''Fasciolopsis'' () is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

trematode Trematoda is a class of flatworms known as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive host ...

s. They are also known as giant intestinal flukes. Only one

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

is recognised: ''Fasciolopsis buski''. It is a notable parasite of medical importance in humans and veterinary importance in pigs. It is prevalent in Southern and Eastern Asia. The term for infestation with ''Fasciolopsis'' is

fasciolopsiasis Fasciolopsiasis results from an infection by the trematode ''Fasciolopsis buski'', the largest intestinal fluke of humans (up to 7.5 cm in length). Signs and symptoms Most infections are light, almost asymptomatic. In heavy infections, sympto ...

''Fasciolopsis buski''

''Fasciolopsis buski'' is commonly called the giant intestinal

fluke Fluke may refer to: Biology * Fluke (fish), a species of marine flatfish * Fluke (tail), the lobes of the tail of a cetacean, such as dolphins or whales, ichthyosaurs, mosasaurs Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ...

, because it is an exceptionally large parasitic fluke, and the largest known to parasitise humans. Its size is variable and a mature specimen might be as little as 2 cm long, but the body may grow to a length of 7.5 cm and a width of 2.5 cm. It is a common

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

of humans and pigs and is most prevalent in

Southern Southern may refer to: Businesses * China Southern Airlines, airline based in Guangzhou, China * Southern Airways, defunct US airline * Southern Air, air cargo transportation company based in Norwalk, Connecticut, US * Southern Airways Express, M ...

and

Southeastern Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...

. It is a member of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Fasciolidae Fasciolidae is a family of trematodes and includes several parasites involved in the veterinary and medical sciences, which cause the disease Fasciolosis. Fasciolidae is divided into five genera by Olson et al. 2003. The family's various species ...

in the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Plagiorchiida Plagiorchiida is a large order of trematodes, synonymous to Echinostomida. They belong to the Digenea, a large subclass of flukes. This order contains relatively few significant parasites of humans. The following families are placed here, organ ...

. The Echinostomida are members of the

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

Trematoda Trematoda is a Class (biology), class of flatworms known as flukes. They are obligate parasite, obligate internal Parasitism, parasites with a complex biological life cycle, life cycle requiring at least two Host_(biology), hosts. The intermedia ...

, the flukes. The fluke differs from most species that parasitise large mammals, in that they inhabit the gut rather than the liver as ''

Fasciola ''Fasciola'', commonly known as the liver fluke, is a genus of parasitic trematodes. There are two species within the genus ''Fasciola'': ''Fasciola'' ''hepatica'' and ''Fasciola'' ''gigantica'', as well as hybrids between the two species. Bot ...

'' species do. ''Fasciolopsis buski'' generally occupies the upper region of the

small intestine The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the p ...

, but in heavy infestations can also be found in the

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

and lower regions of the intestine. ''Fasciolopsis buski'' is the cause of the pathological condition

. In London,

George Busk George Busk FRS FRAI (12 August 1807 – 10 August 1886) was a British naval surgeon, zoologist and palaeontologist. Early life, family and education Busk was born in St. Petersburg, Russia. He was the son of the merchant Robert Busk and his ...

first described ''Fasciolopsis buski'' in 1843 after finding it in the

duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...

of a sailor. After years of careful study and self experimentation, in 1925, Claude Heman Barlow determined its life cycle in humans.

Morphology

''Fasciolopsis buski'' is a large,

dorsoventrally Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

flattened fluke characterized by a blunt Anatomical terms of location, anterior end, undulating, unbranched cecum, ceca (sac-like cavities with single openings), tandem Wiktionary:dendritic, dendritic Testicle, testes, branched ovaries, and ventral Sucker (parasitic worms anatomy), suckers to attach itself to the Host (biology), host. The Acetabulum (morphology), acetabulum is larger than the oral sucker. The fluke has extensive Wiktionary:vitelline, vitelline Follicle (anatomy), follicles. It can be distinguished from other fasciolids by a lack of cephalic cone or "shoulders" and the unbranched ceca.

Life cycle

Adults produce over 25,000 eggs every day; these take up to seven weeks to mature and hatch at 27–32 °C. Immature, unembryonated eggs are discharged into the intestine and feces, stool. In two weeks, eggs become embryonated in water, and after about seven weeks, tiny parasitic organisms called miracidia hatch from the eggs, which then go on to invade a suitable snail intermediate host. Several species in the genera ''Segmentina'' and ''Hippeutis'' serve as intermediate hosts. In the snail the parasite undergoes several developmental stages (sporocysts, rediae, and cercariae). The cercariae are released from the snail and encyst as metacercariae on aquatic plants such as Eleocharis dulcis, water chestnut, water caltrop, Lotus Flower, lotus, bamboo, and other edible plants. The mammalian final host becomes infected by ingesting metacercariae on the aquatic plants. After ingestion, the metacercariae excyst in the

in about three months and attach to the intestinal wall. There they develop into adults (20 to 75 mm by 8 to 20 mm) in approximately three months, remaining attached to the intestinal wall of the mammalian hosts (humans and pigs). The adults have a life expectancy, life span of about one year.

References

External links

Centers for Disease Control and Prevention (CDC)

BioLib

The Taxonomicon

ZipcodeZoo

*Fasciolopsiasis in children: Clinical,Sociodemographic Profile and outcome. Indian Journal of Medical Microbiology2017 vol 35, issue 4 page 551-554 DOI:10.4103/ijmm.IJMM_17_7 * http://www.ijmm.org/text.asp?2017/35/4/551/224440 {{Taxonbar, from=Q3279537 Fasciolidae Trematode genera Monotypic protostome genera Parasitic helminths of humans