Answer to Parasite Case of the Week 583: Immature Taenia sp. proglottids.
I apologize that this was more challenging than I meant it to be. I should have mentioned that these objects were passed through the anus (sorry about that omission!)
Note that the objects seen here are made up of repeating chains of proglottids, some which are longer than they are wide, consistent with a Taenia sp. rather than Diphyllobothrium/Dibothriocephalus sp.
In my mind, the histologic sections don't add much to this case. They show the classic features of a cestode (thin outer tegument with a loose underlying stroma containing calcareous corpuscles and longitudinal muscle fibers) with central reproductive structures. However, there is not enough differentiation of these structure present to allow for definitive confirmation of the gross identification.