Tapeworm

I am a leaching parasite,
I am shrewd, I need no might.
A single worm in a single year,
can lay 1/2 a billion eggs, you hear!
And then we cling to every weed,
hoping that some cow will feed.
Once inside the bovine,
we wait until on meat you dine.
For if one does not cook ones meat,
you'll also get a special treat.
Then way before you even know,
This tiny pest will start to grow.
An inch, a foot, sixteen feet!
The beast inside is hard to beat.
How did I get to be so big?
I cannot eat or take a swig.
You digest my food, you see.
You do all my work for me.
I absorb my food using my skin,
You will lose and I will win.
For as I tear your intestine wall,
You grow weak and very small.
I am a leaching parasite.
I am shrewd, I need no might.