Monday, December 3, 2018

Case of the Week 521

This month's case from Idzi Potters and the Institute of Tropical Medicine, Antwerp, features a stool specimen from a traveler returning from Iran. No clinical data is available, nor any additional lab-results. The following photos show structures that were found in the patient’s stools. The average size of these objects is 42 x 25 µm. Click on the images to enlarge.

What is the diagnosis (& possible clinical relevance)?

Sunday, December 2, 2018

Answer to Case 521

Answer: Dicrocoelium dendricitum eggs

This is relatively rare find in human stool specimens. The eggs are small (35-45 µm long by 20-30 µm wide), thick-walled, and often brown due to bile staining. They are shed in a fully embryonated state, with the embryo often easily seen within the egg (these look like a skull to me!)
D. dendricitum is such a fascinating parasite. Its life cycle typically involves as ruminant, a snail and an ant. The whole life cycle is nicely illustrated by the CDC DPDx group HERE. Here is the accompanying text: 
Ruminants are the usual definitive hosts for Dicrocoelium dendricitum, although other herbivorous animals, carnivores, and humans can serve as definitive hosts. Embryonated eggs are shed in feces. The eggs are ingested by a snail. Many species of snail may serve as the first intermediate host, including Zebrina spp. and Cionella spp. When the miracidia hatch, they migrate through the gut wall and settle into the adjacent vascular connective tissue, where they become mother sporocysts. The sporocysts migrate to the digestive gland where they give rise to several daughter sporocysts. Inside each daughter sporocyst, cercariae are produced. The cercariae migrate to the respiration chamber where they are shed in slime ball from the snail. After a slime ball is ingested by an ant, the cercariae become free in the intestine and migrate to the hemocoel where they become metacercariae. Many ants may serve as the second intermediate host, especially members of the genus, Formica. After an ant is eaten by the definitive host, the metacercariae excyst in the small intestine. The worms migrate to the bile duct where they mature into adults. Humans can serve as definitive hosts after accidentally ingesting infected ants.

What this nice narrative does not mention are the following fun facts:
1. While in the ant intermediate host, the parasite takes control of the ant's nervous system and controls its actions. It directs the ant to climb to the top of a blade of grass every night and clamp down tightly to the blade with its mandibles. At dawn, the ant goes back to its normal activity in its colony. The recurs night after night, with the poor parasitized ant residing on the blade of grass until it is eaten by the grazing definitive host! What a clever way for a parasite to ensure the continuation of its own life cycle. This story reminds me of the effect that Toxoplasma gondii has on its rodent host (a story for another day).
2. As Old One reminded us, "D.d is beautiful critter. So flat you can clearly see all it's major organ systems without the benefit of stains. So thin it is commonly called the Lancet fluke. These dimensions allow D.d to dwell within the biliary ducts where they can allow normal bile flow in small numbers or block the flow with greater numbers."  For this reason, the fluke is less likely to cause symptoms in its host.
3. When humans serve as the definitive host for D. dendricitum, eggs of the parasite may be seen in the stool. However, eggs may also be seen in the stool when humans inadvertently eat the infected liver of another definitive host such as a cow; in this scenario, the presence of eggs would be considered spurious passage or 'pseudo-parasitism'.

This brings us to the question that Idzi posed to us: What is the possible clinical relevance of finding these eggs in a human stool specimen? Luis and Nema both pointed out that it is necessary to rule out spurious egg passage due to ingestion of infected liver. To accomplish this Nema suggested collecting repeat stool specimens (instructing the patient not to eat any more liver!) If follow-up specimens are negative, then this would provide evidence that the patient was not actually parasitized. A related note is that liver ingestion is not common in many parts of the world, so getting a good dietary history (including possible ingestion of ants!) is very helpful.

I'll now leave you with a lovely story from Blaine:
So, there is this old story, or so I am told, about ants getting ready for the winter. They gathered up food stores all day, including slime balls produced by snails. Then along came a lazy grasshopper, which had spent the summer playing and not preparing for the winter. When the winter came, the grasshopper begged the ants for something to eat, even a slime ball!!! The ants refused. In the Spring, the ants had an insatiable urge to climb to the tops of blades of grass and ended up getting eaten by cattle and sheep! The grasshopper did not get eaten by the livestock. The moral of this story? Play all day and you are guaranteed not to become cow chow! 

