Don't Bite Me!

Speaker 1 This BBC podcast is supported by ads outside the UK.

Speaker 2 Ranked number one in innovation 10 consecutive years, Arizona State University isn't just ahead of the curve, it's creating new paths to success. Learn from notable clinical and research faculty.

Speaker 2 Online, that's a degree better. Explore programs at asuonline.asu.edu.

Speaker 3 Sucks!

Speaker 4 The new musical has made Tony award-winning history on Broadway. We demand to be home! Winner, best score! We demand to be be seen.
Winner, best book.

Speaker 4 It's a theatrical masterpiece that's thrilling, inspiring, dazzlingly entertaining, and unquestionably the most emotionally stirring musical this season.

Speaker 5 Suffs!

Speaker 4 Playing the Orpheum Theater October 22nd through November 9th. Tickets at BroadwaySF.com.

Speaker 7 BBC Sounds, Music, Radio, Podcasts.

Speaker 1 I'm Hannah Fry. And I'm Dara O'Brien.

Speaker 9 And this is Curious Cases.

Speaker 1 The show where we take your quirkiest questions, your crunchiest conundrums, and then we solve them.

Speaker 8 With the power of science.

Speaker 1 I mean, do we always solve them?

Speaker 3 I mean, the hit rate's pretty low.

Speaker 1 But it is with science.

Speaker 3 It is with science.

Speaker 3 Do you consider yourself a particularly smelly person, Dara?

Speaker 1 I wash. Is that where you're asking? I'm sorry.
I'm with the other side of a table here.

Speaker 1 Is that obvious?

Speaker 5 I didn't mean to other humans. Oh, okay i meant i meant to insects oh any specific insects mosquitoes right well look

Speaker 1 mosquitoes are the bane of my life in the sense that like no matter how nice the holiday is and how fantastic the place is there is a point after a certain number of days where i go i'd like to go home now please because i'm just over the itching

Speaker 5 absolutely over the itching of it all you get do you get that well i think that like you i smell like a delicious tiramousu yeah steak dinner

Speaker 5 exactly Wafting along to a mosquito. I have discovered over the years, this is not what this program is about, but ways to deal with the bites.

Speaker 9 Burn them.

Speaker 1 Oh, I've gone ice them.

Speaker 9 Shock them, do you?

Speaker 8 Ice them, yeah.

Speaker 5 The thing that I found,

Speaker 5 and don't take my medical advice, I'm not that kind of doctor. No.

Speaker 3 There's a little thing that you can buy that gives them an electric shock.

Speaker 1 Yes, I remember that, yeah.

Speaker 8 Oh.

Speaker 1 That works for you, does that? That works for me. Little zapper thing.
Once on a comic relief trip, one got into my shirt overnight.

Speaker 1 And do you know the thing when you wake up and there's like you can follow its path yeah across my chest and around to my back like whatever I think it was 143 good lord yeah there was um there was one occasion when I was uh I was away I just started dating somebody this is a few years ago and I just

Speaker 5 I was away and I got a mosquito bite on my cheek right and it as it usually does with me swelled up massively like the size of a C D on my face

Speaker 5 and then I called him was like oh you know I can't I can't see you because I've got quite a big mosquito bite I really really, he was like, no, no, no, no, no, don't worry, it doesn't matter what you look like.

Speaker 5 You come here, you honestly, it doesn't matter. You should definitely come.

Speaker 5 And then I found myself on his doorstep, rang the doorbell, open the door, and he was like, you definitely should not have come.

Speaker 1 At least that's honest. Oh, no, no.

Speaker 13 You really

Speaker 8 do look horrifying.

Speaker 9 Should we listen to the questions?

Speaker 8 Yeah, okay.

Speaker 14 Hi, I'm Ailsa. I want to ask: why

Speaker 15 or why do I get bitten by mosquitoes and midges wherever they are and my husband doesn't get bitten at all.

Speaker 16 I'm not convinced that I don't actually get bitten by mosquitoes but they seem to go for pails first that's why I always take her on holiday with me.

Speaker 15 So as soon as we're in the vicinity of mosquitoes I think they must know that I'm there and they just go

Speaker 15 straight towards me. I can get bitten multiple times.
I get bitten on the ankles and the eyes and the legs and the arms.

