Tuesday, December 29, 2020

Case of the Week 620

This week's case is a nice straight-forward one because - spoiler alert - we are going to have a really fun challenge from Idzi Potters next week to start off our new year. 

The following worm was found during routine colonoscopy. Identification? For 'extra credit' - which end is anterior? And is this a male or female?

Sunday, December 27, 2020

Answer to Case 620

 Answer to Parasite Case of the Week 620: Trichuris trichiura, a.k.a. "whipworm". This is a male, as evidenced by its curled tail and copulatory spicule (note the location of the anterior and posterior ends):

Be sure to check out the comments section to see all of the creative comments that go with this case!

Monday, December 21, 2020

Case of the Week 619

 Dear readers,

Wishing you and your family a very happy, safe and healthy holidays. To celebrate the season, I thought I would share a few of my favorite photographs from my 2020 calendar - all decked out for the holidays. Can you tell what they are?

Sunday, December 20, 2020

Answer to Case 619

Answers to Parasite Case of the Week 619: Trichuris trichiura, Schistosoma couple, and Hymenolepis nana.

Monday, December 14, 2020

Case of the Week 618

 This week's case features some photos from a cool histopathology case I found in my archives. The source is "large single liver cyst". Identification? What cool things do you see in these images?

Sunday, December 13, 2020

Answer to Case 618

 Answer to Parasite Case of the Week 618: Echinococcus granulosus sensu lato species complex

There are many cool features in this cool case. Here are just a few that I thought were worth pointing out:

First, note how you can see a portion of all of the layers of the cyst. Going from the outside-inward, you can see the compressed host tissue, outer most parasite-derived layer (laminated layer), the granular layer, and several brood capsules, each containing multiple protoscoleces.

Within the individual brood capsules are many inverted protoscoleces arising from the granular layer. We even managed to get a section showing how one protoscolex is attached to the cyst granular layer by a thin stalk. Numerous, variably-sized, calcareous corpuscles are also seen: 
Another cool feature in this case is the presence of degenerating protoscoleces within some of the daughter cysts, resulting in freed hooklets. The resultant gritty fluid is referred to as hydatid sand. 
Protoscoleces don't usually evert unless they have been ingested by the definitive canid host. They then mature into the adult worm and live in the gut of the host. I'm guessing that eversion occurred in this case as part of the degenerative process.

Thank you for all of the comments!

Monday, December 7, 2020

Case of the Week 617

 Here is our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following were seen in a stool specimens in a patient with diarrhea and recent travel to sub-Saharan Africa. 

Unstained wet mount: 

Combined iron hematoxylin-Kinyoun stain:


Sunday, December 6, 2020

Answer to Case 617

 Answer to Parasite Case of the Week 617: Cystoisospora (formerly Isospora) belli

The diagnostic features in this case include the size of the oocyst (~25 micrometers), oval shape, internal structure (single sporoblast in the wet prep) and acid fast positivity on the iron hematoxylin Kinyoun stain.  The acid fast positivity allows us to rule-out Sarcocystis sp. as the oocysts of this parasite are not acid fast. 

Kamran and Florida Fan noted that the oocysts of C. belli autofluoresce beautifully when examined with an excitation filter of 330 to 365 nm. As Blaine will tell us, they also exhibit a less intense fluorescence when examined with an excitation filter of 450-490 nm. Here is a great example of this autofluorescence from Florida Fan:

Note that this oocyst from Florida Fan has 2 sporoblasts, which is unusual to see in freshly passed stool specimens. Most C. belli oocysts are shed in an immature state - either unsporulated or partially sporulated (with only one sporoblast). They mature further in the environment, with the sporoblast dividing in two so that the mature oocyst has 2 sporoblasts. The sporoblasts become sporocysts with a surrounding cyst wall, and the sporocysts divide twice so that they produce 4 sporozoites each. Here are some great photos from Idzi showing this (you can see the sporozoites in the last image):

Monday, November 30, 2020

Case of the Week 616

 This week's interesting case was donated by Dr. Neil Anderson, one of our former outstanding Clinical Microbiology fellows. The following were seen in a bacterial culture from a stool specimen. What do you think the clinical significance is?

Sunday, November 29, 2020

Answer to Case 616

 Answer to Parasite Case of the Week 616: Fly larva, presumed culture contaminant

Although these bacterial tracks can also be seen in cases of strongyloidiasis, you can nicely see the culprit on the video. Here is a nice still image from this case:

Thanks again to Neil for donating this fun case!

Tuesday, November 24, 2020

Case of the Week 615

In the spirit of the American Thanksgiving holiday, I'd like to present two related cases that were donated by two parasitologists in our wonderful parasitology community: George from Memorial Sloan Kettering and William Sears from the NIH. I'm thankful for many things, and among them are this generous and supportive group that inspires and educates me each week. In his case, George noted the following in a stool concentrate:

William was also kind enough to provide adults of this parasite, complete with more eggs (in utero and free). I've seen similar adult worms in concentrated stool specimens.

Can anyone put this whole picture together for us? 

Monday, November 23, 2020

Answer to Case 615

 Answer to Parasite Case of the Week 615: Strongyloides stercoralis rhabditiform larva, eggs, and adults. Note the eggs inside and out of the beautifully-photographed adult worms by William Sears. As you may know, the parasitic females reproduce without the males using a process called parthenogenesis. 

