Case of the Week 774

This week's case features another great video from Dr. Rasool Jafari - an object identified from skin scrapings. What is this little arthropod?

Answer to Case 774

Answer to the Parasite Case of the Week 774: Demodex! The legs and gnathosoma (with mouthparts) are nicely demonstrated:

I can't quite tell if this is D. brevis, or Demodex folliculorum with a scrunched-up tail. 

We've had some great cases of Demodex on the blog over the years. Here is the list in no particular order:

Case of the Week 535 (with a poem from Blaine Mathison 😁), donated by Dr. Kabeer Shah.

Case 581 - showing an adult D. folliculorum and a video of 2 mites within a hair follicle. Also with a poem by Old One. This case was donated by Theodore Trejo and shows beautiful detail of the adult mite.

Case 702 - from the Mayo Clinic Mycology lab showing D. brevis on calcofluor white fluorescent stain.

Cases 278 - showing a pair of mites on calcofluor white fluorescent staining - with another poem from Blaine! I hadn't realized how many poems we have collected. This case was donated by Florida Fan.

Case 606 - donated by Dr. Sandeep T and showing a lovely long D. folliculorum.

Case 772 - This is the tricky case from last month with the twisted tail. Donated by Dr. Evis Nushi.

Case 503 - from Florida Fan with a really nice side-by-side view on light and fluorescence microscopy.

Case 334 - showing several D. folliculorum mites from eyelash scrapings. Donated by Dr. Robin Chamberland - with yet another poem by Blaine. All of the poems are different from one another, and very fun to read. 

Case 58 - the very first Demodex that I ever posted - 16 years ago!

Case 190 - a beautiful example of D. folliculorum in a hair follicle in an H&E-stained histopathology preparation. It was donated by Dr. Holkmann Olsen and is the best example I've ever seen of the mouthparts and legs in a histopathological section. 

Case 308 - and finally, an amazing case by Florida Fan that shows Sarcoptes scabei and Demodex folliculorum mites in the same image. 

I've been blessed to have so many fabulous case donations over the years. Many thanks to Dr. Rasool Jafari for donating this fascinating case.

Case of the Week 773

This week's case is generously donated by Dr. Rasool Jafari from the Department of Parasitology and Mycology, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran. These objects were isolated from a patient and cultured in Modified TYI-S-33 medium. What parasite is this, and what are we seeing here?

Answer to Case 773

Answer to the Parasite Case of the Week 773: Giardia duodenalis trophozoites with 'falling leaf' motility. As nicely described by Idzi,this is a "Beautiful video material of Giardia trophozoites! Note that it’s official name now is “Giardia duodenalis”. We used to cultivate these critters on Keisters medium for educational purposes. Not easy though, so the more impressing this video by Dr. Rasool Jafari is! Kudos!"

Indeed, you can make out multiple characteristic features of Giardia trophozoites, including the 'tear drop' shape with 2 nuclei and a central axoneme when viewed anteriorly, a concave spoon-shaped appearance when viewed from laterally, anterior sucking disk, and even some trophozoites dividing by binary fission. I believe I've captured one here but defer to Dr. Jafari for confirmation. Many thanks again to Dr. Jafari for sharing this interesting case with us.

 

Case of the Week 772

This week's case is generously donated by Dr. Evis Nushi who identified the following structure in direct microscopy of skin scrapings. What is seen here? 

Answer to Case 772

 Answer to the Parasite Case of the Week 772: Demodex folliculorum

This little mite, also known as the follicle mite, is a common skin commensal and incidental finding in this case. I initially thought it was a larva emerging from an egg, but on closer examination realized that it is a more mature form (with 8 legs rather than the 6 found in the larval stage) and that it's posterior end is twisted around. I've done my best to demonstrate this here:

Thanks again to Dr. Evis Nushi who donated this fun case!

