CDC Diphyllobothriasis

Several members of the _______ family Diphyllobothriidae are known to infect humans.

cestode (tapeworm)

These pseudophyllidean cestodes have a __(grooves), instead of suckers as in the cyclophyllidean cestodes (the group including nearly all human-infecting species).

scolex bearing bothria

All species associated with human diphyllobothriid infections have marine or aquatic life cycles and
transmission occurs via ingestion of __.

undercooked fish

Recent research incorporating morphologic and molecular data has led to the re-classification and re-naming of most of the human
infecting __.

diphyllobothriids

Diphyllobothrium latum), the “____________”, is usually assumed to be the most common agent of human diphyllobothriasis.

broad fish tapeworm

(1) Eggs are passed of defenitive host

unembryonated in feces

(2) Under appropriate conditions, the eggs mature (approximately _days) yield oncospheres which develop into a coracidia

18 to 20

(2) Under appropriate conditions, the eggs mature (approximately 18 to 20 days) yield oncospheres which develop into a _____. hatch from eggs and ingested by the first intermediate host ________.

coracidia, crustaceans.

After ingestion by a suitable crustacean (first intermediate host) the coracidia develop into __

procercoid larvae

Procercoid larvae are released from the crustacean upon predation by the second intermediate host (usually a small fish) and migrate into the deeper tissues where they develop into a _ (spargana), which is the infectious stage for the definitive host

plerocercoid larvae

Because humans do not generally eat these small fish species raw, the second intermediate host probably does not represent an important source of human infection. However, these small second intermediate
hosts can be eaten by larger predator species that then serve as ___.

paratenic hosts

tissue

humans (and other definitive host species) acquire the parasite via consumption of undercooked paratenic host fish

musculature

In the definitive host, the plerocercoid develops into adult tapeworms in the ________.

small intestine

Adult diphyllobothriids attach to the intestinal mucosa by means of two bilateral groves (bothria) of their

scolex

The adults can reach more than _ m in length, with more than ___proglottids.

10, 3,000

Immature eggs are discharged from the (up to 1,000,000 eggs per day per worm) and are passed in the feces.

proglottids

Proglottids are the segments that make up the body___, each containing reproductive organs (hermaphroditic) that produce eggs.

(strobila) of a tapeworm

Eggs appear in the feces ____ weeks after infection.

5 to 6

Intermediate and paratenic hosts include a wide diversity of _, commonly perch and pike for Dibothriocephalus latus and salmon for D. nihonkaiense

freshwater and marine fishes

Diagnostic Stage

Unembryonated egg

Infective Stage

Plerocercoid larva