My experience has been finding a higher population in the stool, and systemic factors as well. Blood cultures done properly will reveal intermediate stages developing, which match morphological structures in the stool. This is often true of finding parasitic fungal spp as well.
In fact, most of the protozoa I have run across, behave much the same way fungi do.
The only protozoa I have found that remain stable in their life cycles are toxoplasma gondii, and cryptosporidium.
I have also run across oomecetes infecting. So, it shows that these stremenopiles (B. Hominis etc.)are often cycling in different areas of the body.
This is true of fungi, and some amoebae. Shroom

I'm afraid the answer to your question is about the failings of the medical community. Its obvious to anyone schooled in the sciences after a review of the recent literature that some subtypes of B. Hominis ARE pathogenic. So why do almost 100% of GPs, GI and Infectious specialists reject even considering the possibility.

Most doctors were educated before B. hominis subtypes and pathogenesis was even discovered. Very few actually do research based on sick patients. They just forward them to a specialist. The GI specialist declares its IBS and wash their hands.

Most doctors in the developed world know very little about parasites and when they check their books, they read the old views. When they ask their specialists in GI, the same thing just ripples down. All in all, doctors in non-teaching hospitals are narrow minded because its easier.

Most doctors don't spend their spare time reading the latest research on B. hominis so fall back on their old books.

Most doctors are afraid to step outside the "box" for fear of legal liability or ridicule or are just plain lazy.

Most doctors won't take even bright well educated patients who have done their homework seriously due to their "Ivory Tower" syndrome. See I can invent terms like IBS too.

Most doctors are specialized and the number of parisitologists is tiny and most have the same problem as the other doctors.

The state of the art in treatment in medicine runs between 10-20 years behind with very few exceptions.

B. hominis is self limiting and ruins lives but doesn't kill so most of the attention goes to exciting diseases that kill or easy to treat base on the textbooks.

B. hominis symptoms mimic many other conditions and most doctors are too lazy to to a proper differential diagnosis. For example, they will run a single stool test and declare it negative when even the extremely conservative CDC understands it takes 5 microscopic stool tests just to achieve a 90% probability of finding B. hominis.

B. hominis is not easy to identify and not considered pathogenic so is typically missed anyway. Many doctors are too lazy to even study test accuracy and sensitivity.

The "gold standard" treatment Flagyl fails more often than not and doctors don't understand Flagyl is a lousy empirical test for B. hominis. They are afraid to use the multiple medication approach that has been shown to be effective in 80% of cases due to legal fears.


It goes on and on.

If doctors were engineers, we would still be fussing with tube technology. Its SAD. Then there is the "thin white wall" and their herd mentality.