Tuesday, October 26, 2021
Tuesday, October 19, 2021
Sunday, October 17, 2021
Answer to the Parasite Case of the Week 657: Plasmodium vivax
Thanks to all of the great comments on this case! There are so many classic features of P. vivax here, that it makes for a fabulous teaching slide. Florida Fan very nicely outlined all of the diagnostic features along with his thought process for coming to the final identification:
1/ The ring is fairly large, and the infected red cell is larger than the not infected. As such, there is a predilection for reticulocytes. Either P. vivax or P. ovale.
2/ The mature trophozoites are ameboid form, showing them to be highly Vivacious. More than likely P. vivax.
3/ The schizont in the third picture demonstrates more than twelve merozoites, P. ovale does not usually have that many. (on average, 8)
4/ The gametocyte in the fourth picture is not Falciform, it occupies almost the entire red cell. Though there is a little bit of fimbriation, all evidence gathered so far including the geographic area are consistent with an identification of P. vivax.
Here is a composite image of the 4 forms shown in this case:
Tuesday, October 5, 2021
It's time for our monthly case with Idzi Potters and the Institute of Tropical Medicine, Antwerp:
The following was seen in a urine sediment from a backpacker returning to Belgium following a 2-month's trip in Northern Senegal. During his travels, he reports being bitten by insects, drinking and eating local foods, and swimming in fresh water lakes. He is asymptomatic, but is concerned that he may has picked up a parasite along the way.
How would you interpret this finding?
Monday, October 4, 2021
Answer to the Parasite Case of the Week 656: mite, probable contaminant from the environment. Not likely of human medical significance.
As several readers noted, this mite is not one of the 2 human pathogenic mites, Sarcoptes scabei or Demodex. Instead, it is likely a mite from the environment, such as Dermatophagoides, the dust mite. The presence of many squamous epithelial cells in the background would support this idea:
You can read the following posts for more information for how to differentiate the various mites found in human specimens:
Case of the Week 634: Free-living mite found in stool
Case of the Week 196: Differentiating Sarcoptes scabei from other mites
Case of the Week 601: Key identifying features of Sarcoptes scabei
Monday, September 27, 2021
Sunday, September 26, 2021
Answer to the Parasite Case of the Week 655: Microsporidia spores. Nucleic acid amplification/sequencing and/or electron microscopy is required for genus and species level identification.
Microsporidia that are commonly implicated in corneal infection include Vittaforma corneae and Encephalitozoon hellem.
As noted by Dr. Harsha Sheorey, the Ryan’s modified Trichrome stain was created by his friend and colleague, Dr Norbert Ryan. This stain has now become a standard staining technique for these organisms, and what was used in this case. The microsporidia spores stain bright red against a blue background.
Monday, September 20, 2021
This week's case is of a middle-aged man with a painful lesion on the dorsum of his foot. He recently returned from Brazil, during which he swam in the ocean, walked barefoot on the beach, and ate local foods. An excisional biopsy was performed and submitted to the clinical microbiology lab to rule out a possible parasite. The specimen received was an excised ellipse of skin on which there was a central defect measuring ~ 5 mm in diameter:
Sunday, September 19, 2021
Answer to the Parasite Case of the Week 654: Tunga sp. flea
I encourage you to check out the posts in the Comments section by Kosta and Florida Fan who give us an excellent description of the taxonomy, morphology, epidemiology, and clinical presentation of this parasitic flea.
Here are some of the diagnostic features from this case:
Tunga sp. eggs measuring ~0.6 mm long:
Monday, September 13, 2021
This week's case was generously donated by Drs. Alex Fenwick and Julie Ribes at the University of Kentucky. The following structure was retrieved from bronchial washings of a patient with end-stage lung disease due to cystic fibrosis.
Sunday, September 12, 2021
Answer to the Parasite Case of the Week 653: Not a human parasite; most likely a mucus cast.
As noted by Florida Fan, "The object did not have any internal organization nor visible external anatomy. It displays a ribbon like morphology being flat and slender especially at the bend."
