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DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/taeniasis.

Taeniasis

[Taenia asiatica] [Taenia saginata] [Taenia solium]

Taenia spp. eggs in unstained wet mounts.

Taenia sp. egg in unstained wet mounts.


Mature proglottid of T. saginata, stained with India ink. Note the number of primary uterine branches (&gt12).  Image courtesy of the Orange County Public Health Laboratory, Santa Ana, CA.

Proglottid of T. saginata injected with India Ink. Image courtesy of the Orange County Public Health Laboratory, Santa Ana, CA.


 Higher magnification of the image in Figure B, showing a close-up of the eggs.  Note the characteristic striations, typical for the taeniids.  Not visible in these images are the hooks commonly seen in cestode eggs. Hooks do not stain with H&E but are refractile

Eggs of Taenia sp. in a gravid proglottids, stained with hematoxylin and eosin (H&E). Note the characteristic striations, typical for the taeniids. Not visible in these images are the hooks commonly seen in cestode eggs. Hooks do not stain with H&E but are refractile.


Causal Agents

The cestodes Taenia saginata (beef tapeworm), T. solium (pork tapeworm) and T. asiatica (Asian tapeworm). Taenia solium can also cause cysticercosis.


Life Cycle

Life cycle of Taeniasis

Taeniasis is the infection of humans with the adult tapeworm of Taenia saginata, T. solium or T. asiatica. Humans are the only definitive hosts for these three species. Eggs or gravid proglottids are passed with feces The number 1; the eggs can survive for days to months in the environment. Cattle (T. saginata) and pigs (T. solium and T. asiatica) become infected by ingesting vegetation contaminated with eggs or gravid proglottids The number 2. In the animal's intestine, the oncospheres hatch The number 3, invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci. A cysticercus can survive for several years in the animal. Humans become infected by ingesting raw or undercooked infected meat The number 4. In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years. The adult tapeworms attach to the small intestine by their scolex The number 5 and reside in the small intestine The number 6. Length of adult worms is usually 5 m or less for T. saginata (however it may reach up to 25 m) and 2 to 7 m for T. solium. The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (approximately 6 per day). T. saginata adults usually have 1,000 to 2,000 proglottids, while T. solium adults have an average of 1,000 proglottids. The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces. T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid respectively.

Geographic Distribution

Taenia saginata and T. solium are worldwide in distribution. Taenia solium is more prevalent in poorer communities where humans live in close contact with pigs and eat undercooked pork. Taenia asiatica is limited to Asia and is seen mostly in the Republic of Korea, China, Taiwan, Indonesia, and Thailand.

Clinical Presentation

Taenia saginata taeniasis produces only mild abdominal symptoms. The most striking feature consists of the passage (active and passive) of proglottids. Occasionally, appendicitis or cholangitis can result from migrating proglottids. Taenia solium taeniasis is less frequently symptomatic than Taenia saginata taeniasis. The main symptom is often the passage (passive) of proglottids. The most important feature of Taenia solium taeniasis is the risk of development of cysticercosis.

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  • Page last reviewed November 29, 2013
  • Page last updated November 29, 2013
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
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