Parasites, Hookworms and Allergies

13 November 2005
Presented by Kat Arney, Mandy Morton



This week Prof. David Pritchard gets to the bottom of why parasites may help to get rid of allergies, Elizabeth Bernays describes how caterpillars acquire a taste for plants containing toxic chemicals when they have parasites, Chris Smith visits Westbourne High School in Ipswich to carry out fitness experiments for Healthcare Science Week, and Dave and Derek go bang with an explosive electrolysis experiment in the Naked Scientists Laboratory.

In this episode

Why a Bucket of Stale Food Is Attractive

Scientists in America have found that people are more willing to eat stale food if it's served to them in a big bucket. The study discovered that if people were given large buckets of popcorn at the cinema, they ate 45 per cent more than people given stale popcorn in a normal size bucket. They also tested normal tasty popcorn, and found that people eating out of large buckets ate even more. So if you give someone food in a big serving, they'll eat it even if it tastes bad. Researchers think that people assume that large portions are actually normal size portions, and so are more willing to eat it all.

Trying in Vein To Take Blood

Vein-hungry and frustrated junior doctors could soon have a new weapon at their disposal to help them in their quest to locate the best veins for siting cannulas, or collecting blood samples. US firm Luminetx have developed the ultimate vampires assistant with their VeinViewer system which uses an infrared camera to pinpoint the positions of veins beneath the surface of the skin, and then projects in green a 'roadmap' of the blood vessel network onto the overlying skin. The system can also be used in cosmetic surgery to track down the so-called 'feeder vessels' which supply thread veins on the skin surface. These are often invisible and unless they are removed the problem recurs. The VeinViewer can make them much easter to spot and treat. It can also be used to improve the safety of Botox therapy - by ensuring that the wrinkle-ironing injection is placed in the muscle and not a vein. A compact version of the system has now been made for use in the clinic and should go on sale from early 2006.

How Meditation May Increase Grey Matter

Researchers in America have shown that meditation not only boosts your well-being, but also the size of your brain. They showed that people trained in Buddhist meditation had increased cortical thickness, a part of the brain associated with the things we feel, hear and see. These effects were observed in people who meditated for an average of 40 minutes per day, so it seems there's no need to be a monk to see the benefits of meditation.

- Using Parasites To Get Rid of Allergies

The Naked Scientists spoke to Professor David Pritchard, University of Nottingham

Using Parasites To Get Rid of Allergies
with Professor David Pritchard, University of Nottingham

Kat - I understand that for your research, you infected yourself with parasites. Tell us about that.

David - This is true. I'm one of ten people who infected themselves with worms.

Kat - Why?

David - We did it because we believe that giving people worms under a controlled regime can benefit people suffering from allergy or auto-immunity.

Kat - I'm just going to bring in Sarah here. What is an allergy?

Sarah - Allergy is actually from the Greek words 'allos' and 'ergos', which means altered reactivity. People that have allergies have immune systems that have increased activity to pollens and things like dust. This causes the common symptoms we think about such as a runny nose, itchy eyes, wheezing, hives or nettle rash type effects. People who have allergies produce an antibody called IgE, which lines our nasal passages and respiratory tract. When people have an allergy to something like pollen, they produce too much IgE, which then binds to histamine receptors on mast cells. The mast cell then pops, releasing lots of histamine, which causes all the symptoms like the itchy nose and eyes. To try and prevent this, people take antihistamine, which binds to the histamine receptors and stops the histamine from getting there. This can prevent an allergic reaction.

Kat - So it's basically our immune system going ver the top. So David, are the kinds of diseases you're looking at like that or slightly different?

David - Well I can add to that by saying that the allergic response actually evolved in people to expel worms. So that's why we have an allergic response. Worms have then developed a response to combat allergy, and it's those strategies that we're trying to harvest to treat disease.

Kat - So what sort of diseases are you looking at?

David - At the moment we're targeting rhinitis for the next pollen season, but we have colleagues in Australia that are targeting Crohn's disease. The idea is that the worm will switch off all hyperactive immune responses.

