Monday, February 17, 2020

Case of the Week 581

This week's case was donated by Theodore Trejo. The following were seen in skin scrapings collected from a middle-aged man complaining of itching. The motile objects measure approximately 0.3 mm in length. Identification?
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Monday, February 10, 2020

Case of the Week 580

This week's case was donated by Dr. Neil Anderson. The following objects were seen in an EDTA blood specimen obtained from a patient with recent travel to sub-Saharan Africa (note that the blood was ~10 days old when the video was taken).

What additional analysis might be indicated?

Sunday, February 9, 2020

Answer to Case 580

Answer to Parasite Case of the Week 580: Loa loa microfilariae. As noted by several readers, the nuclei go to the tip of the tail, the microfilariae are relatively large, and there is faint evidence of a sheath, all of which are characteristic features for this species. As I teach my students, the nuclei "flow-a flow-a" (to the tip) in Loa loa. Another memory trick from William Sears is that the nuclei go "lower and lower" in Loa loa. Take your pick for your favorite! Remember that the sheath will not always be seen. Size is a more definitive feature in differentiating Mansonella spp. from the sheathed microfilariae.

William also mentioned that one should always check for the presence of Onchocerca volvulus co-infection, and get a microfilariae count before initiating therapy with the drug of choice for loiasis, diethylcarbamazine (DEC). In this case, the microfilaremia was calculated at 1,960 microfilariae/mL blood, which is well below the threshold of 8,000/mL at which DEC is contraindicated (thank you for calculating this Heather, and for the lovely photos in this case). DEC is also contraindicated in patients with concomitant onchocerciasis since the rapid death of O. volvulus microfilariae in the eye can lead to blindness.

What I found remarkable about this case was how long the microfilariae remained alive. They were still moving (albeit, somewhat choppily) at 10 days after blood draw, and the following image was taken of a smear make with 14 day-old blood. Not bad! According to filariasis expert, Shelly Michalski, the Project Liaison for the NIH Filariasis Research Reagent Resource Center, microfilariae are remarkably hardy, and can survive freezing -80°C. Wow!

And finally, to celebrate Valentine's day, here is this beautiful Brugia from Blaine Mathison:

Monday, February 3, 2020

Case of the Week 579

Here is our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following were seen in a direct wet preparation of an unfixed stool specimen from a patient with bloody diarrhea and recent travel to sub-Saharan Africa. The objects in question measure approximately 20 micrometers long. Identification?

Sunday, February 2, 2020

Answer to Case 579

Answer to Parasite Case of the Week 579: Entamoeba histolytica

This great case by Idzi nicely shows the directional motility of an E. histolytica trophozoite - something that is less commonly seen in the clinical laboratory as more fecal specimens are received in a fixative. This case also highlights the characteristic ingestion of red blood cells (erythrophagocytosis) by the trophozoites.

Dr. Graham Clark reminds us that non-pathogenic Entamoeba species may also ingest red blood cells that are in the environment, so correlation with clinical presentation, biopsy, antigen and/or PCR tests is also warranted.