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Nonpathogenic (Harmless) Intestinal Protozoa FAQs

What are nonpathogenic intestinal protozoa?

They are single-celled parasites that are commonly found in the intestine but never cause illness. They do not harm the body, even in people with weak immune systems.

The nonpathogenic intestinal protozoa include:

  • Chilomastix mesnili
  • Endolimax nana
  • Entamoeba coli
  • Entamoeba dispar
  • Entamoeba hartmanni
  • Entamoeba polecki
  • Iodamoeba buetschlii

Where are these protozoa found in the body?

They are found only in the lumen (cavity) of the intestinal tract. They are not found in the cells that line the intestine, and they do not spread to other parts of the body.

How are these protozoa detected?

By microscopic examination of stool specimens.

I was told that my stool tested positive. How do people get these protozoa?

By swallowing them, for example, by ingesting food or water contaminated with feces. This is called fecal-oral transmission. The presence of these protozoa in your stool simply indicates that you had a fecal exposure sometime in the past.

I have not been feeling well. Could these protozoa be causing my symptoms?

No. These nonpathogenic protozoa do not cause illness. Other possible causes of your symptoms should be considered. To see whether you are infected with a pathogen (a disease-causing agent), your health care provider might want to check your stool for bacteria, viruses, or other parasites. Another possibility is that your symptoms are not caused by an infection.

How long could these protozoa stay in my intestine?

For weeks, months, or years.

To be on the safe side, should I be treated to get them out of my intestine?

No. These protozoa are harmless.

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This information is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the parasites described above or think that you may have a parasitic infection, consult a health care provider.

  • Page last reviewed: December 14, 2012
  • Page last updated: December 14, 2012
  • Content source:
    • Global Health - Division of Parasitic Diseases and Malaria
    • Notice: Linking to a non-federal site does not constitute an endorsement by HHS, CDC or any of its employees of the sponsors or the information and products presented on the site.
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