Taenia saginata, the Beef Tapeworm


http://www.healthinplainenglish.com/health/infectious_diseases/tapeworm

Introduction

The beef tapeworm, Taenia saginata, is a cestode parasite acquired in humans through the ingestion of raw or poorly cooked meat of infected cows. These cows have been infected via the ingestion of human feces containing the eggs of the parasite and these cows contain viable cysticercus larvae in the muscle. Humans act as the host only to the adult tapeworms and can grow up to 25 meters in the lumen of the intestine, but are usually closer to 5 meters in length. T. saginata is closely related but distinct from the pork tapeworm, Taenia solium, which comes from eating infected or poorly cooked pig. Yet another tapeworm, T. asiatica, has been recently distinguished from T. saginata over the past 15 years. A study by Eom and Jun estimated a 4.8% genetic divergence between the two tapeworms. The mitochondrial genomes of the two tapeworms were amplified using PCR and restriction maps were constructed using 13 different restriction enzymes. In T. saginata, the tapeworm is very flexible and fragile and does not obstruct the intestine. The beef tapeworm is found all over the world, including the United States, and is often found in many countries to have greater prevalence than that of T. solium.

Agent

Binomial name: Taenia saginata

Classification and Taxonomy:

Kingdom: Animalia
Phylum: Platyhelminthes
Class: Cestodes
Order: Cyclophyllidea
Family: Taeniidae
Genus: Taenia
Subgenus: Taeniarhynchus
Species: saginata

Synonyms

Beef tapeworm, "unarmed" tapeworm

History of Discovery

Taenia saginata was first distinguished from its close relative Taenia solium by Goeze in 1782. The first report of T. saginata was in 1700 by Audry, but was unable to distinguish the proglottids of the two tapeworms. Goeze was the first to correctly describe the worm as he did in his treatise on helminthology. Leuckart was the first to show experimentally that proglottids of T. saginata fed to calfs developed into cysticerci in the calf's muscles in 1863. Lastly, Oliver was the first to discover that when humans ingested "bladder worms," they developed adult T. saginata.

Contact Information

Jon Wong, Class of '06, jonwong@stanford.edu
Stanford University
Parasites & Pestilence: Infectious Public Health Challenges
Prof. D. Scott Smith, ssmith@stanford.edu


This site was created for Human Biology 103: Parasites & Pestilence at Stanford University. Last updated 5/23/06.