n.
Any of various ribbonlike, often very long flatworms of the class Cestoda, that lack an alimentary canal and are parasitic in the intestines of vertebrates, including humans.
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tapeworm - Cestoda
American Heritage Dictionary:
tape·worm |
n.
Any of various ribbonlike, often very long flatworms of the class Cestoda, that lack an alimentary canal and are parasitic in the intestines of vertebrates, including humans.
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Britannica Concise Encyclopedia:
tapeworm |
(click to enlarge)
Principal features of the beef tapeworm (Taenia saginata). The head, (credit: © Merriam-Webster Inc.)
Principal features of the beef tapeworm (Taenia saginata). The head, (credit: © Merriam-Webster Inc.)
For more information on tapeworm, visit Britannica.com.
McGraw-Hill Science & Technology Encyclopedia:
Cestoda |
A subclass of tapeworms including most of the members of the members of the class Cestoidea. All species are endoparasites of vertebrates, living in the intestine or related ducts.
Like other members of the class, the cestodes have no digestive tract or mouth. Nutrition presumably occurs by absorption of food through the body surface. The body is usually very elongated and tapelike and frequently divided into segments, or proglottids, with replication of the hermaphroditic reproductive systems. In a few species there is duplication of both male and female organs within a single segment. The anterior end is usually modified into a holdfast organ, the scolex. Since a digestive tract is completely absent, the scolex is of solid construction, typically highly muscular with sucking depressions and hooks (see illustration).
Scolices and mature proglottids of (a) Taenia saginata, (b) T. solium, and (c) Dibothriocephalus. (After T. I. Storer and R. L. Usinger, General Zoology, 3d ed. McGraw-Hill, 1957)
The worms require carbohydrate for growth and reproduction, and this requirement is satisfied only from the host ingesta. On the other hand, nitrogenous nutrients and many micronutrients may be obtained from the body stores of the host; deleting such materials from the host's diet has no appreciable effect on the worms.
Most authorities agree that the tapeworms are ancient parasites, probably evolving as parasites of the earliest fishes. It seems probable that the tapeworms did not evolve from trematodes or other present-day groups of parasitic flatworms. Their ancestry may be directly derived from the acoele or rhabdocoele turbellarians and represents a line of evolution which is completely independent of other parasitic flatworms. These relationships remain obscure in the absence of any fossil record. See also Cestoidea; Turbellaria.
Oxford Food & Nutrition Dictionary:
tapeworm |
Parasitic intestinal worm; infection is acquired by eating raw or undercooked infected pork (Taenia solium), beef (T. saginata), or fish (Diphyllobothrium latum). Eggs are shed in the faeces and infect the animal host. Cysticercosis is infection of human beings with the larval stage by ingestion of eggs from faecal contamination of food and water.
Columbia Encyclopedia:
tapeworm |
tapeworm, name for the parasitic flatworms forming the class Cestoda. All tapeworms spend the adult phase of their lives as parasites in the gut of a vertebrate animal (called the primary host). Most tapeworms spend part of their life cycle in the tissues of one or more other animals (called intermediate hosts), which may be vertebrates or arthropods.
Anatomy and Function
An adult tapeworm consists of a knoblike head, or scolex, equipped with hooks for attaching to the intestinal wall of the host (which may be a human), a neck region, and a series of flat, rectangular body segments, or proglottids, generated by the neck. The chain of proglottids may reach a length of 15 or 20 ft (4.6-6.1 m). Terminal proglottids break off and are excreted in the feces of the host, but new ones are constantly formed at the anterior end of the worm. As long as the scolex and neck are intact the worm is alive and capable of growth. A rudimentary nervous system and excretory system run the length of the worm, through the proglottids. However, there is no digestive tract; the worm absorbs the host's digested food through its cuticle, or outer covering.
Reproduction
Each proglottid contains a complete set of male and female reproductive organs that produce the sex cells. Fertilization is internal; in most species cross fertilization between two adjacent worms is necessary, but in a few species self-fertilization may occur between two proglottids of the same worm, or within the same proglottid. In some species the fertilized eggs are shed continuously and leave the host's body in the feces; in others the fertilized eggs are stored until the proglottid is filled with them and the entire proglottid is then shed. The eggs develop into embryos with a hard outer shell; these do not hatch until they are eaten by a suitable intermediate host.