Monday, November 26, 2018

Case of the Week 520

This week's case is a small "worm" submitted for identification following removal during screening colonoscopy. It was tan-white and measured approximately 1.3 cm in length. The following are photos of its microscopic appearance:


Sunday, November 25, 2018

Answer to Case 520

Answer: Adult hookworm, Necator americanus
The hookworms are easily recognized by their piercing mouth parts - used for attaching to the small intestinal wall and drawing blood from the host. N. americanus has cutting plates, while Ancylostoma duodenale has sharp pointed teeth.
Thanks to all who wrote in with the great comments and ancient Chinese wisdom!

Monday, November 19, 2018

Case of the Week 519

Happy Thanksgiving day to my American friends! Here's a question for your consideration: which parasites can you get from eating undercooked turkey (the centerpiece of the classic Thanksgiving day feast)? Here is one of them in a squash preparation of a brain biopsy. What is it?
Giemsa, 100x objective with oil
 Transmission electron microscopy:

Sunday, November 18, 2018

Answer to Case 519

Answer: Tachyzoites of Toxoplasma gondii. 

My accompanying request was to list other parasites that can be acquired from eating (undercooked) turkey. The two excellent responses I received from Bernardino Rocha were Gnathostoma spp. (likely, but we're not sure), and Trichinella pseudospiralis. Did we miss anything? Please write in if you can think of others.

Now, a few fun facts for the curious:
The tachyzoites are the rapidly-dividing form of T. gondii [tachy is from the ancient Greek ταχύς (takhús, “swift”)], and are the predominant form seen in acute and re-activated infections. In this case, the presence of numerous extracellular forms is evidence of an active infection. In contrast, tissue cysts containing bradyzoites, the slowly-replicating forms [brady is from the ancient Greek βραδύς (bradús, “slow”)] are seen during latent infection. The word zoite derives from the ancient Greek ζῷον (zôion, "animal"). I always make sure to point out word origins to my students when they are useful for remembering parasite names. For example, most medical students know the difference between tachycardia and bradycardia, and know to think of a 'zoo' as a place where animals are found. Helping them apply the knowledge they already have helps them learn these new, and often very foreign-sounding words.

T. gondii can infect any nucleated cell and tachyzoites are commonly seen within host cells during active infection. In this case, we can see both free and intracellular tachyzoites:

For those of you who like etymology, you may also be interested to know that the word Toxoplasma comes from the ancient Greek words τόξον (tóxon, "bow" or "arc") and  πλάσμα (plásma, “something molded”); thus the name nicely describes arc-shaped form of this parasite. I love when parasite names actually make sense!  You can especially appreciate this shape in air-dried touch preparations. Disappointingly, the arc shape is only rarely seen in sections of formalin-fixed, paraffin-embedded tissue, since the parasites tend to shrink and round up during fixation, taking on a more ovoid appearance. This makes it much trickier to differentiate them from small yeasts such as Histoplasma capsulatum and the amastigotes of Trypanosoma cruzi and Leishmania spp.

Transmission electron microscopy allows us to take a closer look at the T. gondii tachyzoites. As mentioned by Bernardino, the apical complex containing conoids and rhoptries is nicely seen:
HERE is an open access book chapter by the Global Water Pathogen Project that contains a reprint of the classic Dubey et al. 1998 figure showing the major structures of T. gondii tachyzoites and bradyzoites. 

Monday, November 12, 2018

Case of the Week 518

This week's case is a bit of a puzzle for you to put together. The following object was seen in a urine sediment. It was initially moving, but very quickly died. It measures approximately 130 micrometers in length.
Wet prep, 10x objective
 Wet prep, 40x objective

Identification? Images are by one of our Clinical Microbiology fellows, Dr. Sarah Jung.

Sunday, November 11, 2018

Answer to Case 518

Answer: Schistosoma haematobium miracidium, newly hatched with egg remnant.

