Tuesday, November 16, 2021

Case of the Week 661

The following microfilariae were seen on Giemsa-stained preparations of whole blood following the Knott's concentration procedure. They are between 180 to 200 microliters in length. No travel history was initially available. Identification?

Thanks to Heather Morris for these beautiful photos.


Anonymous said...

Beautiful case, we may not see this microfilarium except when challenged in a proficiency. This is my pathway of reasoning. First these microfilaria are from the blood, we can rule out all tissue or sub cutaneous microfilaria. Second, these don’t have a sheath and this rule out Wucheria bancrofti, Loa loa as well as the two species of Brugyia. We are left with the species of Mansonella.
Both Mansonella streptocerca and ozardi usually present themselves with a curved tail or the nuclei end at the tail, only Mansonella perstans has a truncated tail lie the ones in the photographs.
Florida Fan

Idzi P. said...

Pretty sure that it is Mansonella perstans.
One trick to identify it as Mansonella is to compare the microfilaria's diameter to the diameter of the WBCs' nuclei. Mansonellas are about half of this diameter - all the others have about the same diameter.
After that, note the more intensely staining nucleus in the tip of the tail (it seems "bigger" than the previous ones), which is quite typical for M. perstans.

Idzi P. said...

One additional remark: the more intensely staining nucleus in the tip of the tail is best seen after Giemsa staining.
Presence (or absence) of a sheath is tricky after Giemsa staining, as not all microfilriae sheaths will reliably stain with Giemsa.

Asaf said...

Mansonella pentrans, due to the size, blunt tail and short head space.

Bernardino Rocha said...

Mansonella perstans, indeed.

Salbrent said...

Awesome. Thanks again!