Digenea (Gr. ''Dis'' – double, ''Genos'' – race) is a

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 differently ...

trematodes 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 ...

in the

Platyhelminthes The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") are a phylum of relatively simple bilaterian, unsegment ...

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclatu ...

, consisting of

parasitic 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 ha ...

flatworm The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") are a phylum of relatively simple bilaterian, unsegme ...

s (known as ''flukes'') with a

syncytial A syncytium (; plural syncytia; from Ancient Greek, Greek: σύν ''syn'' "together" and κύτος ''kytos'' "box, i.e. cell") or symplasm is a multinucleate cell (biology), cell which can result from multiple cell fusions of uninuclear cells (i.e ...

tegument Tegument may refer to: * Integumentary system, a protective organ system forming the outermost layer of an animal's body * Tegument (helminth) Tegument is a term in helminthology for the outer body covering of members of the phylum Platyhelminthe ...

and, usually, two suckers, one ventral and one oral. Adults commonly live within the digestive tract, but occur throughout the organ systems of all classes of

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, wi ...

. Once thought to be related to the

Monogenea Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they have both male and female reprod ...

, it is now recognised that they are closest to the

Aspidogastrea The Aspidogastrea (Ancient Greek: ' “shield”, ' “stomach/pouch”) is a small group of flukes comprising about 80 species. It is a subclass of the trematoda, and sister group to the Digenea. Species range in length from approximately one ...

and that the Monogenea are more closely allied with the

Cestoda 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 m ...

. Around 6,000 species have been described to date.

Morphology

Key features

Characteristic features of the Digenea include a syncytial tegument; that is, a tegument where the junctions between cells are broken down and a single continuous cytoplasm surrounds the entire animal. A similar tegument is found in other members of the

Neodermata Neodermata is a clade of rhabditophoran flatworms containing the parasitic groups Trematoda, Monogenea and Cestoda. Description All neodermatans are parasites, in many groups having a free-swimming larval stage. The most striking feature uniti ...

; a group of

platyhelminths The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") are a phylum of relatively simple bilaterian, unsegment ...

comprising the Digenea,

and

. Digeneans possess a

vermiform Vermiform (ˈvərməˌfôrm) describes something shaped like a worm. The expression is often employed in biology and anatomy to describe usually soft body parts or animals that are more or less tubular or cylindrical. The word root is Latin, ''ve ...

, unsegmented body-plan and have a solid

parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word π ...

with no

body cavity A body cavity is any space or compartment, or potential space, in an animal body. Cavities accommodate organs and other structures; cavities as potential spaces contain fluid. The two largest human body cavities are the ventral body cavity, and ...

(

coelom The coelom (or celom) is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it ...

) as in all platyhelminths. Peerj-292-fig-7 Zoogonidae

There are typically two suckers, an

anterior 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 ...

oral The word oral may refer to: Relating to the mouth * Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid **Oral administration of medicines ** Oral examination (also known as an oral exam or ora ...

sucker surrounding the

mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on t ...

, and a

ventral 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 ...

sucker sometimes termed the

acetabulum The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) tha ...

, on the ventral surface. The oral sucker surrounds the mouth, while the ventral sucker is a blind muscular organ with no connection to any internal structure. A ''monostome'' is a worm with one sucker (oral). Flukes with an oral sucker and an acetabulum at the posterior end of the body are called ''Amphistomes''. ''Distomes'' are flukes with an oral sucker and a ventral sucker, but the ventral sucker is somewhere other than posterior. These terms are common in older literature, when they were thought to reflect systematic relationships within the groups. They have fallen out of use in modern digenean taxonomy.

Reproductive system

The vast majority of digeneans are

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have ...

s. This is likely to be an adaptation to low abundance within hosts, allowing the life cycle to continue when only one individual successfully infects the final host.

