? Diphyllobothrium
Proglottids of D. latum
Scientific classification
Kingdom: Animalia Phylum: Platyhelminthes Class: Cestoda Subclass: Eucestoda Order: Pseudophyllidea Family: Diphyllobothriidae Genus: Diphyllobothrium
Species
D. latum D. pacificum D. cordatum D. ursi D. dendriticum D. lanceolatum D. dalliae D. yonagoensis Image File history File links Diphyl_proglottidE.JPG proglottids of Diphyllobothrium latum. ... Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anenomes) Placozoa (trichoplax) Subregnum Bilateria (bilateral symmetry) Acoelomorpha (basal) Orthonectida (flatworms, echinoderms, etc. ... Classes Monogenea Trematoda Cestoda Turbellaria The flatworms (Platyhelminthes, Greek platy: flat; helminth: worm) are a phylum of relatively simple soft-bodied invertebrate animals. ... Orders Subclass Cestodaria Amphilinidea Gyrocotylidea Subclass Eucestoda Aporidea Caryophyllidea Cyclophyllidea Diphyllidea Lecanicephalidea Litobothridea Nippotaeniidea Proteocephalidea Pseudophyllidea Spathebothriidea Tetraphyllidea Trypanorhyncha In biology, Cestoda is the class of parasitic flatworms, called tapeworms, that live in the digestive tracts of vertebrates as adults and often in the bodies of various animals as juveniles. ... Pseudophyllid cestodes (order pseudophyllidea) are a kind of flatworm with multiple segments (proglottids) and two bothria or sucking grooves as adults. ...

Diphyllobothriasis is caused by the infestation of tapeworms, of the genus Diphyllobothrium. The principal species causing Diphyllobothriasis is Diphyllobothrium latum, known as the broad or fish tapeworm, or broad fish tapeworm. D. latum is the longest tapeworm in humans, averaging ten meters long. Adults can shed up to a million eggs a day. D. latum is a pseudophyllid cestode that infects fish and mammals. It is morphologically very similar to other members of the genus Diphyllobothrium, but can sometimes be distinguished by host. Even this is not always possible, as there have been twelve other species of this genus reported to infect humans, especially Diphyllobothrium dendriticum (the salmon tapeworm), which has a much larger range (the whole northern hemisphere). D. latum is endemic to Scandinavia, western Russia, and the Baltics, though it is now also present in North America, especially the Pacific Northwest. Tapeworm can mean: Tapeworm, parasitic flatworms that live as adults in the digestive tracts of vertebrates. ... In biology, a genus (plural genera) is a grouping in the classification of living organisms having one or more related and morphologically similar species. ... Tapeworm can mean: Tapeworm, parasitic flatworms that live as adults in the digestive tracts of vertebrates. ... Orders Subclass Cestodaria Amphilinidea Gyrocotylidea Subclass Eucestoda Aporidea Caryophyllidea Cyclophyllidea Diphyllidea Lecanicephalidea Litobothridea Nippotaeniidea Proteocephalidea Pseudophyllidea Spathebothriidea Tetraphyllidea Trypanorhyncha In biology, Cestoda is the class of parasitic flatworms, called tapeworms, that live in the digestive tracts of vertebrates as adults and often in the bodies of various animals as juveniles. ... Groups Conodonta Hyperoartia Petromyzontidae (lampreys) Pteraspidomorphi (early jawless fish) Thelodonti Anaspida Cephalaspidomorphi (early jawless fish) Galeaspida Pituriaspida Osteostraci Gnathostomata (jawed vertebrates) Placodermi Chondrichthyes (cartilaginous fish) Acanthodii Osteichthyes (bony fish) Actinopterygii (ray-finned fish) Sarcopterygii (lobe-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) A fish is a poikilothermic (cold-blooded) water-dwelling... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... Comparative anatomy is the study of similarities and differences in organisms. ... Species Diphyllobothriasis is caused by the infestation of tapeworms, of the genus Diphyllobothrium. ... Endemic, in a broad sense, can mean belonging or native to, characteristic of, or prevalent in a particular geography, race, field, area, or environment; Native to an area or scope. ... World map showing North America A satellite composite image of North America North America is a continent in the northern hemisphere bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the south by the Caribbean Sea, and on the west by the...