Sam had a similar thought and suggested that since the "patient had cystic fibrosis it may be some kind of mucous plug."
To test these hypotheses, we can gently manipulate the object. Mucus usually separates easily whereas a true nematode has a firm, rubbery cuticle and is harder to tear. As CA noted, although not a first choice, we could also put a section through for histopathology. Histopathologic examination can be extremely helpful in several instances, such as when looking for the characteristic lateral cords of the anisakids (see Case of the Week 177) or the uterine branches of Taenia spp. proglottids (See Case of the Week 361).
Thanks again to Drs. Ribes and Fenwick for donating this interesting case!
Monday, September 6, 2021
Happy Labor Day weekend to my American readers! It's the first Monday of the month, and time for our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following structures were seen in Ziehl-Neelsen stained sputum specimen for acid fast bacilli, thus prompting additional examination of direct wet mounts. The patient had recently from Sicily.
Ziehl-Neelsen stained sputum specimen:
Direct wet mount:
Sunday, September 5, 2021
Answer to the Parasite Case of the Week 652: Strongyloides stercoralis L3 (filariform) larvae.
As nicely described by Luis, "We can see in photo 2 an esophagus almost as long as the intestine, the tail is sharp and has notches (photo 3)."
The notches are classic and can be seen in both the the Ziehl-Neelsen (ZN) stained preparation and wet prep (inset), (arrows).
The ZN stain had been performed to screen for acid fast bacilli (AFB). AFBs would stain bright red with the carbol fuchsin dye, whereas the larva is only stained here with the methylene blue counter stain.
This case goes well with last week's, in which we saw L1 (rhabditiform) larvae of S. stercoralis.
Thanks again to Idzi for donating this great case!
Monday, August 30, 2021
This week's case is from Dr. Ioana Bujila and her colleagues at the Department of Parasitology at the Swedish Public Health Agency. The following were seen in a formalin-ethyl acetate concentration of feces from a young girl with recent travel to India.
Identification? Any additional tests that you would like to conduct?
Sunday, August 29, 2021
Answer to the Parasite Case of the Week 651: Strongyloides sp. rhabditiform larvae, as evidenced by the short buccal cavity and genital primordium. ALSO in this interesting case are unembryonated and fully embryonated eggs. Eggs are NOT usually shed in the stool in Strongyloides stercoralis infection. So how do we explain these findings? Are these Strongyloides eggs? Or something else? Is there a mixed infection here?
Based on my own interpretation and your comments, I've come up with the 5 possible scenarios to explain the findings in this case:
Scenario 1. Both the larvae and eggs are those of S. stercoralis. As mentioned above, S. stercoralis eggs are not usually shed in stool. However, eggs may rarely be seen in very heavy cases of strongyloidiasis, such as our previous Case of the Week 615 which showed larvae, adults and eggs containing fully embryonated larvae. This scenario would mean that this patient has a potentially serious infection with heavy diarrhea, resulting in passage of eggs before they can hatch in the bowel. As mentioned by Anonymous, it would be helpful to inquire about signs and symptoms of respiratory tract involvement, and if present, examine the sputum for S. stercoralis filariform larvae. Simiarly, Nema suggested obtaining a complete blood count to assess for peripheral eosinophilia, which is commonly seen in cases of hyperinfection.
Scenario 2. We have a MIXED infection, with S. stercoralis larvae (not eggs) AND hookworm eggs. The hookworm egg in the video was fully embryonated, which is unusual for hookworm, but can be seen if the specimen is allowed to sit at room temperature for a while without being placed in fixative.
Scenario 3. A minor variation of the above is that we have a MIXED infection with S. stercoralis eggs (fully embryonated), hookworm eggs (unembryonated), and S. stercoralis rhabditiform larvae.
Scenario 4. A completely different consideration is that this is Strongyloides fuelleborni infection. S. fuelleborni is a zoonotic parasite of non-human primates and humans in Africa and parts of Asia (e.g., Papua New Guinea) in which eggs rather than larvae are shed in stool. The eggs are usually shed in an embryonated state, rather than unembryonated like hookworm, so this doesn't explain why we are also seeing unembryonated eggs. Also, larvae are not usually seen with S. fuelleborni infection. Therefore, this scenario is unlikely.
