Diphyllobothriidean

(also referred to as Pseudophyllidean) tapeworms

Diphyllobothrium latum

Adult Diphyllobothrium spp. occur in the small intestine of fish-eating mammals. Adults are 2-12 m long, yellowish-grey in color with dark central markings caused by the centrally located uterus and eggs. With an indirect life-cycle, Diphyllobothrium latum uses first a copepod to harbor the development of the coracidium to a procercoid, and then fresh-water fish as a second intermediate host where the pleurocercoid develops. These pleurocercoids accumulate in the fish and are then infective to mammals ingesting them.

In place of having suckers on the scolex, as many members of other classes of cestode have, Diphyllobothrium has two narrow, deep muscular groves called bothria. These bothria are often indistinct. It's name, a borrowing from the Greek di- (two) + phyllodes (like leaves) + bothrion (trench); reflects the morphology of its scolex.

​The egg of Diphyllobothrium latum is 58-76 µm x 40-51 µm and bears an operculum.

Spirometra mansonoides

Spirometra mansonoides adult in cat jejunum. Adults may be found in wild carnivores and in domestic dogs and cats. These worms are morphologically similar to Diphyllobothrium with the exception that the uterus is spiraled and the vagina and uterus open separately on the ventral surface.

Adult Spirometra mansonoides found in cat vomit. Adults may survive for several years, causing little to no pathogenesis within the host.

Pleurocercoid (sparganum) of Spirometra spp. develop and grow in subcutaneous tissues.

Egg of Spirometra sp. Eggs are 65-70 µm x 35-37 µm , yellowish-brown in color, and are operculated.