Microbiology & infectious diseases

Parasites-gastrointestinal (not liver)

Taenia species

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PubMed Search: Taenia saginata[TI] cestodes full text[sb]

Nat Pernick, M.D.
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Cite this page: Pernick N. Taenia species. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/parasitologytaeniaspecies.html. Accessed February 24th, 2024.
Definition / general
  • The cestodes Taenia saginata (beef tapeworm), T. solium (pork tapeworm) and T. asiatica (Asian tapeworm)
  • T. solium can also cause cysticercosis
  • Humans are the sole definitive host
  • When humans ingest infected raw or incompletely cooked beef, the cysticercus develops into a reproductive adult in the small intestine in 2 - 3 months
  • Symptoms are rare but may include abdominal discomfort and diarrhea
Diagrams / tables

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Life cycle

Clinical features
  • For humans in good health, there are few serious symptoms associated with tapeworm infection
  • For both T. saginata and T. solium, patients may have diarrhea, constipation, flatulence, hunger pain, weight loss; rarely appendicitis
  • Most common complaint is embarrassment and discomfort when proglottids crawl out of anus
  • Taeniasis infection may compromise the immune system; in young children this may have a profound effect on their health
  • Takes 5 to 12 weeks for worm to mature into adulthood in the human intestine
  • Usually only a single worm is present at one time, although multiple worms have been reported
  • Diagnosis is made by finding eggs in stool, using direct or concentration techniques or in the perianal folds, using the cellophane tape technique
  • Eggs are spherical and measure 31 - 43 μm in diameter
  • You cannot differentiate the 3 species based on the egg alone; location (T. asciatica if infection acquired in Asia), morphologic features of the adult worm (T. saginata / T. asiatica versus T. solium) and molecular testing (T. saginata versus T. asiatica) are needed
  • The eggs of Echinococcus species have a very similar appearance but would be found in the stool of infected dogs and other canids and NOT in human stool
Microscopic (histologic) description
  • Eggs of all Taenia species are indistinguishable and should be reported only as Taenia eggs
  • Proglottids of taeniids have a characteristic lateral protrusion known as the genital pore
  • Careful injection of India ink through the genital pore, using a tuberculin needle and syringe, may succeed in outlining the uterus
  • Gravid uterus of T. saginata has 15 - 20 lateral branches, compared with 7 - 13 for T. solium
  • Proglottids may also be cleared overnight in glycerol or stained with carmine or hematoxylin using published procedures
  • If recovered, the scolex of T. saginata can be identified by the presence of four suckers and the absence of hooks on the crown or rostellum
  • Shell is thick, radially striated and contains a six hooked embryo
Microscopic (histologic) images

Contributed by Bobbi Pritt, M.D.

Taenia species eggs

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