All signs of an infectious organism - 99.9% of conventional testing will miss this. Most likely parasitical and a very good chance it being protozoa. Many of those areas are teeming with protozoa including e histolytica, blastocystis, isospora, cyclospora, cryptospordium, giardia etc.
Flagyl (metrodazole) is an old school drug that is still widely used but seldom effective with lots of side effects. Most of these infections require a cocktail of drugs. As a side note, there are variations of Flagyl that has less side effects such as tindazole and secnidazole.
Many of protozoa are transmitted via water or fresh produce grown in water (aquaculture).
Proper testing is critical - here are links that will be helpful: