Monday, August 2, 2021

Case of the Week 648

 This week's case was donated by Dr. Seema B. The following objects were seen in a Papanicolaou-stained bronchoalveolar lavage specimen. No further history is available. They measure approximately 500 micrometers long. Most likely identification?





Monday, July 26, 2021

Case of the Week 647

 The following objects were seen on Giemsa-stained touch preps of a skin biopsy from a patient with a slowly enlarging ulcer. He had recently travelled to Costa Rica. Identification? What additional testing is indicated?





Sunday, July 25, 2021

Answer to Case 647

 Answer: Leishmania species amastigotes within a host phagocytic cell. Note the characteristic "dot-dash" morphology of the amastigotes, representing the nucleus and rod-shaped kinetoplast:



Given the travel history to Costa Rica, additional testing is indicated to determine the species of Leishmania present. Some species in Latin America are capable of causing mucocutaneous leishmaniasis - a destructive form of disease that is difficult to treat. If the patient is infected with one of these species (e.g., L braziliensis), then more aggressive treatment is warranted. 

Species identification is best accomplished by first growing the organism in culture and then performing isoenzyme analysis, or more commonly today, sequencing. 

Monday, July 19, 2021

Case of the Week 646

 This week's case was donated to us by Dr. Will Sears. He and his wife found the following worm in a puddle in Zion national park. This interesting worm is also occasionally submitted to the clinical parasitology laboratory. What is it?









Sunday, July 18, 2021

Answer to Case 646

 Answer to the Parasite Case of the Week 646: Gordiid/nematomorph, a.k.a. horsehair or Gordian worm (Nematomorpha: Gordiida). Not a human parasite. 

This is one of my favorite human parasite mimics. It is occasionally submitted to the human clinical parasitology laboratory - often after being found in the toilet or other body of water - and can be easily differentiated from true human parasitic worms by its long slender shape, said to resemble a horse hair. 

In their 2012 publication, "Going Solo: Discovery of the First Parthenogenetic Gordiid (Nematomorpha: Gordiida), Hanelt et al. write: 

The Nematomorpha is the sister phylum to the Nematoda. Although these phyla share many features such as their general body shape, color, cuticle, and body organization, several key differences delineate these phyla. First, all members of the Nematomorpha are parasites as juveniles but free-living as adults. Second, due to their parasitic lifestyle, the nematomorph gut is largely non-functional, and juveniles feed by absorbing materials directly through their cuticle. Freshwater nematomorphs (Nematomorpha: Gordiida), or gordiids, are a unusual group of parasites that mate and oviposit outside of their hosts. Members of this phylum are strongly sexually dimorphic and until now have been described as dioecious. The unique gordiid life cycle involves transition of parasites within terrestrial arthropod hosts to free–living aquatic adults, which is partially achieved by parasite manipulation of hosts to commit ‘suicide’ by jumping into water triggering worms to escape. Freshwater gordiids use various definitive hosts including hemimetabolous insects such as orthopterans (crickets, grasshoppers, and locusts), cockroaches, and mantids, and holometabolous insects such as beetles.

This is the third time we have posted a case of a Gordian worm emerging from its cricket host. Check out the other posts here:

Case of the Week 549 and Answer

Case of the Week 185 and Answer

As noted by Idzi "Always spectacular! Poor cricket…"


Monday, July 5, 2021

Case of the Week 645

 This week's case was donated by Seanne Buckwalter, and her golden doodle, Ruby. Ruby acquired this interloper from Seanne's back yard in southeastern Minnesota. Identification? And do you think the geographic location fits with the identification? Finally, what pathogens does this arthropod transmit?





Sunday, July 4, 2021

Answer to Case 645

 Answer to Parasite Case of the Week 645: Amblyomma americanum adult female tick.

TheOracle nicely described what we are seeing here and its implications: "Given the position of the capitulum, we can immediately argue this is a hard tick (family Ixodidae). Even though we don't have a ventral picture, the number of legs, the quite long mouthparths and, more importantly, the white spot on the scutum allow us to diagnose an adult female of Amblyomma americanum, even though Minnesota isn't the expected geographic location. This may possibly reflect the tremendous effects of climate change... 



TheOracle further commented that "Amblyomma americanum doesn't transmit Lyme disease; nevertheless it can transmit infections sustained by Ehrlichia, Francisella and Rickettsia species."

A. americanum is also associated with STARI and meat allergy. 

Regarding the geographic location - Minnesota is not historically within the range of the Lone Star tick, but I believe that is changing with global warming. That doesn't bode well for Minnesotans, given the aggressive biting nature of both male and female Lone Star ticks! Thanks again to Seanne and Ruby for donating this case.

