Animals on the Move

As we’re heading into winter here in the Northern hemisphere, and if you’re spending rather more time inside your home at the moment, you’re probably not getting as much sunlight on your skin as in the summer months. And the body actually uses sunlight to make vitamin D, which is important for healthy teeth, bones and muscles. This week, a paper published in The Lancet: Diabetes and Endocrinology has looked at whether levels of vitamin D may be related to how someone might fare with Covid-19. And Chris Smith spoke to respiratory physician David Thickett, who wasn't involved in this study…

David - There are several strands of evidence that point to vitamin D protecting against viral respiratory infections. And there are similarities between the patterns of infection across the globe between the coronavirus seasonal influenza and the swine flu pandemic, whereby the greater the distance you move from the equator, the higher the case rates for those viral infections, which has implicated sunlight exposure, and potentially vitamin D deficiency is one of the possible causes of that.

Chris - What does it actually do to the immune system though? Because most people will be familiar with vitamin D in terms of its role in maintaining healthy bones and skeleton. So what's it got to do with immunity?

David - It's actually a very broad acting steroid hormone. It affects a very large number of cells outside of the bone, which is the classical actions of vitamin D, but it's certainly been implicated in immune health. Blood cells, such as lymphocytes respond to the vitamin D. And also other organs, such as the heart muscle strength, has been linked to having a good level of vitamin D. So it's a fairly protective hormone and very wide effect, which potentially have some advantages in the sort of severe lung injury that COVID pneumonia causes.

Chris - Presumably then someone has done the obvious experiment where they've measured vitamin D levels and then they've looked at people who have, or haven't had, severe infections with coronavirus and have tried to marry the two together?

David - Yeah. So we've done that pre-coronavirus. What Covid patients get is something called the acute respiratory distress syndrome, which is the very severe lung inflammatory response. And it can be due to pneumonia, viral pneumonia. You can get it after trauma or smoke inhalation, those sorts of things. And we'd shown that levels of vitamin D are very low in people who develop that syndrome. And gradually as the pandemic has gone on more and more papers have been published saying that this is possibly the same with coronavirus infections.

Chris - So, to answer my question then, is there data yet linking vitamin D levels when people are challenged with coronavirus and whether or not they do get severe Covid?

David - Yeah, basically the vitamin D deficiency is very common in Covid patients. And there are a number of papers that have come out recently that implicate it in the severity of the exaggerated immune response, but most of the studies are quite small. They have a limited number of controls, which there are some issues with because of the difficulties of doing this sort of research during a pandemic.

Chris - Obviously one other explanation is that it's just that other lifestyle factors that happen to be there alongside a low level of vitamin D are what's really causing the increased risk, and that the vitamin D is just an innocent bystander.

David - Yeah. So I mean, those studies are all observational. There are no large trials of treating Covid patients with vitamin D, but there is one trial called the Cordoba study and that study did show some positive responses to vitamin D treatment.

Chris - Are we in some respects treating the wrong people if we come in with vitamin D once a person is sufficiently unwell to have come to the notice of a doctor? Would it not be potentially more effective to give people supplementation with vitamin D before they even become infected with coronavirus? Because A that would help the fact that it looks like people who live in countries like ours across winter are chronically short of this important vitamin anyway, but also they would be therefore in better shape to cope with coronavirus if they caught it?

David - Well, I think there are two aspects - is vitamin D abuse as a preventative agent, and is it useful as a treatment once you've got Covid. In terms of prevention, there is evidence that it reduces viral respiratory tract infections. It's not huge, 12% reduction probably in the number of infections, but it may also impact the severity. So the government recommends 400 units a day during the winter, but that's probably an underestimate of what is needed. But there aren't any trials to show that giving vitamin D to prevent coronavirus, currently, where the results are available. Though one has been started in the UK very recently, it won't report 'til the spring at the earliest.

Chris - What are your instincts telling you? Do you think that we're going to end up in a position where it will turn out, actually, this is quite a useful intervention. And given that most of us are vitamin D deficient across winter in high latitudes, it wouldn't do any harm to advise people to just up their vitamin D intake anyway?

