Case #284 – September, 2010

A 10-year-old immigrant from Haiti was screened for parasites at a refugee screening clinic. Stool specimens were collected in 10% formalin and polyvinyl alcohol and sent to the local state health laboratory for testing. Figures A, C, and E show what was observed at 400x magnification in a wet mount prepared from the formalin-preserved stool. Figures B, D, and F show the same fields, respectively, but in different focal planes. The objects in Figures A and C measured on average 65 micrometers long by 40 micrometers wide. The object in Figure E measured 90 micrometers long by 45 micrometers wide. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

Figure D

Figure E

Figure F

This case demonstrated a mixed infection of ascariasis, caused by Ascaris lumbricoides, and giardiasis, caused by Giardia duodenalis. Diagnostic morphologic features included:

unembryonated, fertile eggs of A. lumbricoides within the size range for the species and demonstrating a thick wall with a mammillated layer (Figures A and C).
an infertile egg of A. lumbricoides within the size range for the species (Figure E).
cysts of G. duodenalis (arrows, Figures B, D and F).

Figure B

Figure D

Figure F