Speaker 15 I wouldn't even mind donating a bit of blood, but they then leave something in me that makes me itch like crazy.

Speaker 16 I think Elsa's just a bit juicier. It must be something to do with her blood that attracts them or the smell of the pheromones.

Speaker 17 I reckon that I'm just tasty and Keith is a little bit hairier than me, so maybe they can't get through the jungle of hair to bite him.

Speaker 1 It is notable that these people are Scottish and midges in Scotland are amongst the most demonic of these creatures. There was a survey of people going, would you come back to Scotland on holiday?

Speaker 1 Scotland's an incredibly beautiful country. There's lots of really amazing things.
And like 48% said no, midges.

Speaker 1 Yeah, because they got bitten. You know, they go off salmon fishing or something and they have to do it in a net.
Have you ever seen that?

Speaker 1 People in Scotland wearing like veils, like bridal veils, while fishing on a loch somewhere. Beautiful.
It's a weird scenario.

Speaker 3 What I want to see is a wedding in that scenario

Speaker 5 with an actual bride on the wedding.

Speaker 1 You may kiss the bride. No, no, it's okay, fine.
We'll wait. We'll We'll wait till we endure it.
Wait till it's a wrong.

Speaker 8 Come on under my net. Yeah.

Speaker 1 So it's about attractiveness. Are we taking a look at how attractive you are?

Speaker 3 Yeah, how much of a steak dinner are you to mosquitoes?

Speaker 1 Well, here to help us get to the bottom of this animal attraction, our Professor Leslie Voshol from Rockefeller University in the US studies why some of us are mosquito magnets.

Speaker 5 And we are also joined by Professor John Pickett from Cardiff University, who is particularly interested in why some of us aren't.

Speaker 1 Leslie, let's start with you. Firstly, how many different types of mosquitoes are there and how many actually bite?

Speaker 18 There are a thousand species of mosquitoes. Some of them feed on blood, some of them do not.
A very small number of species specialize on people and they are the ones who pester us.

Speaker 18 But it is a minority of mosquitoes who pester and feed on the blood of humans.

Speaker 5 Hashtag not all mosquitoes. Yeah.

Speaker 18 Not all mosquitoes.

Speaker 18 Don't be mad at all mosquitoes.

Speaker 1 Okay, I don't want to misrepresent mosquitoes because I know they're a powerful lobby.

Speaker 18 There's some very sweet and beautiful vegan mosquitoes who do not want to kill us.

Speaker 1 But nonetheless, you did say sentence like true, the words, feed on our blood. And specifically, there is something in blood that they need.

Speaker 18 So there's vegan mosquitoes who get everything they need from plants, but the blood-feeding mosquitoes have figured out how to get a giant protein-rich meal, mostly from humans, and they need that to make eggs.

Speaker 9 Is it just the girls then?

Speaker 18 It is just the girls then. This is a female problem.
So when you smack that mosquito on your arm, please use the correct gender. So she is a she

Speaker 18 Because she needs that blood to make eggs. So if female mosquitoes stop biting us today, that would be the end of malaria.
It would be the end of...

Speaker 18 dengue and all the arborviruses and it would be the end of mosquitoes. So it's the need for the blood that is everything.

Speaker 1 And what is it within our blood that's so useful for them?

Speaker 18 Again, it's proteins, though. They chew those proteins into individual amino acids and then pump that into the ovaries to be able to make eggs.

Speaker 5 I mean, this is honestly changing my view.

Speaker 9 If this is now just like girls going through PMT, right?

Speaker 11 Gorging on ice cream.

Speaker 1 Oh, man. They're no sympathetic to you.

Speaker 9 Suddenly, I have had it.

Speaker 8 Oh, my God.

Speaker 18 Okay. Yeah, it's true.
We shouldn't be mad. They're being good moms.
They want to provision their offspring with the biggest meal possible. So we should not be angry with them.

Speaker 1 And how much blood will one buy take from us?

Speaker 18 In the lab, it's about two microliters, which is not an amount that your readers care about, but think about doubling their body weight. So females in the lab double their body weight.

Speaker 18 So I'm a big girl. I'm 160 pounds.
So I would be twice that if I were a female mosquito.

Speaker 18 It's an enormous, enormous meal.

Speaker 5 That's a lot of ice cream. It is.

Speaker 18 Yes.

