Case of the Week 790

This week's case was generously donated by Dr. Tudo Rares Olariu, the head of the clinical laboratory at the Municipal Clinical Emergency Hospital in Timisoara, Romania. The following object was seen in a stool specimen from a child with multiple mucosanguineous stools. It measures approximately 45 micrometers in greatest dimension. What is your diagnosis?

Answer to Case 790

Answer to the Parasite Case of the Week 790: Rodentolepis (formerly Hymenolepis) nana egg.

This is a classic example of an R. nana egg showing the inner and outer membranes, oncosphere with large splayed hooklets, and polar thickenings from which filaments extend into the space between the oncosphere and outer membrane. It's hard to make out the polar filaments in this particular example, but the smaller size allows us to differentiate it from the larger Hymenolepis diminuta egg.

Interestingly, most readers on social media are still referring to this parasite as Hymenolepis nana. However, I can confirm that Rodentolepis is now the preferred genus. For further reading, I recommend the systematic study of hymenolepidid cestodes by Haukisalmi and colleagues which supports the split into separate genera for a more practical and stable classification. 

Thanks again to Dr. Tudo Rares Olariu for donating this classic 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?

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.

Case of the Week 788

Happy Autumn, everyone! It's the first Monday of the month and time for our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following were seen in a direct wet mount specimen of stool from a patient with chronic constipation. What is your identification?

Answer to Case 788

Answer to Parasite Case of the Week 788: Pentatrichomonas hominis trophozoites

Note the classic 'jerky' motility of P. hominis trophozoites. I've never seen so many P. hominis in a specimen before! 

Like Trichomonas vaginalis, there is no known cyst stage of this protozoan parasite. P. hominis trophozoites move using 5 flagella: 4 are directed anteriorly, while the 5th is directed posteriorly, forming the outer edge of an undulating membrane. This results in characteristic motility that Dr. Richard Bradbury likes to describe as "a man trapped inside a plastic bag"!  You can see a very nice video and still images of this phenomenon in Case of the Week 737. For those of you who have been following this blog since the beginning (2007!), you may recall that P. hominis was the parasite highlighted in Case of the Week 5. Check out the fun video that Alex Ball made for me back then in the Answer to the Case of the Week 5.

Thanks again to Idzi Potters and the Institute of Tropical Medicine Antwerp for donating this great case!