The pile being long and shaggy can collect stuff that traps in the pile. The best thing is to have a trampoline. Put it upside down and shake the crap out of it once a month. Otherwise vacuum as normal.
It would be good to find out what yarns are in the rug. I'm not saying not to get one, but just my normal 'caveat emptor' message!
Ash.
Will ask tomorrow!