Case of the Week 784

This week's case was generously donated by Rebecca Black, a Veterinary Medicine student training in Minnesota, USA. She was able to help this poor little kitty get the care it needed. What is your diagnosis? Does this organism pose a risk to humans?

Answer to Case of the Week 784

Answer to the Parasite Case of the Week 784: Myiasis causing fly larva, most likely Cuterebra species. 

Thankfully, Rebecca Black and her colleagues were able to remove the larva from this poor kitty! 

As noted by Florida Fan and others, we don't have the posterior spiracles to make a definitive identification. However, based on the presentation, geographic location, dark color, and overall appearance, we can still make an identification of Cuterebra sp. third instar stage larva.

Note the dark color and small spines covering most of the body. 

If you are interested, you can read more about this infection in animals at the following excellent sites:

Cuterebra Infestation in Small Animals - Integumentary System - Merck Veterinary Manual

Companion Animal Parasite Council | Cuterebriasis

Genus Cuterebra - Rodent and Lagomorph Bot Flies - BugGuide.Net

The usual hosts of Cuterebra are rodents and lagamorphs. Flies lay eggs on vegetation or woody ground debris, often near the opening of rodent burrows. The eggs hatch to release a first instar stage larva when there is exposure to increased temperature, indicating the presence of a nearby host. The larva then enters host through any natural body opening such as the mouth or existing wounds. It will then migrate to the subcutaneous tissues and enlarges rapidly. It creates a pore from which it can breathe and eventually exit the host, usually in 3-6 weeks. 

As you all know, my interest is in human infections, and therefore I posted this case as both a pet lover and a human medical parasitologist. Cuterebra infections (cuterebriasis) can rarely occur in humans, and as with other forms of myiasis, removal of the larva is curative.

Thanks again to student veterinarian, Rebecca Black, for donating this case! 

Case of the Week 783

This week's case was generously donated by Dr. Richard Bradbury. The following were seen in a stool specimen from a middle-aged man with diarrhea. Preparations are a concentrated wet prep and trichrome stained permanent mount. Object measure 10-15 micrometers long. What is your identification?

Answer to Case 783

Answer to the Parasite Case of the Week 783: Chilomastix mesnili cysts and trophozoites. Note the classic morphology:

C. mesnili is a non-pathogenic flagellate and therefore not the cause of this patient's diarrhea.

Thanks again to Dr. Bradbury for donating this great case!

Case of the Week 782

This week's case was generously donated by Dr. Adrienne Showler. The following image is from a video capsule endoscopy performed on an immunocompromised patient with diarrhea. The patient has not travelled outside of the US and has no other risk factors for parasitic infection. Numerous of these objects were seen - none were moving. Identification?

Answer to Case 782

 Answer to the Parasite Case of the Week 782: Not a parasite. 

Most closely resembles banana "seeds" (tannin bodies). 

While we will never know for sure, the beaded/fragmented appearance and dark color of these objects allow us to identify this as a non-parasitic object that closely resembles banana tannin bodies. You can read more about banana tannin bodies in my previous cases 139 and 468. In particular, I recommend checking out Case 468 which shows my experiment to recreate a partially-digested banana.

Thanks again to Dr. Adrienne Showler for donating this interesting case!

Case of the Week 781

This week's case features a beautiful video from Dr. Rasool Jafari. The specimen is skin scrapings. What is your identification?

Answer to Case 781

 Answer to Parasite Case of the Week 781: Demodex sp.  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 780

This week's case was generously donated by Dr. Manohar Mutnal. The following were seen in a peripheral blood smear from a patient with an unknown travel history. What is your differential diagnosis? What additional information would you like?

Answer to Case 780

Answer to Parasite Case of the Week 780: Trypanosoma brucei trypomastigotes. 

As noted by Florida Fan, "This is definitely a case of trypanosomiasis. The flagellate doesn’t show a prominent kinetoplast nor assume a C shape in general. This rules out Chagas disease caused by T. cruzi. We have Trypanosoma brucei, yet morphology alone doesn’t warrant a differential diagnosis of subspecies gambiense nor rhodesiense." 

Idzi also noted that "In the first picture we can clearly see the difference between the two morphologies of T. brucei: the "short stumpy" form (adapted for survival in the tsetse fly vector --> transmission) versus the "long slender" form (which multiplies in the host)!" Here is an annotated version of this image showing these two morphologies:

I had also asked what additional information is needed in this case - and you all responded with excellent suggestions. In summary,  

• We first, we need to know the travel history to determine the likely subspecies. PCR could also be performed. This is important for treatment and prognostic implications. 
• Second, we need to know the stage of disease, as this will also drive treatment decisions. As noted by Idzi, "A lumbar puncture will be able to tell us if the patient has evolved to stage II of the disease, where the parasite has invaded the central nervous system. Even if no tryps are found in the CSF, a raised number of WBCs in the CSF will still be indicative of stage II disease (when tryps are found in the blood).

The WHO released updated treatment guidelines for Human African Trypanosomiasis (HAT). Treatment is complex and can have significant side effects. This is especially true for rhodesiense-HAT, in which intravenous suramin is used for first stage disease and melarsoprol, an arsenic derivate, is used for second stages disease. It's shocking that we are still using arsenic to treat infectious diseases. Melarsoprol has many adverse effects, including reactive encephalopathy which has a 3–10% fatality rate!

Getting back to this case: additional history revealed that the patient had been on a hunting trip to Zambia, and therefore we can infer that the patient has East African HAT caused by T. b. rhodesiense. Idzi predicted this, stating that "chances are very very big that this is T. b. rhodesiense because this is the subspecies that will get quickly to a parasitemia high enough to be able to detect the trypanosomes in a thin blood film." 

Many thanks again to Dr. Mutnal for donating this interesting case.