Case of the Week 578

This week's case is from one of our former fellows, Dr. Rachael Liesman. The structures in question were seen in H&E-stained sections of small bowel.

Identification?

Answer to Case 578

Answer to Parasite Case of the Week 578: Hymenolepis species. I agree with Blaine and Idzi that this is likely H. nana based on the size of the eggs, but I also couldn't see the polar filaments to be certain.

What we can see in this case are the following features:

1. Thin outer tegument with loose underlying stroma, and segmented nature (proglottids) consistent with a tapeworm.
2. Multiple individual eggs measuring approximately 35 micrometers in greatest dimension, with inner and outer membranes. 
3. Internal refractile hooklets in some eggs (pink arrow heads in image below and inset). 

Combined, these features all point towards Hymenolepis nana.  I emphasized that the eggs are found singly to differentiate them from the eggs of Dipylidium caninum which are generally found in packets - even in tissue sections. You can see a previous case of D. caninum in tissue section HERE. Note how the "rice grain" proglottids of D. caninum are much different than the continuous chain of proglottids seen here.

Finally, I mentioned the presence of inner and outer membranes of the eggs in this case to differentiate them from the eggs of Taenia species which have a single striated shell. You can see a case of Taenia in tissue section HERE. The proglottids of Taenia sp. are much larger than those of Hymenolepis, and the eggs are found with the thin central uterine stem and lateral branches.

Thanks again to Dr. Rachael Liesman for donating this educational case!

Case of the Week 577

This week's very cool case was donated by Dr. Mike Feely. We haven't had anything like this one before on the blog!

The specimen below was submitted by a young woman who found this "worm" by her arm, right below her mouth, upon waking from a nap. She reported having abdominal pain with associated diarrhea for several weeks prior to presentation, but was otherwise healthy.

 After being in formalin:

Histologic sections (H&E):

Identification? Any additional information that you would like?

Answer to Case 577

Answer to Parasite Case of the Week 577: Planarian worm, Bipalium species, commonly known as the "hammerhead worm". This is not a human parasite. Upon further questions, the patient mentioned that she was taking a nap outdoors, thus explaining the finding of this interesting flatworm on her arm.

There is a lot of great discussion in the comment section on this case, including some recommended reading. HP recommends this open access article in BioInvasions Records, which includes images of both gross and histologic features, both of which are consistent with this case. The University of Florida also has this nice post on land planarians which are invasive species in Florida. Thanks again to Dr. Feely for this cool case!

Case of the Week 576

Happy New Year! Our first case of 2020 was provided by Heather Arguello, my awesome Parasitology Technical Specialist. The following worm was found in a specimen obtained during colonoscopy. It measured approximately 2 mm long. Identification?

Answer to Case 576

Answer to Parasite Case of the Week 576: Enterobius vermicularis (a.k.a., pinworm), adult male

Thanks to all who wrote in with the correct answer. Florida Fan noted the presence of several identifying features: cephalic alae confirming the identity of pinworm in this adult nematode, and the curved tail with visible copulatory spicule defining the gender as male.

Meanwhile, Idzi reminded us that Enterobius vermicularis was formerly known as Oxyuris vermicularis. This is why you will sometimes see the infection referred to as oxyuriasis. Finally, Marc shared that he knew the answer but couldn't seem to "pin" it down 😉.