Yes they can live in a healthy body. Matter of fact the healthier your body gets the healthier the parasite gets. It's the solvent connection Dr. Clark talks about.
For sure pathogens and all kinds of nasties live on the rotting debris you have in your colon and it is well to get rid of that stuff. But even with your body clean as a whistle you can still have parasites. Again, it's the solvent connection Clark goes into detail about.