Diagnostic features are:
- Presence of a sheath. Usually the sheath does not stain well with Geimsa, however it is partially visible in images A, C and D.
- Image D clearly show that the nuclei in the tail are evenly dispersed and seem to stop before the end of the tail. This morphologic feature distinguishes W. bancrofti from Loa loa as the nuclei in the tail extend all the way to the tip of the tail in L. loa microfilariae.
- Size is slightly larger than the range for W. bancrofti (244 to 296 μm) in stained blood films, but the amount of shrinkage may be a variable. The other morphologic features seen are sufficient to make an identification.