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Taenia spp

Human Tapeworms: Taenia spp. 

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Taxonomy and Origin

Tapeworms of the genus Taenia are parasitic flatworms belonging to the class Cestoda within the phylum Platyhelminthes. They are endoparasites that inhabit the small intestine of humans and other mammals. Read more

  • Phylum: Platyhelminthes
  • Class: Cestoda
  • Order: Cyclophyllidea
  • Family: Taeniidae
  • Genus: Taenia

The genus Taenia comprises several species, but three are of major medical importance in humans:

  1. Taenia saginata (beef tapeworm)
  2. Taenia solium (pork tapeworm)
  3. Taenia asiatica (Asian tapeworm)

Brief Facts

  • T. saginata can reach up to 10 meters in length.
  • T. solium causes both intestinal infection (taeniasis) and tissue infection (cysticercosis), which can affect the brain (neurocysticercosis).
  • T. asiatica is morphologically similar to T. saginata but is associated with pig viscera.
  • Humans are the definitive host, while cattle (T. saginata) and pigs (T. solium, T. asiatica) serve as intermediate hosts.
  • Transmission occurs through ingestion of raw or undercooked infected meat.

Developmental Stages

The developmental cycle of Taenia involves both intermediate and definitive hosts:

  1. Eggs (oncospheres): Released in human feces and contaminate the environment.
  2. Larvae (cysticerci): Develop in the muscle tissues of intermediate hosts (cattle or pigs) after ingestion of eggs.
  3. Adult worms: Form in the small intestine of humans when undercooked infected meat is consumed.

Lifecycle of Human Tapeworms

  1. Humans ingest raw or undercooked infected meat.
  2. The cysticercus larva evaginates and attaches to the intestinal mucosa via its scolex (head).
  3. The worm matures into an adult, producing segments (proglottids) that contain eggs.
  4. Gravid proglottids are released in human feces, contaminating soil and water.
  5. Intermediate hosts (cattle or pigs) ingest the eggs.
  6. Oncospheres hatch, migrate to muscles, and develop into cysticerci.
  7. Cycle repeats when humans consume the infected meat.

Lifecycle Diagram of Three Human Tapeworms

  • T. saginata: cysticerci in cattle muscle.

  • T. solium: cysticerci in pig muscle and possibility of human cysticercosis if eggs are ingested directly.

  • T. asiatica: cysticerci in pig liver and viscera. see more