Answer to Case 742

 Answer to theParasite Case of the Week 742:Wuchereria bancroftimicrofilariae.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 withLoa loa,Wuchereria, or theBrugiaones, not with any little peskyBrugia. The next consideration is that the column of nuclei is continuous, the terminal nuclei are not separate from the immediate anterior nuclei. This eliminates the possibility of theBrugia malayiandtimori, over that these are “far fetched” geographically. We are left with two candidatesLoa loaandWuchereria bancrofti. Though the tail is not so obvious, the Carrazi stain did show that the nuclei column terminates well short from the end of the tail. This rules outLoa loa. The only culprit left isWuchereria bancrofti.An anonymous commenter also noted that " Its nuclear column is relatively loose, and individual nuclei can be visualized throughout the column. The sheath is does not stain pink with Giemsa stain (as inBrugia malayi). "These features can be nicely visualized in the photo of the Carazzi-stained Knott ' s concentration. Note that the Carazzi stain is a hematoxylin-based stain (rather than conventional Giemsa) that helps to demonstrate the sheath. It is a very useful stain to have!...
Source: Creepy Dreadful Wonderful Parasites - Category: Parasitology Source Type: blogs