What is a parasite?
A parasite is an organism that lives in or on another organism,
called the host. The parasite benefits by gaining nutrients at the
host's expense. Parasites can make their hosts sick, or even kill
Parasites can live on the surface of their host, like the fleas
you see on cats and dogs, or inside their host, like tapeworms.
Every non-parasitic species has at least one species that
parasitises it. The number of parasitic species greatly exceeds the
number of non-parasitic species. Some parasites are more gruesome
than others. Here are our top 5 gruesome parasites:
Zombie parasite #1 - the fungus
Ophiocordyceps fungus grows inside insects and gets
inside the brain. The fungus causes the infected insect to climb as
high as possible. Then, the fungus explodes out of the insect,
killing the insect and sending out fungal spores on the breeze to
infect the next victim.
The higher the insect climbs, the further the fungal spores can
travel. Have a look at this video showing the zombie fungus in
Tongue-eating sea louse
Imagine waking up and instead of a tongue you've got a...
parasitic louse! The sea-dwelling parasitic sea louse burrows
through the gills of fish. After eating the fish's tongue, the
parasite lives inside the fish's mouth and feeds on blood or fish
Surprisingly, the fish can use the parasite just like a normal
tongue and doesn't seem to be damaged in any other way.
Zombie parasite #2 - the worm
Even if you don't like snails, you've got to feel sorry for one
infected by a parasitic worm which takes over its brain. When an
unsuspecting snail accidentally eats a tiny worm, the worm produces
lots of baby worms inside the snail. These baby worms change the
snail's eyestalks to look like caterpillars - much more appetizing
Birds eat the eyestalks, which contain baby parasites and the
cycle is complete. Still, the parasitic worm inside the snail isn't
done. The snail will probably survive the bird's attack and grow
new eyestalks. Unluckily for the snail, more parasites are growing
inside its body and will infect its re-grown eyestalks.
Have you seen a giant, parasitic plant that smells like rotting
flesh. No, it's no science-fiction. It's a rafflesia! Have a look
Zombie parasite #3 - the wasp
There are lots of species of parasitic wasps, but
Glyptapanteles is the most gruesome. The adult wasp lays
its eggs inside the body of a caterpillar. Eventually, up to 80
wasp larvae eat their way out of the caterpillar body. They cocoon
themselves, waiting to turn in to adult wasps, much like
butterflies turn into caterpillars.
With any other species of parasite, this would probably kill the
host. Not with this tiny wasp. The parasite has altered the
caterpillar's brain so that it stands guard over the wasps,
occasionally spinning silk over the cocoons to keep them protected.
The caterpillar doesn't even move to eat.
If anything approaches the caterpillar, it thrashes around
violently to scare off any potential predators of the wasps.
Eventually, the caterpillar dies due to a lack of food. The adult
wasps hatch, ready to parasitise another unsuspecting
What about humans?
There are lots of parasites that affect humans. One of the
parasites posing the biggest problem to humans is malaria. To find
out more about malaria, go to
Malaria, one of the world's deadliest diseases.