HYMENOLEPIS DIMINUTA

Rat tapeworm

Common name

Adult worm lives in the small intestine of:

• Rats (definitive host)

• Occasionally humans (accidental host)

HABITAT

Rat flea

arthropods (grain beetles, fleas, or flour beetles)

IH

Rats (Norway Rats)

DH

• Rat

• man (accidental host)

Final host

T

T or F

H. diminuta is common in rodents, accidental infection in humans

Cysticercoid larva

Larval stage

Cysticercoid larva

Infective stage

Ingestion of Cysticercoid larva

MOT

accidental host

The role of man in H. diminuta is ____________

• With 4 cup-like suckers

• With unarmed rostellum

Scolex

800-1000 segments/ prolottids

No. of segments

Sac-like uterus filled with eggs

Gravid proglottids

20-60 cm

Adult length

sunny-side up fried egg

The egg of H. diminuta is said to have the appearance of a _____________________

• Round to oval

• Thick shell

• No polar filaments (key difference from H. nana)

Egg

Present

Egg: Polar thickening

absent

Egg: Polar filaments

• Indirect life cycle (requires intermediate host)

1. Eggs passed in rat feces

2. Ingestion by arthropods (grain beetles, fleas, or flour beetles)

3. Larva develops into cysticercoid inside insect

4. Rat (or human accidentally) eats infected insect

5. Larva develops into adult worm in intestine

Life cycle

• Usually asymptomatic in humans

• Heavy infection (rare):

  • Abdominal discomfort

  • Diarrhea

  • Mild weakness

Pathogenesis

• eggs in stool

Diagnostic stage

• Stool examination (direct or concentration techniques)

• Identification of characteristic eggs

Laboratory Diagnosis

• Praziquantel (drug of choice)

• Albendazole may also be used

Treatment