Kat - What is Crohn's disease?

David - Crohn's is an auto-immune disease that attacks the bowel and causes inflammatory bowel diseases.

Kat - And so how do you think these worms are actually helping?

David - The worms are obviously doing something to the immune system that says, 'stop reacting'. We're trying to harness that property. The main thrust of the lab's aim is to make new drugs from these organisms, but the clinicians in Nottingham have decided to go one step back and use live infection in treating rhinitis sufferers. In January, we are embarking on a study where we'll be infecting cohorts of rhinitis patients with live worms and then monitoring them throughout the hayfever season to see I they assist.

Kat - Can people get on this trial? Can they volunteer to be on it?

David - People have already been recruited, but we do have a contact number if people wanted to be on the trial. However, there's a quite vigorous selection procedure, so they would have to contact us independently.

Mandy - Tell us a little bit more about the worm itself, because people's perception of worms is usually something wriggly! Just before we came on air you showed me a photograph of one and it's not at all as you'd expect.

David - These are quite small worms. They're microscopic to begin with. We've studied these worms in the Tropics for over 20 years, and what we were astonished by was the fact that these worms will live inside you for five years or more despite the fact that there's an immune response to them. They're transmitted to people through the soil. Microscopic worms, transmitted to the soil through faecal matter, will enter the skin, find blood vessels, migrate through the lungs, are coughed up, swallowed and then end up in the small intestine. They will stay there for five years. You don't usually know you have the worms until they reach the gut. Once they reach the gut, if you have too many, you certainly feel that you've got them. During a safety study in Nottingham we were able to establish the safe dose that would get rid of the allergy but not create other symptoms.

Mandy - Now you actually transported these worms through customs by infecting yourselves with them all the way from Papua New Guinea. Presumably you got rid of them.

David - No. My colleague still has them and has been carrying a quite substantial worm burden for five years now.

Mandy - Do they reproduce as well?

David - No, they mate as separate sexes in the small intestine and produce eggs. The eggs pass out in faecal matter and then develop into infective larvae in the soil, which can detect human skin and burrow back through. This is how the cycle is perpetuated.

Sarah - How many worms do you have to give a patient?

David - We've estimated from field studies where worm infection has been linked to a reduction in respiratory wheeze to dust mites, that you can give ten worms to alleviate asthma. Ten worms certainly do not cause any symptoms in recipients. We know this from our safety study. If you go up to twenty five, fifty or definitely with one hundred, you feel sick and have a pain that tells you something is definitely going on in your gut. Saying that, it's not as bad as having gastric flu for example. It's just the uneasy feeling that you have something inside you that perhaps shouldn't be there. However ten can impart benefits. If there are any problems, it's very easy to get rid of them simply by taking drugs similar to those you'd give to your pet.

Sarah - After the worms have gone, do you still have the benefits?

David - It's a good question. In the tropics, people are acquiring worm infections from a very young age. Once children are old enough to move away from their houses, they will start walking on contaminated soil and will pick up worms. These worms will accumulate throughout life. Because they're suppressing the immune system, you tend to gather an increasing worm burden with age. The average worm burden of a person in Papua New Guinea is 25 worms. It's this sort of level that we think is beneficial. Whether we can mimic this in a hospital in Nottingham is difficult to say, because we'll be giving ten worms in one dose after the person has already developed allergy. So the trial may not work this time. We may have to go back to 'trickle infections' where we give small numbers over an increased length of time.

Mandy - What about bringing things like this into the country? Would you need a permit?

David - I think if you bring them in inside you, then no. If you were carrying them in tubes then I think you should declare them. It actually an interesting story. The study being conducted in Australia is using worms taken from Nottingham. However, these worms originated in New Guinea, which as you know is just north of Australia. So these are well travelled worms.

Sarah - It's difficult to know how allergies develop, and we think it's a combination of genes and environment. Maybe if we don't get these worm infestations in the UK anymore, do you think that's playing a role in allergies?

