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Case #370 - April 2014

A 21-year-old female presented with swelling of the eyelid, wrist, and knee. The symptoms started after returning from a three-month trip to Cameroon in 2011.  A blood specimen was collected by her health care provider at 11:30 A.M. and smears were made and stained (NOS). Her eosinophilia at the time was 48%.  A filarial IgG4 antibody test performed a month prior and was negative.  Two worm-like structures were observed by laboratory technicians after scanning 10 stained thick smears. Images of both structures were captured (Figures A and B) and shared with CDC personnel.  As follow-up to the images, a tube of EDTA blood was sent to the DPDx Team for further evaluation.  Figure C shows what was found on a wet mount of the blood; Figures D and E are from thick and thin Giemsa-stained smears, respectively.  What is your diagnosis?  Based on what criteria?


Figure A


Figure B


Figure C


Figure D


Figure E

Case Answer

This was a case of loiasis caused by Loa loa. Morphologic features shown included:

  • presence of microfilariae in blood collected during the day.
  • robust microfilariae with a short head space and a tapered tail with nuclei spaced irregularly to the tip of the tail (Figures A, B, D, and E)
  • evidence of a sheath that did not stain with Giemsa (Figure C)

More on: Loaisis

This case and images (in part) were kindly provided by Purdue University, Indianapolis, IN. 

Images presented in the monthly case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.

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  • Page last reviewed: August 24, 2016
  • Page last updated: August 24, 2016
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