This 'composite' case didn't have any accompanying clinical information, but a classic scenario would be hyperinfection infection in a profoundly-immunocompromised patient.  

It's important to note that it's not possible to definitely make the diagnosis on the images from this case alone, especially since the buccal cavity of the rhabditiform larva is not visible. You all did an excellent job coming up with the differential diagnosis. I'd highly recommend reading all of the comments on the blog (or on Twitter @Parasitegal) to see great descriptions and stories. 

Here are the options of what this case could be:

1. S. stercoralis hyperinfection (For another example, see the previous Case of the Week 469 and the accompanying Answer). It's important to realize that embryonated eggs and adults may rarely be seen in stool specimens in heavy infections. Here's a great photo from Case 469 to demonstrate the size difference between adults and rhabditiform larvae:

2. Strongyloides fuelleborni infection, in which eggs containing rhabditiform larvae are found in stool. In this case, we wouldn't have expected to see adult worms in the stool. See the previous Case of the Week 593 donated by Idzi Potters for more information.

3. Hookworm infection, in which unfixed stool was allowed to sit for some time prior to examination, allowing eggs to embryonate and hatch. Great thought! This doesn't account for the adults in stool, however, which would not be expected in hookworm infection.

4. Mixed hookworm and Strongyloides infection. Allowing the eggs to hatch (e.g., using the Harada-Mori culture technique) and then examining the rhabditiform larvae would allow for differentiation of hookworm and Strongyloides. Alternatively, molecular testing at a specialized research laboratory could also help to sort this out.

5.  Spurious passage of a soil/plant nematode.

Wishing you all a very happy and safe Thanksgiving day!

Monday, November 9, 2020

Case of the Week 614

 This week's case is from my lab, with the photos taken by our excellent technical specialist, Heather Morris. The following structures were seen in lung cyst fluid. Identification?

Sunday, November 8, 2020

Answer to Case 614

 Answer to Parasite Case of the Week 614: Cystic echinococcosis caused by a member of the Echincoccus granulosus complex. 

As Clinton White nicely explained in the case comments, "We now know that human infection is caused by several species and genotypes within what was once thought of as a single species." The species implicated in human disease are E. granulosus (genotypes G1-G3), E. ortleppi (G5), and E. canadensis (G6-G8, G10). Most of these have a wide geographic distribution, including regions of North America, Europe, Asia, and the Middle East. In South America, 2 additional species cause neotropical cystic echinococcosis, E. vogeli and E. oligarthra. Echinococcus multilocularis causes a very different form of disease called alveolar echinococcosis. Unlike the species that cause cystic echinococcosis, E. multilocularis expands throughout the tissue in an infiltrative pattern, much like a malignancy, forming microscopic and macroscopic cysts without a well-defined surrounding laminated layer. Protoscolices are rarely seen in human E. multilocularis infections.

Molecular analysis, as well as correlation with the radiologic findings and the patient's exposure/travel history are used to determine the causative species. In this case, the patient had not travelled outside of North America and had a single pulmonary cyst, consistent with a diagnosis of simple cystic echinococcus (CE; CE1 on the World Health Organization classification scale).

This case shows characteristic protoscolices and free hooklets of E. granulosus complex. The hooklets are especially beautiful with Wheatley's trichrome staining, in which they have a somewhat iridescent appearance:

Monday, November 2, 2020

Case of the Week 613

This week's case is something that we only occasionally get to see in my laboratory - kindly donated by Dr. Ryan Relich. The patient presented with a past history of malaria, and she had not completed her full course of anti-malarial therapy. Therefore, her physician ordered peripheral blood films which revealed the following. Travel history is unknown at this time. It's a little hard to tell from the images, but the nuclei go to the tip of the tail.


Sunday, November 1, 2020

Answer to Case 613

 Answer to the Parasite Case of the Week 613: Loa loa microfilariae

Although some readers suggested that these structures could be artifacts (e.g. fibers that got onto the blood films), we can tell that these are microfilariae by the size, shape and presence of nuclei within the worms. The tail nuclei weren't entirely visible in the images, so I gave the hint that the nuclei go all the way to the tip of the tail. That leaves us with just 2 microfilariae to consider: Loa loa and Mansonella perstans. 

As nicely described by Idzi, the size of the microfilariae is the most important feature for differentiating these two: "Mansonella is ruled out by its thickness. A nice trick is to compare the diameter of the microfilaria to the nuclei of the white blood cells. Mansonella would be half of the WBC nuclei’s diameter while the others are more or less the same."  Loa loa microfilariae are also sheathed, whereas those of M. perstans are not. Unfortunately, it is not always possible to see the sheath of Loa loa (as well as Wuchereria bancrofti) on Giemsa-stained blood films. 

Florida Fan offered up a very nice example of where the sheath is visible:

You can see the sheath extend from the tip of the tail, up towards the "20" of the scale bar.

If you have your heart set on seeing the sheath, another neat trick you can use it to stain your blood films with hematoxylin. The Delafield's hematoxylin protocol is usually recommended for this purpose, but the routine hematoxylin and eosin (H&E) stain in your anatomic pathology lab will also do in a pinch. Here are some microfilariae images from this case using H&E staining - what a beautiful sheath! 

Some also appeared as negative outlines:

Thanks again to Dr. Ryan Relich (a.k.a. MicrobeMan) for donating this case.