Hymenolepiasis is infestation by one of two species of tapeworm: Hymenolepis nana or H. diminuta. Alternative names are dwarf tapeworm infection and rat tapeworm infection. The disease is a type of helminthiasis which is classified as a neglected tropical disease.
Taenia solium, the pork tapeworm, belongs to the cyclophyllid cestode family Taeniidae. It is found throughout the world and is most common in countries where pork is eaten. It is a tapeworm that uses humans as its definitive host and pigs as the intermediate or secondary hosts. It is transmitted to pigs through human feces that contain the parasite eggs and contaminate their fodder. Pigs ingest the eggs, which develop into larvae, then into oncospheres, and ultimately into infective tapeworm cysts, called cysticerci. Humans acquire the cysts through consumption of uncooked or under-cooked pork and the cysts grow into adult worms in the small intestine.
Spirometra is a genus of pseudophyllid cestodes that reproduce in canines and felines, but can also cause pathology in humans if infected. As an adult, this tapeworm lives in the small intestine of its definitive host and produces eggs that pass with the animal's feces. When the eggs reach water, the eggs hatch into coracidia which are eaten by copepods. The copepods are eaten by a second intermediate host to continue the life cycle. Humans can become infected if they accidentally eat frog legs or fish with the plerocercoid stage encysted in the muscle. In humans, an infection of Spirometra is termed sparganosis.
Taenia is the type genus of the Taeniidae family of tapeworms. It includes some important parasites of livestock. Members of the genus are responsible for taeniasis and cysticercosis in humans, which are types of helminthiasis belonging to the group of neglected tropical diseases. More than 100 species are recorded. They are morphologically characterized by a ribbon-like body composed of a series of segments called proglottids; hence the name Taenia. The anterior end of the body is the scolex. Some members of the genus Taenia have an armed scolex ; of the two major human parasites, Taenia saginata has an unarmed scolex, while Taenia solium has an armed scolex.
Taenia saginata, commonly known as the beef tapeworm, is a zoonotic tapeworm belonging to the order Cyclophyllidea and genus Taenia. It is an intestinal parasite in humans causing taeniasis and cysticercosis in cattle. Cattle are the intermediate hosts, where larval development occurs, while humans are definitive hosts harbouring the adult worms. It is found globally and most prevalently where cattle are raised and beef is consumed. It is relatively common in Africa, Europe, Southeast Asia, South Asia, and Latin America. Humans are generally infected as a result of eating raw or undercooked beef which contains the infective larvae, called cysticerci. As hermaphrodites, each body segment called proglottid has complete sets of both male and female reproductive systems. Thus, reproduction is by self-fertilisation. From humans, embryonated eggs, called oncospheres, are released with faeces and are transmitted to cattle through contaminated fodder. Oncospheres develop inside muscle, liver, and lungs of cattle into infective cysticerci.
Echinococcus granulosus, also called the hydatid worm or dog tapeworm, is a cyclophyllid cestode that dwells in the small intestine of canids as an adult, but which has important intermediate hosts such as livestock and humans, where it causes cystic echinococcosis, also known as hydatid disease. The adult tapeworm ranges in length from 3 mm to 6 mm and has three proglottids ("segments") when intact—an immature proglottid, mature proglottid and a gravid proglottid. The average number of eggs per gravid proglottid is 823. Like all cyclophyllideans, E. granulosus has four suckers on its scolex ("head"), and E. granulosus also has a rostellum with hooks. Several strains of E. granulosus have been identified, and all but two are noted to be infective in humans.
Dipylidium caninum, also called the flea tapeworm, double-pored tapeworm, or cucumber tapeworm is a cyclophyllid cestode that infects organisms afflicted with fleas and canine chewing lice, including dogs, cats, and sometimes human pet-owners, especially children.
Dwarf tapeworm is a cosmopolitan species though most common in temperate zones, and is one of the most common cestodes infecting humans, especially children.
Taenia pisiformis, commonly called the rabbit tapeworm, is an endoparasitic tapeworm which causes infection in lagomorphs, rodents, and carnivores. Adult T. pisiformis typically occur within the small intestines of the definitive hosts, the carnivores. Lagomorphs, the intermediate hosts, are infected by fecal contamination of grasses and other food sources by the definitive hosts. The larval stage is often referred to as Cysticercus pisiformis and is found on the livers and peritoneal cavities of the intermediate hosts. T. pisiformis can be found worldwide.
Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda. Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cestodaria. All tapeworms are endoparasites of vertebrates, living in the digestive tract or related ducts. Examples are the pork tapeworm with a human definitive host, and pigs as the secondary host, and Moniezia expansa, the definitive hosts of which are ruminants.
Spirometra erinaceieuropaei is a parasitic tapeworm that infects domestic animals and humans. The medical term for this infection in humans and other animals is sparganosis. Morphologically, these worms are similar to other worms in the genus Spirometra. They have a long body consisting of three sections: the scolex, the neck, and the strobilia. They have a complex life cycle that consists of three hosts, and can live in varying environments and bodily tissues. Humans can contract this parasite in three main ways. Historically, humans are considered a paratenic host; however, the first case of an adult S. erinaceieuropaei infection in humans was reported in 2017. Spirometra tapeworms exist worldwide and infection is common in animals, but S. erinaceieuropaei infections are rare in humans. Treatment for infection typically includes surgical removal and anti-worm medication.
Hymenolepis is a genus of cyclophyllid tapeworms that cause hymenolepiasis. They parasitise mammals, including humans. Some notable species are:
Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of many similar units known as proglottids—essentially packages of eggs which are regularly shed into the environment to infect other organisms. Species of the other subclass, Cestodaria, are mainly fish infecting parasites.
Diphyllobothrium mansonoides is a species of tapeworm (cestodes) that is endemic to North America. Infection with D. mansonoides in humans can result in sparganosis. Justus F. Mueller first reported this organism in 1935. D. mansonoides is similar to D. latum and Spirometra erinacei. When the organism was discovered, scientists did not know if D. mansonoides and S. erinacei were separate species. PCR analysis of the two worms has shown the two to be separate but closely related organisms.
Raillietina is a genus of tapeworms that includes helminth parasites of vertebrates, mostly of birds. The genus was named in 1920 in honour of a French veterinarian and helminthologist, Louis-Joseph Alcide Railliet. Of the 37 species recorded under the genus, Raillietina demerariensis, R. asiatica, and R. formsana are the only species reported from humans, while the rest are found in birds. R. echinobothrida, R. tetragona, and R. cesticillus are the most important species in terms of prevalence and pathogenicity among wild and domestic birds.
Taenia asiatica, commonly known as Asian taenia or Asian tapeworm, is a parasitic tapeworm of humans and pigs. It is one of the three species of Taenia infecting humans and causes taeniasis. Discovered only in 1980s from Taiwan and other East Asian countries as an unusual species, it is so notoriously similar to Taenia saginata, the beef tapeworm, that it was for a time regarded as a slightly different strain. But anomaly arose as the tapeworm is not of cattle origin, but of pigs. Morphological details also showed significant variations, such as presence of rostellar hooks, shorter body, and fewer body segments. The scientific name designated was then Asian T. saginata. But the taxonomic consensus turns out to be that it is a unique species. It was in 1993 that two Korean parasitologists, Keeseon S. Eom and Han Jong Rim, provided the biological bases for classifying it into a separate species. The use of mitochondrial genome sequence and molecular phylogeny in the late 2000s established the taxonomic status.
Moniezia expansa is commonly known as sheep tapeworm or double-pored ruminant tapeworm. It is a large tapeworm inhabiting the small intestines of ruminants such as sheep, goats and cattle. It has been reported from Peru that pigs are also infected. There is an unusual report of human infection in an Egyptian. It is characterized by unarmed scolex, presence of two sets of reproductive systems in each proglottid, and each proglottid being very short but very broad.
Raillietina tetragona is a parasitic tapeworm belonging to the class Cestoda. It is a cosmopolitan helminth of the small intestine of pigeon, chicken and guinea fowl, and is found throughout the world.
Raillietina cesticillus is a parasitic tapeworm of the family Davaineidae. Sometimes called "Broad-headed tapeworm", it infects the small intestine of chicken and occasionally other birds, such as guinea fowl and turkey, which are generally in close proximity to backyard poultry. It is a relatively harmless species among intestinal cestodes in spite of a high prevalence. In fact it probably is the most common parasitic platyhelminth in modern poultry facilities throughout the world.
Joyeuxiella is a genus of flatworms belonging to the family Dipylidiidae.
