Bedbugs, pig organ transplants, and 1918 flu deaths

Plus, the street drugs being linked to deaths in the UK
13 October 2023
Presented by Chris Smith


A bed bug nymph (Cimex lectularius) as it was in the process of ingesting a blood meal from the arm of a “voluntary” human host


This week on The Naked Scientists, the rise of the bedbugs. Leading bedbug expert, James Logan, will tell us all we need to know. Also, could genetically modified pig kidneys soon be transplanted into humans? The clinical trial is now awaiting approval. Plus, why it might be time for us to reappraise the impact of the 1918 flu pandemic.

In this episode

A bed bug nymph (Cimex lectularius) as it was in the process of ingesting a blood meal from the arm of a “voluntary” human host

What are bedbugs and why are they making a comeback?
James Logan, London School of Hygiene and Tropical Medicine

“Night night. Sleep tight. Don’t let the bedbugs bite!” will be a familiar bedtime rhyme for many across the world. But it’s fast becoming one that you may need to take more seriously, because these critters are back with a vengeance and causing very real problems in some major cities…and there are also fears they are on the move. To separate the fact from the fiction, Professor James Logan is a bedbug expert at the London School of Hygiene and Tropical Medicine…

James - bed bugs are really quite fascinating insects in their own right. A lot of people get them mixed up with house dust mites. So when you think about bed bugs in your home, you think about something microscopic that's crawling around on your bed, but those tend to be dust mites. bed bugs, when they're adults, are actually pretty big about the size of an apple pip. When they're younger, they can be a bit smaller than that and sort of translucent. They need blood to produce eggs and to survive. Although one of the incredible things about them is that they can survive for up to a year without feeding on any blood, which makes them really formidable insects to control.

Chris - How do they find us and why do they go for us?

James - Well, they will feed on pretty much any animal. So if you've got a pet at home, they might feed on that pet as well, although they tend to prefer to feed on us. And like most insects, they use their sense of smell. So they're attracted to chemicals that are given off in our body odour and in our breath. So let's set the scene. Imagine you've come back from holiday and you've been staying in a hotel with bed bugs. When you get back home, the bed bug comes out of your suitcase. The first thing it will do is run off and it will hide somewhere. It will get into a little tight space until it feels safe. Then when the lights go off and it can smell a human, it will come out and it'll follow that trail of odour and heat to find you where it'll then feed and then as soon as it's done that it goes all the way back to its safe refuge.

Chris - And how do you know you've fallen victim to a bed bug and not say a mosquito or a flea?

James - It can be quite difficult to determine the difference between bites. Reactions vary and so it's difficult to kind of pinpoint it. But with a mosquito, you tend to just get one bite, maybe two. With a bed bug, you often get a cluster of bites. Sometimes they're in a line as well. So if you imagine you're lying on your bed and your arm is sort of outside of the sheet, a bed bug might crawl onto the bed onto the mattress and it will feed and it will probably sort of move along the arm. It'll take multiple bites along the arm. So you might get a line of bites if you're staying somewhere where there's a really bad infestation. You know, it's quite rare, but it does happen if there's a bad infestation. People report having hundreds and hundreds of bites, which can be really quite debilitating.

Chris - And how do the bed bugs themselves reproduce?

James - The male essentially penetrates through the cuticle of the female and inserts sperm into the female, which is quite traumatic for the female as you can imagine. But that's quite an unusual way of mating. But once that's happened, then after a few weeks the female will lay eggs and she can lay hundreds of eggs. And if you've got an infestation, you can often see those eggs either sort of in a crack in furniture or along the mattress. And they're tiny. They're really, really small. Sort of white, sort of transparency, white sort of colour as well. Once they hatch out, it takes a couple of weeks for them to then become adults themselves. All the time they require blood, so they'll be feeding every few days until the point at which they then begin to lay eggs, once they've mated as well. So an infestation can go from one pregnant bed bug laying eggs to thousands of bed bugs within a matter of weeks.

Chris - And is this why we keep seeing these reports of cities in America, cities in Europe, like Paris and now people are saying London might be at risk as well? Is that what's going on?

