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:
Monday, September 20, 2021
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.