Answer to Case 789

Answer to the Parasite Case of the Week 789:  Taenia sp. proglottid

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.

Answer to Case 795

Answer to the Parasite Case of the Week 795: Taenia saginata/suihominis gravid proglottid. 

As noted by Anonymous, Patrik, Antoine A, Florida Fan, Menzler, and others, we have a proglottid of Taenia saginata/Taenia suihominis (formerly known as T. asiatica) characterized by >12-13 primary uterine branches on each side of the central uterine stem and a Taenia spp. egg characterized by an internal hooked oncoschere and a thick radially striated outer shell. Assuming the image of the egg was acquired using a 40x objective, we can estimate a size of 35 micrometers in greatest dimension which is consistent with Taenia species. We don't have a patient travel history, so I would sign this case out as "Taenia saginata/Taenia suihominis". 

This beautiful preparation shows a fresh proglottid pressed between glass and backlit to show the characteristic branching pattern. I particularly like this technique since it requires only minimal manipulation of the proglottid. It can easily be done with a fresh proglottid, but preserved proglottids need to be cleared and softened through exposure to lactophenol or other preparation. 

Injecting India ink into the lateral genital pore of Taenia proglottids can also be used to highlight the uterine branches, but we don't perform this in my lab given the potential infectious risk associated with T. solium.

Regarding motility as a diagnostic feature - I dug into this in Case of the Week 789 by scouring the old literature and found only anecdotal evidence. However, it does seem that Taenia saginata proglottids are more likely to be motile than T. solium. I can't speak to T. suihominis, so if anyone has information to share on this species, I would love to hear it. 

Thanks again to Idzi and Loranne for donating this great case!

Case of the Week 789

This week's case was donated by Dr. Blake Cirks. The following object was passed per rectum by an otherwise asymptomatic individual living in Laos. Based on the image and video, what is the most likely diagnosis?