Monday, July 6, 2020

Case of the Week 598

Welcome to the first case of the month provided by Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following object was obtained during colonoscopy from a 35-year-old woman. It measures approximately 4 cm in length. Travel history is unknown. Identification?

Monday, June 29, 2020

Case of the Week 597

This week's case is very timely, as we are seeing a lot of these objects in some of our stool specimens submitted for routine ova and parasite exam. They measure approximately 8-10 micrometers in dimension (shown at 500x and 1000x). Identification? What additional stain or study would you like to do?

Sunday, June 28, 2020

Answer to Case 597

Answer: Cyclospora cayetanensis oocysts, unsporulated

I figured this was a very timely posting, as we are currently experiencing an outbreak of cyclosporiasis in the Midwestern United States. It's a good reminder to keep an eye out for these round refractile structures in routine stool preparations and follow-up with confirmatory testing (e.g., modified acid fast, modified safranin, examination for autofluorescence, molecular amplification).

I also figured this was a timely case for my United States readers as the confirmatory modified acid fast and safranin stains provide beautiful red, white and blue images for the 4th of July celebrations (American Independence day; my apologies to my British friends)

Here is a gorgeous image from a modified safranin stain of C. cayetanensis oocysts from Florida Fan:
(from Case of the Week 447):

Monday, June 22, 2020

Case of the Week 596

This week's case was donated by Dr. Bobby Boyanton. The images show cross-sections of an appendix from a young girl with chronic abdominal pain. The pathologist became concerned when they saw the following objects within the lumen of the appendix (taken using 4x, 10x, 20x, 20x and 40x objectives, respectively). Identification?

Sunday, June 21, 2020

Answer to Case 596

Answer to Parasite Case of the Week 596: Plant material; likely plant epidermis from leafy material. There appears to be a cuticle present, and part of an epidemal cell layer attached.
There are several nice images of dichotomous leaf epidemal structure HERE. Mary Parker, a botanist, noted that "in aqueous conditions, I  would expect an epidermal layer to curl with the cuticle inwards (which is the case in the images) as the cuticle is waterproof and doesn't swell, whereas the epidermal cells would be hydrated and expand forcing the layer into a spiral." Thank you Mary for your valuable input! Mary has also provided assistance with Case 534 in which we showed plant stomata, and Case 468 that showed banana material. Parasitologists and pathologists commonly see food material in fecal and intestinal specimens, as well as in cases of bowel rupture/fistula and food aspiration (i.e., in respiratory specimens). Therefore, it's helpful to have some basic familiarity with how plant material appears in routine preparations. 

Several writers asked if this could be Enterobius vermicularis or Trichuris trichiura. While the size and location may fit with either of these roundworms, the cuticle and attached cellular structure shows some subtle differences that are useful for excluding them. Specifically, the thick acellular roundworm cuticle is adjacent to a muscular layer, as shown in the images below. In comparison, the plant cuticle is adjacent to the boxy cells of the epidemis. I also highlighted some features that are useful for specifically identifying E. vermicularis and T. trichiura (i.e., lateral ala and bacillary band). 
One additional study that would have been helpful in this case would be to use a polarizer to see if the cuticle and cells are birefringent. Plant cell walls often are, whereas nematode cuticles are not.
Thanks again to Bobby Boyanton for donating this interesting case!

Monday, June 15, 2020

Case of the Week 595

This week's case was generously donated by Dr. Marc Couturier and Blaine Mathison. The patient is a young adult male from the South Central United States. No travel history is available. Review of his peripheral blood film reviewed the following:

Identification? What are the structures seen in the last 2 images?

Sunday, June 14, 2020

Answer to Case 595

Answer to Parasite Case of the Week 595: Plasmodium vivax with exflagellated microgametocytes. Free microgametes are seen.

The following excellent description was written by Marc Couturier and Blaine Mathison, the contributors of this case.

There are several features of this slide that are supportive for P. vivax.

First, many of the infected cells are reticulocytes (which are larger than mature RBCs), which P. vivax and P. ovale have predilection to infect. Second, the gametocytes are enlarged and fill almost the entire space within the parasitized RBC. Some of the infected RBCs also take the shape of neighbouring RBCs (distorted, pleomorphic); particularly in the areas where cells are dense. Third, the mature schizonts contained upwards of 18-20 merozoites with yellowish brown pigment present, which strongly points toward P. vivax, since the range of P. ovale tends to reach 14 merozoites at maximum. Fourth, some developing trophozoites were grossly amoeboid. Plasmodium ovale usually demonstrates some amoeboid characteristics, but it is usually more exaggerated with P. vivax. Notice also none of the infected RBCs were fimbriated (which, when present supports P. ovale but the absence of which does not rule-out P. ovale).

In the images provided, there was an absence of Schüffner’s stippling. There were some parasitized cells that did display stippling (not shown), but the majority did not. It is important to remember that stippling can be helpful to support an identification, but the absence of stippling does not rule-out the species that usually present with stippling (P. vivax and P. ovale).  Stippling is a pH dependent feature and Giemsa stained slides are the best to display this due to the optimized pH (Wright and Wright-Giemsa are suboptimal for this). 

