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?

Answer to Case 786

 Answer to the Parasite Case of the Week 786: Cystoisospora belli

Idzi nicely described this finding as an "Immature oocyst of Cystoisospora belli (formerly known as Isospora belli) containing only one sporoblast, which will evolve to two sporoblasts and later on will sporulate to become infective." 

While we don't know the definitive details of the images that Dr. Bradbury provided, Idzi suggested that "the last one could be autofluorescence at 450-490 nm." and noted that "All coccidia (including Cystoisospora belli) will demonstrate fluorescence (without prior staining) when placed under UV-light. They will show up as bright blue structures when using an excitation filter of 330-365 nm, or green at 450-490 nm. Of note: Cryptosporidium is not placed among the coccidians anymore (moved to the Gregarines), and does not demonstrate autofluorescence either!"

If you are interested about how autofluorescence can be used for diagnosis, you should check out Blaine's and Dr. Marc Couturier's recent paper "Shedding new light on Cyclospora: how the use of ultraviolet fluorescence microscopy can improve diagnosis of cyclosporiasis".

Case of the Week 785

It's the first of the month and time for a case from Idzi Potters and the Institute of Tropical Medicine, Antwerp! 

The following images show an object that dropped out of a patient's nose 😮. What is your identification?

Wishing all of my American readers a very happy and restful Labor Day.

Answer to Case 785

Answer to the Parasite Case of the Week 785: Oestrus ovis larva.

This is a fascinating case of a probable 2nd instar stage of Oestrus ovis, commonly known as the sheep nasal botfly. O. ovis, can occasionally cause infection of the eye (ophthalmomyiasis) or, less commonly, the nose and sinuses (rhinomyiasis) in humans. Human infection is an accidental zoonosis and results from deposition of first-instar larvae by adult flies, typically in the ocular or nasal mucosa. Human cases are most prevalent in Mediterranean and other subtropical regions, with seasonal peaks in summer and spring. 

Most infestations are self-limited as larvae rarely progress beyond the first instar in humans. Therefore, this is a very interesting presentation of what appears to be a 2nd instar larva involving the nose and/or sinuses. 

Diagnosis is based on clinical suspicion and examination of the larvae. First-stage larvae are small (approximately 1–2 mm) and mostly translucent As noted above, this is the most common form seen in humans. 

Second-stage larvae are larger (up to 7 mm), more robust, and display increased segmentation, with the body becoming more opaque and the cuticle developing small spines. The oral hooks are more prominent, and the posterior spiracles begin to show more complex structure. This is what I believe this specimen to be.

Third-stage larvae are the largest (up to 21 mm), cylindrical, and have a thick, heavily pigmented cuticle with pronounced transverse bands of spines and well-developed oral hooks in their mature form; the posterior spiracles are fully formed and more sunken into the body. Also, the body is distinctly segmented, and takes on a brown color in the mature form.

Check out these two publications for some great photos of the different stages:

b105_pp382-387.pdf

Prevalence Rate and Molecular Characteristics of Oestrus ovis L. (Diptera, Oestridae) in Sheep and Goats from Riyadh, Saudi Arabia

Thanks to all who wrote in on this interesting case, and to Idzi for donating it! Special thanks to Blaine Mathison for his input on larval stage.

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. 

Case of the Week 779

This week's case was generously donated by Dr. Richard Bradbury. A patient living in The Gambia presented with high fever, body aches, and altered consciousness. Images from the Giemsa-stained thick and thin blood films are shown below. 

Due to a shortage of coartem, quinine was administered. Shortly afterwards, the patient's urine turned dark brown:

What is this condition, and what is it caused by?

Answer to Case 779

Answer to the Parasite Case of the Week 779: "Black Water fever" - a massive hemolytic event associated with P. falciparum infection and quinine administration. 

