I had done a half dozen colon cleanses, two Master Cleanse fasts and seventeen Liver Flushes before I ever discovered I had a parasite problem. Build up mucus, old fecal material, congested livers and other symptoms of a toxic body can hide parasites for a long time. You can get parasites from pets, food, other people, walking barefoot, well, its hard to imagine how anyone can really keep to being exposed to parasites.
The P&Bs might have just cleared out enough junk from the colon to allow the embedded parasites a chance to expose themselves. Most attach themselves to the intestinal walls and thrive in the built upunk.