Humans as Tapeworm Hosts
Human tapeworm infestations are most common in regions where there is fecal contamination of soil and water and where meat and fish are eaten raw or lightly cooked. In the case of the human tapeworm most common in the United States (the beef tapeworm, Taenia saginata) the usual intermediate host is a cow, which ingests the proglottid while drinking or grazing. The round-bodied embryos, equipped with sharp hooks, hatch and bore through the cow's intestinal wall into the bloodstream, where they are carried to the muscles. Here each embryo encloses itself in a cyst, or bladder; at this stage it is called a bladder worm. During the bladder worm stage the embryo develops into a miniature scolex; it remains encysted until the muscle is eaten by a primary host, in this case a human. If the scolex has not been killed by sufficient cooking of the meat, it sheds its covering and attaches to the intestinal wall, where it begins producing proglottids.
A human tapeworm common in Mexico, the pork tapeworm (T. solium), has a similar life cycle, with a pig as the usual intermediate host. The fish tapeworm, Diphyllobothrium latum, transmitted to humans from fish, especially pike, is common in Asia and in Canada and the northern lake regions of the United States. This tapeworm has a more elaborate life cycle, involving both a fish and a crustacean as intermediate hosts. The dwarf tapeworm, Hymenolepsis nana, is transmitted through fecal contamination and is common in children in the southeastern United States. There are also several tapeworms for whom humans the usual intermediate host; among these, the dog tapeworm, Echinococcus granulosis, spends its adult phase in the intestines of dogs.
Consequences of Infestation
Intestinal tapeworm infestation frequently occurs without symptoms; occasionally there is abdominal discomfort, diarrhea, constipation, or weight loss. The presence of tapeworm proglottids in clothing, bedding, or feces is the usual sign of infestation. Treatment is with quinacrine hydrochloride (Atabrine) or niclosamide, which kill the worm.
The most serious tapeworm infestation in humans is caused by the ingestion of T. solium eggs through fecal contamination, which results in the person serving as the intermediate, rather than the primary, host. The embryos migrate throughout the body, producing serious illness if they lodge in the central nervous system. In many poorer regions of the world, the larvae of T. solium are a major cause of human epilepsy. The embryos of the dog tapeworm encyst in various internal organs of humans, most commonly in the liver. The cysts produced by these embryos are called hydatid cysts, and the infestation of the liver is called hydatid disease.
Classification
Tapeworms are classified in the phylum Platyhelminthes, class Cestoda.
Dictionary of Cultural Literacy: Health:
tapeworm |
A worm with a long, flat body that can live in the human intestines as a parasite. Infestation with a tapeworm usually occurs as the result of eating raw meat or fish that contains the immature form of the worm.
Oxford Dictionary of Biochemistry:
tapeworm |
any parasitic flatworm (phylum Platyhelminthes) belonging to the class Cestoda.
| tanning, tannin, tannic acid | |
| tare, target, target discovery |
Saunders Veterinary Dictionary:
tapeworm |
Members of the genera Taenia, Diphyllobothrium, Dipylidium and Echinococcus; includes infestation with members of the tapeworm class Eucestoda. Most tapeworm infestations have little apparent effect on the health of farm livestock and are mostly esthetic problems in companion animals.
- armed t. — taenia solium.
- beef t. — taenia saginata.
- broad t. — diphyllobothrium latum.
- dog t. — dipylidium caninum.
- fish t. — diphyllobothrium latum.
- hydatid t. — echinococcus granulosus.
- pork t. — taenia solium.
- unarmed t. — taenia saginata.
Random House Word Menu:
categories related to 'tapeworm' |
- Diseases and Infestations - tapeworm: parasitic flatworm that lives in human intestine
- Worms
Rhymes:
tapeworm |
Bradford's Crossword Solver's Dictionary:
tapeworm - Cestoda |
See crossword solutions for the clue Tapeworm.
Wikipedia on Answers.com:
Cestoda |
This article describes the flatworm. For the medical condition, see Tapeworm infection.
"Tapeworm" redirects here. For the band, see Tapeworm (band). For the early name for a computer "worm", see Computer worm.
| Cestoda | |
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Scientific classification  |
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| Kingdom: | Animalia |
| Phylum: | Platyhelminthes |
| Class: | Cestoda |
| Subclasses and orders | |
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Cestoda (Cestoidea) is the name given to a class of parasitic flatworms, commonly called tapeworms, of the phylum Platyhelminthes. Its members live in the digestive tract of vertebrates as adults, and often in the bodies of various animals as juveniles. Over a thousand species have been described, and all vertebrate species can be parasitised by at least one species of tapeworm. Several species parasitise humans after being consumed in underprepared meat such as pork (Taenia solium), beef (T. saginata), and fish (Diphyllobothrium spp.), or in food prepared in conditions of poor hygiene (Hymenolepis spp. or Echinococcus spp.).