Overall the RBC morphology was quite good, suggesting that the blood was processed soon after collection. However, we suspected that there was a delay in slide processing which likely led to exflagellation of microgametocytes, with free microgametes seen among the RBCs: 
Exflagellation of microgametocytes in blood specimens post-collection can occur due to multiple factors including decreased temperature, decreased CO2, increased O2 and subsequent increased pH. Free microgametes can be confused with other blood parasites such as Trypanosoma or relapsing fever Borrelia spp. (RFB). The key differences between these organisms are as follows: RFB are thin, faint staining, and in thin films will typically maintain a sinusoidal amplitude. The staining is uniform throughout the length of the bacteria and the width of the spirochetes is also consistent along the length of the organism. As can be seen with the free microgametes, there is irregular amplitude, and chromatin visible within the structure (causing heterogenous thickness).  Trypanosoma spp. on the other hand are irregularly shaped compared to RFB; however, they should be identified based on the presence of a characteristic large nucleus in the central part of the organism, a posteriorly located kinetoplast, a flagellum, and an undulating membrane (not always visible).  The long, slender nature of the microgametes might also be suggestive of microfilariae; however, microfilariae would never be this small. Here is an image of these structures shown side-by-side for comparison:

Tuesday, June 9, 2020

Case of the Week 594

This week's case was donated by Florida Fan - a lovely classic protozoan parasite seen in a concentrated wet prep of stool, and trichrome-stained specimen. Each line on the scale bar in the first 2 images represents 2.5 micrometers. Identification?

Sunday, June 7, 2020

Answer to Case 594

Answer to Parasite Case of the Week 594: Entamoeba coli cysts and trophozoite.

This case shows all of the classic features of Entamoeba coli, with large organisms and, most importantly, cysts that contain more than 4 nuclei. According to the CDC DPDx, "karyosomes may be compact or diffuse and are usually eccentrically located. Peripheral chromatin is present and is often coarse, granular, and irregularly arranged along the nuclear membrane but may be more uniform. The cytoplasm of mature cysts may contain diffuse glycogen. Chromatoid bodies are seen less frequently than in E. histolytica. When present, they are usually splinter like with pointed ends, whereas the chromatoid bodies of E. histolytica have rounded ends. The cytoplasm [of trophozoites] is usually coarsely granular and vacuolated (often described as “dirty” cytoplasm). Pseudopodia may be seen and are often short and blunt."
While I would hesitate to make the diagnosis on any one of these features alone, together they strongly support the diagnosis of E. coli. Again, the presence of >4 nuclei in the cyst is the strongest diagnostic feature.

Thanks again to Florida Fan for donating this classic case!

Monday, June 1, 2020

Case of the Week 593

This week's case is from Idzi Potters and the Institute of Tropical Medicine Antwerp. Warning - it's a tough one! The patient is a young woman with recent travel to the Democratic Republic of the Congo. While there, she worked with primates, and developed a short episode of fever, rash and diarrhea. Upon return to Belgium, a check-up was done, including a stool parasite exam. Apart from Giardia duodenalis and Trichuris trichiura, the following structures were found (measuring about 50 to 55 µm in length). What is your differential diagnosis?

Sunday, May 31, 2020

Answer to Case 593

Answer to Parasite Case of the Week 593: Strongyloides fuelleborni

This fascinating zoonotic parasite is endemic to parts of sub-Saharan Africa and infects both human and non-human primates. It is likely under-reported, which may be due to the resemblance of its eggs to those of the hookworms. Unlike hookworm eggs which are shed in an unembryonated state, the eggs of S. fuelleborni typically contain fully-developed larvae.

Similar appearing eggs with larvae may also be seen with heavy infections with Strongyloides stercoralis; however, the eggs are seen in conjunction with larvae, and occasionally adult worms, which are not seen with S. fuelleborni cases. Here are a couple of past examples of S. stercoralis from my blog with adults, larvae and eggs:
Case 469 Question and Answer
Case 499

Idzi Potters and his colleagues suspected S. fuelleborni in this case based on the appearance of the eggs, and were later able to confirm the identity through sequencing of the 18S rRNA gene.

After leaving the specimen in the refrigerator for 5 days, Idzi was also able to observe larvae from the parasite including the following example:
You can read the whole report in his recent publication:

Thanks again to Idzi and the Institute of Tropical Medicine Antwerp for donating this case!

Monday, May 25, 2020

Case of the Week 592

This week's interesting case was donated by Drs. Lee Decollings and Dejan Nikolic. The patient is a middle-aged male with travel approximately 2 months ago to Ethiopia, Nigeria and Cameroon. In the past few years, he has also traveled broadly in sub-Saharan Africa, Asia and South America. He presented with fever and myalgias following a recent medical procedure.

Diagnosis? Where did he likely acquire this infection?

Sunday, May 24, 2020

Answer to Case 592

Answer to Parasite Case of the Week 592: Plasmodium malariae; likely recrudescent infection, given that he has been without symptoms for > 2 months since his last travel to sub-Saharan Africa. While P. knowlesi is also in the differential based on the morphologic overlap between P. knowlesi and P. vivax, the long period of time since his travel to SE Asia would be atypical for P. knowlesi infection.

