Sunday, May 19, 2019

Case of the Week 545

This week's case was donated by Dr. David Pritchard. The following worm was noted in the toilet of a patient with an extensive international travel history. Likely identification?

Monday, May 13, 2019

Case of the Week 544

This week's case features an interesting finding in a concentrated stool specimen. The photos are from my awesome technical specialist, Heather Arguello. The individual structures are approximately 25  micrometers in length, while the longer tubular structure is 330 micrometers long.


Sunday, May 12, 2019

Answer to Case 544

Answer to Parasite Case of the Week 544: Ascus with ascospores (presumed mushroom) spores. Interestingly, it is morel season in many parts of the United States, and these appear to be a perfect match to morel ascospores!
While we commonly see mushroom spores in stool specimens (and have to differentiate them from  helminth eggs), and intact ascus (a sac in which the spores of ascomycete fungi develop) is rarely seen. Thanks again to my lead tech Heather who took the time to snap a photo of this cool finding!

Monday, May 6, 2019

Case of the Week 543

This week we are featuring our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp.

The patient is a 15 year old boy returning from swimming camp, who presents with several-day history of profuse watery diarrhea. A stool specimen was submitted for parasite examination, and multiple small (3-6 µm), round structures were identified. The following photos are taken after:

1. Negative fuchsine staining according to Heine (brightfield microscopy)
2. Negative fuchsine staining according to Heine (phase-contrast microscopy)

3. Ziehl-Neelsen staining (“cold” modified technique)

Sunday, May 5, 2019

Answer to Case 543

Answer to Parasite Case of the Week 543: Cryptosporidium sp. oocysts

The case shows how Cryptosporidium oocysts look in a variety of different preparations including phase contrast (very cool). As we are all taught during training, Cryptosporidium spp. oocysts are red-pink using a modified acid fast stain (as shown in image 3 of this case) and measure 4-6 micrometers in diameter, thus allowing their differentiation from the similarly-appearing Cyclospora cayetanensis oocysts (which are 8-10 micrometers in diameter). Florida Fan reminded us that not all of the oocysts will reliably stain with the modified acid fast stain, and thus some may appear as 'ghost' cells or negative outlines. A modified safranin stain can also be used and has been reported to more reliably stain the oocysts.

Florida Fan mentioned that the direct fluorescent antibody (DFA) for Cryptosporidium spp. oocysts - widely regarded as the most specific microscopic method - doesn't necessarily detect all Cryptosporidium species, and thus there is the potential false negative results. In certain cases, confirmation with another method may be helpful.

Finally, Old One tells a tale of prior infection in our case comments that he thankfully survived! It is indeed possible that his prior infection stimulated development of a protective immune response - likely an interferon-gamma mediated memory T cell response. However, it is not clear if this immune response would prevent future infections with all different species of Cryptosporidium.

Thanks again to Idzi for sharing this beautiful and classic case!

Monday, April 29, 2019

Parasite Case of the Week 542

This week's case is a lovely gif image compiled by our excellent parasitology technical specialist, Heather Arguello. The following structures were seen on a non-nutrient agar culture that had been inoculated with corneal scrapings. The plate had been overlain with Escherichia coli to provide a food source for parasites that may be present in the specimen. The central structure is ~40 micrometers in maximum dimension, while the rounded structure to the left is ~15 micrometers in diameter. Identification?

Sunday, April 28, 2019

Answer to Case 542

Answer to Parasite Case of the Week 542: Acanthamoeba sp. trophozoite and cysts

The free-living amebae, Acanthamoeba species and Naegleria fowleri (but not Balamuthia mandrillaris) can be grown on non-nutrient agar overlain with bacteria to provide a food source for the organisms. In this case, the presence of a characteristic double-walled cyst and trophozoite, along with the source (corneal scrapings) allow us to identify this ameba as an Acanthamoeba species.
We sadly did away with our free-living amebae culture a while back and replaced it with a multiplex real-time PCR assay. It's faster than culture, while providing equal sensitivity, so it is better for patient care. However, I do miss seeing these cool organisms grow in culture!

Monday, April 22, 2019

Case of the Week 541

This week's case was generously donated by Drs. Mauro Saio and David Hamer. The patient is a middle-aged male who noted the following objects in his stool. Individually, they measured approximately 1 cm in length. Identification?

