Welcome back to our microfilariae block from Idzi Potters and the Institute of Tropical Medicine, Antwerp! We are down to the last TWO specimens. This week's case is from a skin specimen - both skin samples AND a subcutaneous nodule (removed from the upper arm). The patient is a young man from Brazil. Here is the nodule: And here are the skin scarification specimens (read more about scarification vs. skin snips HERE): Carazzi stain: Giemsa stain: The microfilariae are approximately 300 micrometers in length. What is your diagnosis ..read more

 Answer to the Parasite Case of the Week 745: Mansonella streptocerca microfilariae Florida Fan and Anonymous pointed out the small size and the source of skin as key features for  diagnosing Mansonella streptocerca infection. Idzi also noted on LinkedIn that "A nice little detail is the etiology of the name “streptocerca”! It is derived from “strepto” meaning “twisted chain” and “cerca” meaning “tail”. The row of single round nuclei in its tail do resemble a chain (or necklace) in my opinion. The prefix “strepto” is also used for streptococcus - which indeed also forms “chains ..read more

We have moved onto microfilariae found in SKIN SNIPS - what fun! There are only a couple to choose from. Can you tell which one this is? The microfilariae are approximately 200 micrometers long. Carazzi stain Giemsa stain ..read more

 Answer to the Parasite Case of the Week 744: Mansonella perstans microfilariae. As described by Florida Fan, "This is a rather small microfilaria, its width is only about half the diameter of the surrounding neutrophils. The Carrazi stain [a hematoxylin-based stain] did not show a sheath either. As such, we can definitely rule out all the sheathed and large microfilaria. We know that we are dealing with Mansonella species. The tail of this Mansonella is not curved , this allows us to eliminate Mansonella streptocerca (strepto = curved, cerca = tail) [and also the source is not tissue]. T ..read more

 We are in the home stretch for the microfilariae! Can you believe that we have just a few more to go? (Unless I decide to repeat some ?)  This week's case shows microfilariae that are approximately 200 micrometers long. The patient is a resident of Brazil and has moderate peripheral eosinophilia. He is otherwise asymptomatic.  Carazzi stain (Knott's concentration): Giemsa stain (thick blood film ..read more

 Answer to the Parasite Case of the Week 743: Brugia timori microfilariae. This was one of the tougher cases, but everyone did a great job narrowing the differential to Brugia. As noted by Florida Fan and Anonymous, we can immediately rule out Mansonella species based on the small size (length and diameter) of the microfilariae. Florida Fan also notes that the sheath is visible, confirming that we are dealing with Loa loa, Wuchereria bancrofti or the Brugia genus.  He then details his method for coming to an exact diagnosis: "First the column of nuclei is so compact that we can ..read more

Welcome back for more microfilariae from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following microfilariae were seen in Giemsa-stained thick blood films from a man living on Alor Island, Indonesia. They measure approximately 305-315 micrometers in length.  What is your identification? What is your primary differential ..read more

 Answer to the Parasite Case of the Week 742: Wuchereria bancrofti microfilariae. I really enjoyed reading the comments on this case. FloridaFan provided this excellent description of his approach to microfilariae identification: "First the width of the worm is about the same as that of the surrounding neutrophils. Second, its length is greater than 200 micrometers. Third, it has a sheath. Now we know we are dealing with Loa loa, Wuchereria, or the Brugia ones, not with any little pesky Brugia. The next consideration is that the column of nuclei is continuous, the terminal nuclei are not ..read more

This week's case features another beautiful example of microfilariae in blood. The patient is from sub-Saharan Africa and presents with chronic swelling of his left leg. The microfilariae measure approximately 270 µm in length.  Carazzi stain (Knott's concentration): Giemsa Stain (thick blood film) What is your identification? What time should blood be collected for this examination ..read more

 Answer to the Parasite Case of the Week 741: Mansonella ozzardi As many of you noted, we can get to an identification of Mansonella sp. by the small size (length of just 175 micrometers, and the width less than the surrounding white blood cells). There is also no visible sheath, which is supportive of the diagnosis.  So the next question is - which Mansonella is present?? As FloridaFan mentioned, the tip of the tail is pointed rather than blunt, which leads us away from M. perstans. Also, the source is not skin snips, so M. streptocerca is unlikely. That leaves M. ozzardi by de ..read more