Microbiology & infectious diseases
Parasites-gastrointestinal (not liver)
Taenia species
Author: Nat Pernick, M.D.
Last author update: 1 June 2018
Last staff update: 5 October 2020
Copyright: 2003-2024, PathologyOutlines.com, Inc.
PubMed Search: Taenia saginata[TI] cestodes full text[sb]
Table of Contents
Definition / general | Pathophysiology | Diagrams / tables | Clinical features | Diagnosis | Microscopic (histologic) description | Microscopic (histologic) images | Additional referencesCite this page: Pernick N. Taenia species. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/parasitologytaeniaspecies.html. Accessed April 18th, 2024.
Definition / general
- The cestodes Taenia saginata (beef tapeworm), T. solium (pork tapeworm) and T. asiatica (Asian tapeworm)
- T. solium can also cause cysticercosis
Pathophysiology
- 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
Images hosted on other servers:
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
- 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