Black water fever was previously an important cause of death and was prominently reported in British soldiers in the early 20th century. Thankfully, it is rarely seen today with the advent of synthetic antimalarials (e.g., chloroquine) and artemisinin combination therapies. The exact etiology is poorly understood, and seems to be attributed to a complex interaction between the host RBC, the parasite, and antimalarial drugs. It may also occur more often in people with G6PD deficiency.

Case of the Week 778

This week's case features the intestinal biopsy of a middle aged man with abdominal pain and diarrhea. The astute pathologist noted these small objects (~20 microns in greatest dimension) associated with ulcerated colonic mucosa. Stain is hematoxylin and eosin (10x, 40x, and 100x objectives). What is your diagnosis? 

Answer to Case 778

Answer to the Parasite Case of the Week 778: Amebiasis due to Entamoeba histolytica. 

As noted by Dr. Jacob Rattin, "It looks like there is ulceration in the adjacent mucosa and Entamoeba histolytica trophozoites with visibly ingested red blood cells." Several others also noted the ingested RBCs within the trophozoite cytoplasm. 

When seen in stool specimens, the presence of RBCs within Entamoeba trophozoites allows us to presumptively call this E. histolytica rather than one of the identical-appearing amebae such as E. dispar. However, in this case, we have another important clue that allows us to presumptively identify the ameba, even if we don't see ingested RBCs: the presence of trophozoites associated with or invading into the ulcerated mucosa. E. dispar is not considered a pathogen, and other doppelgangers (e.g., E. moshkovskii, E. bangladeshi) have not been definitively shown to be pathogenic. Thus, the presence of invasive Entamoeba trophozoites points us towards E. histolytica. Note that the trophozoites look somewhat different in tissue than they do in stool as the central chromatin dot is often not present. However, the outer rim of chromatin is easily visible. 

Case of the Week 777

 Dear Readers,

I am excited to announce that we are celebrating our 777th case! 

In honor of this milestone, we have a selection of 3 helminth eggs for you to identify. You win the parasite jackpot if you can get all three. There is an 'easy' and 'hard' version, so you get to take your pick.

EASY VERSION

Egg 1 (50 micrometers long)

Egg 2 (55 micrometers long)

Egg 3 (35 micrometers long)

HARD VERSION

Egg 1 (45 micrometers in diameter)

Egg 2 (95 micrometers long)

Egg 3 (One of 15 objects freed from a 4mm structure)

Answer to Case 777

 The Answer to the Parasite Case of the Week 777 is up - and it's a jackpot of parasite eggs! 

Easy version:

• Trichuris trichura
• Ascaris lumbridoides
• Taenia sp.

Hard version:

• Bertiella sp.
• Acanthocephalan egg (M. moniliformis - expressed from the worm so slightly immature, which is why it's not as clear as you would expect)
• Inermicapsifer or Raillietina (Actually Inermicapsifer, but as Idzi mentioned, you cannot tell the egg capsules apart from these two). 

How many of you got the jackpot?!?

Thank you for playing for more than 18 years and 777 cases 😉

Answer to Case 776

 Answer to the Parasite Case of the Week 776: Toxoplasma gondii tachyzoites. As the name implies, the tachyzoite is the rapidly dividing stage of the parasite (tachy is from the Greek takhus meaning rapid, swift). Tachyzoites invade cells and divide rapidly within parasitophorous vacuoles, ultimately rupturing infected cells. Tachyzoites divide by endodyogeny, an interesting form of replication seen with some coccidia in which two daughter cells develop internally within the parent cell without nuclear conjugation. The parent cell is consumed in the process - yikes!

Shown here is the classic arc-shaped tachyzoite and 2 daughter cells resulting from the process of endodyogeny:

Case of the Week 776

This week's case is a brain biopsy from a middle-aged man with untreated HIV. The specimen appeared necrotic and bloody. Touch preps were made from the material and stained with Giemsa. From the images below taken with the 100x oil objective, what is your diagnosis?