Well then you should worm them all the time... cause they will have worms all the time.. same as you have worms i have worms and every living thing has worms... My fem coastal just passed a worm, so i am worming as soon as the product gets to me.. however i will be worming my animals every 6 months from then on in.. Every prey item you give your animal be it frozen, fresh, live, dead will have worms and other parasites.. yeah ok freezing will kill most of the bacteria, and some of the worms but there are some that get through..
I have been doing some asking around to people who are more in to the science of life in terms of parasites and stuff, very interesting, but also worrying if you think about it too much...