Sunday, April 21, 2019

Answer to Case 541

Answer to Parasite Case of the Week 541: not a parasite; citrus juice vesicles.

This is a not-uncommon finding in stool that is helpful to recognize, since it is occasionally submitted as a potential parasite. In this case, the patient reported eating clementines regularly. So here is a dissection of a clementine for comparison:

Pretty good, huh? Of course it's not possible to recognize the type of citrus from this case alone, and a report of "not a human parasite" is usually sufficient for patient care.
Wikipedia has a nice article on juice vesicles if you would like more information.

Monday, April 15, 2019

Case of the Week 540

This week's beautiful photographs are from Emily Fernholz at my lab. These objects were seen in a human stool specimen and measure approximately 80 micrometers in length. Identification?

The features are nicely appreciated on this video:

Sunday, April 14, 2019

Answer to Case of the Week 540

Answer to Parasite Case of the Week 540: Macracanthorhynchus species, one of the acanthocephala ("thorny-headed worms"). M. hirudinaceus or M. ingens would be the most likely culprits, although as mentioned by Florida Fan, we would need the head of the worm to morphologically identify this to the species level. The acanthocephala are common parasites of animals, but only rarely infect humans. Infection is acquired through ingestion of an infected arthropod such as a millipede or beetle.

The eggs are very striking. They are ovoid and measure 80-100 micrometers in length. As described by Bernardino Rocha, they are dark brown egg with a thick rugged textured shell. Within the egg is the characteristic larval form (acanthor) with rostellar hooks (which you can sort of make out in this egg).

Interestingly, Macracanthorhynchus eggs are rarely seen in human stool. Blaine Mathison mentioned that this worm can occasionally reach sexual maturity in the human host and can even produce mature eggs; for some reason, however, the eggs are either not readily shed from the female, or are shed in such low numbers that they aren't commonly seen. Blaine also speculated that the eggs could be missed in O&P exams due to lack of technologist familiarity with them. Finally, there is the possibility of spurious passage from ingestion of soil or pig intestines containing the eggs/worms.

Of note, this particular patient had a follow-up specimen several days later which still contained Macracanthorhynchus eggs. Thus, my hypothesis is that this represents true infection rather than spurious passage.

Monday, April 8, 2019

Case of the Week 539

This week's beautiful case was donated by Florida Fan - a finding in a concentrated stool specimen:
The scale bars each represent 2.5 micrometers.

Sunday, April 7, 2019

Answer to Case 539

Answer to Parasite Case of the Week 539: Hymenolepis nana

This beautiful egg donated by Florida Fan nicely demonstrates all of the classic features of H. nana, including the thin inner membrane surrounding the hooked oncosphere [*] from which polar filaments arise. The polar filaments arise from opposite poles of the inner membrane (arrows) and spread out into the space between the inner and outer membranes, thus providing a key differentiating feature from the filamentless-Hymenolepis diminuta.
Blaine wrote a poem for this parasite back when I featured it in 2013. Here it is again for your enjoyment:
There once was a kid from Indiana
Who with his oatmeal did like banana
But with his food he did eat
A most wonderful treat
The cestode known as Hymenolepis nana

If you google "oatmeal" and "bugs," you will find multiple consumer complaints (and some nice YouTube videos) to explain the oatmeal reference!

Monday, April 1, 2019

Case of the Week 538

Here is our fun monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp:
Your boss brings in some wormy things and mentions that “his cat regurgitated these in the morning”.
What is your diagnosis? Risk for humans?

Sunday, March 31, 2019

Answer to Case 538

Answer to Parasite Case of the Week 538: Toxocara species
Another case with lots of great discussion! There was quite a bit of debate on whether or not this was T. cati vs. T. leonina. This differentiation is potentially important since the former is commonly associated with human larva migrans (visceral, ocular and neural), whereas the latter only rarely is. As noted by Old One, a number of morphologic characteristics can be used to differentiate between the two, including the worm size, male spicule morphology, egg morphology and shape of the cervical alae. The cervical alae are short and wide in T. cati, and long and narrow in T. leonina. As the cervical alae in this case also appeared to be long and narrow, several readers were favoring T. leonina. However, the angle of the photographs made it difficult to really characterize the alae. Thus Old one suggested that we look at the eggs. Therefore, here is a new photograph for your consideration:
The scalebar represents 50 µm, putting the egg at ~70 µm long, within the size range of both species. Importantly, it has a pitted shell which is characteristic of T. cati. In comparison, the shell of T. leonina is smooth. Thus we have a nice case here of Toxocara cati! Mystery solved 😊.