Monday, June 28, 2021

Case of the Week 644

This week's case is from Blaine Mathison and Marc Couturier at ARUP Laboratories. They partnered with Techcyte to validate an exciting new system that uses artificial intelligence to identify parasites on digitally-scanned slides (see their recent article). 

Here is a case in which the following objects from a trichrome-stained stool specimen were identified by AI for the technologist's review. They measure approximately 8 to 9 micrometers in diameter. Identification?



Sunday, June 27, 2021

Answer to Case 644

 Answer to the Parasite Case of the Week 644: Cyclospora cayetanensis oocysts on trichrome stain. Additional confirmatory testing (e.g., modified acid fast, UV autofluorescence) is recommended for confirmation. As I mentioned previously, the image from this case was the display screen from the Techcyte AI analysis of a digitally-scanned trichrome-stained slide. You can see that the digital algorithm did an excellent job identifying objects of interest and displaying them to the technologist for review. Use of AI platforms is the future of clinical parasitology, as it drastically reduces the time that technologists have to spend screening negative slides and increases sensitivity for detecting positive cases. Most parasitology labs have an extremely low positive rate for O&P testing - often 95% or more are negative. So a technology that allows our highly trained microscopists to quickly rule out negatives and focus on the positives allows for much better use of their skills, and generally increases job satisfaction! Thanks again to Blaine and Marc for donating this case.


Monday, June 21, 2021

Case of the Week 643

 This week's case is one I've previously shown before, but from many years ago. It's so cool looking that I thought it was worth showing again. The following object was found in a iodine-stained stool concentrate by Florida Fan. Any thoughts on what it is?





Sunday, June 20, 2021

Answer to Case 643

 Answer to the Parasite Case of the Week 643: Not a parasite; plant material. 

As mentioned by Idzi, Bernardino, and Phil G-J, this beautiful structure is a peltate trichome, possibly from an olive (Olea) leaf. Bernardino Rocha provided a great link to this open access article and the photos look just like what we are seeing. 

To obtain further insight, I contacted our knowledgeable botanist reader, Dr. Mary Parker, and was pleased to hear that she agrees with our assessment! She commented that this structure is definitely a peltate trichome and could quite possibly be from the lower epidermis of a leaf of an olive tree. The trichome could have been a contaminant of olives or olive products (e.g., preserved olives, tapenade, unfiltered olive oil) and thus ingested to end up in our specimen. She also mentioned that herbs like mint have glandular peltate hairs on their leaves, but that there are usually fewer of the radiating head cells; therefore, Olea is a more likely source. She provided this striking photo of the lower epidermis of an ash leaf with a trichome. You can also see the guard cells of the epidermis - something we have featured before on this blog (Case of the Week 534 and answer)

We get to see so many fascinating things as parasitologists, and while it's not necessary for us to always know exactly what we're looking at, it's really fun when we can make an identification like this. Thanks again to our faithful contributor, Florida Fan, for donating this case.


Monday, June 7, 2021

Case of the Week 642

It's time for our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. As always, Idzi has a great case for us - courtesy of Anna Rosanas and Pieter Guetens from ITM's Malariology Department: a patient with extensive recent travel - leaving Belgium to trek across rural areas of Peru, Niger, Mali, and finally the Philippines. He didn't take any malaria prophylaxis while traveling and now presents with fever and general malaise after being home for 3 weeks. The following are thick and thin Giemsa-stained blood films from this patient (pH 8.0). The percent parasitemia was calculated at 1%. Identification?














Sunday, June 6, 2021

Answer to Case 642

Answer to the Parasite Case of the Week 642: Plasmodium sp. infection with relatively high (1%) parasitemia; differential diagnosis includes mixed P. falciparum/P. malariae infection and P. knowlesi infection. Recommend nucleic acid amplification testing for definitive identification.

PCR testing confirmed that this was P. knowlesi infection!

This interesting case highlights the difficulty in diagnosing P. knowlesi infection, given that many of its key morphologic features in humans overlap with those of P. falciparum and P. malariae. Like P. falciparum, high parasitemias may be observed, and thin delicate rings - occasionally with double chromatin dots ("headphone" forms) and applique forms - may be seen. Conversely, all stages of P. knowlesi are commonly seen in peripheral blood, unlike most cases of P. falciparum, so that late stage trophozoites and schizonts are also seen. Many of these later stage forms resemble those of P. malariae, such as "band form" late stage trophozoites. Of note, P. malariae does not reach high levels of parasitemia (1% would be unexpectedly high).


Given this complexity, PCR confirmation is important for understanding the nature of infection and guiding therapy.