David - Yeah, I mean, I'm taking 4,000 units a day. Most of my consultant colleagues who work in intensive care in Birmingham are already taking vitamin D supplements. It's particularly important I think if you're of non-Caucasian ethnicity, those individuals are at much higher risk of vitamin D deficiency. So in targeted individuals, it could be extremely effective, I think, and you know, I'm taking it. And I recommend it to my patients when I find they're vitamin D deficient.

Everyone’s praying for a vaccine against the coronavirus. But when it finally comes, who gets it? And how much will they have to pay? It’s not the first time we’ve talked about this crucial issue, and there’s a number of moral arguments to be made, but now economists from the research organisation RAND Europe have predicted the economic impacts of one country keeping the vaccine for themselves. Marco Hafner led the modelling and he spoke to Phil Sansom...

Marco - We did a lot of economic modeling under different scenarios, but in one scenario we found that if, for instance, only those countries or regions, which are currently developing a vaccine, and can also have the potential to manufacture that scale, like the European union, the UK, the US, China, Russia, and India, if only those countries would have initially access to vaccine, and can immunise their populations efficiently, the global economic costs would still be about 1.2 trillion every single year.

Phil - Really? Why?

Marco - So this is because, what we model in our study is, we look at COVID-19 induced, reduced activity, in service sectors with close physical proximity, such as the hospitality sector, the recreation sector, but also transportation. So reduced activity in those sectors can have negative consequences for countries across the globe.

Phil - Oh, so you're saying that because economies rely on the service industry, on tourism, on other things, then you've got this economic loss, because everyone else still has coronavirus except for your country.

Marco - Exactly. If you are in a country, and you can vaccinate your population, your domestic demand in those sectors will gradually improve. But if other regions or countries in the world will not have access to vaccines, those economies will still suffer, which has negative consequences on international trade costs, but also on international demand.

Phil - Does it depend on which country you're in?

Marco - It doesn't necessarily depend on which country you're in. As long as, if you're a country who will be able to vaccinate your population, demand in that country will improve. But as long as all the other regions will not have access in those regions, the negative consequences will still be low [high]. And even if you're a country who can vaccinate your population sufficiently, you will still suffer economically, because you live in a globalised world and you are interrelated into global supply chains.

Phil - I mean, we're making an economic argument here, for someone looking at economics, is the cost that you're calculating, that would come from other countries around you having COVID, really higher than the cost of you making a bunch more vaccines, because vaccines surely are not cheap?

Marco - Yeah. They're probably not going to be cheap. Obviously there's a lot of uncertainty around how they will be priced and so on. But in our study we show that even if only the poorest countries in the world, and that's the countries that are classified by the World Bank as low income countries, if only those would initially kind of, miss out on vaccines, we estimate that the high-income countries would still lose combined, about 119 billion a year in GDP terms. And current existing estimates suggest that vaccinating the poorer countries would probably cost around 25 billion US dollars a year. And if you take them into perspective, that means that for every dollar high-income countries would spend in giving access to low income countries, they probably will get a return up to about 5 dollars.

Phil - Oh really? Gives you a lot of bang for your buck.

Marco - Yeah. You could say that basically.

Phil - I mean, this is a real change from the rhetoric of someone like, well, I hate to bring up Donald Trump, because he's on the news almost every day, but someone like that, who would say, you know, we're going to make a vaccine and my country's going to get it, priority number one. You're saying that actually, the moral argument is the economic argument as well, in that if one country has the coronavirus, that's kind of bad for everyone.

Marco - Yes. I mean, obviously there's a point to be made of having some sort of nationalistic behavior across different leaders, because obviously they are responsible to their own populations and probably want to, you know, make sure that their population gets access first, but you can make this, not only a moral argument, but also an economic argument. And actually, if there's a way to provide equitable access to vaccines across the globe, there's definitely a return on that.

Now not all migratory species have the capacity to cover great distances unaided. Back in 2006, Cambridge University mollusc expert Richard Preece published research of snails making a rather phenomenal journey, and he told Katie Haylor about his work...

