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Tapeworm

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Revision as of 00:13, 3 December 2009

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Tapeworm
Tenia solium scolex-tapeworm.jpg
Scientific Classification
Orders

Subclass: Cestodaria

Subclass: Eucestoda

Contents

Introduction

Class Cestoda(paracitic flatworms), commonly known as the tapeworms consists of long(6m or 20 ft.), soft-bodied, legless invertebrates with bilateral symmetry. They have a primitive nervous system but have the characteristic of cephalization(having all the sensory organs concentrated in the anterior or head region). They develope from three cell layers(from outside to inside): epidermis, mesoderm, and the gastroderm, with a thick tegument protecting them from the host's digestive jucies. Also they spend their entire adult life inside the small intestine of a vertebrate. They live in the small intestine because they have no digestive system of their own and thus must rely on absorbtion of already digested nutients.(Porch, pg455) They can cause infections in many vertebrates inluding fish, dogs, cats and humans.[1]

Anatomy

The tapeworm is a long(6m or 20 ft.), soft-bodied, legless invertebrate with bilateral symmetry.[2] They are made up of a knoblike head or scolex(where most of the sensory organs are located-cephalization), a short, unsegmented neck following the scolex, and multiple flat, rectangular body segments or proglottids forms the strobila. On the external surface of the scolex there are hooks or suckers that allow the tapeworm to latch onto the inside of a host's intestines where it lives for most of its adult life.[3] Adult tapeworms have no external cilia or flagellum. The worm's body covering consists of a thick tegument which protects it from the digestive jucies of its host.(Porch, p458)

Almost all of the taeworm's metabolism is dedicated to reproduction; inside the scolex is a complete set of male and female reproductive organs. There are hardly any sensory organs in an adult tapeworme, the nerve center of a tapeworm is its scolex as well as a nerve cord running the length of the body even through the proglottids(they stop working upon detachment). They also have an excretory canal which is the only digestive system associated organ. The tapeworm has no organs for respiration or circulation and acheieves this on a celular level.[4] Each proglottid fertilizes and stores hundreds of eggs, the more mature proglottids are at the posterior end of the tapeworm. Proglottids that break off are called terminal proglottids.(Porch, p458)

Reproduction

A tapeworm's life cycle starts as an egg(once contained in a proglottid) that has been excreted in a host's feces. Once eaten by the intermediate host the egg travels to the intestine where it hatches. The newly hatched larvae(in most species it has a fully developed scolex) than burrows into and through the intestine wall into an organ or the body cavity. [5] The larvae stays in an organ(for example; the muscles, eyes, brain or almost any other organ of the body) of the intermideate .(Porch, p458) Once it is eaten by the intermedeate host it goes through the digestive system to the small intestine wherhost(which can be almost any vertebrate) untill it is consumed by the final host, though some species have multiple intermedeate hosts the scolices of larvae attatch. After attatchment to the inside of the intestine the tapeworm starts producing proglottids and the strobila(the bulk of the tapeworm's body) forms. After more developement the proglotteds start producing eggs.[6] When fully matured a proglottid breaks off(a terminal proglotted) it is excreted in the host's feces.[7]

Each proglottid contains one set of male reproductive organs and one set of female reproductive organs. In most species the male reproductive organs develope first, though there are some species in which the female reproductive organs develope first.[8]

Ecology

Tapeworms are parasitic flatworms meaning they spend their adult life inside of a host.[9] As an egg it stays on the ground or in the feces of the parent's host untill consumed by the intermediate host. The egg passes through most of the digestive system, thus at that short stage of life their enviornment is the digestive tract of the intermediate host. Once they reach the small intestine they hatch and the larvae burrows through the intestine wall. The second enviornmentin which they stay is in an organ(the brain, muscles, eyes and nearly any other organ) in their intermediate host. The tapeworm's final enviornment is its final host where it stays in the small intestine.(Porch, p458)

The tapeworm stays in the small intestine of its host for its entire adult life protected by a thick tegument. It must live there due to the fact that it has no digestive tract of its own thus it must absorbe the nutrents where most of the digestive work has been done.[10]

The tapeworm does not have any natural enimies, its only enimies are good hygene and anthelmintic agents. Humans can advoid becoming a host it by thorough cooking meats(to a temperature of 57° C or 135° F), keeping drinking water separate from sewage and feces, deworming pets, and freezing meats for a long period of time. If a human or pet becomes a host there are effective anthelmintic agents that basically wash out the tapeworm.[11]

Tapeworm Infection

Tapeworms can be caught by eating uncooked or undercooked pork, beef, or freshwater fish containing cysts. Because of this the Old Testiment dietary laws fobade the eating of pork to prevent such infections.(Porch, p461) Humans can catch them as well as pets and almost any other mammal. [12] A human can become either the final, or even intermeadate host.(Porch, p458)

Symptoms and Diagnosis

The symptomes, if any(some people do not get any), for the tapeworm infection are; nausea, weakness, abdominal pain, loss of appetite, diarrhea, weight loss and inadequate absorbtion of vitamins and nutrients(though these symptoms may vary depending on what species of tapeworm you may have and are for an intestinal infection). For an invasive infection or one in which the tapeworm leaves the intestine and forms cysts in tissues the common symptomes are; bacterial infections, neurological symptoms or seizures, fever, cystic masses or lumps, and allergic reactions to the larvae(these symptomes also differ between species). If someone thinks they have an intestinal infection, there are tests they can take to determine wether or not they really have it or not such as taking a stool test or the "scotch tape test". If they have have invasive infection a doctor may test their blood for antibodies their body may have produced to fight the tapeworm infection.[13]

Prevention and Treatment

To advoid catching the tapeworm infection you should throughly cook meats and freash water fish at a temperature of 135° F or 57° C, prolonged freezing also works, finally, careful evaluation of meat and fish will help advoid eating any of the contaminated meat. The treatments for the intestinal tapeworm infection include a single dose of praziquantel, drugs such as albendazole or praziquantel(antiparasitic drugs) and corticosteroids are used for an invasive infection. Though these drugs depend on the location of the cysts though none of these drugs are used for infections in the eyes or spinal cord because they can damage nearby tissue. [14]

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References

External Links

See Also

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