Of an educational note, the gut is one of the most vulnerable places for infection. There are a number of pathogens that can harbor there. Obviously parasites (worm) but also bad bacteria, fungal/yeast, viruses etc. Protozoa parasites are often overlooked and can be problematic. The reason I bring this up is that some of the other bugs may require a different strategy.
Diagnosing parasites or other pathogens is a hit or miss experience.