Tuesday, June 1, 2021

Case of the Week 641

This week's case was generously donated by Dr. Alexander Fenwick and includes some beautiful images. 

The following objects were seen in a sputum specimen from a patient living in Eastern Kentucky. This patient was receiving corticosteroid therapy for poorly-controlled COPD. Identification?

Gram stain (10x and 100x magnification)


Wet mount:




Sunday, May 30, 2021

Answer to Case 641

 Answer to the Parasite Case of Week 641: Strongyloides stercoralis L3 (filariform) larvae.

As mentioned in the comments, other items on the differential diagnosis include larvae of the hookworms and Ascaris lumbricoides. The larvae of these nematodes are only rarely seen during the initial stage of infection, in which larvae migrate to the lung before reaching their permanent destination in the intestinal tract. For that reason, it is very rare to identify them in clinical specimens. In comparison, S. stercoralis has an ongoing autoinfection cycle in humans which results in recurrent migration of L3 larvae through the lung. This normal low-level of autoinfection is often subclinical and allows the infection to persist for decades. However, immunocompromised patients (such as those receiving corticosteroids like this patient) are at risk for hyperinfection, during which large numbers of L3 larvae leave the intestinal tract and migrate to the lungs and other organs. This is the common scenario in which larvae are found in respiratory specimens.

In addition to the clinical indicators of strongyloidiasis (patient from Kentucky, receiving immunosuppressive agents), there are a few morphologic features that can be used for differentiating S. stercoralis larvae from other nematode larvae found in the lung. One of the primary features is the shape of the tail. S. stercoralis L3 larvae have a subtly-notched tail, whereas the hookworm L3 larvae (the stage found in the lung, and rarely in unfixed stool examined several days after passage) have a pointed tail. I believe that A. lumbricoides L3 larvae also have a pointed tail - can anyone tell me for sure?



Monday, May 24, 2021

Case of the Week 640

Here's a fun case for you all - submitted for arthropod identification. Thoughts?



Sunday, May 23, 2021

Answer to Case 640

 Answer to the Parasite Case of the Week 640: Pseudoscorpion

Despite the scary look of this arthropod's front pincers (enlarged pedipalps), it is not a scorpion and does not harm humans. In fact, pseudoscorpions can be helpful; Dwight Ferris pointed out that they feed on other arthropods pests that you don't want in your house such as carpet beetles, book lice, ants and clothes moths. 

The main way to tell a pseudoscorpion apart from a true scorpion is that the former is much smaller (usually < 5 mm long) and lacks a telson (venom bulb) and aculeus (stinger) at the end of their abdomen. Of note, both pseudoscorpions and scorpions are arachnids and have 8 legs in their adult form - just like ticks and mites.

Pseudoscorpions may occasionally be submitted to the laboratory after concerned individuals find them in their home and bring them to their physician. That is probably how we received this one. However, Chuck Blend also noted that they are commonly found in the library, 'hanging out' between the pages of old books. You can also find them out in nature, under stones, leaf litter, tree bark and mulch. 

Monday, May 17, 2021

Case of the Week 639

This week's case was generously donated by Drs. Timothy Y. Chou and Roberta J. Seidman. The specimen is a corneal biopsy in an elderly woman who had been receiving ocular steroid treatment (but no systemic immunocompromising agents). The patient went on to develop bilateral punctate keratitis, and corneal biopsy showed the following objects:

H&E, 600x and 1000x

Tissue Gram stain, 1000x
What is the most likely diagnosis? What additional studies would you recommend to confirm the diagnosis?


Sunday, May 16, 2021

Answer to Case 639

Answer to Case of the Week 639: Microsporidia spores. 

As many of you noted, the differential diagnosis includes Toxoplasma gondii tachyzoites. 

Here are some of the key morphologic features:

  • Location in the cornea. [T. gondii is usually found in the posterior chamber of the eye (e.g., retina)]
  • Small oval shape with well-defined contours on H&E:

Unfortunately, T. gondii tachyzoites are much less defined on H&E - they can be very difficult to see. They often don't even have a nice crescent shape like we seen on Giemsa-stained air-dried impression smears. They often just look like little blobs in tissue.
  • Strong Gram-positivity on tissue Gram stain. (In comparison, T. gondii tachyzoites do not stain well, and may appear Gram-negative).
Other considerations would include small fungi such as Candida glabrata. Therefore, a panel of histochemical stains may also be useful. Microsporidia spores may be focally GMS positive, but aren't usually uniformly positive like yeasts are. Also, microsporidia spores will stain focally positive with an acid fast stain, strongly positive with warthin-starry stain, and have a polar dot-like positivity with PAS. They are also often birefringent with polarized light.

