Answer to Case 625

Answer to the Parasite Case of the Week 625: Not a parasite; rotifer

This fascinating "wheel animal" (from Latin rota "wheel" and -fer "bearing") has been seen a couple of times in the past on this blog. Check out our previous cases with great photos and videos:

Case 517 (unstained with video)

Case 304 (another Pap-stained case)

Here are some of the diagnostic features in this case:

Old one gives us a great description of the rotifer seen here: "Bdelloid rotifer with a retracted corona, large orange ovary, with 2 lateral germovitellaria with posterior stomach. Tail section appears to be visibly segmented with one of its toes visible at the terminal segment."

As I've noted in my previous posts, there is no clinical significance to this finding. Rotifers are found in environmental water sources, so it is likely that the organism entered the specimen through the collection process - possibly from a toilet using untreated well water.

Some of you suggested that this could be a miracidium of Schistosoma haematobium. While this is a good thought given the size and location, we can exclude this organism based on the overall shape of the organism, lack of circumferential cilia, and presence of a segmented foot (retracted, but still visible)..

Thanks again from our colleagues at Altru Health System for donating this fun case!