This discussion still doesn't address Idzi's follow up question of what potential risk is posed to humans from contact with the infected cat and these worms. The adult worms themselves are not a risk to humans, but mature eggs, if ingested, can hatch to release larvae that cause larva migrans. While we clearly have at least 1 gravid female here, it is important to note that the eggs are shed in an unembryonated state and need to mature in the environment for 4 or more days (longer at lower temperatures) before becoming infectious to humans. Therefore, there is no immediate risk to humans in this case. However, eggs that may have been shed into the environment from the infected cat MAY pose a risk if accidentally ingested. Thus I would recommend carefully cleaning the litter box (wearing gloves, followed by meticulous hand washing) and getting the cat treated asap! As always, hand washing after soil contact (e.g. gardening) is also prudent.

Thank you all for the great comments!

Tuesday, March 26, 2019

Google+ is going away - email me to get new post updates!

To my 594 Google+ followers,
Thank you for following me for all these years! You may have heard that Google+ is going away, and therefore you will no longer be notified when there are new posts on my blog. Therefore, if you still want to receive notifications (I don't want to lose you as a reader!), please email me at and I will add you to my email distribution list. Alternatively, you can follow me on Twitter (@ParasiteGal) or on my FaceBook page, Creepy Dreadful Wonderful Parasites. I also post new cases weekly to LinkedIn.

Sunday, March 24, 2019

Case of the Week 537

This week's case comes from my lab with photos and video taken by Emily Fernholz. The objects shown were seen in a liver cyst aspirate. Identification?

Low power view (4x objective):
40x objective:

Here's a fun 'bird's eye' view (hit the play button twice):

Saturday, March 23, 2019

Answer to Case 537

Answer to Case of the Week 537: Echinococcus species

Shown here are the classic protoscoleces of Echinococcus, each with a rostellum containing a row of hooklets (i.e. an 'armed' rostellum). The rostellum is the anterior protrusion found on some tapeworms.
As Old One mentioned, "There are 4 species of Echinococcus that infect humans: E. granulosus, E. multilocularis, E. vogeli, and E. oligarthus. Without more information such as host location, medical imaging, measurement of rostellar hooklets, one cannot be certain of the species. However one can make an educated guess.

E. multilocularis cysts are [usually] sterile (no protoscoleces) [in humans], E. oligarthus is exceedingly rare in humans, E. vogeli photoscoleces contain very few calcareous corpuscles, leaving E. granulosus as the best guess."  I will also add that infections with E. oligarthus or E. vogeli are extremely uncommon in humans and occur in Central and South America. E. granulosus is, by far, the most common species causing human infection in the United States, and causes a form of disease called cystic echinococcus. Usually a single cyst is produced, within which multiple daughter cysts may develop. In comparison, E. multilocularis causes alveolar echinococcus which infiltrates normal host tissue without remaining confined to a single cyst.

I did not provide enough clinical or epidemiologic information to provide a species level ID. However, in this case, we also believe that E. granulosus was the most likely identification.

Sunday, March 17, 2019

Case of the Week 536

I have a fun case for you this week, donated by Dr. Richard Davis, Blaine A. Mathison, and Dr. Marc R. Couturier from ARUP Laboratories and the University of Utah School of Medicine.

The following objects were found in stool of a toddler living in the Oceania region. There were motile and described as "rice like".
Manipulation of the object and microscopic examination of the expressed material revealed the following structures measuring approximately 200 µm in diameter with a dark center. Within the dark area were numerous smaller objects measuring 25-35 µm in diameter:


Saturday, March 16, 2019

Answer to Case 536

Answer: Raillientina species, a parasite primarily of rodents and poultry. Kudos to Idzi for mentioning this in his differential!

As many noted, this parasite bears a striking resemblance to Dipylidium caninum, with production of small 'rice grain' like proglottids (which may be motile in freshly-passed stool) and collections of eggs - each containing a hooked larva.

This was definitely a challenging case. I didn't provide a high power view of the proglottid. If I had, you would have noted that it only had a single lateral or dorsal uterine pore (depending on the species) rather than the two lateral pores - one on each side - of D. caninum. 

