CDC Hymenolepiasis

[Hymenolepis diminuta] [Hymenolepis nana]

Hymenolepiasis is caused by two cestodes (tapeworm) species, _________

Hymenolepis nana, Hymenolepis diminuta

Hymenolepis nana (the dwarf tapeworm, adults measuringmm in length)

15 to 40

Hymenolepis diminuta

rat tapeworm

Hymenolepis diminuta adults measuring ______ in length).

20 to 60 cm

Cestode of rodents infrequently seen in humans and frequently found in rodents.

Hymenolepis diminuta

Eggs of Hymenolepis nana are immediately infective when passed with the stool and cannot survive more than _______ in the
external environment

10 days

(1) Embryonated egg, (infective stage) when eggs are ingested by an arthropod intermediate host (2) (various species of ______ may serve as intermediate hosts), they develop into cysticercoids, which can infect humans or rodents upon ingestion

beetles and fleas

(2) they develop into_____, which can infect humans or rodents upon ingestion(they developed in insect)

cysticercoids

(3) develop into adults in the

small intestine

A morphologically identical variant, H. nana var. fraterna, infects rodents and uses arthropods as ______

intermediate hosts

(4) When eggs are ingested (in contaminated food or water or from hands contaminated with feces), the
______ contained in the eggs are released.

oncospheres

(4) The oncospheres (hexacanth larvae) penetrate the intestinal villus and ________

develop into cysticercoid larvae

(5) Upon rupture of the villus, the cysticercoids return to the intestinal lumen, evaginate ( folds or pushes outward to form an extension, pouch, or tube.) their_____

scoleces (skolex)

(6) attach to the intestinal mucosa and develop into adults that reside in the ileal portion of the small intestine producing _______

gravid proglottids

(7) Eggs are passed in the stool when released from proglottids through its ______or when proglottids disintegrate in the small intestine

genital atrium

(8) An alternate mode of infection consists of internal autoinfection, where the eggs release their ______, which
penetrates the villus continuing the infective cycle without passage through the external environment

hexacanth embryo

(9) The life span of adult worms is _____, but internal autoinfection allows the infection to persist for years.

4 to 6 weeks

_____ Developed in insect

Cysticercoid

(3)

cysticercoid-infected arthropods.

(5)

Oncosphere

(8)

genital atrium, passed in stool

(9)

autoinfection

Eggs of Hymenolepis diminuta are passed ____________ of the infected definitive host (rodents, man)

out in the feces

(1) The mature eggs are
ingested by an intermediate host (various___________)

arthropod adults or larvae

(2) and __________ are released from the eggs and penetrate the intestinal wall of the host

oncospheres

(3) which develop into cysticercoid larvae. Species from the genus Tribolium are common intermediate
hosts for H. diminuta.

The cysticercoid larvae persist through the arthropod’s morphogenesis to adulthood. H. diminuta infection is acquired by the mammalian host after______________ carrying the cysticercoid larvae

ingestion of an intermediate host

(4) Humans can be
accidentally infected through the ingestion of insects in___________, or other food items, and directly from the environment
(e.g., oral exploration of the environment by children).

precooked cereals

(4) After ingestion, the tissue of the infected arthropod is digested releasing the_____________ larvae in the stomach and small intestine.

cysticercoid

(5) Eversion (turns outward and attaches) of the _________
occurs shortly after the cysticercoid larvae are released.

scoleces

(5) Using the ________ on the scolex, the parasite attaches to the small intestine wall. Maturation of the parasites occurs within 20 days and the adult worms can reach an average of 30 cm in length

four suckers

(6) Eggs are released in the _______ from gravid that disintegrate after breaking off from the adult worms. The eggs are expelled to the environment in the mammalian
host’s feces

small intestine

(1) diagnostic stage

feces

(2)

arthropod

(3)

oncospheres

(4) Infective Stage

cysticerci

(5)

scolex

(6)

small intestine

(7)

gravid proglottids

Hymenolepis nana is the most _______________, and is encountered worldwide. In temperate areas its incidence is higher in children and institutionalized groups. Hymenolepis diminuta, while less frequent, has been reported from various areas of the world

common cause of all cestode infections

Scolex of H. nana