Case of the Week 587

This week's case features objects seen in a concentrate from a diarrheic stool specimen. The objects measure approximately 60 micrometers in greatest dimension. Identification?

Answer to Case 587

Answer to Parasite Case of the Week 587: Balantioides (formerly Balantidium, Neobalantidium) coli. Note the characteristic circumferential cilia and large "kidney bean" shaped macronucleus:

I was impressed by how many people knew about the complicated taxonomy of this organism. Blaine Mathison and I had published on Neobalantidium coli in our Medical Parasitology Taxonomy Update (J Clin Microbiol. 2019;57:e01067-18) only to discover shortly afterwards that Balantioides has priority over Neobalantidium (we are now working on a correction). From our research, we discovered that Alexeieff was the first to describe Balantioides to accommodate B. coli in 1931. Unfortunately this French manuscript went largely unnoticed for decades, and Pomajbikova et al. alternatively described Neobalantidium in 2013 to accommodate B. coli. We can credit Pomajbikova and Stensvold for later uncovering the 1931 manuscript for us and shedding light on current state of taxonomy of Balantioides coli.

I have a pdf of the 1931 French manuscript (with my own translation) if anyone is interested in it. I should note that my French is very rusty, so there may be some errors! Just send me a message at b_pritt@yahoo.com if you would like a copy.

I'd also encourage you to read all of the interesting comments from this case. There are a lot of great pearls in there.

Case of the Week 586

It's now time for our monthly case by Idzi Potters and the Institute of Tropical Medicine, Antwerp:

The following structures were found in an unstained wet mount from a Belgian patient without any recent travel abroad. The patient reports intestinal discomfort for approximately 1 week. The structures measure approximately 20 micrometers in length.

Identification?

Answer to Case 586

Answer to Parasite Case of the Week 586: Mushroom spores. Not a parasite.

As many of you pointed out, mushroom spores are a challenging parasite mimic, resembling hookworm eggs, Cystoisospora belli oocysts, and Giardia cysts. Fortunately, you can rule out the first two based on the small small size of these objects (20 micrometers long), whereas G. duodenalis can be ruled out by the lack of internal structures (e.g., nuclei, axoneme, median bodies). Two other viewers initially thought there was a lateral spine present (indicating Schistosoma mansoni) but later realized it was just an artifact.

Florida Fan pointed out that I had previously shown a case of mushroom (morel) spores in May of 2019 (Parasite Case of the Week 544). Great memory Florida Fan! That case showed mushroom spores within an ascus, which was a fun twist.

Florida Fan also mentioned that Spring is here at our door, and now is the time to go out and hunt for mushrooms - something that can be done while social distancing! I hope you and your families are all staying safe (and sane) during this challenging time.

Case of the Week 585

And now for something completely unrelated to COVID-19.

For those of you able to get outdoors, keep a look out for these little critters. For those of you stuck inside, you might be happy that you are missing them:

Identification?
Generously donated by Florida Fan.

Answer to Case 585

Answer to Parasite Case of the Week 585: Hard tick, Ixodes scapularis, unengorged adult female with intact mouth parts.

As several of you mentioned, it would be important to know the location for where this tick was obtained. This particular tick was obtained in Florida, although similar-appearing ticks are found on the west coast of the United States (Ixodes pacificus) and Europe (Ixodes ricinus). All three of these ticks serve as the vector for members of the Borrelia burgdorferi sensu lato species complex that cause human Lyme disease (Lyme borreliosis).

There are a couple of features below which can get you to the genus level pretty quickly: specifically, the inverted "U-shaped" anal groove and the lack of festoon. The following image shows these, and some other morphologic features.

You will then want to refer to specific keys for the morphologic identification of Ixodes ticks in the different regions of this world.

Thanks again to Florida Fan for donating this case!

Case of the Week 584

This week's fun case was generously donated by Dr. José Poloni, one of my Twitter buddies (@JoseTesser). The object below was found in the undergarments of a 35 year-old woman. No other history is provided. Identification? How would you sign this case out?

Answer to Case 584

Answer to Parasite Case of the Week 583: Dipteran fly pupa, possibly a fruit fly pupa (Drosophilidae); not a human parasite.

As Old One commented, "...I probably have endless numbers of these critters residing in my kitchen waste recycling bin. Jokes on me."

This fun case donated by Dr. Poloni has some interesting morphologic features that we don't usually get to see in the clinical microbiology laboratory, such as long anterior respiratory spiracles.

Case of the Week 583

This week's case was donated by Dr. Daniel Cohen. The following specimen was submitted to surgical pathology for examination. No additional history was available.

Like all specimens in surgical pathology, it was sectioned and made into H&E-stained slides.

Identification? What structures are we seeing here?

Answer to Case 583

Answer to Parasite Case of the Week 583: Immature Taenia sp. proglottids.

I apologize that this was more challenging than I meant it to be. I should have mentioned that these objects were passed through the anus (sorry about that omission!)

Note that the objects seen here are made up of repeating chains of proglottids, some which are longer than they are wide, consistent with a Taenia sp. rather than Diphyllobothrium/Dibothriocephalus sp.

As Blaine mentioned, the far left proglottid *might* have a lateral uterine pore which would support a diagnosis of Taenia sp.

In my mind, the histologic sections don't add much to this case. They show the classic features of a cestode (thin outer tegument with a loose underlying stroma containing calcareous corpuscles and longitudinal muscle fibers) with central reproductive structures. However, there is not enough differentiation of these structure present to allow for definitive confirmation of the gross identification.