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For the musical collaboration named Tapeworm, see Tapeworm (band). Tapeworm is also an older name for a type of computer virus.
Cestoda is a class of parasitic flatworms, commonly called tapeworms, that live in the digestive tract of vertebrates as adults and often in the bodies of various animals as juveniles. Taenia saginata, the beef tapeworm, can grow up to 40 feet long (12 m); other species may grow to over 100 feet (30 m).[1]
[edit] SymptomsAccording to The Merck Manual, Tapeworm infestation does not usually cause any symptoms. Infection is generally recognized when the infected person passes segments of proglottids in the stool (looks like white worms), especially if a segment is moving. Some report abdominal discomfort, diarrhea, and loss of appetite. Anemia may develop in people with the fish tapeworm. Rarely, worms may cause obstruction of the intestine. And very rarely, T. solium larvae can migrate to the brain causing seizures and other neurological problems. This condition is called cysticercosis. [edit] TreatmentAccording to Medline Plus, a service of the U.S. National Library of Medicine and the National Institutes of Health; "Tapeworms are treated with medications taken by mouth, usually in a single dose. The drug of choice for tapeworm infections is niclosamide. Praziquantel and albendazole can also be used." [edit] Ingestion of eggsTapeworm eggs are generally ingested through food, water or soil contaminated with human or animal (host) feces. For example, if a pig is infected with a tapeworm, it may pass eggs or segments (proglottids) of the adult tapeworm through its feces into soil. Each segment contains thousands of microscopic tapeworm eggs. One can then ingest these eggs by eating food contaminated with the feces. Once one consumes the eggs, they develop into larvae, which can migrate out of one's intestines and form cysts in other tissues such as your lungs or liver. This type of infection is not common with beef or fish tapeworms, but can occur with the pork tapeworm — called cysticercosis — and can also occur with dog and sheep tapeworms — called echinococcosis. [edit] Ingestion of larvae cysts in meat or muscle tissueYou can also get tapeworm infection by eating raw or undercooked meat from an animal or a fish that has the larval form of the tapeworm cysts in its muscle tissue. Once you ingest them, the larvae then develop into adult tapeworms in your intestines. Adult tapeworms can measure up to 50 feet long and can survive as long as 20 years. Some tapeworms attach themselves to the walls of the intestine, where they cause irritation or mild inflammation, while others may pass through to your stool and exit your body. Unlike other tapeworms, the dwarf tapeworm can complete its entire life cycle — egg to larva to adult tapeworm — in one host. This is the most common tapeworm infection in the world and can be transmitted between humans. While being treated for certain tapeworm infections, you can reinfect yourself by ingesting tapeworm eggs shed by the adult worm into your stool. That's why you should take care to wash your hands after using the toilet. [edit] Anatomy[edit] ScolexThe worm's scolex ("head") attaches to the intestine of the definitive host. In some species, the scolex is dominated by bothria, 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. Tapeworms have sharp hooks on one side of the head which dig into the lining of the host's intestine. Once docked like a boat to the host intestinal wall, the tapeworm begins to grow a long tail. (The tapeworm’s body is basically a head segment to hold on with, a neck, and many tail segments). Each segment making up the tail is like a separate independent body, with an independent digestive system and reproductive tract. The tapeworm absorbs nutrients through its skin as the food being digested by the host flows past it. 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. When the segment drops off, it is basically just a sac of tapeworm eggs. [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. [edit] Body SystemsThe main nerve centre of a cestode is in its scolex; as a cerebral ganglion. 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. These are in the proglottids, and stop working with a detach. [edit] ProglottidsThe body is composed of successive segments (proglottids). The sum of the proglottids is called a strobila, which is thin, resembling a strip of tape, and is the source of 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. It has been suggested by some biologists 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. [edit] Life cycle
Many tapeworms have a two-phase life cycle with two types of host. The adult taenia saginata, for example 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. In the cow's body the juvenile forms migrate and establish themselves as cysts in body tissues such as muscles, rather than the gut; they cause more damage to this host than the intestinal form to its host. The parasite completes its life cycle when the grass-eater is eaten by a compatible carnivore—possibly a human with a preference for rare meat—in whose gut the adult taenia establishes itself. While being treated for certain tapeworm infections, you can reinfect yourself by ingesting tapeworm eggs shed by the adult worm into your stool.[3] [edit] TaxonomyThere are fourteen recognised orders of Cestodes: the Amphilinidea, Gyrocotylidea and 12 orders belonging to the Eucestoda. Within the Eucestoda the Spathebothriidea appear to be a sister group to the remaining 11 orders. [4] The Pseudophyllidea and Haplobothriidea appear to form a clade as do Cyclophyllidea, Nippotaeniidea and Tetrabothriidea. eworm." Bill Nye 1850-1896[5] [edit] See also
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