As part of the Natural History Season on the brilliant BBC Four (one of the best TV channels there is, it is renowned for its brilliant science and history documentaries), Dr Michael Mosley, a medical doctor and former City banker, turns his body into a living laboratory by infecting himself with parasites.
In Infested! Living With Parasites, to be shown tonight at 9pm, Michael infests his body with parasites such as tapeworm, head lice and leeches. He also takes a test to find out if he’s infected by toxoplasma gondii, which is contracted from cat faeces, and a new imaging technique is used to show his blood cells being taken over by the malaria parasite in a test tube.
Here, Michael tells us more about it...
How parasites manipulate us
19 February 2014
BBC News Magazine
Dr Michael Mosley
Humans infected with parasites could behave in surprising ways. Michael Mosley subjected himself to tapeworms and leeches to find out more.
Over the last couple of months I have been deliberately infecting myself with a range of parasites in an attempt to understand more about these fascinating creatures. Perhaps the greatest surprise is the extent to which parasites are able to subtly (and sometimes not so subtly) manipulate their host to their advantage.
The first parasite I experimented with was a beef tapeworm, taenia saginata. This parasite only infects humans and cattle. In Victorian times women would, allegedly, swallow tapeworm eggs as a way of losing weight. This would almost certainly have been a waste of time as tapeworm eggs are not infectious to humans. They first have to be eaten by a cow or bull, where they form a cyst, and it is only if we eat raw, infected meat that we acquire a worm.
Even if you were infected would you lose weight? Despite hosting three worms I actually put on weight. It could be that the tapeworms were actually encouraging me to eat more, or it could be that I was unconsciously compensating for them there. Either way, they don't seem to be a great weight loss aid.
A far more lethal and dangerous parasite is plasmodium, the parasite that causes malaria. Like all parasites it needs to find ways to spread itself, jumping from one host, the mosquito, to us and then back again. Scientists are only just beginning to understand the ways it manoeuvres us to achieve its ends.
You have probably had the experience of going on holiday with a friend and discovering that one of you gets bitten far more than the other. The reason is that while mosquitoes are attracted by the heat and carbon dioxide we produce, they can be repelled by chemicals in our body odour.
To test this idea out I went into a closed room with Dr James Logan of the London School of Hygiene and Tropical Medicine. Then mosquitoes were released. Over the next 15 minutes James was bitten 25 times, while I was only bitten once. It turns out that I have a body odour that is far more strongly repellent to mosquitoes than James. He said, however, that if there had been a third person in the room who had malaria then that person would have been bitten the most. New research has shown that the malaria parasite is able to alter our smell, making us more attractive to mosquitoes.
Once the mosquito has drunk blood from a human with malaria, the parasite infects the mosquito's brain, making it more likely to target another human. By manipulating mosquitoes and humans the parasite is able to spread itself extremely successfully.
However, by doing this sort of research James and his colleagues are hoping to find ways to create natural smells that might be effective at repelling mosquitoes. Since malaria kills around a million people a year and mosquitoes are becoming increasingly resistant to insecticides, new approaches are urgently needed.
An even more remarkable mind-manipulating parasite I've looked at is is toxoplasma gondii. It infects many warm blooded mammals, but the best studied relationship is that between rodents and cats. Normally a rat or mouse will keep to the shadows, thus avoiding cats. But when they are infected by toxoplasma the parasite completely changes their behaviour. An infected mouse is attracted to the smell of cat urine and will move out into the open, displaying reckless behaviour. The reason, of course, is the parasite wants the mouse to be eaten by a cat, so it can then infect its new hosts.
Humans also get infected by toxoplasma, though it is only really serious when a woman is pregnant as toxoplasma can damage the unborn child. But new research suggests that toxoplasma may influence us in more subtle ways.
We know, for example, that people who have antibodies to toxoplasma are more than twice as likely to be involved in a traffic accident. It could be that the parasite is making us, like rodents, behave in a more reckless fashion. Research also suggests it may slow down reaction times, with the intention of making us more vulnerable to large predators. Either way it is a chilling thought that parasites may be influencing how we behave in ways we do not yet begin to understand.