David - There is an hypothesis out there called the hygiene hypothesis, which say that the reason we're so allergic these days is because we live in a very clean environment with thick carpets and dust mites in abundance. By having worms we're reintroducing dirt back into the system. It's a nice idea, although I'm not sure how true it is. We're approaching it from a different angle. Allergic responses definitely occurred to fight worms, so by using them and their products we can turn the system back on itself and switch off allergy.

- Healthcare Science Week

The Naked Scientists spoke to Dr Chris Smith visits Westbourne High School in Ipswich

Healthcare Science Week
with Dr Chris Smith visits Westbourne High School in Ipswich

Chris - I've gone back to school because I'm at Westbourne High School in Ipswich, which is officially the first school in the whole of the UK to betaking part in Healthcare Science Week. This kicks off around the rest of the country from tomorrow and it will eventually see about 2000 pupils measuring their fitness levels with the help of a healthcare scientist from their local hospital. But the aim isn't just about finding out how fit people are. It's all about telling children about the huge range of jobs for budding scientists that are available in the healthcare system throughout the country. One of the people organising the event is Bev Bailey, who's here with me now. Bev, what's Healthcare Science Week all about and what are you trying to achieve?

Bev - There're two reasons for this. One is that there are around 50 000 scientists working within the health service who very often remain unrecognised for the enormous contribution that they make towards public health within our hospitals and within our communities. The second reason is to try and get more young people interested in science as a long term career. There are over 50 careers within healthcare science itself and it's all to do with research, development, IT, scientists working in the laboratory and scientists working in the community. So there's an enormous scope for any child with even the remotest interest in science to get a good long term career.

Chris - Thanks Bev. Well one of the scientists helping out here today is Andy Poynter from Ipswich Hospital. Andy, what do you do?

Andy - I'm Head of Radiotherapy Physics at Ipswich Hospital. My job is to provide scientific support and expertise for oncologists that work in the department treating cancer patients. I'm delighted to be able to take part in this event because I think there's a real need to promote the work of healthcare scientists. People are just not aware of the important job they play in hospitals today.

Chris - So what are you going to be doing here today with the kids at Westbourne High?

Andy - We'll be measuring three different indices which will give us a snapshot of the students' health. The first one we're going to measure is body mass index, which is basically the weight divided by the square of the height. This gives an index of how over or under weight a student is. We're also going to be measuring their peak expiratory flow, which gives us a good indication of the health of their lungs and how well they can get air out of their lungs. And finally we'll be measuring their rest and racing pulse recovery rates. This means that we get the student to run on the spot for a few minutes and see how quickly their pulse goes up. We'll then be measuring to see how long it takes for the pulse to return to the rest level.

Chris - One of the people that's volunteered to have a go at this is Kim. What have you been up to?

Kim - We took our pulse rate and did some exercise for a minute. We then took our pulse rate again and again after three minutes to see if our pulse rate had got back to normal.

Chris - So how does this help us to work out whether people are fit or not?

Andy - What we're looking for here is that in a fit person, the heart rate will go up very quickly with exercise to provide the blood they need for their muscles. As soon as they stop exercise, the pulse rate will drop to their normal resting level quickly. These are all good signs of excellent cardiovascular health. If we look here at Kim's result, we start with a rest beat of 70. After one minute jogging on the spot she went up to 150, and then after two minutes of stopping, she was back to 90. Four minutes after that she was back to 80 and five minutes after that she was back to 70. This is excellent.

Chris - Would you describe yourself as in excellent fitness Kim?

Kim - I wouldn't say that, but I try.

Chris - Do you take a lot of exercise?

Kim - Yes, I walk to school and back every day and I go swimming every weekend.

Chris - Do you think you're representative of most people your age in terms of the amount of exercise you take, or do you think you're a bit fitter than most?

Kim - I'm probably a bit fitter than most. I do more exercise than most of my friends. They just walk to school and don't do much after that.

Chris - Do you think exercise is important? People are always telling you that it is but do you really believe that it makes a difference to your health?

