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):
What is your identification? What time should blood be collected for this examination?
6 comments:
More microfilaria? OK, the plot thickens. We can learn from the first case and apply the gained knowledge to this case.
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, Wucheria, 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 separate from the immediate anterior nuclei. This eliminates the possibility of the Brugia malayi and timori, over that these are “far fetched” geographically. We are left with two candidates Loa loa and Wucheria 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 out Loa loa. The only culprit left is Wucheria bancrofti.
Many thanks to Idzi and Dr. Pritt for another educational opportunity.
Florida Fan
Oops, I almost forgot to stay up to collect the blood.
Florida Fan
Geographically, Wuchereria bancrofti overlaps several other medically important filaria, a critical evaluation of all morphologic criteria (especially size and nuclear arrangement) should be done to ensure a correct diagnosis. Microfilariae of W. bancrofti are 240-300μm long, possess a relatively short headspace, the tail is anucleate (in contrast to Loa loa) and tapers to a point. 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 in Brugia malayi).
W. bancrofti exhibits nocturnal periodicity, and the optimum time for blood collection for microscopy (blood smears) is at night, for antigen detection blood can be collected at any time.
W. bancrofti was named after physician Otto Wucherer and parasitologist Joseph Bancroft.
Fun fact: Otto Wucherer studied medicine at the University of Tuebingen and there is a very popular local Wucherer‘s bakery across the street of the Institute for Tropical medicine.
just a quick note of gratitude... much appreciation and many thanks to all the originators and contributors for this invaluable and wonderful resource! it really can't be said enough what a great learning/teaching tool this website is! cheers to you!
Wuchereria bancrofti with mf sheath not staining on giemsa, very fine body nuclei and 1:1 cephalic space ratio (lenght and width); night blood sampling
Thank you for the kind words, Sean. I'm glad you've found the blog to be a useful research!
Bobbi
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