Microscopy

Eggs
Diphyllobothrium spp. eggs are oval or ellipsoidal and range in size from 55 to 75 µm by 40 to 50 µm. There is an operculum at one end that can be inconspicuous, and at the opposite (abopercular) end is a small knob that can be barely discernible. The eggs are passed in the stool unembryonated.

A	B

A, B: Eggs of D. latum in an iodine-stained wet mount. Note the knob at the abopercular end in Figure B. Images courtesy of the Oregon State Public Health Laboratory.

C	D

C, D: Eggs of Diphyllobothrium latum.

Adults
Adults of Diphyllobothrium spp. may be 4-10 meters in length.  The scolex is elongated, 1mm by 3mm, with two shallow, longitudinal grooves. As proglottids mature, they may break off from the stroblia, in lengths containing few to many segments.  Proglottids are broader than they are long and range from 2 to 4 mm long by 10 to 12 mm wide.  The uterus is coiled in rosette appearance and the genital pore is at the center of the proglottid.  There are numerous testes that appear in the lateral fields of each proglottid.

E	F

E: Section of an adult D. latum containing many proglottids.  The scolex was not present in this specimen.  Image courtesy of the Florida State Public Health Laboratory.
F: Close-up of a few of the proglottids from the specimen in Figure E, showing the rosette-shaped uterus at the center of each proglottid.

G	H

G, H: Carmine-stained proglottids of D. latum, showing the rosette-shaped ovaries.

I

I: Scolex of D. latum.

J	K

J, K: Eggs within the proglottids of Diphyllobothrium sp., observed in an intestinal biopsy specimen stained with hematoxylin and eosin (H&E).  Images taken at 500x magnification.  Images courtesy of the University of Washington Medical Center, Seattle, WA.