James - We're certainly seeing a trend for bed bug infestations increasing across the world. We've seen reports in France and the UK, New York. But really bed bugs are a global issue. They can be found pretty much anywhere in tropical regions. There's a slightly different species. So for example, the ones that we encounter are Cimex lectularius and the ones that you find in more tropical regions are Cimex hemipterus. Now we're seeing a rise in the number of bed bugs because of a few different factors. One is that bed bugs have become resistant to insecticides and that's causing a big problem. So the toxic chemicals we normally use to kill them are no longer as effective for many populations around the world. The second thing is that as humans, we like to travel and travel over the years has increased substantially. And now we're sort of beginning to get back to the sort of pre pandemic levels of travel. And so that helps to spread bed bugs. And then there's other things as well, like people like to upcycle second hand furniture, which can contain bed bugs if you're not careful. So it's always worth checking that. And then there's climate change to consider as well. Now we don't really know what's happening with climate change and bed bugs. However, as a general trend, we know that warmer temperatures, when there's more months of the year that are warmer, there's more chance of insects surviving better for longer and breeding quicker.

Chris - And so if one does fall victim to an infestation, how do you rid yourself of the pest?

James - You want to pray that you don't. The way to get rid of it essentially is to call a pest controller. Now you can try and tackle it yourself, but the chances are you won't be successful. And there are some products out there that you can use. There are insecticides that you can put down. But as I said, you know, insecticides may no longer work on the bed bugs that might be in your home. What you can do is use some of those products to maybe just sort of control it to a certain extent, but it probably won't get rid of the problem. So unfortunately the best thing you can do is call a pest controller and that's going to cost a bit of money.

Chris - Prevention's always better than cure. What steps can we take to keep ourselves from being infested?

James - So the good news is that there are things that you can do to minimise the risk of bringing home bed bugs. So the first thing I would do is I would check the reviews before you go or before you book a hotel, check the reviews and just check that there aren't reports of bed bugs being there. And if there are reports the hotel may have got rid of the bed bugs and they should say that if they have. Once you're there, and if you think there are bed bugs because you see them or you feel you're being bitten a lot in the room, then ask to move rooms. Or if it's really bad, move hotels. The telltale signs of bed bugs are a) the bites b) looking out for little brown spots on the bed sheets, which are little droplets of poo from the bed bugs. That can be a telltale sign or if indeed you see them. Now if there are bed bugs there, and in fact even if there aren't bed bugs wherever you are, whether it's a five star hotel or it's a youth hostel, it doesn't matter. Keep your luggage off the floor. So use the luggage racks, keep your luggage zipped up. Any clothes that you unpack. Make sure you hang them up in the wardrobe. I wouldn't put them in drawers just in case because that's a likely place with bed bugs possibly to be hiding. Hang them up, don't leave them on the floor. When you then go home, before you go, check your clothes along the seams, just make sure there are no bed bugs hiding in there. Check inside your luggage. When you get back, if you know you've stayed somewhere where there were bed bugs or likely to be bed bugs, unpack your bag in the garden. Bed bugs won't survive outside. So that's a good place to do that. And then if you're really worried, what you can do is you can bag up your clothing and stick it in the freezer for a couple of days, which should kill anything that's there. The other thing you can do is wash your clothing at 60 degrees and that would kill any bug that is there as well.


Pig kidneys transplanted successfully into primates
George Church, Harvard University

A team of scientists claim that they successfully achieved long-term functioning kidney transplants from genetically modified pigs into non-human primates. It’s hoped that the work could mean that organs from the pigs, which have been gene-edited to remove potentially harmful viruses and signatures that would otherwise provoke immune attack, can soon also be transplanted routinely into humans. The geneticist behind the study is Harvard’s George Church…

George - Our solution is to genetically engineer pigs which have organs that are the right size and physiology for transplant so that they're not rejected and in many other ways are compatible.

Chris - Do we know why they are rejected without the sorts of modifications that you are talking about?

George - There's one set of factors that cause very, very swift rejection, which are the sugars on the surface of the cells. And there's another set that causes rejection because they're either recognised as their proteins are different or incompatible with the blood components.

Chris - And so your goal is to change those in the pig in some way so that when the organ does end up in a person, the immune system doesn't recognise those things as foreign.

George - That's right. We changed 69 places in the genome. Three of them are the hyperacute sugars reaction. Seven of them are putting in human proteins that downregulate reactivity. The remainder are to avoid viruses that are hidden inside of the pig genome.

