Case of the Week 581

This week's case was donated by Theodore Trejo. The following were seen in skin scrapings collected from a middle-aged man complaining of itching. The motile objects measure approximately 0.3 mm in length. Identification?

View on full-screen for best visibility:

Answer to Case 581

Answer to Parasite Case of the Week 581: Demodex folliculorum, the human follicle mite.

Demodex are fascinating arthropods that live in our follicles and sebaceous glands. There are 2 species found in humans: D. folliculorum and the shorter D. brevis. Many of us have them - especially as we get older - and they are mostly commensals, not causing any symptoms. However, they may cause rosacea and blepharitis (inflammation of the eyelids) in some individuals.

As with all arachnids, they have 8 legs as nymphs and adults, and 6 legs as larvae. Adults have a genital opening right below the legs, which allow them to be distinguished from nymphs:

The video from this case shows how many mites can live in a single follicle. Kosta Y. Mumcuoglu noted that there are at least 6 specimens of D. folliculorum present, with at least two of them embedded in the follicle. By viewing the video on full screen mode, I think there may even be more - up to 8 based on the movement I see within the follicle. Wow!

Thanks again to Theodore Trejo for donating this very nice case. I'll close with the fun poem from Old One:

DEMODEX

This micromite is called Demodex

It can be found in many acarology text

Not designed to move very far

8 stubby legs and the shape of a cigar

It dwells in the follicles of old ones brow

And if you didn’t know this by now

Usually nonpathogenic but occasionally is thought

To cause rosacea however this theory is fraught

with controversy. We have only to thank Herr Dr. Jake Henie

Who discovered this mini monster dwelling within Thee

Case of the Week 580

This week's case was donated by Dr. Neil Anderson. The following objects were seen in an EDTA blood specimen obtained from a patient with recent travel to sub-Saharan Africa (note that the blood was ~10 days old when the video was taken).

Identification?
What additional analysis might be indicated?

Answer to Case 580

Answer to Parasite Case of the Week 580: Loa loa microfilariae. As noted by several readers, the nuclei go to the tip of the tail, the microfilariae are relatively large, and there is faint evidence of a sheath, all of which are characteristic features for this species. As I teach my students, the nuclei "flow-a flow-a" (to the tip) in Loa loa. Another memory trick from William Sears is that the nuclei go "lower and lower" in Loa loa. Take your pick for your favorite! Remember that the sheath will not always be seen. Size is a more definitive feature in differentiating Mansonella spp. from the sheathed microfilariae.

William also mentioned that one should always check for the presence of Onchocerca volvulus co-infection, and get a microfilariae count before initiating therapy with the drug of choice for loiasis, diethylcarbamazine (DEC). In this case, the microfilaremia was calculated at 1,960 microfilariae/mL blood, which is well below the threshold of 8,000/mL at which DEC is contraindicated (thank you for calculating this Heather, and for the lovely photos in this case). DEC is also contraindicated in patients with concomitant onchocerciasis since the rapid death of O. volvulus microfilariae in the eye can lead to blindness.

What I found remarkable about this case was how long the microfilariae remained alive. They were still moving (albeit, somewhat choppily) at 10 days after blood draw, and the following image was taken of a smear make with 14 day-old blood. Not bad! According to filariasis expert, Shelly Michalski, the Project Liaison for the NIH Filariasis Research Reagent Resource Center, microfilariae are remarkably hardy, and can survive freezing -80°C. Wow!

And finally, to celebrate Valentine's day, here is this beautiful Brugia from Blaine Mathison:

Case of the Week 579

Here is our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following were seen in a direct wet preparation of an unfixed stool specimen from a patient with bloody diarrhea and recent travel to sub-Saharan Africa. The objects in question measure approximately 20 micrometers long. Identification?

Answer to Case 579

Answer to Parasite Case of the Week 579: Entamoeba histolytica

This great case by Idzi nicely shows the directional motility of an E. histolytica trophozoite - something that is less commonly seen in the clinical laboratory as more fecal specimens are received in a fixative. This case also highlights the characteristic ingestion of red blood cells (erythrophagocytosis) by the trophozoites.

Dr. Graham Clark reminds us that non-pathogenic Entamoeba species may also ingest red blood cells that are in the environment, so correlation with clinical presentation, biopsy, antigen and/or PCR tests is also warranted.

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!