Non-pathogenic intestinal protozoa are single-celled parasites commonly found in the intestinal tract but never associated with illness. The non-pathogenic protozoa can be divided into two groups: amebae and flagellates. Analysis of 722 faecal DNA samples revealed that the prevalence of G. lamblia was 9.3% according to PCR, as compared to 5.7% by microscopy. Further more, G. lamblia infection was detected in 15 (6.6%) of 228 faecal samples submitted to the laboratory for bacterial culture only. C. parvum/C. hominis infections were not diagnosed by routine procedures, but DNA from these organisms was detected in 4.3% of 950 DNA samples.
Good sanitary practice, as well as responsible sewage disposal or treatment, are necessary for the prevention of E.histolytica infection on an endemic level. E.histolytica cysts are usually resistant to chlorination. Colonization of the nonpathogenic amebae occurs after ingestion of mature cysts in faecally-contaminated food, water, or fomites. Excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine. The trophozoites multiply by binary fission and produce cysts, and both stages are passed in the feces.