Chris - Ah, so you haven't just taken things away. You're actually putting some things in to further manipulate the immune system when the organ ends up in the person.

George - Seven of them are human proteins that the genes have been inserted.

Chris - What does this do to the pig when you make these edits?

George - The pigs are healthy in every way that we've measured.

Chris - That's very reassuring. And there's no risk that you could introduce some kind of latent disease in the pig when you make these changes that could affect the way that organ then behaves once it goes into a recipient.

George - I hesitate to say there's no risk, but I can say there's probably less risk because we've actually eliminated some of the latent viruses. 59 of them actually. They're retroviruses, which have been shown to cause cancer. So I think intrinsically lower risk than ever before.

Chris - And what have you done now with this paper to prove or at least reassure us that this is the right direction of travel and that this is going to work?

George - So we have over two year survival of a kidney in at least one non-human primate recipient. We're aiming for a point where we routinely get more than one year, then we go into clinical trials. Hopefully we'll be having discussions with the FDA over the next three months on getting things ready for human clinical trials.

Chris - So you are literally at the cusp now where these organs are going to start going into significant numbers of patients?

George - That's correct, yes.

Chris - You mentioned that the organs are lasting about a year. So why is it only a year, given that you've done all this genetic engineering to make them as compatible as possible? Why are they still only going on for a year and possibly in one exceptional case two years?

George - So almost all the endpoints are not due to the organ failing because it's being rejected. They have to do with the fact that it's much harder to do these experiments in primates than in humans. In almost every way, it's expected that the human clinical trials will be much easier than the animal trials. That's been the experience of many people.

Chris - Will you be going straight into living human recipients? I know that sounds a bit strange, but what I'm getting at is that one intermediate step in a situation like this can sometimes be to work on people who have, for instance, been declared brain dead because of an accident or something. And so rather than take organs out of them, sometimes you can put things in to test things under those circumstances, families are very kind and they let those sorts of experiments go on. Would that be one way to test whether or not these things are safe and that they work?

George - Yes. That is a growing possibility. It's been used twice, I think, so far. There have also been compassionate use cases so far, but we're interested in very long-term survival.

Chris - So you are really going in with patients and you are looking to say, we're going to change the life of that person with this pig derived organ?

George - Yes. There are hundreds of thousands of people that are very anxious to have some alternative to the current problems. I mean, it's about 10% of the population that is at risk. It's a very important step that we're taking.

A line of differently-shaped pills.

Super strength nitazene opioid drug linked to UK deaths
David Nutt, Imperial College London

A coroner has said that super strength street drugs have been linked to multiple deaths across Northern Ireland. The same thing is happening elsewhere in the UK and in the US. The drugs responsible - which are called nitazenes - were first developed - and rapidly dropped - in the 1950s. They mimic the effects of natural opiates such as morphine. Like their cousin fentanyl, another powerful synthetic opioid, they are considerably stronger, meaning that it’s easy to overdose and cause a respiratory arrest. But unlike fentanyl, they’re not illegal and the chemicals you need to make them are not regulated, which is why they’re rearing their heads now, over half a century later. So what do we know about them, and their potential impacts? Professor David Nutt is a neuropsychopharmacologist and former government drug “Tsar”...

David - The problem with nitazenes and the fentanyls is that some of them are exceptionally powerful. Let's say morphine is one, and let's say heroin is two, fentanyl is a hundred. It's 50 times more potent than heroin. And the nitazenes are up there, they're alongside fentanyl and there are nitazenes which are even more potent. That potency has a huge impact because it's difficult to know how much you're taking because the amounts are so small. Even the people who are selling it don't know how to weigh it out accurately. The more potent the opiates, the more likely it is to stop you breathing. Now fentanyls have become very popular in the states because there was a heroin shortage induced by the United Nations who tried to control the misuse of heroin by reducing the production of the opium poppy. And all that did was encourage, particularly the Mexican cartels, to find alternatives. And I suppose we should be grateful because they could have found these alternatives back in the 50s when fentanyl was first discovered. But they took them till about 2000 to realise there were alternatives they could make. And the problem now is that fentanyl is easy to make. It's 50 times more potent and half the price. So you can see the profit margin for fentanyl is way better than that for heroin. So the American market, illegal market, has been flooded with fentanyls for the last 10 years and last year over a hundred thousand Americans died of fentanyl overdose. So more died last year of fentanyl than died in the whole of the Vietnam War.