Richard - Some have been shown to travel enormous distances as passengers on the back of birds or other organisms. The ones I'm about to tell you about are about a centimetre long, two or three millimetres in width; long, slender things called Balea. I was fortunate enough to go on an expedition to the Tristan da Cunha islands in 1982. I spent most of the time on an island called Inaccessible Island, which as the name suggests is rather a difficult place to get to! These are volcanic islands right in the middle of the South Atlantic, about midway between South Africa and South America. With my interest, I was obviously keen to look at the species of snail that occur on those islands and nowhere else. Very few people have had the opportunity to do any field work there. I was also keen to see what introduced snails and other things occur on those islands, given their extreme remote position.

Katie - And it turns out that Richard isn't the first to go looking for snails on this island.

Richard - In fact, the first person to have collected snails on Tristan was a chap called Captain Carmichael, sent out to Tristan with the initial garrison; because basically the founding human population there were sent there to try and deny the French a base from which to rescue Napoleon; so we're talking in the immediate aftermath of Waterloo, a British garrison was set up there. And he was obviously bored out of his mind, and he actually resorted to collecting snails amongst other things; and he found some of these snails that no one else had ever seen before.

Katie - The question of how land snails ended up on remote islands was one that Charles Darwin himself pondered.

Richard - He comes into the story in a general way, because one of the things that fascinated him was trying to address the huge problem - how on earth do land snails - with such proverbially poor powers of dispersal - how on earth can they get to such remote islands? And these are islands that are oceanic, so they've never had any connection with mainland at all; so they must have gained access to those islands through some sort of aerial means. And since they don't actually physically fly, some other mechanism must be involved. And this was a subject that fascinated him for years, and indeed his very last paper was written about dispersal in molluscs.

Katie - Richard explained that there are two groups of snails on Tristan - the recent imports, several European species that have got there under human agency, likely from South Africa where they've also been introduced; and then there are two families, Balea and Succinea, which belong to a much more ancient colonisation. And they don't swim; they don't fly; but somehow at least one brave specimen made its way all the way over from Europe. Could they have been stowaways on a boat visiting the island? Well, Chris Smith asked Richard this previously on the Naked Scientists, and Richard explained that since the islands were only discovered in 1506, the amount of variation that now exists couldn't have occurred in that timeframe. Instead, it seems they hitched a ride. So how does a little snail manage to hitch a ride on migratory bird, cling on rather than falling into the depths of the ocean, and not only survive, but thrive, on an island so far from home?

Richard - Well this is a very interesting question, and a lot of people have tried to explore this. There is a little book written in the 1890s trying to document all the cases of passive dispersal in land snails, land and freshwater snails. Bivalves are known to clip themselves on to the legs of intersects or newts; birds have been shot and snails have been found amongst the plumage; but others have been shown to travel through the gut of a duck or something like that, a wader, and have actually survived the passage in the live state. So that is obviously another mechanism.

Katie - Rather handily, these snails are hermaphrodites, allowing a lonesome snail to start a colony potentially. And Richard's done some DNA detective work to check these really are the descendants of European snails.

Richard - I collected material that we dissected, and we showed from the dissections that, in fact, they were anatomically indistinguishable from Balea, European Balea. And we followed that up by looking at some DNA from the snails from Tristan, and indeed, everything points to the fact that they are indeed Balea. That family does not occur in Africa or anywhere in between, so that there's no other source population from which they could have arisen.

From animals moving by their own agency, let’s consider the other side of the coin, when us humans get involved in moving animals around. Invasive species - foreign species introduced by humans to a new habitat - are a major concern for maintaining the diversity of species on the globe, and whereas some cases of introductions are purposeful, many are accidental. Australia is well known for its unique wildlife, and much effort goes into protecting it with various measures to prevent and deal with invasive species to minimise the impact on native animals and plants, and subsequent impacts on society. This is known as biosecurity, and expert Simon McKirdy at Murdoch University in Perth, Western Australia, has recently analysed a 1,500 cabin cruise ship for stowaway insect life, to better understand the biosecurity risks posed by these global transport links to vulnerable habitats...

