to fly okay still. If you remove maybe 10 of the screws, you might find that you start to have a few problems. your armrest might be wiggling a bit loose or you might notice a bit of shuddering in the plane or something like that. If you remove kind of a hundred screws in the plane, then you might start to run into some functional difficulties where the plane is no longer able to fly. And Paul Ehrlich

kind of applied this to ecosystem saying, well if you lose one or two species, the ecosystem is probably still going to be able to function as it is. If you lose 10 species, you're going to start to notice a few differences. If you lose a whole suite of species, and remember we said parasites probably make up kind of a majority of species in a lot of our ecosystems, it's hard to argue that that isn't going to lead to some kind of pretty important and pretty detrimental effects to the ecosystem, if not full out major ecosystem collapse. Yeah, so having said that, you know, we've talked about there being so many parasites and how essential they are to the very secret systems they live in. And you work on sort of looking at endangered parasites. So

what can you tell us about that? Yeah. So as a researcher, I'm looking at parasite conservation. And I'm investigating a few different things around it. But I think because it's such a far out idea and your intrinsic reaction is to kind of go, why on earth would we want to conserve something like parasites? It's good to really start with the basics. So parasite, conservation as an idea kind of emerged around the early 90s, and it basically came from parasitologists saying, people always talk about biodiversity conservation. Parasites are a massive part of biodiversity, but no one ever mentions parasites in relation to conservation, or if they do, it's always about getting rid of them or worrying about them as a kind of disease threat. And over the next 30 years,

are sense of the benefits that parasites have, but both hosts and ecosystems has really developed, and we've really begun to appreciate them as a really valuable part of the natural world. So what sort of things might that involve then? How would we go about that? I guess the first step is understanding which parasites are at risk from extinction.

So parasites are quite unique, although they share this with kind of all symbiotic animals, and that they're really vulnerable to something called co-extinction. And co-extinction is when one species goes extinct following the extinction of a species that it was dependent upon. So if you imagine just a tick species that's specific to one kind of deer, if that deer species goes extinct, that tick species no longer has any habitat or anything to feed upon. And so that tick will also naturally go extinct. And so kind of the first step that we're doing for parasite conservation is to try and understand which parasites are most at risk. and that will really be any parasite that parasitizes on an endangered host,

particularly one specific to an endangered host, is going to be at risk of extinction. So people might be familiar with the IUCN red list. It's kind of the gold standard of assessing species extinction risk. So when you hear that a species is endangered or critically endangered, that's an assessment by the IUCM. And the IUCN now has a specialist group which is working on assessing specifically parasites to try and increase their profile within conservation and also kind of guide some

conservation actions. And I should say, we actually maybe have some endangered parasites in the UK. So there's only one species that's been formally assessed on the red list so far. That's a sucking louse of the pygmy hog. It's a kind of like tiny little wild boar that lives in India and it has this one host-specific ectoparasite. So that's the only parasite that's been specifically. assessed. But in the UK, we have something called the Manx Shearwater flea. People might be familiar

with Manx Shearwater. They're related to puffins. You kind of see them out over the middle of the sea or the middle of the ocean kind of gliding along. There's a specific breeding colony of these Manx Shear waters on the Isle of Rum, up in Scotland in the Inner Hebrides, and it happens to be the only place in the world that you find this one specific species of flee. And so that's endangered because if anything happens to that breeding colony on rum, then that parasite will be wiped off the face of the earth. So yeah, we even have some rare parasites at home in the UK. And I guess, yeah, getting back to your original question, which is what my parasite conservation involve. The amazing news is the main things we can do for parasite

conservation are actually things that we're doing already. So in general, if you conserve the host and conserve the ecosystem in a kind of whole enough and healthy enough state, then you'll also conserve the parasite. So that's the major thing that we can do. But there are a few specific concerns with parasites. So there are a few examples in the past where hosts have been bought in for captive breeding programs, particularly really at-risk hosts where there are only a few individuals left in the wild. So something like the California Condor,

the last remaining individuals were rounded up in California put into a breeding program, and they were treated quite heavily with antiparacetic treatments. The rationale is obviously you don't want your host to be suffering with kind of illness and disease when you're trying to breed the last remaining population on earth. But the effect this had is that it ended up eradicating a host-specific species of Laos that lived on the condor. And so one of the things that we're kind of working on as parasite conservationists

is to just build some awareness that the idea that parasites can also be threatened with extinction and to try and encourage host conservationists to adopt slightly more parasite-friendly processes. There are still cases where it will be really important to treat hosts. If they're suffering with specific illnesses that might be passed on by certain kinds of parasite, then ultimately, you know, the host welfare probably will take priority. But there are also cases where parasite treatments have kind of been overused or used where they weren't strictly necessary. And so that's something we're trying to look at. The final thing we're looking at is whether we should be conserving parasites more proactively. So you might be familiar with

host conservation. We have a suite of things that we term like ex situ actions. So they're things that we do to host kind of out of place, things like translocations or reintroductions, captive breeding. And so there's a bit of discussion now about whether there are times when it might be possible to include parasites within the host's kind of ex situ conservation. We do actually have one example of this happening now. So there's a parasitologist who lives and works out in Japan, and he actually has a captive bred population of a species of tick called the Ryuku Rabbit Tick, and this tick only feeds on this one specific species of rabbit that's endemic to the island of Ryuku in Japan.

And so he's kind of breeding this captive-bred colony of ticks so that if the wild population ever does go extinct, he'll be able to kind of repopulate the rabbit population with this tick species. There's similar examples where people are maybe hoping it might be possible to reintroduce parasites with their host species. Thank you for listening to this episode of Inson Genius, brought to you from the team behind BBC Science Focus.

That was Timothy Brown. If you'd like to what you just heard, and please do consider subscribing to Instant Genius on your preferred podcast platform. If you'd like to see our guests and hosts in person, then why not check out our YouTube channel at Science Focus. The currently issue of BBC Science Focus magazine is out now. Pick up a copy wherever you buy your favourite magazines or download us on your app store of choice. You can also find us on Apple News or online at sciencefocus.com.

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