Chris - So why are they exploring nitazenes if they've already got fentanyls?

David - Because the American government has been putting a lot of pressure on the Chinese to stop making the precursors for fentanyls. They've made most known fentanyls illegal. So then the market has looked to see if it can find alternatives to fentanyl that are legal because these nitazenes were never made illegal in the 50s because they weren't used. So there was no reason to make them illegal. Now they're being made and being used, but they're legal, so they can be sold more easily than the fentanyls. And that's why people have moved to them, to get around the ban on fentanyls.

Chris - And who is actually making them?

David - The precursors are usually being made in China or India, and then they're being sold onto cartels again, particularly Mexican, but also within America cartels in the USA, who are then just finalising them or importing the actual final product themselves.

Chris - Are we making it illegal here now to combat the fact that, as you've said, it's a designer agent? To an extent, it's not regulated at the moment.

David - The black market doesn't really care whether drugs are illegal or illegal. The solution is to have testing facilities so that people know what they're taking. So if they discover what they think is heroin is nitazene or it's fentanyl, they don't use it. And we need safe injecting rooms, safe overdose prevention centres. But they've just started in Scotland where people can take the drugs and if they accidentally overdose because they don't know what they're taking, they've been given too much, they can have it reversed because there are reversal agents such as Naloxone and Naltrexone.

Chris - In the past you've been quite vocal about the fact that there are, sitting on the shelf, some potentially promising agents that might help with certain forms of mental illness and so on that have been dismissed because they were written off of drugs of abuse. Are there any positives that could come out of the nitazenes that that could find their way back into clinical use? Or are they just too dangerous?

David - We have enough powerful painkillers with both the plant opioids and also with the fentanyls. We don't need new painkillers. What we need are for people not to be using painkillers recreationally.

Influenza virus particles

Healthy and young people not worse off from 1918 Spanish flu
Amanda Wissler, McMaster University

A new study has found that the claim that the 1918 flu pandemic was much more likely to wipe out young, healthy adults than the old and infirm is probably wrong. Anecdotal evidence from that pandemic suggested that young healthy individuals were much more likely to be victims of the virus. Some had speculated that their fitter, youthful immune systems were their undoing. But hallmarks of health, and pre-existing disease, on the skeletons of pandemic victims have now enabled McMaster University, Canada, bio-archaeologist Amanda Wissler to lay this claim to rest…

Amanda - There are a lot of assumptions that we have about the 1918 influenza pandemic, and one of them is this idea that healthy adults were just as likely to die as unhealthy adults, or sometimes even some people say even more likely to die. Doctors were reporting that they were finding that healthy young men were even more likely to die than the unhealthy ones. So I wanted to set out, to find out if that was true, because healthy people should not die. That's not what it means to be healthy.

Chris - I know exactly what you mean because I myself have done this when commenting on past pandemics and things we've all said, and the striking thing here was this brought down even the hail and hearty, you are arguing then that this might be on shaky ground.

Amanda - I think it is. I think there's been a lot of research also particularly into the Black Death that has also tested this idea that, you know, oh my gosh, everybody was likely to die. It didn't matter who you were. But really that's not the case that they also found it in there. And so I think that's also what I expected to find with the 1918 flu.

Chris - This was more than a century ago. So how did you try and probe this?

Amanda - Most work on the 1918 flu has relied on archival records and hospital records and things like that, but there's a lot that we can't get from there. We can't look at the health of these people, especially their health over their whole lifetime. And so I look at human skeletal remains. So the skeletons are actually of people who died during and from the 1918 flu.

Chris - Are there many such specimens available?

Amanda - There aren't for good reason. You know, people belong in the ground if that's where they want to be, but no, there are probably only a handful of collections in the world that would have these individuals. And so my collection, it is relatively small, only about a hundred people who died during the time period that I was looking at.

Chris - And so what can you learn from the skeleton? How did you actually look at the remains?

Amanda - So looking at the skeleton, what happens is when a person is experiencing some stress event, and so this could be emotional stress or environmental, mal malnutrition or a long-term chronic disease stress. So what happens is your immune system and everything is trying to compensate and, and help you with that. And as a result, you get what are sort of these spongy looking markers on the bone. And so I looked specifically at the tibia, which is the shin bone, and I can see who has all of these little spongy markers on their tibia that shouldn't be there in a normal healthy person.