Another feature that allows differentiation of this parasite from D. caninum is the presence of dark-centered eggs capsules rather than egg packets. Egg capsules are a characteristic of cestodes in the genera Inermicapsifer and Raillietina. They measure 100-200 micrometers in diameter and contain 1-12 eggs, each containing a hooked larva.
Differentiation of Inermicapsifer and Raillietina is achieved by examing the scolex; Raillietina has an 'armed' scolex (containing hooklets), while Inermicapsifer has an unarmed scolex. Unfortunately the scolex was not recovered in this case - it is rarely recovered from humans - and so morphology alone could not be used to differentiate the 2 cestodes. However, Richard, Blaine and Mark were able to exclude Inermicapsifer in this case due to the location of the patient and lack of travel history. You can read more about this case HERE.

Monday, March 11, 2019

Case of the Week 535

This week's case is by our awesome dermatopathology fellow and former chief resident, Kabeer Shah. The following was seen in a scraping of a papule from a patient with rosacea. Identification?

Check out the way this little guy moves!

Sunday, March 10, 2019

Answer to Case 535

Answer to Parasite Case of the Week 535: Demodex sp. mite

There are two described Demodex species that are parasites of humans: D. folliculorum and D. brevis. They are characteristically differentiated by their location on the host and the length of their body. Demodex folliculorum lives in hair follicles and has a long opisthosoma (abdomen/posterior end), whereas D. brevis lives in sebaceous glands attached to hair follicles and has a shorter opisthosoma. Molecular analysis (e.g. using 16S rDNA) can also be used to differentiate the two species, and generally correlate with the morphology-based identifications.

Here is a general overview of the Demodex body segments:
Some of you wrote in trying to guess which of the two species is represented in this case. Unfortunately, the features aren't clear cut, and so we will have to call this simply Demodex sp.

Now here's a poem by Blaine:
So many people think they live immaculate lives
but among their hair follicles another creature thrives
you can shower and scrub to your heart's content
but all that effort won't make a dent
because the mite Demodex folliculorum continues to survive

Monday, March 4, 2019

Case of the Week 534

It's time for our fun monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following objects were seen in a stool specimen (direct wet prep) from a child with watery diarrhea. The objects measure approximately 40-45 µm in length. Identification?

Sunday, March 3, 2019

Answer to Case 534

Answer to Parasite Case of the Week 534: Not a parasite; plant material. This is a neat finding since these structures (guard cells with stomatal pores) might be mistaken for parasite eggs such as Hymenolepis nana  due to their large size and morphologic features.

A quick biology review:
Guard cells are really neat. They are specialized cells in the epidermis of leaves and other parts of the plants that control gas exchange with the environment.They are produced in pairs and have a central opening called a stomatal pore. When a pair of guard cells are swollen (turgid) with water, the stomatal pore opens allowing carbon dioxide to flow in and oxygen (produced through photosynthesis) to flow out. While this gas exchange is essential to the plant, water is also lost through the stomatal pore; thus the plant has to balance the amount of CO2 absorbed from the environment with the amount of water lost through the pores.

Mary Parker kindly contributed the following image of stomata from the lower surface of an ash leaf and mentioned that "in a fresh sample as in the image, the plastids would contain greenish chlorophyll, but after gut transit, this would be lost."
Very cool! Thank you Mary!

Monday, February 25, 2019

Case of the Week 533

This week's case is from the very cool Belize Vector & Ecology Center run by Drs. Nicole L. Achee and John P. Grieco in Orange Walk, Belize. These arthropods are being reared to better understand their role as vectors of a human pathogen in this region. What pathogen is this?

See them in action!

Sunday, February 24, 2019

Answer to Case 533

Answer to Case of the Week 533:
The vector: Triatomine bugs (also called reduviid bugs, “kissing” bugs, and cone-nosed bugs).
The pathogen: Trypanosoma cruzi
Resultant disease: Chagas disease, a.k.a. American trypanosomiasis

Thank you all for the great comments! Hopefully we will see more cases from the Achee/Grieco lab in the future.

Monday, February 18, 2019

Case of the Week 532

This week's case was generously donated by Dr. Richard Bradbury and Dr. Sarah Sapp from the Morphology lab at the US Centers for Disease Control and Prevention. The following objects were seen in a wet mount of a concentrated stool specimen. The specimen was obtained from a West African baboon, but this finding may also be seen in human stool specimens. Identification?