This really neat photo, captured by our clinical microbiology fellow, Dr. Sarah Jung, nicely captured the miracidium right after it had exited the egg - AND - the egg remnant is still recognizable by its characteristic terminal spine. Great job Sarah!
I've tried to the best of my ability to label all of the components of the miracidium:
We rarely get to see these in the lab - although there is a hatching test you can try if you'd interested - and so it was a real treat to see the newly-hatched form of this parasite. Sarah mentioned that this was the best type of call to get called in from home for.

If you haven't already, I encourage you to go back and read the comments on this case - they are very interesting. I am so fortunate to have such a knowledgeable group of contributors who are always willing to share information and answer each other's questions. The comments also included a poem from Blaine which I will share here:
Humpty Haematobium sat on a wall
Humpty Haematobium had good fall
All the King's horses
and all the King's men
Couldn't put Humpty Haematobium back together again!

Excellent as always Blaine! Sarah and my lab staff have just a slight modification to your poem:

Humpty Haematobium sat in some pee
Humpty Haematobium yearned to be free
All of my fellows
Both women and men
Couldn't put Humpty together again!

Monday, November 5, 2018

Case of the Week 517

Case of the Week 513
This week features our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp.

A 45-year-old female patient, suspected of having an infection with Strongyloides stercoralis, provided a stool specimen for Baermann concentration. The following structure was found, measuring about 300 µm in extended state. Diagnosis please.

Sunday, November 4, 2018

Answer to Case 517

Answer: rotifer

Wow, great comments on this case!  The Old One mentioned that this is a bdelloid rotifer. He comments "In this year of the women, it should be noted that bdelloid rotifers are all female. Able to be successful for millennia while maintaining genetic diversity by taking DNA from other creatures." Fascinating! According to the Encyclopaedia Britannica, "Rotifer, also called wheel animalcule, any of the approximately 2,000 species of microscopic, aquatic invertebrates that constitute the phylum Rotifera. Rotifers are so named because the circular arrangement of moving cilia (tiny hairlike structures) at the front end resembles a rotating wheel." 

There is no clinical significance to this finding. Rotifers are found in environmental water sources, so it is likely that the organism entered the specimen through the collection process - possibly from toilet water contaminated with untreated water.

We've seen a rotifer before on this blog - in Case of the Week 304. Check out the photos from the case contributor, Ahrong Kim in South Korea - they're beautiful!

Friday, November 2, 2018

Halloween Parasite #5

HERE is Halloween Parasite #5, the last in my series of creepy dreadful wonderful parasites for the Halloween season. These pieces are written for the general public, including children, and aim to interest more people in the fascinating world of parasitology.

Thursday, November 1, 2018

Halloween Parasite #4

Happy Halloween Week everyone! As you all know, parasites can be creepy dreadful, but also fascinating, and sometimes even helpful. As a special Halloween treat, I'll be highlighting 5 different parasites on the Mayo Clinic News Network - 1 each day. HERE is parasite #4 - "worms in love" These are written as educational pieces for the general public. Feel free to use the text and images for your own educational purposes.

Wednesday, October 31, 2018

Halloween Parasite #3

Happy Halloween Week everyone! As you all know, parasites can be creepy dreadful, but also fascinating, and sometimes even helpful. As a special Halloween treat, I'll be highlighting 5 different parasites on the Mayo Clinic News Network - 1 each day. HERE is parasite #3 - . These are written as educational pieces for the general public. Feel free to use the text and images for your own educational purposes.

Tuesday, October 30, 2018

Halloween Case #2

Happy Halloween Week everyone! As you all know, parasites can be creepy dreadful, but also fascinating, and sometimes even helpful. As a special Halloween treat, I'll be highlighting 5 different parasites on the Mayo Clinic News Network - 1 each day. HERE is parasite #2 - scalp explorers. These are written as educational pieces for the general public. Feel free to use the text and images for your own educational purposes.

Monday, October 29, 2018

Halloween Case #1

Happy Halloween Week everyone! As you all know, parasites can be creepy dreadful, but also fascinating, and sometimes even helpful. As a special Halloween treat, I'll be highlighting 5 different parasites on the Mayo Clinic News Network HERE - 1 each day.

I unfortunately will not be having a Halloween party this year since I am at the annual meeting of the American Society of Tropical Medicine and Hygiene in New Orleans. Therefore I won't have any costume photos from my party, but I promise to post photos later if I see any particularly parasite-like costumes on Bourbon street!