Speaker 1 But we should not register that. They're not going to bleed us dry, mosquitoes.
So it's just the reaction we have to it is a problem.

Speaker 18 That is correct.

Speaker 10 Okay, I would happily donate that amount of blood.

Speaker 9 Could you not just sort of leave some out in a tray overnight?

Speaker 18 You know, but they really, they love everything about humans. So it's not going to be as alluring an experience to them.
So, they need the blood to be warm, they need to be attracted.

Speaker 18 They like the feeling of piercing skin.

Speaker 12 Okay, my sympathy is gone.

Speaker 8 Yeah, yeah.

Speaker 18 If we just put out buckets of blood, they don't like it nearly as much as if we, even if we put some artificial membrane, they really like that piercing feeling.

Speaker 1 And the action of piercing, do they put anticoagulants in?

Speaker 1 What effect are they having independent of the blood?

Speaker 18 Just like when we eat like a steak, we use saliva as part of the process. So, so females inject a lot of mosquito saliva under the skin, and that has a couple of purposes.

Speaker 18 One is a local anesthetic so that we do not feel the bite until after they've left.

Speaker 18 And the second is that it does sort of tenderize things, and that's where you get the immune reaction, the itchiness and the swelling.

Speaker 1 And also, presumably, if they've managed to invent a local anesthetic, they've also invented a very good syringe or like a very good hypodermic needle.

Speaker 18 Yeah, and it's one of the most beautiful structures in biology. It's like a flexible structure that can go under the skin and look for a capillary.
With like sort of laser focus, find the capillary.

Speaker 18 With a bevel tip, pierce the capillary, and then the pump gets activated and then the blood is drawn into the mid-gut of the animal. It's amazing.

Speaker 1 Can I say, by the way, one of the joys about doing the show is you meet people who study insects or animals or functions of nature that the rest of us have just casually dismissed.

Speaker 1 And they describe them as things of great beauty. They clearly are.

Speaker 1 I'm delighted I've given my life to studying these animals. They are incredible.
And you're painting a picture of a very, very evolved creature.

Speaker 18 Okay, they're terrible and they're beautiful.

Speaker 18 They are so beautiful. It's like a three-dimensional chess game and they are 50,000 steps ahead of us.
Everything about them is perfectly designed to get our blood.

Speaker 1 And just to get back to the initial question that was asked, different people react in different ways to those bites?

Speaker 18 Yeah. So we, in our early days of recruiting, hundreds of people thought we would do this smart thing and ask people, are you a mosquito magnet or are you not?

Speaker 18 And it ends up being completely useless because there's a big difference in how people react to bites.

Speaker 18 So, some people react very, very strongly and they always think that they are victims and they are mosquito magnets.

Speaker 18 But there is no correlation between how attractive you are and how strongly you react. So, everybody in my lab is bitten all the time.
So, we're very tolerized.

Speaker 18 We can get a couple hundred bites on our arm and then an hour later forget that we have been bitten.

Speaker 18 Whereas a regular human being being bitten will have itchy bites for would stay up for a week scratching.

Speaker 5 What you're saying here then does imply that some people are more attracted to mosquitoes.

Speaker 10 So what is it? Do you know what it is that makes people more attractive?

Speaker 18 Our most attractive person is more than 100 times more attractive to mosquitoes than our least attractive person.

Speaker 8 Why?

Speaker 18 I think it's still a mystery. We did some work a few years ago to show that the more carboxylic acids that you have on your skin, the more likely you are to be a mosquito magnet.

Speaker 18 But we know that it is not the only factor.

Speaker 5 Okay, I want you to talk me through just the process of choosing a victim.

Speaker 7 So how does it actually work?

Speaker 5 You said these are really, really highly tuned creatures.

Speaker 18 Humans, like all animals, give off carbon dioxide. So carbon dioxide activates mosquitoes, but that is not a signal of a human.

Speaker 18 They are attracted to heat, but that is not enough to tell them that it is a human. So it is the body odor that differentiates human from non-human animals.

Speaker 18 And then also the individual odor of different people can make someone a hundred times more attractive hold on though they haven't got noses these are flying syringes that are out to get our blood they are so sophisticated they have antennae that are full of neurons so nerve cells that are attuned to the smell of humans then they have these things called maxillary palps also full of neurons that sense also carbon dioxide because they love our breath and then the mouth parts like the tongue equivalent also can smell us so it's kind of psychedelic, like if your tongue could smell.

