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Philophthalmiasis

[Philophthalmus spp.]

Causal Agents

Pentatrichomonas hominis, a nonpathogenic flagellate.


Life Cycle

lifecycle

Only trophozoites of Pentatrichomonas hominis are shed in feces The number 1, as there is no known cyst stage for this species. Infection occurs after the ingestion of trophozoites in fecal-contaminated food or water, or on fomites The number 2. Pentatrichomonas resides in the large intestine, where it is regarded as a commensal and is not known to cause disease.

Geographic Distribution

Worldwide

Clinical Presentation

Pentatrichomonas hominis is considered nonpathogenic. The presence of trophozoites in stool specimens can however be an indicator of fecal contamination of a food or water source, and thus does not rule-out other parasitic infections.

Pentatrichomonas hominis trophozoites.

 

There is no known cyst stage for Pentatrichomonas hominis. Trophozoites are pyriform in shape, measuring 6-20 µm long. 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

Figure A: Trophozoite of P. hominis in a stool specimen, stained with trichrome.

Figure B

Figure B: Trophozoite of P. hominis in a stool specimen, stained with trichrome.

Figure C

Figure C: Trophozoite of P. hominis in a stool specimen, stained with trichrome.

Figure D

Figure D: Two trophozoites of P. hominis in a stool specimen, stained with trichrome.

Figure E

Figure E: Trophozoites of P. hominis in a stool specimen, stained with trichrome.

Figure F

Figure F: Trophozoite of P. hominis in a stool specimen, stained with iron hematoxylin.

Laboratory Diagnosis

Pentatrichomonas hominis is identified through the detection of trophozoites in stool specimens. Identification is best accomplished by direct wet mounts that reveal the characteristic, jerky movement of the organisms. They may also be identified in permanent stained smears, although their affinities for stain are inconsistent and with their small size are often overlooked.

More on: Morphologic comparison with other intestinal parasites.

Treatment Information

As this species is considered nonpathogenic, there are no treatment recommendations for this organism.

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DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/.

  • Page last reviewed: May 3, 2016
  • Page last updated: May 3, 2016
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