Monday, October 22, 2018

Case of the Week 516

This week's case was generously donated by Dr. Josette McMichael, an American dermatologist currently working in east Africa. The patient is an elderly woman who presented with a 2-week history of 10 pruritic burning nodules involving her left upper arm, face, breast, chest, trunk, and legs. Here is a video of one of the lesions:

This object was removed and placed in a sterile container without preservative:
It was still quite lively!

Approximately 1 week later, it was sent to my lab for identification. Even though it had darkened significantly, the diagnostic features were still apparent. Here is the posterior end:

Sunday, October 21, 2018

Answer to Case 516

Answer: Cordylobia anthropophaga, the mango or tumbu fly.

As Florida Fan nicely outlined, there are several initial features that lead us to the identification:

1. The patient is from Africa, where we can find the tumbu fly.
2. The size of the larva is about one third or one fourth the diameter of the cup, roughly 13-15 mm in length, compatible to that of this fly's larva size.
3. There is no discernible peritreme nor ecdysial scar.
4. The spiracles open through sinuous slits.

The following image shows the posterior spiracles, with the sinuous slits (arrow head). Note that the peritreme is not easily discernible (arrow).
Blaine and I covered this classic causes of myiasis in our CAP Arthropod Benchtop Reference Guide. The key morphologic features are its robust form, cuticular spines on all body segments (not clearly shown here), spiracular plat with a very weak peritreme, and sinuous slits. As Blaine pointed out, you can differentiate C. anthropophaga from the similar-appearing species, C. rodhaini, by its much more sinuous slits.

Monday, October 15, 2018

Case of the Week 515

This week's case is a "worm" found in the cecum - an incidental finding during colonoscopy. It measures approximately 4 cm long. Identification? Images by my Parasitology technologist extraordinaire, Heather Rose Arguello.

Sunday, October 14, 2018

Answer to Case 515

Answer: Trichuris trichiura, a.k.a. "whipworm"

As noted by Florida Fan, "we can clearly see the thread-like anterior portion and an inflated posterior, giving the worm resemblance to a whip". I always like to ask my students which end they think is anterior - they invariably (incorrectly) guess that it's the broader end! This gives me the opportunity to walk them through the life cycle and how the adult worms are embedded within the mucosa of the large bowel. It always seems to make more sense to them when I ask which end would be easier to thread into the wall of the bowel - the thin end or the thick end? This helps explain why the anterior end is thinner than the posterior. I also note that having a broader posterior end allows it to fill with eggs in the female worm, and these can then easily be shed into the intestinal lumen . I'm kind of old-fashioned, so my explanation is usually accompanied by some hand-drawn images.
Florida Fan also noted another two other important morphologic features: the stichosome comprised of multiple stichocytes, and the immature ova within the uterus in the posterior end.

And now for our poem by Blaine referencing the dreaded complication of whipworm infection - rectal prolapse!

When your booty's been turned inside-out
and you go to your doc to get it checked out
You'll feel yourself start to squirm
as he describes the culprit, whipworm
cuz Trichuris trichura like to let it to all hang out

Monday, October 8, 2018

Case of the Week 514

This week's case is a classic case from Heather Rose Arguello, my fabulous parasitology specialist. This is a wet preparation of liver cyst fluid (40x objective):

Sunday, October 7, 2018

Answer to Case 514

Answer: Hydatid sand of Echinococcus sp.; mostly likely Echinococcus granulosus due to the abundant protoscoleces/hooklets and presence within a single cyst. 

The photo from this case shows numerous free hooklets in the background of degenerating protoscoloces. As Blaine pointed out, the mixture of disintegrating protoscoleces with free hooklets and calcareous corpuscles is often referred to as "hydatid sand."
As Old One pointed out, the protoscoleces have a rostellum with 2 rows of hooklets - one row of large hooklets and one row of small hooklets - making this cestode "armed". He further notes that having an armed rostellum puts this cestode into the family Taeniidae.

Echinococcus species are one of several members of the Taeniidae that can cause human disease. Echinococcus granulosus is now recognized as a complex of closely-related organisms, with E. granulosus sensu stricto being the most common species causing human disease worldwide. Other members of this complex that cause human disease are E. canadensis and E. ortleppi. Differentiation of the members of the E. granulosus complex is primarily accomplished through molecular means.

