If your kitty has ever had a flea problem, the kitty could've gotten worms from that. They seem to go hand-in-hand, somehow.
If you've not had a recent flea problem, it could simply be that your kitty needs his anal glands expressed. Kitties usually do this while going to the bathroom, but sometimes don't, and they get a bit impacted, and butt-scooting is their way of trying to handle it (I'm thinking it itches, or something along those lines).
Another thought...is your kitty overweight and cannot reach his bum to clean it? If he's overweight, it might be the problem, and he's trying to handle that by scooting.
Another thought, is that he could be being lazy about cleaning his bum. Sometimes our Hobbes does this. He's really well trained and stops and cleans his bum when we tell him to, so it handles that way...but he does occassionally try the scooting-instead-of-cleaning trick...the stinker!
All that aside, a vet visit is definitely in order. Just to be safe, rather than sorry...
Hope everything goes well!