Case of the Week 549

This week's rather creepy and very cool case was donated by Dr. Matt Bolek and Christina Anaya. While the host shown here is not a human, this parasite emerging from the cricket is occasionally submitted to human clinical parasitology laboratories. What is its significance for human health?

Answer to Case 549

Answer to Parasite Case of the Week 549: "Gordian" or "horsehair" worms, belonging to the group Nematomorpha. I had asked what its significance is for human health; this was a trick question, since gordian worms have no direct clinical significance, other than scaring people when they are found in toilet water! When submitted to the clinical parasitology laboratory, they can easily be differentiated from other large worms such as Ascaris lumbricoides by their long slender bodies:

I have to admit that I was amazed by how many worms emerged from the poor cricket in this fascinating video donated by Matt and Christina. The good news is that the cricket survived the ordeal and went on to chirp another day!

There is an excellent description of this group of worms on the University of Kentucky entomology website.

Case of the Week 548

This week's case was generously donated by Dr. Tara Ness, with filming credit to the Lab Hlathi Team in eSwatini. The following arthropod was found in the urine specimen of a man with HIV and a history of dysuria. Identification?

Answer to Case 548

Answer: Mite, most likely Dermatophagoides species (dust mite).

As mentioned by several readers, we are lacking sufficient details to make a definitive identification. However, we can conclude that this is a contaminant in this specimen and not a cause of the patient's symptoms. As Blaine mentioned, this is a "Conta-mite-nt"!

Some readers mentioned that Sarcoptes scabei should be considered. While this is also a mite, its distinctive features, including its short legs and overall body shape, allow for differentiation from Dermatophagoides:

Thanks again to Dr. Ness and her lab for donating this case.

Case of the Week 547

Here is our monthly case by Idzi Potters and the Institute of Tropical Medicine, Antwerp.

The following 1-cm long structure was extracted from a Belgian patient returning from Ghana. Identification?

Answer to Case 547

Answer to Parasite Case of the Week 547: Cordylobia rodhaini, also known as Lund's fly.

As noted by Bernardino, this is a 3rd instar larva, with a characteristic shape, size, irregularly-placed, weakly-pigmented cuticular spines and spiracles for this species. The more sinuous spiracles allows us to differentiate this from Cordylobia anthropophaga, the "tumbu fly" which is more commonly seen on humans. Both are found in the African subtropics.

From Old One:
Hooray for Bernardino a wiz at diagnostics
Lund’s fly no match for his skillful forensics
The folks on the blog all think he is swell
Never missing his mark, the new William Tell

You can read all about this fascinating parasite in Idzi's latest publication which is freely available HERE. An important point to note is that the adult flies of C. rodhaini and C. anthropophaga deposit their eggs on soil or clothing. Contact with the warm-blooded host then causes the larvae to hatch and penetrate the skin. This is why it is common practice in endemic areas to iron your clothes - including undergarments - after taking them off the line! This important point can be remembered from Blaine's fun poem:

In Africa, if you allow your laundry to air dry
Make sure you iron it! Wanna know why?
'cuz this diabolical dipteran lays its eggs on fomites
especially on clothes and sheets dried by sunlight
and that's how you get exposed to the tumbu fly!

Thanks again to Idzi for sharing this case with us!

Case of the Week 546

This week's case has been generously donated by Blaine Mathison at ARUP. Two different types of objects were seen in a trichrome-stained stool specimen that was screened by a digital slide image and machine learning platform. How did it do? Did it find real parasites?

The following objects are approximately 8 to 13 micrometers in diameter:

These objects are 10 to 15 micrometers in greatest dimension.

Identification?

Answer to Case 546

Answer: Blastocystis sp. and Entamoeba sp.

From Blaine: These images were captured by software trained to detect intestinal protozoa in trichrome-stained stool specimens. The final report was Entamoeba histolytica/E. dispar and Blastocystis sp. It is difficult to determine the species of Entamoeba from only four examplars, but the even peripheral chromatin and discrete karyosome are supportive of E. histolytica/E. dispar which is how this case was signed out from both the slides and the whole-slide scanned image. I see a lot of respondents placing weight on the cytoplasm, which I always take as a ‘soft’ feature – I prefer peripheral chromatin.

The software we are training (still in validation stage) is designed to detect Entamoeba based on the nucleus (the amorphic forms of trophozoites created too many false positives when we tried to detect the entire organism). The software is not designed (at least at the moment) to identify the Entamoeba to the species level. All slides flagged as positive with a high score of being positive are to be manually backread for confirmation and species-level ID. The software is more of a screening tool, in hopes of cutting down manual read of 70% of our negative trichromes.

So to those who questions if artificial intelligence is going to make parasitologists obsolete - the answer is "no"! Dr. Marc Courturier assures us in his comment: "Have no fear. We will all have jobs as expert parasitologists. This technology that Blaine and I have been working on will make our work MUCH easier, faster, and more accurate. And fun...because lets face it...no one likes sitting for 8 hours at a scope.The future is bright for parasitology."

Thanks again to Blaine (and Marc) for donating this case!

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?

Answer to Case 545

Answer: Not a human parasite: earthworm (Phylum Annelida, subclass Oligochaeta, Family Lumbricidae). It could very well be a Lumbricus species as some readers suggested, but I don't know enough about the different genera of earthworms to tell you for sure. Perhaps a knowledgeable reader can educate us on this topic?

So, wow, I've been on a roll with these parasite mimics! I'll try my best to include some true parasites in upcoming posts. Those of you who have followed this blog for a while probably know that I am fond of mimics - probably because they are so commonly seen in the clinical microbiology lab and provide an interesting challenge to clinicians, patients and laboratorians alike. In this case, I'm sure the patient wouldn't have hesitated to identify this object as an earthworm if it had been in a bait and tackle shop. It's when mimics end up in unfamilar settings (i.e., the toilet bowel) that they become a cause for alarm.

So how did this earthworm end up in the toilet? My plumber friend tells me that this is not an uncommon occurrence since pipes break due to the wear and tear of being in the ground. Tree roots, it would seem, are the enemy of sewage pipes.

For those of you wondering how to tell an earthworm apart from other large worms (e.g., Ascaris lumbricoides), here are some of the defining features that are not seen in human parasites:
1. Clitellum - the thickened glandular non-segmented portion of the earthworm's body found in sexually-mature adults.
2. Segmented body with setae. Setae are the small bristles found on each segment that help the worm move through soil.
3. A mucin-secreting epithelial layer beneath a thin cuticle. This is best appreciated on histopathologic exam; you can see a nice example in my previous CASE 234.

With that, I'll leave you with an interesting 'conversation' between two of our faithful readers, Old One and Florida Fan:

Florida Fan: "Hey Old One are you going fishing?". 
Old One: " Yeh". 
Florida Fan: " Got worms?" 
Old One: " Yeh, but I'm going fishing anyway."

And here is a poem from Blaine Mathison:
To see a worm wiggling in a toilet bowl
would certainly on anyone take its toll
but there's nothing to fear
for it didn't come out your rear
but a crack in your pipes allowed contamination from the soil!

For those of you who would like a more serious poem (with no offense to Blaine's), Florida Fan and Sir Galahad remind us of the poem by Jacques Roubaud, "Le lombric" (the Earthworm). You can find a passable translation HERE. Enjoy!