Kim - Yes I think so because it gives you a healthy body and ensures you can do every day things without getting exhausted.

Chris - Do you think that by taking part in something like this, it helps people to understand how to be fit and healthy?

Kim - Yes, making it fun makes people want to do it more and more.

Chris - So Bev, once everyone has collected all this data, what will you do with the information?

Bev - As the students are collecting their measurements, each school can enter their data directly onto a website that we've set up especially for Healthcare Science Week. As soon as they've entered their measurements, it will calculate and individual chart for that student as well as an indication of where that child's measurements fit in the rest of their class group. Those results are then anonymously downloaded onto the national database

Chris - So this is going to be really useful to find out how fit the nation's school children are. Bev - We're very much hoping so. They're the three main indicators of health, and to the best of our knowledge, there hasn't been anything done like this before. There will be about 2000 individual measurements of children aged between 14 and 16 initially, and then as soon as Healthcare Science Week is over, the website opens up to as many schools as want to do it. The information will continue to grow and we'll end up with a very large database of base line data.

Chris - Right, well I'm off to measure my peak expiratory flow now to see if my lungs are working properly. So from all of us here at the launch of Healthcare Science Week, from Westbourne High School, Bev, Andy and Kim, thank you very much, and back to the studio.

- How Caterpillars Fight Back Against Parasites

The Naked Scientists spoke to Professor Elizabeth Bernays, University of Arizona

How Caterpillars Fight Back Against Parasites
with Professor Elizabeth Bernays, University of Arizona

Kat - We've been talking about human parasites, but you're going to talk about caterpillar parasites. What have you been looking at?

Elizabeth - I've been looking at caterpillars that live in Southern Arizona, and they get parasites from flies that lay their eggs on the outside of the caterpillar. The eggs hatch, the parasites dig in and eat out the entire caterpillar.

Kat - That sounds really horrible. What do caterpillars do about this?

Elizabeth - One thing that they do is to eat a certain plant that contains a chemical that protects them a bit from the parasites. If they eat enough of this chemical it will kill some of these maggots and allow the caterpillar to continue living.

Kat - How do the caterpillars know which plants to eat?

Elizabeth - That's a good questions and that's one of the things that I've been studying. They have a special taste bud that's sensitive to some of the chemicals in the plant. The chemicals are toxic and taste very bitter to humans, but caterpillars love them. This is a good adaptation because when they come across a plant with these chemicals, they like to eat that plant. One of the problems is that they eat a lot of different plants. When they have parasites, their taste for this chemical gets stronger and stronger. This makes their taste buds go wild when they taste this chemical. This makes sure that they eat a lot of that chemical.

Kat - So they acquire a taste for it when they need it.

Elizabeth - Well they have a taste for it but it becomes much more sensitive when they need it.

Kat - How did you find this out? How did you test for this?

Elizabeth - Well I've been working on the taste buds of these caterpillars for some time, and found that they have one that's sensitive to sugar, and one that's sensitive to bitter substances. And then I found that there was one sensitive to these chemicals. This lead me to think that they must be good for them. Just by chance, I found that the sensitivity varied a lot. We did a test that showed that when they have parasites, they get more sensitive. We've also showed that the caterpillars that eat these chemicals survive much better.

Kat - Do you think that anything like this happens in other animals?

Elizabeth - We haven't been able to find it any other stories of animal taste, so we don't really know how prominent it is. There's no suggestion of it in humans, but maybe we just aren't looking at the right things. Maybe it's just that insects are different and their taste buds vary more depending on what they need.

Sarah - Are the chemicals good for the creatures that eat the caterpillars?

Elizabeth - The caterpillars that prey on them have special mechanisms to stop them from being poisonous. But the chemicals do protect them from parasites and predators. One other interesting detail is that the chemicals that usually taste bitter to them don't bother caterpillars at all when they have parasites. That makes them eat other plants with other toxins, and that also helps to kill some of the parasites.

- Why are some children born with fair hair that darkens with age?

Why is it that some children are born with dark hair and then go very fair when they get older, and similarly, why do some children born ...