In adults, proglottids are usually relatively wide (hence the name broad tapeworm). As in all pseudophyllid cestodes, the genital pores open midventrally. Orders Subclass Cestodaria Amphilinidea Gyrocotylidea Subclass Eucestoda Aporidea Caryophyllidea Cyclophyllidea Diphyllidea Lecanicephalidea Litobothridea Nippotaeniidea Proteocephalidea Pseudophyllidea Spathebothriidea Tetraphyllidea Trypanorhyncha In biology, Cestoda is the class of parasitic flatworms, called tapeworms, that live in the digestive tracts of vertebrates as adults and often in the bodies of various animals as juveniles. ...

Several other Diphyllobothrium species have been reported to infect humans, but less frequently; they include D. pacificum, D. cordatum, D. ursi, D. lanceolatum, D. dalliae, and D. yonagoensis.

Life cycle

Life cycle of D. latum. Click the image to see full-size.

Adult tapeworms may infect humans, canids, felines, bears, pinnipeds, and mustelids, though the accuracy of the records for some of the nonhuman species is disputed. Image File history File links D_latum_LifeCycle. ... Image File history File links D_latum_LifeCycle. ... Genera Alopex Atelocynus Canis Cerdocyon Chrysocyon Cuon Dusicyon Fennecus Lycalopex Lycaon Nyctereutes Otocyon Pseudalopex Speothos Urocyon Vulpes Canidae is the family of carnivorous and omnivorous mammals commonly known as canines. ... Subfamilies Felinae Pantherinae Acinonychinae Machairodontinae (extinct) All cats are members of the family Felidae. ... Genera Ailuropoda Ursus Tremarctos Arctodus (extinct) A bear is a large mammal of the order Carnivora, family Ursidae. ... Families Odobenidae Otariidae Phocidae Pinnipeds (fin-foots, lit. ... Subfamilies Lutrinae Melinae Mellivorinae Taxidiinae Mustelinae Mustelidae is a family of carnivorous mammals. ...

Immature eggs are passed in feces of the mammal host (the definitive host, where the worms reproduce). Under appropriate conditions, the eggs mature (in approximately 18 to 20 days) and yield oncosphere larvae which develop into coracidia (ciliated larvae). After ingestion by a suitable freshwater crustacean such as a copepod (the first intermediate host) the coracidia develop into procercoid larvae. Following ingestion of the copepod by a suitable second intermediate host, typically a minnow or other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum). The plerocercoid larvae are the infective stage for the definitive host (including humans). In parasitology, an intermediate host is an organism that is infected with a parasite that will not reproduce sexually within it, while a definitive host is one in which the parasite reproduces. ... cross-section of two cilia, showing 9+2 structure A cilium (plural cilia) is a fine projection from a eukaryotic cell that constantly beats in one direction. ... Classes Class Branchiopoda Subclass Phyllopoda Subclass Sarsostraca Class Remipedia Order Enantiopoda Order Nectiopoda Class Cephalocarida Order Brachypoda Class Maxillopoda Subclass Mystacocarida Subclass Copepoda Subclass Branchiura Subclass Pentastomida Subclass Tantulocarida Subclass Thecostraca Infraclass Cirripedia Class Ostracoda Order Metacopina Subclass Myodocopa Subclass Podocopa Class Malacostraca Subclass Eumalacostraca Subclass Hoplocarida Subclass Phyllocarida The... Orders Calanoida Cyclopoida Gelyelloida Harpacticoida Misophrioida Monstrilloida Mormonilloida Platycopioida Poecilostomatoida Siphonostomatoida Copepods are small animals living in the sea and nearly every freshwater habitat. ... In parasitology, an intermediate host is an organism that is infected with a parasite that will not reproduce sexually within it, while a definitive host is one in which the parasite reproduces. ... A larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians). ...

Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, for example, trout, perch, and walleyed pike. In this case, the sparganum can migrate to the musculature of the larger predator fish and mammals can acquire the disease by eating these later intermediate infected host fish raw or undercooked. After ingestion of the infected fish, the plerocercoids develop into immature adults and then into mature adult tapeworms which will reside in the small intestine. The adults attach to the intestinal mucosa by means of the two bilateral grooves (bothria) of their scolex. The adults can reach more than 10 m in length in some species such as D. latum, with more than 3,000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces. Eggs appear in the feces 5 to 6 weeks after infection. Rainbow trout (Oncorhynchus mykiss) Biwa trout (Oncorhynchus masou subsp) Trout is the common name given to a number of species of freshwater fishes belonging to the salmon family, Salmonidae. ... Diagram showing the small intestine In biology the small intestine is the part of the gastrointestinal tract between the stomach and the large intestine (colon). ... The mucous membranes (or mucosa) are linings of ectodermic origin, covered in epithelium, that line various body cavities and internal organs. ...

The best way for humans to avoid infection is not to eat undercooked fish. Also, because human feces is an important mechanism for spreading eggs, proper disposal of sewage can cut down on infection of fish and thus of humans.

Geographic distribution

Diphyllobothriasis occurs in areas where lakes and rivers coexist with human consumption of raw or undercooked freshwater fish. Such areas are found in the Northern Hemisphere (Europe, newly independent states of the former Soviet Union (NIS), North America, Asia), and in Uganda and Chile. Northern Hemisphere highlighted in yellow. ... A satellite composite image of Europe Europe is the worlds second-smallest continent in terms of area, covering around 10,790,000 km² (4,170,000 sq mi) or 2. ... World map showing North America A satellite composite image of North America North America is a continent in the northern hemisphere bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the south by the Caribbean Sea, and on the west by the... Asia is the largest and most populous of the Earths continents. ...

Clinical features

Diphyllobothriasis can last for decades if untreated. Most infections are asymptomatic. Manifestations may include abdominal discomfort, diarrhea, vomiting, and weight loss. Vitamin B12 deficiency with pernicious anemia may occur, but has not for several decades in D. latum infections, possibly because of improved nutrition. In one test, nearly half of the ingested vitamin was absorbed by D. latum in otherwise healthy patients, while 80-100% was absorbed by the worm in patients with anemia. It is not known why anemia occurs in some cases but not others. Massive infections may result in intestinal obstruction. Migration of proglottids can cause cholecystitis or cholangitis. Pernicious anemia refers to a type of autoimmune anemia. ... Nutrition is the study of the relationship between diet and states of health and disease. ... Cholecystitis is inflammation of the gallbladder. ... Primary sclerosing cholangitis (PSC) is an inflammatory disease of the bile duct, which leads to cholestasis (blockage of bile transport to the gut). ...

More women are infected than men, and this is probably because they are more likely to be cooks, rather than because of morphological differences. Female (left) and male Common Pheasant, illustrating the dramatic difference in form between the sexes Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. ...

Diagnosis and treatment

Microscopic identification of eggs in the stool is the basis of specific diagnosis. Eggs are usually numerous and can be demonstrated without concentration techniques. Examination of proglottids passed in the stool is also of diagnostic value.

Diagnostic tool:

• Microscopy
• Morphologic comparison with other intestinal parasites

Though it is difficult to identify the eggs or proglottids to the species level, the distinction is of little medical importance because, like most adult tapeworms in the intestine, all members of this genus respond to the same drugs. Praziquantel is the drug of choice. Alternatively, niclosamide can also be used to detach the worms so they can be passed with feces. Microscopy is any technique for producing visible images of structures or details too small to otherwise be seen by the human eye, using a microscope or other magnification tool. ... Praziquantel (Biltricide) is an antiparasitic medication primarily used for the treatment of schistosomiasis (Snail Fever) and fascioliasis (Liver Flukes). ... Niclosamide is a teniacide (tenia- referring to tapeworm) in the Anthelmintic family especially effecive against cestodes that infect humans. ...

References

• http://www.dpd.cdc.gov/dpdx/HTML/Diphyllobothriasis.htm
• Roberts, Larry S. and Janovy, John Jr. Gerald D. Schmidt and Larry S. Roberts' Foundations of Parasitology, Seventh edition. 2005.