Answer to Case 62

Great comments for this case!
Answer: microfilariae, not otherwise specified.

Although Loa loa, Wuchereria bancrofti, Mansonella spp. and Brugia spp. are all possibilities, we cannot determine the species identification without performing addition testing; specifically by making permanently stained smears of the fixed (dead) organism, and examining features such as the tail nuclei, length of the worm, and presence/absence of a sheath. Essentially, we need it to stop moving AND apply a special stain such as Giemsa or hematoxylin so that we can more adequately study its defining characteristics.

One commenter mentioned Strongyloides; this is also a possibility if the patient has disseminated strongyloidiasis, but is a less likely than the filariasis. Again, a permanently stained preparation would be necessary to make this diagnosis.

Finally, two commenters noted the presence of rouleaux formation (stacking of RBCs so that they resemble a stack of coins). I believe that this is an artifact, perhaps due to the type of anticoagulant used in this case.