Speaker 18 So their whole head is covered with nerve cells that are very acutely tuned to the smell of humans. And again, it's not like underarm body odor if you exercise too much or like the...

Speaker 18 the smells of your anogenital regions really it's just like the odor of the skin that we as humans may not even be aware of and that stuff you can't cover with deodorant you can't cover it with perfume it's just this pervasive sort of general smell of human skin that again is not that body odor.

Speaker 1 It's not that you can shower, wash, soap up, whatever, to become invisible to mosquitoes.

Speaker 18 Yeah, no, no. I mean, when we collected scent for our study, we had people scrub their arms with hot water and soap just to have a baseline.

Speaker 18 Then they would wear nylon fabric on their arms, and there was enough in that nylon to attract a very large number of mosquitoes.

Speaker 18 So there's just something on our skin, again, that if you were to go around the studio and smell other people's arms, you wouldn't find it offensive.

Speaker 18 But the mosquitoes are incredibly sensitive to it.

Speaker 5 Okay, not to play God here, but can you not just like genetically engineer them to knock out this ability?

Speaker 18 Oh, yes. And the Bill and Melinda Gates Foundation invested heavily 14 years ago for scientists to do this.

Speaker 18 And so we systematically spent their money to make mutant mosquitoes that could not smell people. And so we had our great idea to knock out a gene called Orco.

Speaker 18 And then we put them in a cage and they had no problem finding people and biting them. Then we knocked out the carbon dioxide receptor and those mutants had no problems finding a person.

Speaker 18 Then we knocked out a bunch of other genes and they have no problems. And so again, three-dimensional chess game, mosquitoes are 50,000 steps ahead of us.

Speaker 18 They have built in multiple layers of backup plans.

Speaker 18 I'm not giving you a message of hope here today. It is a depressing message.
I just don't even know how we're going to stop them because they're always just 50,000 steps ahead of us.

Speaker 2 At Arizona State University, we're bringing world-class education from our globally acclaimed faculty to you.

Speaker 2 Ranked number one in innovation for 10 consecutive years and number two among public universities for employability. ASU isn't just ahead of the curve.
It's creating new paths to success.

Speaker 2 Earn your degree from the nation's most innovative university. Online, that's a degree better.
Explore more than 350 plus undergraduate, graduate, and certificate programs at asuonline.asu.edu.

Speaker 4 With a Wealthfront cash account, your uninvested cash earns 4% annual percentage yield from partner banks with free instant withdrawals, even on weekends and holidays.

Speaker 4 4% APY is not a promotional rate, and there's no limit to what you can deposit and earn. Wealthfront, money works better here.
Go to WealthFront.com to start today.

Speaker 4 Cash account offered by Wealthfront Brokerage LLC member FINRA SIPC. Wealthfront is not a bank.

Speaker 4 The APY on cash deposits as of December 27, 2024 is representative, subject to change and requires requires no minimum.

Speaker 4 Funds in the cash account are swept to partner banks where they earn a variable APY.

Speaker 3 What about what you eat and drink?

Speaker 5 I mean, this does particularly strike me as being bad on holiday, which might be because I'm in a sunny climate where mosquitoes are more prevalent, but it also might be because I drink more beer.

Speaker 18 Yeah, so there's one really, really great paper on beer that shows very compelling evidence that the same person who drinks a pint of water versus the same person drinking a pint of beer is a much more attractive after they've consumed a pint of beer.

Speaker 18 Now why that is, would you have the same effect if you had a single malt whiskey? Is it the alcohol? Is it the beer? Is it the person's behavior if they've had a beer? So it's sort of unresolved.

Speaker 18 But clearly, if you want to attract mosquitoes, drink a pint of beer.

Speaker 1 I mean, it just feels like they've increased their powers due to a general ruining every part of the holiday.

Speaker 18 Exactly, because you want to be outside drinking beer in a bikini or whatever. And so they are the same.

Speaker 1 That is my dream holiday.

Speaker 8 You know, if I could be free to be out there in a bikini, that'd be wonderful.

Speaker 18 Yeah, and they're with you.

Speaker 5 Okay, well, I think we all want to rid our minds of that image.

