Case of the Week 791

This week's case is from Drs. Matt Pettengill and Sean Moss. Approximately 10 of the following object were recovered from the hair of patient. She had applied calendula to her scalp earlier in the day. What is your identification?

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!

Case of the Week 787

 This week's case is from Dr. Beth Adams who encountered a patient in the Moskitia region of Honduras who had coughed up the following object. What is your presumptive identification?

Answer to Case 787

 Answer to the Parasite Case of the Week 787: Adult Ascaris sp.

As Florida Fan and Idzi noted, the curved posterior end suggests that this is a male adult. 

Ascaris is the largest nematode to reside in the human intestinal tract. Adults live in the small bowel and must move against peristalsis to avoid being expelled in the stool. The fact that they are freely moving and not attached to the intestinal wall means that they can occasionally end up in ectopic locations such as the biliary tree or appendix. In this case, the worm migrated up the intestine, stomach, and esophagus, and was expelled through the mouth (!) Given its large size, heavy infections can lead to the potential deadly complication of small bowel obstruction.  

Some readers made the interesting point that this could be either Ascaris lumbricoides or the zoonotic Ascaris suum, which raises the controversial topic of Ascaris taxonomy!.Although they were long thought to be separate species, Ascaris suum was found to be genetically similar to the human species A. lumbricoides in a 2014 comparative analysis of microRNA profiles, arguing against separation into Ascaris two species. However, a 2020 analysis using whole genome sequencing found significant genetic differentiation between A. lumbricoides and A. suum populations. Therefore, it looks like the two populations are genetically distinct and likely deserve separate classifications. We can hopefully look to future analyses to more fully understand their taxonomic status.

Thanks again to Dr. Beth Adams who donated this case, and to Drs. Mike Adams and Bill Stauffer who shared the image and video with me initially.

Case of the Week 786

 This week's case was generously donated by Dr. Richard Bradbury from James Cook University in Australia. The following object was seen in the stool from a patient with advanced HIV infection living in Tanzania. Shown are preparations using differential interference contrast (DIC), darkfield, and fluorescent microscopy (wavelengths unknown). The objects measure approximately 25-30 micrometers in length. What is your identification?