Well I admit this is mostly heresay, but I've been informed that fish have LOTS of worms in the wild, and if the flesh is raw, well...
Since I'm not a huge sushi eater, I took this info and wrote off the food.
I suggest doing more research on the subject - perhaps check the parasite Support forum on this site - I will too, 'cuz although I can live without sushi, I'd like to know for sure myself.