What do worms eat in your body?

I am concerned about parasites in the human body. Recently, I read that a man was about to have a tumor removed from his brain but they later learned it was a worm in his brain. What other parts of the body do these parasites infest? I have lots of problems with my bladder, incontinence, frequently urination but recently, I have noted a funny unusual crawling sensation in my bladder. I wonder what that means.