Case of the Week 771

This week's case was generously donated by Dr. Emily Snaverly. The following images show an incidental finding from screening colonoscopy, measuring approximately 1cm long. The patient is an asymptomatic, middle-aged male with no known travel history whose previous colonoscopy did not show any parasites. What is your identification?

Answer to Case 771

Answer to the Parasite Case of the Week 771: Rodentolepis (Hymenolepis) nana, the dwarf tapeworm

As nicely described by Florida Fan, Idzi Potters, and Menzler, the craspedote positioning of the proglottids, armed rostellum, and characteristic (although immature) eggs with prominently splayed, large hooklets all point to R. nana. If you look very closely, you can make out the polar filaments:

Thanks again to Dr. Snaverly for donating these beautiful photos!

Case of the Week 770

This week's case is from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following structures were seen in a stool specimen from a child living in a rural area of Laos. They measure approximately 60 micrometers in greatest dimension. What is your identification?

Answer to Case 770

 Answer to the Parasite Case of the Week 770:  Schistosoma mekongi

The following excellent discussion is by our guest author, Dr. Asra Hasan:

This week’s answer is Schistosoma mekongi! With that, we’ve shown a Schistosoma trio already for the new year—S. haematobium, S. mansoni, and now S. mekongi. Great job, Florida fan! You correctly spotted the inconspicuous lateral spine and the internal miracidium of S. mekongi. And a shoutout to our anonymous writer—your answer was pretty close, as S. mekongi looks a lot like S. japonicum, just smaller, and with a slightly different geographic range. 

The endemic area for S. mekongi is along the lower Mekong River—Laos, Thailand, and Cambodia—hence, the population at risk is comparatively smaller than for other Schistosoma species.

Have a read of the clinical vignette below:

“A 42-year-old male rice farmer from a rural village in Cambodia presents to a local clinic with complaints of chronic diarrhea, abdominal pain, and progressive weight loss over the past six months. He also reports intermittent fever and generalized weakness. On examination, he has hepatosplenomegaly and mild ascites. Laboratory results reveal eosinophilia, and stool microscopy shows small, subspherical eggs with a minute lateral spine at one end. The patient has frequent exposure to river water while working in the fields.” And that would qualify as a typical case for this week—S. mekongi!

The life cycle is similar to other Schistosoma species discussed on this blog (for example, Case 766), except that the definitive hosts are both humans and dogs, and the intermediate host is the snail Neotricula aperta. S. mekongi primarily affects the intestines, liver, and spleen, and rarely, disseminated sites such as the brain.

Diagnosis

Microscopic examination of stool after sedimentation concentration is used to detect eggs.

Antigen tests: Point-of-care lateral flow assays detecting CCA are used for field screening. In the lab, ELISA has been used to detect circulating schistosome antigens in serum and urine and may be the preferred method for confirming diagnosis. Since stool examination can detect schistosome eggs weeks after cure, detection of circulating antigens (CAA & CCA) in blood or urine provides evidence of an ongoing active infection, as both antigens are rapidly cleared from circulation.

Antibody tests can detect evidence of infection, but cannot distinguish current from past infection, and are not particularly useful due to cross-reactions with other helminth infections.

Treatment

Praziquantel is the drug of choice.

Prevention of schistosomiasis involves universal treatment campaigns and that has shown dramatic decrease in disease burden although it has not been helpful in eliminating the disease completely requiring repeated campaigns. Travelers can prevent schistosomiasis by avoiding bathing, swimming, wading, or other contact with freshwater in disease-endemic countries.

And finally, a mention about the World Health Organization. The World Health Organization's roadmap for eliminating neglected tropical diseases recommends targeting Schistosoma mekongi for elimination. Current strategies in affected communities include: Preventive chemotherapy targeting at-risk populations (e.g., entire villages along the Mekong) and distribution of information and education, improvements in water, sanitation, and hygiene.

Some more reading:

CDC resources: https://www.cdc.gov/schistosomiasis/resources/