Sorry if I sound a bit brusque but I've clicked on at least three screamy threads about threadworms, oh god, oh no, how awful, how disgusting, I must burn the contents of my house followed by my own children.
And thousands more in search engines.
Here is the thing. They are totally, entirely, absolutely NORMAL. They are no more or less disgusting than any other parasite type thing - nuts or whatever- very common in children and very easy to treat.
They can be very painful for children around their bottoms because their skin is soft and sensitive. This is why you should freak out, because your child is in pain, not because 'oh, ewwww.'
All the daft over the top reactions do is perpetuate the problem as people don't talk about it thinking it's some grim, gross, horrifying thing when actually they are perfectly normal, extremely easy to treat and no matter how much you boil wash and encourage hand washing your kids may well get them for the simple reason kids put things in their mouths more than adults.
So seriously lighten the fuck up!