The bad parasites

A parasite lives on or inside its host organism in a very unequal relationship.  The parasite takes all of its food from its host and doesn’t give anything back – it is very selfish!

In humans, parasites usually cause discomfort or disease.  Lice for example are a parasite that can be found in your hair or on your body.  There are over 3,000 species of lice (which are just wingless insects) and the feed on your skin, the oils that your skin and hair secrete and your blood.  You can tell if lice have fed on your blood because their colour changes from the normal beige or grey to a much darker shade! 

Lice have special adaptations that allow them to infest your body, but these depend very much on the type of louse (a single ‘lice’) and where they live.  They have strong short legs with claws that cling on very tightly to your hair or skin and they are small and flat which make them very hard to get rid of.  They lay eggs (called nits) and attaching them to the host using very special saliva that glues the eggs to hair.  These nits are extremely difficult to get rid of unless you use special chemical products.  

Parasites cause lots of different diseases in humans.  Diseases like malaria are caused by protozoa, a single-celled organism that, in the case of malaria, is spread by a certain type of infected mosquito in particular areas of the world.  When the mosquito bites a human, the malaria protozoa parasite gets into their bloodstream and travels to their liver where it makes lots of copies.  These new parasites return to the bloodstream, where they grow even more and multiply so quickly that they burst blood vessels, spreading the parasite and causing huge problems.  Malaria can be treated with drugs but it is very unpleasant even so.  It can stay in the liver for a very long time and symptoms can reappear at any time. 

Protozoa can cause other diseases like amoebic dysentery or problems like liver abscesses.  None of these are fun so your best bet is to avoid getting infected in the first place! 

Some bacteria are parasites, they can invade your body and cause diseases like tuberculosis (TB) and typhoid fever.  Viruses are also common parasites, viruses need a host to grow and multiply but it can survive for a long time without a host, hibernating until one arrives!

Another major type of parasite are the helminths – the worms, like tapeworms or hookworms.  You can get many types of worms from your pets (so make sure your pets are properly wormed!) and these cause lots of problems.  Hookworms have hooks on their bodies that allow them to attach themselves to the inside of your small intestine.  These can cause malnutrition because they eat all of your food!

There are lots of other parasites that can make your life quite unpleasant.  Lice, ticks, fleas and bedbugs all eat your skin, hair, blood and other body fluids!  These parasites are usually very small, but you will still be able to see most of them without a microscope.  You can get these parasites in your home, on your pets, on yourself – anywhere in fact.  You will know they have eaten when you have been bitten – the bite gets very itchy and can be sore.  Some parasites, like fleas, can pass on serious diseases while others, like ticks, burrow deep into your skin and lay their eggs, which can be very difficult to get rid of.  Your best protection from them is to make sure that you pay attention to your personal hygiene and that you make sure your home and environment is clean and tidy!

Did you know…?

You might like to kiss under the mistletoe at Christmas, but did you know that mistletoe is a parasite?  It grows on other tress and can kill them.  You can do your bit by making sure you decorate your home with lots of mistletoe at Christmas (and you might even get some kisses!).