El Blastocystis a menudo aparece con otros organismos, por lo que no se sabe si causa alguna enfermedad. Las tasas del organismo en las heces aumentan cuando hay un saneamiento inadecuado y una higiene personal deficiente. Puede correr un mayor riesgo si viaja a donde la higiene es inadecuada o donde el agua no es segura, si vive en lugares con esas condiciones, o si maneja animales contaminados, como cerdos y aves. Complicaciones Si tienes diarrea asociada con Blastocystis hominis, es probable que sea autolimitante. Evita los alimentos de vendedores ambulantes. No comas huevos pasados por agua.

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Both cysts and trophozoites of Enteromonas hominis and Retortamonas intestinalis are shed in feces; only trophozoites of Pentatrichomonas hominis no known cyst stage are shed in feces.

Infection occurs after the ingestion of cysts E. Excystation of E. These three species colonize and replicate in the large intestine, where they are regarded as commensal organisms and are not known to cause disease. Hosts Humans are the primary host for all three of the discussed flagellates. Occasionally these species are found in apes and monkeys. Geographic Distribution Non-pathogenic flagellates occur worldwide, and are more prevalent in areas with inadequate sanitation leading to fecal contamination.

Retortamonas intestinalis is the least frequently encountered among the three species discussed here. Clinical Presentation Enteromonas hominis, R. Enteromonas hominis cysts. Cysts may contain one, two or four nuclei, with binucleate forms being the most common. In binucleate forms, the nuclei are often at opposite polar ends of the cyst; in forms with four nuclei, they are often paired at opposite ends.

Nuclei possess a large, central karyosome, often surrounded by a clear area, and do not contain peripheral chromatin. Figure A: Cyst of E.

Figure B: Cyst of E. They possess two flagella, one directed anteriorly and one extending posteriorly. A cytostome is present at the anterior half of the trophozoite and is bordered by a fibril. The single, spherical nucleus is located at the anterior end and contains a small karyosome and a fine layer of peripheral chromatin.

Figure A: Trophozoite of R. Figure B: Trophozoite of R. Mature cysts contain a single nucleus, with a compact central karyosome and varying amounts of peripheral chromatin.

The fibril associated with the cytostome may be been seen in close proximity to the nucleus. Figure A: Cyst of R. Figure B: Cyst of R. Figure C: Cyst of R. Figure D: Cyst of R. Trophozoites of Pentatrichomonas hominis There is no known cyst stage for Pentatrichomonas hominis.

They possess five flagella: four directed anteriorly and a fifth directed posteriorly, that forms the outer edge of the undulating membrane and projects beyond the posterior as a free flagellum. The axostyle is slender and projects from the posterior end. The single nucleus is located at the anterior end and contains a small karyosome. Figure A: Trophozoite of P.

Figure B: Trophozoite of P. Figure C: Trophozoite of P. Figure D: Two trophozoites of P. Figure E: Trophozoites of P. Figure F: Trophozoite of P. Laboratory Diagnosis Enteromonas hominis, R. Identification is best accomplished by direct wet mounts of freshly produced stool that reveal the characteristic motility of the organisms.

These protozoa may also be identified in permanent stained smears, although their affinities for stain are inconsistent and individual flagella may not be readily visible. Pentatrichomonas hominis trophozoites degrade rapidly and timely fixation after passage is required to detect trophozoites in permanently stained slides. Suggested Reading Bradbury, R. Despommier, D. Nonpathogenic Protozoa. In Parasitic Diseases pp. Springer, New York, NY. DPDx is an educational resource designed for health professionals and laboratory scientists.

For an overview including prevention, control, and treatment visit www. Page last reviewed: July 31,


Enteromonas hominis



Non-pathogenic Flagellates




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