This case nicely shows how 'fluke-like' a single motile proglottid can appear as it contracts and moves. It's not surprising how many viewers thought this might be a trematode!
HERE is another case of a motile Taenia proglottid donated by Idzi Potters back in 2018 that shows how a proglottid can even curl up and look somewhat nematode-like.
Note that you can see the lateral uterine pore, which helps to identify this object as a Taenia proglottid and differentiate it from a trematode or nematode:
Thanks to everyone for the great comments on this case. Idzi noted that the "Size and typical way of movement are perfectly compatible with Taenia proglottids. This very active movement of mature, gravid, and freshly passed proglottids rules out Taenia solium (whose proglottids remain immobile when passed). This leaves us with T. saginata and T. suihominis (Mathison 2021 - syn. T. asiatica) as a possibility. Both of these species seem to be endemic in Lao PDR, so my final answer would be Proglottid of Taenia saginata /Taenia suihominis."
Antoine A. also noted that "Given the appearance and mobility, I would also lean toward T. saginata, since T. solium is normally excreted passively in chains in the stool."
These features were noted in a 1972 publication which summarizes a number of reports and case series. The authors of this publication note that "the most frequent symptom of T. saginata infection is the discharge of proglottids" and discuss how the patients feel a sensation in the rectum for 5-10 minutes of the proglottid passing. The authors of a 2003 Lancet publication also discuss the differences in motility and form of T. saginata and T. solium proglottids. I don't know how reliable these features are in differentiating the proglottids of T. saginata from T. solium, and if this also applies to T. suihominis. If anyone has literature to share, I would greatly appreciate it!
Also many thanks to Dr. Blake Cirks who donated this case, and to Dr. Edward Mitre who put me in touch with Dr. Cirks.
3 comments:
As I love the old literature, I came up with this article from 1953 in the Lancet: Asher, R., TROUBLESOME TAPEWORMS, The Lancet, Volume 261, Issue 6769, 1953, Pages 1019-1021, ISSN 0140-6736, https://doi.org/10.1016/S0140-6736(53)92161-8.
It states the following about Taenia saginata: "Sometimes segments migrate from the anus spontaneously ; this is pathognomonic of T. saginata and does not happen with T. solium".
About the motility of gravid T.asiatica segments... that's more difficult to find, but... the article "Morphologic descriptions of Taenia asiatica sp. n." (Korean Journal of Parasitology, Vol.31, No.1,1-6, March 1993) describes the following: "Some free gravid proglottids were dropped in AFA bottle for fixation while they were showing motility"! So I assume that these proglottids are -like in T.saginata- actively motile when passed...
Thank you, Idzi!
For those who are interested, I highly recommend that article that Idzi mentioned for its historical context (including treatment with male fern and purgatives!)
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