Scenario 5. Last, but not least, this could be 3-way infection with S. fuelleborni, S. stercoralis, AND hookworm. This unlikely trio would explain the presence of embryonated eggs (S. fuelleborni), unembryonated eggs (hookworm) and Strongyloides sp. rhabditiform larvae (S. stercoralis).
So how do we resolve this conundrum?? Well, we could perform stool PCR or culture to determine the actual identity of the organisms present. However, this is time consuming and these tests are not widely available. Another option is to simply report a probable mixed infection S. stercoralis and hookworm in order to cover all of our bases and ensure that the patient was adequately treated. S. stercoralis is usually treated with ivermectin, whereas hookworm is usually treated with albendazole, mebendazole, or pyrantel pamoate; thus our report could impact the drugs administered.
How would you have handled this case? Feel free to write in and let me know!
UPDATE - we now have PCR confirmation for mixed S. stercoralis and Ancylostoma duodenale!
Tuesday, August 24, 2021
Monday, August 23, 2021
Answer to the Parasite Case of the Week 650: Male Ascaris lumbricoides
As nicely stated by Florida Fan, "Ah Ha, once more the male round worm finds its way out. Judging by the curved tail and the size, it’s a male Ascaris lumbricoides. The female is longer and larger with a straight tail. Hopefully this is the only one in the patient, and though terrifying, it’s good riddance for the host."
A. lumbricoides females can be up to 35 cm long (range of fully mature females is 20-35 cm), whereas males are slightly smaller at 15-30 cm long.
Adults usually reside in the small intestine, but can occasionally migrate to ectopic locations such as the appendix and pancreatic duct. As seen in this case, they can also travel in a retrograde manner against peristalsis, up through the stomach, the eosphagus, and out the mouth or nose. Yikes!
Thanks again to Seema for donating this classic case.
Tuesday, August 10, 2021
Sunday, August 8, 2021
Answer to the Parasite Case of the Week 649: Non-parasitic insect, a springtail (Collembola). As Blaine mentioned, there is no definitive evidence that it is in the actual specimen. To me, it looks like it was squished on top of the slide - perhaps during cover-slipping, or possibly in the stain/other reagents. If this was my case, I wouldn't include it in the final report since that would just cause confusion for the ordering provider and patient. I'd just admire it and show it to my trainees 😊. The iridescent colors are beautiful!
Monday, August 2, 2021
Sunday, August 1, 2021
Answer to the Parasite Case of the Week 648: Most likely Strongyloides stercoralis filariform larva. Recommend examining the tail to look for a characteristic "notched" tail, (which is unfortunately not visible in the images in this case), and obtaining stool specimens for ova and parasite examinations and Strongyloides agar plate culture.
As mentioned by several readers, there are other filariform larvae that should also be considered in this case, such as those of Ascaris lumbricoides and the hookworm larvae. These larvae may rarely be seen during their initial lung migration stage in association with Loeffler's syndrome. S. stercoralis differs from these other nematodes in that the filariform larvae migrate to the lungs repeatedly during the long lifecycle in humans as part of an internal autoinfection process., and are therefore more likely to be found in sputum and BAL specimens than other intestinal nematodes. Also, immunocompromised patients are at risk for strongyloides hyperinfection in which large numbers of larvae migrate to the lung, causing a potentially life-threatening syndrome with bacterial sepsis and lung damage. Many S. stercoralis larvae may be found in respiratory specimens during this syndrome.
I've featured this case from Dr. Seema B. to discuss the differential of nematode larvae in human respiratory specimens, as well as to show the beauty of these helminths in Pap-stained preparations. They make a striking image! Thank you again to Dr. B. for sharing this case.
Monday, July 26, 2021
Sunday, July 25, 2021
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
Sunday, July 18, 2021
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:
As noted by Idzi "Always spectacular! Poor cricket…"
Monday, July 5, 2021
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?