Cestodes (tapeworms) !
- Parasites
Flat, segmented worms with no gut. Humans can host the adult tapeworm in the bowel or, worse, its larva in tissues.
Updated 2026-11-01
What they are
Cestodes are ribbon-shaped flatworms made of a scolex that attaches to the gut and a chain of segments (proglottids). They absorb nutrients through their surface. Serious disease appears when the human acts as intermediate host and the larva forms cysts in tissues.
What they share
- Ribbon body: scolex, neck and proglottids.
- No gut; nutrients absorbed through the tegument.
- Hermaphroditic.
- Cycles with an intermediate host (pig, cattle, dog, fish), except Hymenolepis nana.
Microorganisms in this group
- Taenia soliumPork tapeworm. Undercooked pork gives the gut tapeworm; swallowing its eggs puts cysts in the brain (neurocysticercosis), a major cause of epilepsy.Exam priority: high
- Taenia saginataThe beef tapeworm. It lives for years in the gut and causes few symptoms; unlike the pork tapeworm, it does not cause cysts in humans.Exam priority: medium
- Echinococcus granulosusA tiny dog tapeworm. If a person swallows its eggs, cysts grow for years in the liver or lung (hydatid disease).Exam priority: medium
- Hymenolepis nanaThe smallest and commonest tapeworm in children. It passes from person to person without another animal and can reinfect the same child from within.Exam priority: medium
- Dibothriocephalus latusThe longest human tapeworm; it comes from raw or undercooked fish. It can steal vitamin B12 and cause megaloblastic anaemia.For completeness
Test yourself
Think of the answer, then tap the question to see it.
When does a cestode cause serious disease in humans?
When the human acts as intermediate host and the larva forms tissue cysts, as in cysticercosis or hydatid disease.
Which cestode needs no intermediate host?
Hymenolepis nana.
Which drug is used for most intestinal tapeworms?
Praziquantel.
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: CDC - DPDx - Taeniasis (CDC, 2024); Taeniasis/cysticercosis (WHO, 2022); Echinococcosis (WHO, 2021).
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Representative model, for educational purposes only.