E. multilocularis human infection is fortunately less common, as this parasite is known for its more aggressive and invasive growth pattern. As several readers pointed out, the cysts of E. multilocularis invade host tissue, much like a tumor, and are not contained within a large parent cyst. Protoscoleces are not commonly seen in human infections with E. multilocularis. Finally, E. oligarthra and E. vogeli are rare causes of human echinococcosis in South and Central America.

Monday, October 1, 2018

Case of the Week 513

This week features our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. A Nigerian male patient, returns to Belgium, after having visited his relatives. He presents at the hospital, where a worm was extracted from his eye (length: 5 cm).
In a drop of blood, live “larvae” were seen.
A KNOTT concentration was made and stained with Carazzi’s to visualize the details.
The “larvae” are measuring (on average) 280 µm in length.

Diagnosis please?

Sunday, September 30, 2018

Answer to Case 513

Answer: Loa loa, adult worm and microfilariae
Thanks to Idzi for another spectacular case. This one nicely compliments his last case (see Case of the Week 509) which features a different round worm that can also be found in the eye: Dirofilaria. I've seen several ocular dirofilariasis cases in the past few years - all which had been initially mistaken for Loa loa - so I think it's important for microbiologists and clinicians to know that the two worms can have a similar presentation.

So how can you tell them apart? Here are some helpful features:
1. Travel history: Loa loa is found in West and Central Africa, whereas Dirofilaria has a much broader distribution (Africa, Asia, Europe). If the patient hasn't been to West or Central Africa, then the diagnosis is probably not loiasis.
2. Morphology of the adult worm: The adults of both worms have a similar size and gross appearance. However, Loa loa has irregularly-spaced cuticular bosses ('bumps' on the outer aspect of the cuticle), whereas Dirofilaria has longitudinal ridges. Here are some representative images of the two:

Loa loa (I sadly neglected to include this image from the case earlier):

Dirofilaria repens:
3. Morphology of the microfilariae: Last, but not least, the morphology of the blood microfilariae is another helpful feature for differentiating L. loa from Dirofilaria. While the former are sheathed and have nuclei that go to the tip of the tail, the latter are rarely seen in human blood, are NOT sheathed, and the nuclei do NOT go to the tip of the tail.

Loa loa:
 Dirofilaria repens:
 Note that the sheath of Loa loa (as well as Wuchereria bancrofti and Mansonella ozzardi) is usually colorless with tradition Giemsa stain, but is highlighted using Carazzi's hematoxylin stain as shown here. In comparison, the sheath of Brugia malayi is usually - but not always! - bright pink on Giemsa stain.

Monday, September 24, 2018

Case of the Week 512

The week's case is generously donated by Dr. Peter Gilligan, Cody Craig, and Leslie Dodd. The following objects were noted on a Papanicolaou-stained rectal smear from a male patient. They measure approximately 5 to 10 micrometers in diameter. Images were taken using a 40x objective.


Sunday, September 23, 2018

Answer to Case 512

Answer: Iodamoeba buetschlii

I thought this was a fun example of a relatively common parasite seen with an uncommon preparation. It's nice to see that an alternative stain such as Papanicoloau still allows for morphologic identification of the intestinal amebae.

The key morphologic features of this case are the small size of the organisms (primarily cysts, and possibly one trophozoite), nucleus with large karysome and lack of peripheral chromatin, and large cytoplasmic vacuole in the cytoplasm of the cyst form. As Florida Fan mentioned, the large glycogen-filled vacuole would be deeply stained with iodine if we had a wet mount preparation.

Some of you wanted to understand the basis for the Pap-stained anal/rectal smears, given that this is not something usually performed by the microbiology lab. The purpose is to exam for squamous cell dysplasia and carcinoma secondary to Human Papillomavirus infection - the same type of exam used for female cervical smears. Anal/rectal smears are usually done in the MSM population (men who have sex with men) - particularly when they engage in unprotected anal intercourse which puts them at risk for a variety of infections. Of course, when we exam smears from this source, we are bound to detect the occasional intestinal parasite as a incidental finding!

I published a similar case a few years back with some colleagues which you can read HERE.