Speaker 3 So we've actually decided to put some of these mosquito theories to the test. And what we have done is a little experiment for you where last week Dara and I wore...
what would you call them?

Speaker 3 Pantyhose?

Speaker 1 I call them little footsie socks, tiny bits of tights.

Speaker 5 And they look so good with your bikini.

Speaker 3 And then we sent them off to Professor Sarah Reese from Edinburgh University, who studies malaria in mosquitoes.

Speaker 5 Sarah, what did did you do with that disgusting package?

Speaker 17 Okay, well, it's one of the most exciting experiments we've done because the results were remarkably clear.

Speaker 17 One of you, and I don't know who, is doubly attractive to mosquitoes than the other one of you.

Speaker 8 Whoa,

Speaker 8 okay.

Speaker 17 Yeah, let me talk you through what we did. So we did two kinds of experiments and I'll start with the most exciting one first.

Speaker 17 So we took your socks and we put each of your socks over a little heat pad and we put them on top of a cage of mosquitoes.

Speaker 17 And so the purpose of the heat pad is just to show the mosquitoes oh look there's a a warm-blooded human somewhere around here we should go and hunt it down and so because we put both of your socks on each side of the cage they could choose whose smells they'd be more attracted to so we put a camera in the bottom of the mosquito cage here and there's about 20 mosquitoes in this cage i should say we've replicated it about six times because you know one should replicate your experiments even though you're only a sample size of of two if we look at person A so can you see all these little mosquitoes there's quite a few of them having a go at that sock certainly are oh my god yeah that is an attractive sock to a mosquito there's loads of them around and they're really quite persistent they're really trying hard to stick their proboscis into that sock and get some blood but person b not nearly as many mosquitoes pathetic nothing no they don't care

Speaker 17 this is absolutely they're not persisting there in fact lots of them are giving up you know perhaps regretting their decision to have a look at B and they're going off to person A.

Speaker 1 Do you think they've generally shopped around a bit? They may have, you know, had a little sniff of person B and then got back to person A?

Speaker 17 They absolutely made a decision to go to person A and almost twice as many went to person A across all of our trials. So person A has attracted hundreds of mosquitoes compared to person B.

Speaker 17 So do you know which one of you is person A?

Speaker 5 Yes, we do. And I would like to reveal that I can add female mosquitoes to my fan base.

Speaker 8 Really?

Speaker 8 Oh. Yeah.

Speaker 1 So Hang, does this mean that I can't complain? Yes. Oh, my God.

Speaker 11 Well, you can complain, but only half as much as me.

Speaker 17 Sarah, this will only work for you if you are standing next to Hannah when there are mosquitoes around.

Speaker 1 Look, I enjoy doing the show with Hannah. We haven't extended this to...
Let's go on holiday together.

Speaker 5 I've heard it's holiday, Tara. It's not.
It's not.

Speaker 8 Yeah, it's quite true. You don't have to be around me anyway.

Speaker 1 Okay. I mean, I'm sort of relieved that therefore it could be worse for me.

Speaker 1 Earlier on, we were talking about the person who's most attractive to mosquitoes could be 100 times more attractive than the person who's least.

Speaker 1 If that's a scale, do we know how far along that scale Hannah might be?

Speaker 17 So the other thing I can tell you is when we gave the mosquitoes no choice between the two of you, so we gave mosquitoes only person A to see how attractive they were on their own compared to other mosquitoes getting person B.

Speaker 17 Actually, there's no difference between the two of you. So

Speaker 1 if you're on your own you're equally fair game we made a lot of effort early on just to distinguish the attractiveness to mosquitoes is the same as smelling bad but I'd like to now call that into question again they know that you're the one that they preferred that I'd like that to be my excuse me Leslie was talking about scrubbing the skin and the scent still being there I'd like to really re-emphasize that

Speaker 17 are there certain smells that they they like though Sarah well it might be that actually you both smell kind of the same it's just that Hannah is producing more of those smells.

Speaker 8 Oh, no.

Speaker 1 It's worse and worse. The heads keep coming here, don't they?

Speaker 17 Sorry, Hannah.

Speaker 8 Oh, God.

Speaker 8 That's awful.

Speaker 1 What kind of smells do they like?

Speaker 9 It's definitely Tiramisu.

Speaker 12 Okay, let's move on.