Why are some children born with fair hair that darkens with age?

The answer to this centres around a pigment called melanin. This is a pigment that gives us dark moles, dark skin and dark hair. This is called eumelanin, and there's a slightly lighter version called phaeomelanin, which gives people red-ginger hair. Everyone has genes in their DNA that will give them different levels of these two pigments. So people who have very light and blonde hair don't have very much of these pigments at all. As your cells get older, they will change the way that they use their genes. If you have a child born with very dark hair and then becomes blond, this would suggest that the gene that's making melanin when they're a baby has been turned off. If a child is born with blond hair and becomes dark, it's because genes have started turning on melanin pigment. So it's not fixed, and even later in life you can go from being a blonder person to a darker person.

- Where should I fit a carbon monoxide detector in a room with a log burner?

I was fitting a multi-fuel burner in the living room and want to know where to fit the carbon monoxide detector. Should I fit it high or ...

Where should I fit a carbon monoxide detector in a room with a log burner?

That's a really important question, because carbon monoxide is a gas that's produced when carbon fuels burn but don't burn properly. It's very poisonous and can kill people while they sleep, so it's great that you're thinking of installing a carbon monoxide detector. What you need to know is whether carbon monoxide is lighter or heavier that the rest of the stuff in the air, which is mostly nitrogen and oxygen. The answer is that carbon monoxide is lighter. What you need to do is put your detector either high up on a wall or on the ceiling. However it should be kept 6 to 12 inches from the corners.

- Could tapeworms be used by fat people for weight loss?

If tapeworms make you really skinny, why don't you give them to fat people until they lose weight and then take them out?

Could tapeworms be used by fat people for weight loss?

I'm not sure it's true that people with worms are thinner than people without worms. In fact the person who brought the worms back from New Guinea was the fattest person in the lab and still is despite the fact he's still carrying 300 worms. The other interesting thing related to worms and connected to the previous caller from the States is that they give you an insatiable appetite. When you have these hookworms, you just can't stop eating. Whether you put on less weight despite eating more, I'm not too sure. But I don't think that people are thinner if they had worms, so it probably wouldn't work on fat people.

Why do people fart?

There are a number of reasons why we have gas in our guts. Some of it's just air that we swallow, which contains nitrogen, carbon dioxide and oxygen. The rest of it is made when undigested food and a sugar called lactose passes through into our large bowel, and bacteria start eating the sugar. The bacteria produce quite a lot of smelly gases, especially if the food has quite a lot of sulphur in it. This would include food like cauliflower, eggs and meat. Beans are particularly fart-o-genic, and although they don't make bad smells, they do make you produce quite a lot of gas. This is because beans contain quite a lot of sugars that humans can't digest, but bacteria love them! When you get worm infections, it actually increases your level of flatulence. This is being published in a scientific journal very soon.

- How can maggots be used in health care and experiments?

How can maggots be used in health care and experiments?

How can maggots be used in health care and experiments?

I'm glad you asked that question Peter because my lab is also looking at the effects of maggots in wounds, and we've identified a number of enzymes that maggots use to digest dead and dying tissue to kill bacteria. The same enzymes promote tissue regeneration. So in fact, maggots are actually very good tissue engineers and repair tissues through their secretions. Maggots only eat dead tissue because it's already digested, and they only stay in the wound for three days. The flies then fly off. The latest development is to put the maggots into a nylon tea bag, rather than have them 'free range'.

- Has anyone been seriously ill from taking these worms?

Has anyone been seriously ill from taking these worms?

Has anyone been seriously ill from taking these worms?

The trial we have conducted to date was a safety trial where people were infected with graded numbers of worms. They went from 10 to 25, 50 up to 100. If you give somebody 100 worms, they do not feel well. In that case we had to take the worms out of the system as quickly as possible. You're right to ask this question because we need to be careful not to give too many worms at one time. They itch when they go through your skin, but you don't notice anything again until they reach your gut. I had 50 and it gave me a dull ache under my ribcage.


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