Most of us are oblivious. Did you know that you've most probably had a parasitic worm in you? Urgh. I'm thinking about it right now as I look down at my fingernails moving around as I type. You see, the majority of us probably think only of nasty parasitic worms that affect the young and the poor of the developing world, for example in Africa - you know, those humungous tape worms or the ones that cause sleeping sickness or river blindness - all truly delightful. But a pinworm, for example is a bit more innocuous. This is something we probably all had as children and the female worm would lay some eggs in your bottom and then you'd scratch and get the eggs under your fingernails.....and then most likely chew your nails and ingest more eggs. Are you reading this while eating your breakfast? Sorry!
Ok so, I went to one of the free lectures at Gresham College on Holborn and there are an absolute multitude of interesting topics that are covered every single week. I sort of liked the idea of learning about parasites, not because I have a weird scientific fascination with them but because its the kind of topic that I think I should know a bit about - information to have in my back pocket as it were. And let me just preface what will follow by saying that one of the reasons that I decided to undertake this year-long task is because I don't think my general knowledge is good enough. This means that a lot of the weeks I talk about might be a bit geeky or studious but don't worry - there will be lots of weeks of fun and mess and games. But this week isn't one of them.
Parasites are everywhere. Pretty much all animals and plants are at some point infected with them. But, just because they are ubiquitous doesn't mean we should embrace them - after all, a parasite is something that causes harm to the organism it lives in.
Professor Mark Viney from Bristol University was the speaker; he is a parasitologist, and clearly loves worms. There are two types of parasites: protozoa, which are single celled animals, and worms, which are multi-celled animals. Professor Viney only talked about worms and quite passionately! The two types of parasitic worms are round worms and flat worms. The type of flat worm we all know about is the tapeworm. They live in the gut of their host and live their life growing along the gut feeding and absorbing all the nutrients from the gut as they don't have their own. Here'a a nice picture for you.
Roundworms are called nematodes and an interesting fact about them is that they are the most abundant and species group of multicellular animals on the planet, but probably the least seen. The lovely worm we probably all had as a scratching child is a roundworm nematode.
Parasitic worms basically eat and reproduce - I suppose like any other animal on the planet but the amazing thing about parasites is that they are involved in every other animals' life because of their contamination. The egg of a parasite will end up somewhere outside as it passes through the host's stomach through defecation and then inevitably it will be get ingested by an animal eating grass for example and the process starts all over again. Parasites are pretty clever animals really and rather highly evolved. But they have also helped shape our immune evolution because they are so prevalent and we have had to develop an immune response to them. This may also be connected to the hygiene hypothesis, which essentially says that a child's lack of exposure to parasites and infections (due to us all living cleaner lives) means that they are more susceptible to allergies because the natural development of the immune system is suppressed.
Interestingly, people are rarely killed by parasites. They are not even in the top ten causes of death across the world by the World Health Organisation. However, parasites and worms in particular cause chronic harm to people and take years off people's life expectancy. Worms cause more harm in this way than anything else.
So there you have it - that's what I learnt about parasites. I feel like my chances on University Challenge just got that little bit better.
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