I have never ever had a problem with worms in my dogs in over 10 years of ownership. My dogs have been on raw for over 2 years now. However, just a few weeks ago my oldest keps loosing weight eventhough he was on more food than normal... I wormed him and he has put the weigth back on now, so it looks like it was worms. I don't know whether it is the raw food or something else that he got hold of, but I will be a bit more careful with worming though from now on.