T. saginata, the beef tapeworm, can grow up to 12 m (40 ft); other species may grow to over 30 m (100 ft).[1]
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Contents
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Anatomy
Scolex
The worm's scolex ("head") attaches to the intestine of the definitive host. In some species, the scolex is dominated by bothria (tentacles), which are sometimes called "sucking grooves", and function like suction cups. Other species have hooks and suckers that aid in attachment. Cyclophyllid cestodes can be identified by the presence of four suckers on their scolex.[2]
While the scolex is often the most distinctive part of an adult tapeworm, it is often unnoticed in a clinical setting as it is inside the patient. Thus, identifying eggs and proglottids in feces is important.
Body systems
The main nerve centre of a cestode is a cerebral ganglion in its scolex. Motor and sensory innervation depends on the number and complexity of the scolex. Smaller nerves emanate from the commissures to supply the general body muscular and sensory ending. The cirrus and vagina are innervated, and sensory endings around the genital pore are more plentiful than other areas. Sensory function includes both tactoreception and chemoreception. Some nerves are only temporary.
Proglottids
The body is composed of successive segments (proglottids). The sum of the proglottids is called a strobila, which is thin, and resembles a strip of tape. From this is derived the common name "tapeworm". Like some other flatworms, cestodes use flame cells (protonephridia), located in the proglottids, for excretion. Mature proglottids are released from the tapeworm's posterior end and leave the host in feces.
Because each proglottid contains the male and female reproductive structures, they can reproduce independently. Some biologists have suggested that each should be considered a single organism, and that the tapeworm is actually a colony of proglottids.
The layout of proglottids comes in two forms, craspedote, meaning proglottids are overlapped by the previous proglottid, and acraspedote which indicates a non-overlapping conjoined proglottid.[3]
Once anchored to the host's intestinal wall, the tapeworm absorbs nutrients through its skin as the food being digested by the host flows past it and it begins to grow a long tail, with each segment containing an independent digestive system and reproductive tract. Older segments are pushed toward the tip of the tail as new segments are produced by the neckpiece. By the time a segment has reached the end of the tail, only the reproductive tract is left. It then drops off, carrying the tapeworm eggs to the next host, since, by that point, the proglottid is, in essence, a sac of eggs.[4]
Reproduction and life cycle
![[icon]](http://en.wikipedia.org/wiki/File:Wiki_letter_w_cropped.svg){kind=small} |
This section requires expansion with: more detail including reproduction, references. |
True tapeworms are exclusively hermaphrodites; they have both male and female reproductive systems in their bodies. The reproductive system includes one or many testes, cirrus, vas deferens and seminal vesicle as male organs, and a single lobed or unlobed ovary with the connecting oviduct and uterus as female organs. There is a common external opening for both male and female reproductive systems, known as genital pore, which is situated at the surface opening of the cup-shaped atrium.[5][6] Even though they are sexually hermaphroditic, self-fertilization is a rare phenomenon. In order to permit hybridization, cross-fertilization between two individuals is often practiced for reproduction. During copulation, the cirrus of one individual connects with that of the other through the genital pore, and then exchange their spermatozoa.
The life cycle of tapeworms is simple in the sense that there are no asexual phases as in other flatworms, but complicated in that at least one intermediate host is required as well as the definitive host. This life cycle pattern has been a crucial criterion for assessing evolution among Platyhelminthes.[7] Many tapeworms have a two-phase life cycle with two types of host. The adult Taenia saginata lives in the gut of a primate such as a human. Proglottids leave the body through the anus and fall onto the ground, where they may be eaten with grass by animals such as cows. This is known as the intermediate host. The juvenile form migrates and establishes as a cyst in the intermediate hosts body tissues such as muscles, rather than the gut. They cause more damage to this host than it does to its definitive host. The parasite completes its life cycle when the intermediate host passes on the parasite to the definitive host, this is usually done by the definitive host eating an infective intermediate host, such as possibly a human with a preference for raw meat—in whose gut the adult Taenia establishes itself.[8]
See also
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Wikimedia Commons has media related to: Cestoda |
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Wikispecies has information related to: Cestoda |
Footnotes
- ^ "The Persistent Parasites". Time Magazine (Time Inc). 1957-04-08. http://www.time.com/time/magazine/article/0,9171,809356-1,00.html.
