Case #172 – January 2006

A 45-year-old female noticed a long, worm-like object in her stool. The object was collected and, along with tissue sections prepared by the hospital where she was seen, submitted to the Florida public health laboratory for examination. The specimens were forwarded to CDC’s parasitology diagnostic reference laboratory for identification. Examination methods were: whole worm was examined for morphologic features (Figure A); a portion of the worm was removed (Figure B), cleared using lacto-phenol solution, flattened using two 2″ by 3″ glass slides, and examined under a dissecting microscope (Figure C); and the proglottid was ruptured to release some of the eggs and examined with a compound microscope. Images of the eggs were captured at 40× (Figure D), 100× (Figure E), and 200× (Figure F) magnification. What is your identification? Based on what criteria? Would you recommend any additional confirmatory diagnostic testing?

Figure A

Figure B

Figure C

Figure D

Figure E

Figure F

This was a case of diphyllobothriasis, caused by a cestode in the genus, Diphyllobothrium. Diagnostic morphologic features included:

a stroblia consisting of proglottids that were broader than they were long.
centrally located genital pores (Figure C, red arrow) and rosette-shaped uteri (Figure C, green arrows). These features ruled-out Taenia sp.
operculated eggs (Figure F, blue arrow) within the size range for Diphyllobothrium spp.

Figure C

Figure F

DNA was extracted from a few proglottids and a fragment of approximately 2100 base pairs was amplified by PCR from the Diphyllobothrium 18S rRNA gene. DNA sequencing analysis was performed on the amplified fragment, and the sequence showed 99% similarity with Diphyllobothrium latum 18S rRNA sequence deposited in GenBank under accession number DQ316793.