Answer to Case 747

 Answer: Dirofilaria sp. microfilariae

This is the perfect challenge for the end of our microfilariae series! The history of finding a worm in the eye will usually make us think of Loa loa (indeed, this case was initially misdiagnosed as such), but the location of the patient (Senegal) and the unique features of the microfilariae are important clues to the actual diagnosis. You can read all about this cases HERE. I've seen a number of cases of nematodes removed from the eye - particularly from India - that were misdiagnosed as Loa loa but actually represented Dirofilaria. Adult worms from these parasites can be differentiated by size (Loa loa has a maximum length of ~7 cm, whereas Dirofilaria can be 10+ cm) and features of their cuticle. Case of the Week 513 shows the differences in cuticle nicely.  

Dirofilaria repens rarely releases microfilariae in humans, making this case particularly unique! Idzi and I both noted the interesting nuclear pattern within the microfilariae - being rather swirly with two elongated nuclei at the tip:

Thanks again to Idzi and ITM Antwerp for sharing this amazing series of cases. Next week we will move onto something entirely different 😊.

Case of the Week 746

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?

Answer to Case 746

Answer to the Parasite Case of the Week 746: Onchocerca volvulus microfilariae

This case nicely contrasts with Case 745 which shows the significantly smaller microfilariae of Mansonella perstans. Both are found in skin snips and skin scarification samples. Note that the nuclei do not go to the tail of O. volvulus as they do with M. streptocerca. 

Another great feature of this case is that Idzi included an image of a resected onchocercoma - the subcutaneous nodule containing the adult filariae:

Onchocerciasis, also known as river blindness, is a devastating disease found in parts of Sub-Saharan Africa and Latin America. It is classified as a neglected tropical disease by the World Health Organization. 

Case of the Week 745

We have moved onto microfilariae found in SKIN specimens - 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:

Answer to Case 745

 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”…" What a fun insight!

Here is an image from this case that nicely highlights these features:

Thank you all for sticking with us for this fun series of microfilariae. We have TWO left for you, so stay tuned!
 

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):

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?

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?