- ^ "flatworm." Encyclopædia Britannica. Encyclopaedia Britannica Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2010.
- ^ http://www.nhm.ac.uk/research-curation/research/projects/cestode-life-cycle/database/glossary.jsp
- ^ Marvistavet.com
- ^ Cheng TC (1986). General Parasitology (2nd edn). Academic Press, Division of Hardcourt Brace & Company, USA, pp. 402-416. ISBN 0121707555
- ^ McDougald LR (2003). Cestodes and trematodes. In: Diseases of Poultry, 11th edn (YM Saif, HJ Barnes, AM Fadly, JR Glisson, LR McDougald & DE Swayne, eds). Iowa State Press, USA, pp. 396-404. ISBN 0813807182
- ^ Llewellyn J (1987). "Phylogenetic inference from platyhelminth life-cycle stages". Int J Parasitol. 17 (1): 281–89. doi:10.1016/0020-7519(87)90051-8.
- ^ Mayoclinic.com
References
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This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations. (February 2008) |
- Campbell, Reece, and Mitchell, Biology, 1999
- Merck Manual of Medication Information, Second Home Edition, Online Version, Tapeworm Infection 2005
- Mayo Clinic Website on infectious diseases, Mayo Clinic - Tapeworm Infection, 2006
- Medline Plus - Taeniasis (tapeworm infection)
- University of South Carolina - School of Medicine - Cestodes (tapeworms)
This article incorporates public domain material from websites or documents of the Centers for Disease Control and Prevention.
Medline Plus - Taeniasis (tapeworm infection)
External links
- Knol.google.com
- How Disgusting are Tapeworms? Article from TalktotheVet.com
- Tapeworm
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This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Translations:
Tapeworm |
Français (French)
n. - ver solitaire, ténia
Deutsch (German)
n. - Bandwurm
Ελληνική (Greek)
n. - (παθολ.) κεστοειδής σκώληξ (κν. ταινία)
Português (Portuguese)
n. - tênia (f) (Med.), solitária (f)
Русский (Russian)
длинный, плоский паразит, живущий в желудке и кишечнике животных
Español (Spanish)
n. - tenia, lombriz solitaria
Svenska (Swedish)
n. - binnikemask (zool.), bandmask (zool.)
中文（简体）(Chinese (Simplified))
肠寄生虫
中文（繁體）(Chinese (Traditional))
n. - 腸寄生蟲
العربيه (Arabic)
(الاسم) دودة من ألشريطيات, الشريطيه
עברית (Hebrew)
n. - תולעת טפילה, שרשור
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Copyrights:
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 | American Heritage Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 1994-2012 Encyclopædia Britannica, Inc. All rights reserved. Read more |
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| McGraw-Hill Science & Technology Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Oxford Food & Nutrition Dictionary. A Dictionary of Food and Nutrition. Copyright © 1995, 2003, 2005 by A. E. Bender and D. A. Bender. All rights reserved. Read more |
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| Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2012, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more |
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| Dictionary of Cultural Literacy: Health. The New Dictionary of Cultural Literacy, Third Edition Edited by E.D. Hirsch, Jr., Joseph F. Kett, and James Trefil. Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin. All rights reserved. Read more |
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Oxford Dictionary of Biochemistry. Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved. Read more | |
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| Saunders Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more |
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| Random House Word Menu. © 2010 Write Brothers Inc. Word Menu is a registered trademark of the Estate of Stephen Glazier. Write Brothers Inc. All rights reserved. Read more |
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Rhymes. Oxford University Press. © 2006, 2007 All rights reserved. Read more | |
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| Bradford's Crossword Solver's Dictionary. Collins Bradford's Crossword Solver's Dictionary © Anne Bradford, 1986, 1993, 1997, 2000, 2003, 2005, 2008 HarperCollins Publishers All rights reserved. Read more |
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| Wikipedia on Answers.com. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Cestoda. Read more |
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| Translations. Copyright © 2007, WizCom Technologies Ltd. All rights reserved. Read more |
- How do you get tapeworm?
- What do tapeworms do to you if you have them?
- How do you get a tapeworm?
- What are tapeworms?
- What is tapeworm?
- Is cestoda is the genus tapeworm?
- What is a cestoda tapeworm movement?
- What will tapeworms do to you?
- What does a tapeworm do?
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