severe infestation

I would imagine that if you had worms like that little boy you would be painfully aware of it and probably be in the hospital. What sort of symtoms might you have if you had such a severe infestation? I grew up with various dogs and cats since childhood and I'm sure that I have some unwanted guests but if they were that large and numerous I'm sure I wouldn't have to take paragone ot Clarkia to see them.