Speaker 1 Because I heard they like cheese. You like the smell of cheese?

Speaker 8 Is that one nice?

Speaker 3 Sarah, you dare sign for darlings.

Speaker 17 Okay, I'm going to try and tread very carefully here. I'm not casting any aspersions about your dietary or your washing habits here at all.

Speaker 8 At all.

Speaker 17 So, I mean, there have been a few studies that have shown that this particular kind of cheese made in Belgium, Limburger cheese, the bacteria that are used to ripen that cheese produce these carboxylic acid compounds that Leslie mentioned.

Speaker 17 And those compounds and those bacteria are pretty similar to some of the bacteria that we do. Naturally, I will stress the word naturally find on our feet.

Speaker 17 So it is possible that, you know, because we did the experiment on your foot smells, that perhaps what we're seeing is a differential vigorousness of your feet bacteria.

Speaker 9 Okay, guys, I think this is very harsh. I have extremely good hiding habits.
I wash my socks up to four times a month, okay?

Speaker 11 And if anyone has anything to say about that,

Speaker 1 I personally think I prefer the implication not that you smell of cheese, but you smell the bacteria used to ripen cheese.

Speaker 13 I think the curious case here, Dara, is that in fact it's the other way round.

Speaker 13 So if you actually just look at the smell and take away the contact, all people have attractants, but some have some extra chemistry which tells the mosquito that it may not be a good target for a blood meal.

Speaker 13 And those chemicals are what we call contextual repellents.

Speaker 13 So in the context of the human attractiveness, if you've got heightened levels or the presence of these chemicals, then we get a substantially reduced attractiveness.

Speaker 13 And certainly, there are people that they are completely unattractive to mosquitoes. Scottish biting midge will even fly by them to get to somebody who is attractive.

Speaker 5 So, this isn't that I stink it, that Dara's unattractive.

Speaker 8 Yes, hang on, hang on.

Speaker 1 I mean, this is flipping so fast at this stage. People need the clarity on this.

Speaker 1 I know there's a lot of discussion about the science of mosquitoes here, but we really want to work out who smells more.

Speaker 1 And we're way off. Hannah smells attractively versus I smell unattractively, and which is a better or worse skill to have?

Speaker 13 Well it depends whether we can use the chemicals that are causing that unattractiveness. That's the problem.
And it's two compounds made by our skin that we call terpenoids.

Speaker 13 And when they are oxidised, which can happen during stress,

Speaker 13 these compounds are formed and can indicate stress. And we think it's that that the mosquito is averse to.

Speaker 13 But really some of the people that have got high levels of these compounds smell, I'm sure, just like Dara does, absolutely normally.

Speaker 1 Absolutely wonderful, I think you want to say. It's not just normal, but gently warm, a musky sense of home.

Speaker 5 And I smell like relaxed, chill.

Speaker 3 I'm just a cool Zen girl.

Speaker 8 That's right.

Speaker 1 So I possibly excrete terpenoids.

Speaker 1 And when I'm stressed, say, for example, you've been asked to wear weird socks that have been sent to a lab, like, and that kind of freaks me out a little bit, that I excrete more of these, but these things actively repel mosquitoes.

Speaker 13 Yeah, so some people have got an inherent level which is higher than others of them,

Speaker 13 and those are the people who luckily aren't attractive.

Speaker 9 These compounds, though, can you not just like manufacture them slav them on yourself?

Speaker 13 Oh, yes, yes, that's how we find out that they do this.

Speaker 9 Then, okay, why can't I just go and buy this stuff then?

Speaker 13 Well, that's a pity, isn't it, that we can't do that at the moment.

Speaker 13 But we haven't managed to actually get the idea that this could be an alternative to the kind of repellents that we use and that I use when I go to Africa to work on malaria mosquitoes.

Speaker 1 I mean, mosquito bites are annoying and itchy, but we should say the real problem is that some of those mosquitoes can spread very nasty diseases and they are the biggest killer in the animal world.

Speaker 17 Absolutely.

Speaker 17 And the thing is, from my perspective, we don't need to worry so much about mosquitoes, but it's the things that are inside them, those viruses and those parasites that they're transmitting from person to person.

Speaker 17 And so that's actually what we want to target. I mean, a few hundred million cases of malaria exist every year.
It kills children under five.