Simon - We've been heavily engaged in working with an island that has one of the world's largest natural gas plants on it. And when this project commenced, there was requirements put on by both our federal and state government, that the developers were not allowed to introduce a single what was referred to as a non-indigenous spaces or an invasive species to the island. The island was actually very much as it was pre the separation of this island from the mainland. So for more than 8,000 years, what's been living on that island was quite unique. And for some species that have become extinct on the mainland, this is their only last reserve. And so because of that, there's been very strict requirements put in place as to how that island would be protected.

In developing up a gas plant on the island, a decision was made to bring a cruise vessel, 1500 cabin size, bring it to the island to operate as an accommodation facility for more than 15 months. And because that vessel was operated for most of its working life in the Baltic, we then set up detailed surveillance on that vessel to find out what organisms were actually living on that vessel and what organisms might pose a risk to the island when the vessel arrived. We identified a number of insect species on the vessel that posed a significant risk not only to the Island, but also to Australia as a whole.

Katie - How do you go about surveying and monitoring that enormous boat?

Simon - We actually set up quite an extensive programme. We had scientists on board the vessel every day for that 19 months, extensive maps of the vessel. For the first period it was very much about looking over every part of the vessel in quite an intensive way. Part of that also included actually, you know, lifting carpet, dismantling wooden seating and things to try and get into any of the little holes and nooks where insects might live. And then through a process of starting to map where the insects were at a broad scale on decks, then to focus our efforts in on the particular decks where there was significant populations. So the insects that we were particularly concerned about, which were insects that are normally a concern with stored products, they were all around the decks where there had been bars in the previous life of the vessel - restaurants, dining rooms, nightclubs. So anywhere where people were consuming a lot of food or drink, that's where the insects would be. And our theory in the end on why we continued to find so many insects in those areas was just that when humans are there eating and drinking, we just naturally drop a lot of food and drink. And so it's the mix of, you know, the human detritus skin and that, that we just drop every day, food crumbs and spilt drinks that had become this long-term food source to keep these insects alive.

Katie - Were there any insects that were particularly successful stowaways?

Simon - Yeah, there was one in particular and it was the one that we actually considered was the biggest threat to Australia. And that was an insect called tribolium destructor, a tiny little beetle, we're only talking, you know, a beetle of about five millimetres in length. But despite all the effort we put into hunting for this beetle and baiting and trapping and chemical treatments, even at the end of the 19 months when that vessel sailed away, we had not managed to kill the population. We were still finding larvae on the last few days before it left. You know, we didn't eradicate the insect from the vessel, but what we did manage, and that was also an important part was, we didn't want the beetle to leave the vessel. If it left the vessel and then got introduced to the island and then to Australia, you know, that could have been a significant threat. So we set up a strong biosecurity system on the vessel where every single passenger that left the vessel had their luggage inspected. And we also did a lot of communication with the people that lived on the vessel, which were workers on the island, in communicating to them the importance of making sure they weren't carrying any of these insects as hitchhikers. And to make sure, you know, their luggage was clean when they left. And through that process, we were successful in making sure that the insect did not leave the vessel.

Katie - How would you summarise the significance of this work? Because it sounds like there aren't just lessons here to learn for Australia. Cruise liners go, well by definition, all over the world.

Simon - Yeah. Covid has thrown up an interesting discussion around cruise vessels and what they'll look like for the next, you know, few years. But what we had seen up to before Covid arrived was quite a rapidly increasing industry. And there was this need with passengers to keep visiting more and more remote locations. To us, the biggest message out of this - and from a biosecurity perspective, the concern - is that if we are going to allow cruise vessels to visit remote and vulnerable locations where we have very few or no invasive spaces, then we have to be very conscious of the risk that they may introduce pests into these areas. I don't think we should assume that just because from a surface view a cruise vessel looks very clean, it is possible that, you know, lurking underneath cleanliness layer is a population of insects that could pose a significant risk to a new area.