Infested! Living With Parasites
Continuing BBC Four’s Natural History Season, Dr Michael Mosley turns his body into a living laboratory by deliberately infecting himself with some of the most extraordinary, powerful and surprising parasites of them all.
Almost every animal on Earth has its own parasites – and humans are no exception. These strange creatures will feed on him and even make his body their home.
Michael infects himself with the infamous tapeworm by swallowing live cysts sourced from infected meat in Kenya. Tapeworms have evolved over millions of years to the particular environment of the human gut. By swallowing a tiny camera – the pill-cam - the tapeworms’ stomach churning growth inside Michael’s body can be seen close up.
For his next itchy encounter, Michael is joined by entomologist Dr James Logan as he gets to grips with one of the most widespread childhood nuisances in the UK – the head louse. These little blood suckers are so dependent on humans that Michael has to keep them alive on his own skin. Using a video microscope Michael and James observe the lice exploring Michael’s body and digesting their latest blood meal. They see how perfectly the head louse is adapted to climbing and gripping onto human hair. Through comparing the body shapes of head, pubic and body lice James reveals that they tell us something about our own history.
Another common parasite, which is not visible to the human eye, is thought to alter behaviour by infecting the brain. Surprisingly, around a quarter of the population is infected by toxoplasma gondii which is contracted from cat faeces. Some scientists believe it makes the carrier more likely to adopt riskier behaviour. Michael takes a test to find out if he’s infected.
The life-threatening malaria parasite is carried by mosquitos, and infects human blood. It’s something Michael is not prepared to risk, so a new imaging technique is used to show his blood cells being taken over in a test tube.
But other parasites can cure as well as kill. The leech, once sold by medieval quacks, is now used in cutting edge microsurgery. Michael adds to his parasitic load by being bitten by a leech – and sees how it can consume more than five times its own body weight in blood.
Infested! Living With Parasites is broadcast on Wednesday 19 February, BBC Four, 21:00 GMT. Or catch up with iPlayer.
BBC News - How parasites manipulate us
In Infested! Living With Parasites, to be shown tonight at 9pm, Michael infests his body with parasites such as tapeworm, head lice and leeches. He also takes a test to find out if he’s infected by toxoplasma gondii, which is contracted from cat faeces, and a new imaging technique is used to show his blood cells being taken over by the malaria parasite in a test tube.
Here, Michael tells us more about it...
How parasites manipulate us
19 February 2014
BBC News Magazine
Dr Michael Mosley
Humans infected with parasites could behave in surprising ways. Michael Mosley subjected himself to tapeworms and leeches to find out more.
Over the last couple of months I have been deliberately infecting myself with a range of parasites in an attempt to understand more about these fascinating creatures. Perhaps the greatest surprise is the extent to which parasites are able to subtly (and sometimes not so subtly) manipulate their host to their advantage.
The first parasite I experimented with was a beef tapeworm, taenia saginata. This parasite only infects humans and cattle. In Victorian times women would, allegedly, swallow tapeworm eggs as a way of losing weight. This would almost certainly have been a waste of time as tapeworm eggs are not infectious to humans. They first have to be eaten by a cow or bull, where they form a cyst, and it is only if we eat raw, infected meat that we acquire a worm.
Even if you were infected would you lose weight? Despite hosting three worms I actually put on weight. It could be that the tapeworms were actually encouraging me to eat more, or it could be that I was unconsciously compensating for them there. Either way, they don't seem to be a great weight loss aid.
A far more lethal and dangerous parasite is plasmodium, the parasite that causes malaria. Like all parasites it needs to find ways to spread itself, jumping from one host, the mosquito, to us and then back again. Scientists are only just beginning to understand the ways it manoeuvres us to achieve its ends.
You have probably had the experience of going on holiday with a friend and discovering that one of you gets bitten far more than the other. The reason is that while mosquitoes are attracted by the heat and carbon dioxide we produce, they can be repelled by chemicals in our body odour.