Speaker 17 You know, up to 40% of the world's population do live in areas where there are malaria mosquitoes present.

Speaker 1 Is there anything within the parasite itself, you know, that makes it so good at spreading this disease?

Speaker 17 Well, the parasites also want the lipids, the fats and the proteins. So all the goodness that's in that blood, just like the mosquitoes do.

Speaker 17 And the parasites are competing with the mosquitoes for that foodstuff.

Speaker 17 Because the malaria parasites do a lot of bizarrely complicated development and replication when they're living inside a mosquito.

Speaker 17 It actually takes malaria parasites two weeks to get from entering in a mosquito to being ready to exit that mosquito and enter a new person.

Speaker 17 And that, you know, is beyond the lifespan of the vast majority of mosquitoes in the wild. So it's kind of crazy in a way that malaria is such a problem.

Speaker 9 How does it work then? If that sort of feels like a conundrum.

Speaker 17 If you're a parasite and you need to spend two weeks living inside a mosquito that is unlikely to make it for that length of time. Your best interests is in keeping your mosquito safe.

Speaker 17 So you don't want to cause it to get too ill.

Speaker 17 You don't want to cause it to do too many risk-taking behaviours like getting more blood, where they're quite likely to get swatted and squashed and killed.

Speaker 17 So there has been some ideas that, well, maybe malaria parasites actually make their mosquitoes live a very quiet life for those two weeks, only feeding on sugar until they're ready to be transmitted back to a person.

Speaker 17 And then they make their mosquito very hungry and very keen for blood but again jury's really out as to whether this could be a real phenomenon i mean mosquitoes don't appreciate having malaria it doesn't make them very sick but it's not great either so they maybe live a quiet life simply because they're a little bit ill mosquitoes tend to bite at night right so can you just if you really want to try and avoid them just be extremely careful at night time and then and then be more free during the day that's what you would hope for isn't it so we've been using bed nets for decades uh which stop mosquitoes biting people when they're sleeping during the night time.

Speaker 17 Those bed nets are often treated with insecticide chemicals. So not only do they stop the mosquito from getting any blood, but they also poison the mosquito to death.

Speaker 17 But this is clearly a massive problem if you're a mosquito. So what's the solution?

Speaker 17 Evolution generally finds a way and the solution mosquitoes have found, which relates to the multiple layers of backup plans that Leslie mentioned, is to bite people earlier in the evening and later in the morning when they're not protected by bed nets.

Speaker 17 There's even some suggestions that some mosquitoes are camping out outside schools and biting children when they arrive to start their school day, which is pretty terrifying.

Speaker 18 It is absolutely terrifying and thank you Sarah for raising this point that the mosquitoes say like haha you're all like sleeping under these nets where we can't get at you and so slowly the population moves toward day biting is terrifying because they realize we are not going to walk around wearing bed nets as we go about our day.

Speaker 5 Leslie, that idea of hanging around outside schools to get children as they leave during the daytime, I mean, that sounds pretty aggressive. Does their behavior change if they have dengue or malaria?

Speaker 18 They are super aggressive biters.

Speaker 18 I think that the evidence for dengue is a little bit more convincing on both sides, that dengue-infected mosquitoes may be more aggressive, more restless, take more bites.

Speaker 18 And there is one paper that says that humans smell different when they're infected with dengue and are more attractive but there's only a very small number of papers and so more work is needed to really figure out which side is correct.

Speaker 17 The day biting behavior is what we call behavioral plasticity.

Speaker 17 So they're hungry because they're not getting blood when they want it and so they're just changing their behavior to try out something new that will happen to be successful.

Speaker 17 But one of the the kind of the knock-on consequences of that is, well, what does that mean for malaria transmission? Which brings it back to what do we really care about dealing with here?

Speaker 17 And it's the disease transmission. So we don't really know what ending up in a mosquito at a weird time of day means for either party.

Speaker 17 You know, we feel rubbish if we eat a massive meal just before we go to bed or immediately if we wake up. The same is going to be true for mosquitoes as well.

Speaker 17 Taking a huge blood meal, which is kind of like drinking a bath of soup if you're a human, and doing that at a strange time of day when our circadian clocks aren't expecting it, isn't going to be so good for our health.

Speaker 17 Better than starving, but not great.

