Any angler will know that, in some lakes, it seems like every fish is full of worms. I've always dealt with that by frying the crap out of them -- no medium-rare bass for me, sorry. Alternatively, I'm sure they're fine after a few weeks in the freezer.

Rivers seem to be better, with worm presence (or at least, obvious worm presence) being less common. Additionally, I've never seen worms in bottom-feeding fish like catfish and carp.