Answer to Case 737

 Answer to the Parasite Case of the Week 737: Pentatrichomonas hominis trophozoites. 

P. hominis trophozoites have 5 flagella: 4 are directed anteriorly, while the 5th is directed posteriorly, forming the outer edge of an undulating membrane. This results in characteristic motility that Richard likes to describe as "a man trapped inside a plastic bag" (!)  I managed to capture a couple of still images from the video which show this phenomenon:

As noted by jebarner, P. hominis, as well as Enteromonas hominis,  Retortamonas intestinalis, and Chilomastix mesnili are non-pathogens and indicators of ingestion of fecally contaminated food or water. Therefore, the cause of this child's symptoms is unclear from this finding alone, and additional testing may be indicated.

Thanks again to Dr. Richard Bradbury for sharing this beautiful case!