Speaker 17 Same is probably true for the parasites, except we've shown that mosquitoes are more susceptible to getting malaria infection when they take blood meals in the daytime than the nighttime.

Speaker 5 I'll be honest with you, listening to all three of you, it sounds like you are battling these mortal enemies that you despise and adore in equal measure.

Speaker 19 Maybe deeply respect.

Speaker 1 Yeah, that might be a way of putting it. Yeah, I mean,

Speaker 12 if we are going to respect.

Speaker 17 It's fair to say that these creatures have been ridiculously underestimated by both science and by medicine. They're far more sophisticated than we've given them credit for.

Speaker 17 And evolution always will find a way. The best we can do is to win some of the battles in this long war.

Speaker 17 So we need to both be dealing with the parasites, but as well trying to deal with mosquitoes locally where we can too will be a good idea.

Speaker 1 Well look, the best of luck with that battle. I can see why Hannah would be the high value target in this ongoing ongoing war.

Speaker 1 But thank you all for your efforts and thank you for coming in and talking to us today. Professor Leslie Voshol, Professor John Piggett, and Professor Sarah Reese.

Speaker 1 Who smells more? And for what reason? That was left tantalizingly vague.

Speaker 9 Wasn't it just?

Speaker 11 Yeah. And luckily, this being radio, no one will be able to tell the truth.

Speaker 1 I think they'll guess. They'll definitely guess.

Speaker 1 Subscribe to Curious Cases on BBC Sounds Sounds and make sure you've got push notifications turned on and we'll let you know as soon as new episodes are available.

Speaker 1 You can manage your subscriptions from the My Sounds tab.

Speaker 8 Nature Bang.

Speaker 8 Hello, hello, and welcome to Nature Bang.

Speaker 6 I'm Becky Ripley, I'm Emily Knight. And in this series from BBC Radio 4, we look to the natural world to answer some of life's big questions.

Speaker 7 Like, how can a brainless slime mold help us solve complex mapping problems?

Speaker 6 And what can an octopus teach us about the relationship between mind and body?

Speaker 20 It really stretches your understanding of consciousness.

Speaker 7 With the help of evolutionary biologists. I'm actually always very comfortable comparing us to other species.

Speaker 7 Philosophers.

Speaker 19 You never really know what it could be like to be another creature.

Speaker 7 And spongologists. Is that your job title? Are you a spongologist?

Speaker 3 Well, I am in certain spheres.

Speaker 6 It's science meets storytelling.

Speaker 7 With a philosophical twist.

Speaker 2 It really gets to the heart of free will and what it means to be you.

Speaker 6 So if you want to find out more about yourself via cockatoos that dance, frogs that freeze, and single-cell amoebas that design border policies, subscribe to Nature Bang from BBC Radio 4, available on BBC Sounds.

Speaker 21 At Coldwater Creek, we take a thoughtful approach to design, giving attention to what matters most to you. From quality fabrics to the fits you love, to artful details that captivate.

Speaker 21 Coldwater Creek caters to your wardrobe in every season, for every occasion, and in every size. We create comfortable, confident styles with endless versatility that reflect the life you live.

Speaker 21 Discover why Coldwater Creek is the sought-after choice in women's clothing. For new seasonal looks, shopcoldwatercreek.com.

Speaker 4 Is your cash working hard for you right until the very moment you need it? It could be if it was in a Wealthfront cash account.

Speaker 4 With WealthFront, you can earn 4% annual percentage yield from partner banks until you're ready to invest, nearly 10 times the national average.

Speaker 4 And you get free instant withdrawals to eligible accounts 24-7, 365. 4% APY is not a promotional rate, and there's no limit to what you can deposit and earn.

Speaker 4 And it takes just minutes to transfer your cash to any of Wealthfront's expert-built investing accounts when you're ready. Wealthfront, money works better here.

Speaker 4 Go to WealthFront.com to start saving and investing today.

Speaker 4 Cash account offered by Wealthfront Brokerage LLC member FINRA SIPC. Wealthfront is not a bank.

Speaker 4 The APY on cash deposits as of December 27, 2024 is representative, subject to change, and requires no minimum. Funds in the cash account are swept to partner banks where they earn the variable APY.

Speaker 4 The national average interest rate for savings accounts is posted on FDIC.gov as of December 16, 2024.

Speaker 4 Go to wealthrund.com to start today.