If you still wanted to do additional studies to confirm your diagnosis, I would recommend immunohistochemistry and PCR for T. gondii, and transmission electron microscopy. Microsporidia spores are beautifully detailed on TEM. This is still a conventional method for microsporida genus/species identification. If available, you could perform strong trichrome staining on the tissue or corneal scrapings. Finally, you could perform a broad range amplification and sequencing assay for microsporidia. There are a number of different species that infect the eye, so while you would start with a PCR for Encephalitozoon hellem (PCR for Encephalitozoon species are available in some reference labs), a negative result wouldn't rule out infection with other microsporidia (e.g., Vittaforma corneae, Nosema ocularum, Microsporidium spp., Trachipleistophora hominis).

So some of you may be asking why I included a case of microsporidiosis on my parasite blog. You are correct in that it is not longer considered a parasite! However, microsporidia are still routinely identified in clinical parasitology in many labs, so it's a good entity to be familiar with.  

Tuesday, May 11, 2021

Case of the Week 638

This week's case was generously donated from Drs. Cynthia Magro and Lars Westblade. The following object was identified in an hematoxylin and eosin stained tissue section of toenail in a patient with onychomycosis. Identification?




Sunday, May 9, 2021

Answer to Case 638

Answer to the Parasite Case of the Week 638: Not a human parasite; seed.

This is a small seed that likely became embedded in the nail. Botanist Dr. Mary Parker commented that "I would rule out a grass/cereal seed, as there is clearly an embryo (radicle and cotyledon) embedded in starchy endosperm, the whole surrounded by an epidermis and cuticle. The central vascular strand can be seen in the radicle, with pro-vascular cells in the cotyledon. It must be a small seed but in the absence of a scale bar, it is difficult to say more."  I learned from Dr. Cynthia Magro who donated this case that the patient has onychomycosis, so it is understandable how a small seed could have become trapped within a thick, roughened nail. 

Here are some of the morphologic details for those of you who are interested!



Monday, May 3, 2021

Case of the Week 637

Welcome back to the first Monday of the month! It's time for our monthly case from Idzi Potters and the Institute of Tropical Medicine in Antwerp. The following structures were found in a stool specimen from a patient originally from the Democratic Republic of the Congo. He presented with long standing diarrhea (occasionally bloody), intermittent abdominal pain, decreased appetite and unintentional weight loss. They are approximately 200 micrometers long.


What is the most likely identification?

Sunday, May 2, 2021

Answer to Case 637

 Answer to Parasite Case of the Week 637: Schistosoma intercalatum

This was definitely a tricky case! The eggs strongly resemble those of Schistosoma haematobium, but stool would be an unusual source for this parasite, and the eggs in this case are larger than what would be expected for S. haematobium (usual size is 110 to 170 micrometers long). In comparison, S. intercalatum eggs are most often found in stool and measure 140 to 240 micrometers long. They also characteristically have an equatorial bulge as seen in one of the images from this case:



Of note, Schistosoma intercalatum has a very limited geographic distribution, being found primarily in the Congo area. Therefore, getting a travel history can be extremely helpful. As Marc Couturier pointed out on Twitter, the other major consideration is S. guineensis due to the morphologic similarities of the eggs of the two species. If a location had not been provided, then reporting out "Schistosoma intercalatum/S. guineensis" would be best.   

Monday, April 26, 2021

Case of the Week 636

This week's case was donated by one of our intrepid infectious diseases fellows, Dr. Geno Tai, who was travelling across country and found these arthropods in his lodging. Identification? Photos and video courtesy of his friend and travel-mate, Dr. Chris Hwang.







Sunday, April 25, 2021

Answer to Case 636

 Answer to the Parasite Case of the Week 636: Cimex sp. 

Given the location (hotel in North America), this is most likely Cimex lectularis, the common bed bug.  However, we would want to have a closer examination to be sure. It looks like we have a couple of different life cycle stages here. Also, at least one squished well-fed one - nice job Geno!  


Here is a good resource for information.

Monday, April 19, 2021

Case of the Week 635

This week's case features a fun finding in a concentrated wet prep of stool stained with iodine. The case and photograph are from Blaine Mathison and Madison Sant. The object below measures approximately 35 micrometers in diameter. Identification?


Sunday, April 18, 2021

Answer to Case 635

 Answer: Entamoeba coli, supernucleate cyst. Typical E. coli cysts have 8 nuclei, but I'm counting at least 18 nuclei in this one. My first thought when I saw this photograph was - holy moly E. coli! Thanks again to Blaine and Madison for donating this fun case.