What are parasites?

The Human Bot fly (Dermatobia hominis) The Human Bot fly (Dermatobia hominis) is one of hundreds of parasites that affect humans.What do you think a parasite is? The term is often applied to people who regularly take advantage of the generosity of others without making any useful return, but it actually comes from the classic Greek Parasitos, which means literally "someone who dines at another’s table".

  Common Noddy tested for bird blood parasites Parasites also affect our pets, livestock and wildlife. This Common Noddy is being tested for bird blood parasites.Parasitism is an example of symbiosis, a term used in biology to describe two species living in intimate contact. There are three types of symbiotic relationship:

  • Mutualism: both partners receive some benefit.
  • Commensalism: one partner receives some benefit and the other does not.
  • Parasitism: one partner receives benefit while the other suffers from it.

So, parasites can have a real, and sometimes major, negative impact and can even cause the death of their hosts.

Parasites are a huge part of life on earth - almost half of all living things have taken up this way of life - and their diversity is staggering! Think of mistletoe in host trees, fleas on your pet dog, the parent's nightmare of head lice on their children and worms in the gut of that fish you fought so hard to land (don’t let it put you off eating fish!).

Many people consider parasites disgusting animals and while this may be true for some, the reality is that parasites are a natural part of every ecosystem. They can cause disease and death in our pets, our domestic animals, our wildlife and even in ourselves. But they can also be a powerful force to control population numbers in the same way that predators control prey.

Regardless of our own feelings about parasites we cannot ignore such an abundant group of animals. Even pristine environments are 'riddled' with parasites!

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