Fertilisation Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Pro ...

is internal, with sperm being transferred via the

cirrus Cirrus may refer to: Science *Cirrus (biology), any of various thin, thread-like structures on the body of an animal *Cirrus (botany), a tendril * Infrared cirrus, in astronomy, filamentary structures seen in infrared light *Cirrus cloud, a typ ...

to the Laurer's Canal or genital aperture. A key group of digeneans which are

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproducti ...

are the

schistosomes ''Schistosoma'' is a genus of trematodes, commonly known as blood flukes. They are parasitic flatworms responsible for a highly significant group of infections in humans termed ''schistosomiasis'', which is considered by the World Health Organi ...

. Asexual reproduction in the first larval stage is ubiquitous. While the sexual formation of the digenean

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

and asexual reproduction in the first

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. Th ...

l stage (miracidium) is widely reported, the

developmental biology Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction, metamorphosis, and the growth and differentiation of ste ...

of the asexual stages remains a problem. Electron microscopic studies have shown that the light microscopically visible germ balls consist of

mitotically In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintai ...

dividing

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

s which give rise to

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...

s and to a line of new

germ cells Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embry ...

that become included in these embryonic stages. Since the absence of meiotic processes is not proven, the exact definition remains doubtful.

Male organs

Protandry Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...

is the general rule among the Digenea. Usually two

testes A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testostero ...

are present, but some flukes can have more than 100. Also present are

vasa efferentia The efferent ducts (or efferent ductules or ductuli efferentes or ductus efferentes or vasa efferentia) connect the rete testis with the initial section of the epididymis.Hess 2018 There are two basic designs for efferent ductule structure: * a ...

, a

vas deferens The vas deferens or ductus deferens is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled t ...

seminal vesicle The seminal vesicles (also called vesicular glands, or seminal glands) are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen. The vesicles are 5� ...

ejaculatory duct The ejaculatory ducts (''ductus ejaculatorii'') are paired structures in male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the ureth ...

and a cirrus (analogous to a penis) usually (but not always) enclosed in a cirrus sac. The cirrus may or may not be covered in proteinaceous spines. The exact conformation of these organs within the male terminal genitalia is taxonomically important at the familial and generic levels.

Female organs

Usually there is a single

ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the bod ...

with an

oviduct The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, ...

, a

seminal receptacle Female sperm storage is a biological process and often a type of sexual selection in which sperm cells transferred to a female during mating are temporarily retained within a specific part of the reproductive tract before the oocyte, or egg, is f ...

, a pair of vitelline glands (involved in

yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...

and egg-shell production) with ducts, the ootype (a chamber where eggs are formed), a complex collection of glands cells called ''Mehlis’ gland'', which is believed to lubricate the uterus for egg passage. In addition, some digeneans possess a canal called Laurer's Canal, which leads from the oviduct to the dorsal surface of the body. The function of this canal is debated, but it may be used for insemination in some species or for disposal of waste products from reproduction in other species. Most trematodes possess an ovicapt, an enlarged portion of the oviduct where it joins the ovary. It probably controls the release of ova and spaces out their descent down the uterus. The uterus typically opens into a common genital atrium that also received the distal male copulatory organ (cirrus) before immediately opening onto the outer surface of the worm. The distal part of the uterus may be expanded into a metraterm, set off from the proximal uterus by a muscular sphincter, or it may be lined with spines, as in the Monorchiidae and some other families.

Digestive system

As adults, most digeneans possess a terminal or subterminal mouth, a muscular pharynx that provides the force for ingesting food, and a forked, blind digestive system consisting of two tubular sacs called caeca (sing.

caecum The cecum or caecum is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix, to which it is joined). The w ...

). In some species the two gut caeca join posteriorly to make a ring-shaped gut or cyclocoel. In others the caeca may fuse with the body wall posteriorly to make one or more

anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, d ...

es, or with the excretory vesicle to form a uroproct. Digeneans are also capable of direct nutrient uptake through the tegument by

pinocytosis In cellular biology, pinocytosis, otherwise known as fluid endocytosis and bulk-phase pinocytosis, is a mode of endocytosis in which small molecules dissolved in extracellular fluid are brought into the cell through an invagination of the cel ...

and

phagocytosis Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis i ...

by the

syncitium A syncytium (; plural syncytia; from Greek: σύν ''syn'' "together" and κύτος ''kytos'' "box, i.e. cell") or symplasm is a multinucleate cell which can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus ...

