Monday, August 30, 2021

Case of the Week 651

 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. 

Some of these hardy eggs contained live larvae - despite the formalin:

Identification? Any additional tests that you would like to conduct?

Sunday, August 29, 2021

Answer to Case 651

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

Case of the Week 650

Greetings from New England! I'm on vacation this week, so this will be a very short case - courtesy of Dr. Seema Jabbar. The following was "coughed up" by a patient. Most likely identification?

Monday, August 23, 2021

Answer to Case 650

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

Case of the Week 649

This week's fun case was donated by Dr. Chris Hartley. The following object was seen on from material obtained by endobronchial, ultrasound-guided biopsy (Giemsa-based stain). How would you sign this case out?

Sunday, August 8, 2021

Answer to Case 649

 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

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?

Sunday, August 1, 2021

Answer to Case 648

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.