Chris - How did you use that to then work out whether someone was healthy or unhealthy because these people have died of the flu. So presumably that was pretty stressful.

Amanda - One of the key things here is that your bone actually takes weeks, months, or even years to change. And so these markers that I look at, this spongy looking bone would not have been caused by the flu because the flu happened fast. Like there are records of people who died within two, three days. And so instead what these spongy bone lesions show is sort of a long-term life experience of nutritional, environmental, and social stress. And so I can see the people who have these lesions we're stressed. So I compare people with certain types of lesions that look like they're more stressed versus other ones, to see which group is dying of the flu.

Chris - Got it. So basically you've got a long-term snapshot of someone's general health captured by the bone. And you can then ask, well, do I see as many people with healthy bones arguing they were healthy in life who are in graveyards because of the flu as I do? Or even more of those compared to people who clearly were unhealthy at the time they died of the flu? That would be the question.

Amanda - Mm-hmm. <affirmative>. And what's really interesting about these lesions is that I can tell based on the texture of the bone is who had an active stress when they were dying. So something that was ongoing, maybe an active disease versus someone who had the lesion, but the bone had actually healed and it was nice and smooth. So I can see in those people who with healed bone had overcome their stress, right? So in a way they were more resilient than the people who had an active stress at the time of their death. And we found that people with active stress at the time of their death had a much greater likelihood of dying in 1918 from the flu.

Chris -
So this is all a myth then, and that in fact, just as we see with COVID, preexisting health conditions are your biggest risk factor then.

Amanda - I wouldn't go so far as saying it's a myth, because there is something to it. All of our data that we looked at showed that, overall, everyone was a little bit more likely to die during the 1918 flu. Kind of like with COVID, people who normally wouldn't die were a little bit more likely to die during COVID and also during the 1918 flu. But in general, this just an easy answer of yes, healthy people were just as likely to die. Yeah. We did find that that wasn't entirely true.

Chris - How do you think this took root in the first place then? Was it just a story that improved in the telling and a juicy story was getting more traction than the more mundane, what we would expect. If you are already ill, you're more likely to be claimed by the Spanish flu pandemic. Is that what happened, do you think?

Amanda - You know, we don't fully know yet. We haven't gotten to that part of the story. But I think that part of it might be because the fact that young adults were more likely to die from the flu in 1918 compared to other years is a hundred percent true. That's not a debate. And the thing is, young adults dying is really strange. And so when you lose those people it's unexpected and it's really disruptive. And so I think it just really was just so much more memorable to everyone that people kept telling these stories and it got really incorporated into our folk memory of this event.

Dipping a cup into a body of water.

How did people find water in the past?

Rhys - To answer the question, we enlisted the help of Dr Ellen Arnold. Ellen is an environmental historian and the editor of the Water History journal:

Ellen - Most of the time people found water by closely observing the natural world around them. There were animal species that gravitated towards permanent sources of water. There were birds that flew towards oases in the desert. There were kinds of grasses and plants - and even weeds - that were more present in wetter ground or more present above higher water tables.

Rhys - So, people probably relied on clues from nature. But what about the second question; did our ancestors just dig until the water table was reached?

Ellen - As Donald pointed out on his question: you can always kinda just dig down and find water. The question is: can you dig deep enough using pre-modern tools and technology? And so watching the signs of nature and then somehow signalling to other people both at the same moment - but also in the future - became an essential task for building cities and water systems and permanent supplies of groundwater.”

Rhys - So it was a combination of piecing together clues from the surroundings, some technological know-how and a group effort that got our ancestors within reach of water. Thanks very much to environmental historian Dr Ellen Arnold. Next time this biting enquiry from listener Sarah.

Sarah - I live in an area with a huge number of mosquitoes that I take every opportunity to kill. I assume that the ones I kill are the weakest and least cunning, which is why I can catch them. Am I, in fact, just creating a master race of mosquitoes by killing off the weakest ones?

Rhys - Thank you, Sarah. So are we unwittingly breeding a master race of mosquitoes? If you’d like to hazard a guess, or you have a question of your own, please email us. That’s or jot down your musings on our forum at


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