To test this idea out I went into a closed room with Dr James Logan of the London School of Hygiene and Tropical Medicine. Then mosquitoes were released. Over the next 15 minutes James was bitten 25 times, while I was only bitten once. It turns out that I have a body odour that is far more strongly repellent to mosquitoes than James. He said, however, that if there had been a third person in the room who had malaria then that person would have been bitten the most. New research has shown that the malaria parasite is able to alter our smell, making us more attractive to mosquitoes.
Once the mosquito has drunk blood from a human with malaria, the parasite infects the mosquito's brain, making it more likely to target another human. By manipulating mosquitoes and humans the parasite is able to spread itself extremely successfully.
However, by doing this sort of research James and his colleagues are hoping to find ways to create natural smells that might be effective at repelling mosquitoes. Since malaria kills around a million people a year and mosquitoes are becoming increasingly resistant to insecticides, new approaches are urgently needed.
An even more remarkable mind-manipulating parasite I've looked at is is toxoplasma gondii. It infects many warm blooded mammals, but the best studied relationship is that between rodents and cats. Normally a rat or mouse will keep to the shadows, thus avoiding cats. But when they are infected by toxoplasma the parasite completely changes their behaviour. An infected mouse is attracted to the smell of cat urine and will move out into the open, displaying reckless behaviour. The reason, of course, is the parasite wants the mouse to be eaten by a cat, so it can then infect its new hosts.
Humans also get infected by toxoplasma, though it is only really serious when a woman is pregnant as toxoplasma can damage the unborn child. But new research suggests that toxoplasma may influence us in more subtle ways.
We know, for example, that people who have antibodies to toxoplasma are more than twice as likely to be involved in a traffic accident. It could be that the parasite is making us, like rodents, behave in a more reckless fashion. Research also suggests it may slow down reaction times, with the intention of making us more vulnerable to large predators. Either way it is a chilling thought that parasites may be influencing how we behave in ways we do not yet begin to understand.
Infested! Living With Parasites
Continuing BBC Four’s Natural History Season, Dr Michael Mosley turns his body into a living laboratory by deliberately infecting himself with some of the most extraordinary, powerful and surprising parasites of them all.
Almost every animal on Earth has its own parasites – and humans are no exception. These strange creatures will feed on him and even make his body their home.
Michael infects himself with the infamous tapeworm by swallowing live cysts sourced from infected meat in Kenya. Tapeworms have evolved over millions of years to the particular environment of the human gut. By swallowing a tiny camera – the pill-cam - the tapeworms’ stomach churning growth inside Michael’s body can be seen close up.
For his next itchy encounter, Michael is joined by entomologist Dr James Logan as he gets to grips with one of the most widespread childhood nuisances in the UK – the head louse. These little blood suckers are so dependent on humans that Michael has to keep them alive on his own skin. Using a video microscope Michael and James observe the lice exploring Michael’s body and digesting their latest blood meal. They see how perfectly the head louse is adapted to climbing and gripping onto human hair. Through comparing the body shapes of head, pubic and body lice James reveals that they tell us something about our own history.
Another common parasite, which is not visible to the human eye, is thought to alter behaviour by infecting the brain. Surprisingly, around a quarter of the population is infected by toxoplasma gondii which is contracted from cat faeces. Some scientists believe it makes the carrier more likely to adopt riskier behaviour. Michael takes a test to find out if he’s infected.
The life-threatening malaria parasite is carried by mosquitos, and infects human blood. It’s something Michael is not prepared to risk, so a new imaging technique is used to show his blood cells being taken over in a test tube.
But other parasites can cure as well as kill. The leech, once sold by medieval quacks, is now used in cutting edge microsurgery. Michael adds to his parasitic load by being bitten by a leech – and sees how it can consume more than five times its own body weight in blood.
Infested! Living With Parasites is broadcast on Wednesday 19 February, BBC Four, 21:00 GMT. Or catch up with iPlayer.
BBC News - How parasites manipulate us
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