Monday, April 15, 2024

Case of the Week 745

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:




Monday, April 8, 2024

Case of the Week 744

 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):



Sunday, April 7, 2024

Answer to Case 744

 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]. The tail is also not pointed, this rules out Mansonella ozzardi. We only have one left with a blunt tail: Mansonella perstans which persists." 

This image nicely shows all of these features:

You have all done a great job learning to differentiate the small, unsheathed blood microfilariae (i.e. Mansonella perstans and M. ozzardi) from the larger, sheathed microfilariae. 

Of course, co-infections can occur, and the following is a stunning photograph of M. perstans and Loa loa co-infection. I think we can all appreciated that the Loa loa microfilaria is the top based on its larger size and sheath. 

Thank you for these outstanding cases, Idzi!

Next week we will finish up with the tissue microfilariae. Will you be able to tell them apart?



Monday, April 1, 2024

Parasite Case of the Week 743

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?