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Case #168 – November, 2005

In April 2005, DPDx telediagnosis inquiries received a request for assistance from the Oregon State Public Health Laboratory. Images from a thick and thin blood smear were submitted. Based on information that came with the specimen, the smears were most likely stained with Giemsa. The only case history available was that the patient lived in Africa until the beginning of this year. Figures A-C show what was observed on the thick smear. Figure C is a close-up of the posterior end of the object in Figure B. Figures D-F show what was observed on the thin smear. In Figure D, the object measured 300 micrometers; close-ups of the posterior and anterior ends are shown in Figures E and F, respectively. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

Figure D

Figure E

Figure F

This was a case of Bancroft’s filariasis caused by Wuchereria bancrofti. Diagnostic features included:

the presence of a sheath. Usually the sheath does not stain well with Giemsa, however it is partially visible in Figures A, D, and E.
the nuclei in the tail evenly dispersed and terminating before the end of the tail (Figures C and E). 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.
a size within range for W. bancrofti (240 to 300 μm) in stained blood films.