Some of the classic P. malariae features seen in this case are the small size of the infected red blood cells, schizonts with only 6-12 merozoites, band forms, and a basket form:
A tip for those studying for boards - be sure you know the difference between recrudescence and relapse.

Recrudescence - seen primarily with P. malariae infection, but can also be seen with other Plasmodium species that lack hypnozoites.
Recrudescence refers to recurrence of infection. With P. malariae, recrudescence is thought to be due to the indolent growth of this parasite, enabling survival for many years, even with chloroquine treatment. Chloroquine is the drug of choice for P. malariae infections, and it is preferentially concentrated in the food vacuoles of metabolically active trophozoites. Here it binds to hematin and prevents its polymerization, resulting in oxidative stress to the parasite and eventual lysis. Given the low growth and metabolism of P. malariae asexual stages, some trophozoites can escape the action of chloroquine and later cause disease recrudescence. Recrudescence is different than relapse (see below) in that it doesn't result from activation of hypnozoites.

Relapse - seen with P. ovale and P. vivax infection.
Relapse is due to activation of dormant hypnozoites in the liver.

The final mystery in this case is the location in which the patient acquired infection. He had traveled to Ethiopia, Nigeria and Cameroon approximately 2 months prior to symptom onset, but according to the United States CDC, P. malariae is not found in appreciable amounts in these countries. What the CDC doesn't note in these lists, however, is that P. malariae is found throughout sub-Saharan Africa, and is present in all of the areas where P. falciparum is found. P. malariae is also found in parts of Asia and South America, so he could have acquired infection from many of his previous travels.

Thanks again to Drs. Decollings and Nikolic for donating this interesting case!

Monday, May 18, 2020

Case of the Week 591

This weeks case was generously donated by Dr. Michele Bloomer. The following object was removed from the eye socket of an adult patient. According to the surgeon, there were numerous similar-appearing objects present, but only 1 was submitted to the laboratory. About 1 month prior, the patient had undergone surgery to remove his eye as it was involved by a large cancerous growth that had extended from his eyelid.


Sunday, May 17, 2020

Answer to Case 591

Answer to Parasite Case of the Week 591: L3 larva of Phormia species

As Blaine mentioned, this is a case of facultative myiasis involving an existing wound. The wound was caused by removal of the eye due to a large cancerous growth. What I didn't share is that the growth had been neglected, and the wound may have been as well. Several of you mentioned that this is a third stage (L3) larva, which indicates that the larva was allowed to mature for sometime within the wound.

Although we can't see the tracheal trunks to say if they are pigmented or not, the posterior spiracular plate is clearly visualized and shows an incomplete peritreme, relatively-straight slits without lateral swellings, and slits are directed towards the region where the peritreme is incomplete, consistent with Phormia sp.

Some of you mentioned Lucilia sp. in the differential, although in my interpretation, Lucilia has a complete peritreme with distinct button, unlike what we are seeing here.

The CDC has freely-available pictorial keys online which are a useful starting place when examining fly larvae. Blaine and I also published a guide for Laboratory Identification of Arthropod Ectoparasites. If you don't have access to manuscript, send me an email and I can send you a copy for your own personal use.

Monday, May 11, 2020

Case of the Week 590

This week's fascinating case was donated by Dr. Graham Hickling. He captured the following scene that he entitled "Hatching". What are these newborns?
See them here LIVE (fast motion):

Sunday, May 10, 2020

Answer to Case 590

Answer to Parasite Case of the Week 590: Ixodes scapularis larvae, freshly hatched from an egg mass laid by a captive female. This fascinating video was generously donated by Dr. Graham Hickling who does research on hard tick biology.

While there isn't enough information present to specifically identify these ticks, you can say a few things about them from the video:
  1. The have only 6 legs, and are therefore larvae.
  2. In North America, the long mouth parts and ovoid body would be most consistent with Ixodes species. 
As astutely noted by Old One, "Six legs, newly hatched, long club shaped palps, apparently no visible festoons and no visible inverted U anal plate. Definitely newly hatched seed ticks (I would like to suggest a name change to TICK-ETTE) as in pick up your tickettes here. You might need to FLAG them down."

We've actually seen these little wonders before in a different blog post:
HERE is momma tick laying her eggs, with a video showing the action HERE. I HIGHLY recommend this video - it is fascinating! You may want to check out the other great videos on this site: Thanks again to Graham for sharing his 'babies' and passion for acarology with the rest of the world.

While I. scapularis tick larvae won't usually hatch until this summer, the nymphs that have over-wintered from last year are now out, so be sure to take precautions against tick bites when outdoors!

Monday, May 4, 2020

Case of the Week 589

Happy Monday everyone! It's our first Monday of the Month, and time for our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp.

The following objects were seen in an iron hematoxylin-stained stool preparation from an asymptomatic patient with frequent travels to Asia. The objects measure 10-20 micrometers in greatest dimension.