Answer to Case 718

 Answer to the Parasite Case of the Week 718: ciliated epithelial cells; NOT Lophomonas. Many of our readers suspected this case to represent Lophomonas blattarum - a flagellated protozoan parasite of cockroaches - but there is no convincing evidence that Lophomonas is actually a human parasite. Also, there are a number of helpful features that can differentiate ciliated human epithelial cells from L. blattarum:

1. Human ciliate epithelial cells have a well-defined terminal bar with a compact row of short cilia (arrows) rather than the tuft of long flagella possessed by Lophomonas. 

 This is nicely demonstrated by this additional photograph from the same case:

2. The nucleus is located in a basilar position (rather than apical, as with Lophomonas). 

3. The beating motility of ciliated epithelial cells is very rhythmic and non-direction compared with true Lophomonas.

For those of you who are asking "what about the PCR evidence implicating Lophomonas blattarum as a human pathogen in respiratory samples??" Well, a thorough analysis of the PCR primers conducted by my colleague, Dr. Richard Bradbury revealed these primers to show a lot of cross-reactivity, particularly with the oral trichomonads. Therefore, amplification using this PCR in respiratory specimens would not be conclusively supportive of Lophomonas. Again, though, the difference in motility patterns between ciliated human epithelial cells and Lophomonas are really striking, and allows for definitive differentiation in my mind.