. Most adult digeneans occur in the vertebrate

alimentary canal The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...

or its associated

organs In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a f ...

, where they most often graze on contents of the lumen (e.g., food ingested by the host, bile, mucus), but they may also feed across the mucosal wall (e.g.,

submucosa The submucosa (or tela submucosa) is a thin layer of tissue in various organs of the gastrointestinal, respiratory, and genitourinary tracts. It is the layer of dense irregular connective tissue that supports the mucosa (mucous membrane) and ...

, host blood). The blood flukes, such as schistosomes, spirorchiids and sanguinicolids, feed exclusively on blood. Asexual stages in mollusc intermediate hosts feed mostly by direct absorption, although the redia stage found in some groups does have a mouth, pharynx and simple gut and may actively consume host tissue or even other parasites. Encysted

metacercaria Trematodes are parasitic flatworms of the class ''Trematoda'', specifically parasitic flukes with two suckers: one ventral and the other oral. Trematodes are covered by a tegument, that protects the organism from the environment by providing secr ...

l stages and free-living

cercaria A cercaria (plural cercariae) is the larval form of the trematode 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, l ...

l stages do not feed.

Nervous system

Paired

ganglia A ganglion is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system there are both sympath ...

at the anterior end of the body serve as the

brain The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head ( cephalization), usually near organs for special ...

. From this

nerves A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

extend anteriorly and posteriorly.

Sensory receptors Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The ...

are, for the most part, lacking among the adults, although they do have tangoreceptor cells. Larval stages have many kinds of sensory receptors, including light receptors and chemoreceptors. Chemoreception plays an important role in the free-living miracidial larva recognising and locating its host.

Life cycles

There is a bewildering array of variation on the complex digenean life cycle, and plasticity in this trait is probably a key to the group's success. In general, the life cycles may have two, three, or four obligate (necessary) hosts, sometimes with transport or

paratenic In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

hosts in between. The three-host life cycle is probably the most common. In almost all species, the first host in the life cycle is a mollusc. This has led to the inference that the ancestral digenean was a mollusc parasite and that vertebrate hosts were added subsequently. The alternation of sexual and asexual generations is an important feature of digeneans. This phenomenon involves the presence of several discrete generations in one life-cycle. A typical digenean trematode life cycle is as follows. Eggs leave the

vertebrate Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...

host in

faeces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

and use various strategies to infect the first

intermediate host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

, in which sexual reproduction does not occur. Digeneans may infect the first intermediate host (usually a

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class G ...

) by either passive or active means. The eggs of some digeneans, for example, are (passively) eaten by snails (or, rarely, by an

annelid The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecol ...

worm), in which they proceed to hatch. Alternatively, eggs may hatch in water to release an actively swimming, ciliated larva, the

miracidium The Miracidium is the second stage in the life cycle of trematodes. When trematode eggs are laid and come into contact with fresh water, they hatch and release miracidium. In this phase, miracidia are ciliated and free-swimming. This stage is comp ...

, which must locate and penetrate the body wall of the snail host. After post-ingestion hatching or penetration of the snail, the miracidium metamorphoses into a simple, sac-like ''mother sporocyst''. The mother sporocyst undergoes a round of internal asexual reproduction, giving rise to either ''rediae'' (sing. redia) or ''daughter sporocysts''. The second generation is thus the daughter parthenita sequence. These in turn undergo further asexual reproduction, ultimately yielding large numbers of the second free-living stage, the ''cercaria'' (pl. cercariae). Free-swimming cercariae leave the snail host and move through the aquatic or

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

environment, often using a whip-like tail, though a tremendous diversity of tail morphology is seen. Cercariae are infective to the second host in the life cycle, and infection may occur passively (e.g., a

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% ...

consumes a cercaria) or actively (the cercaria penetrates the fish). The life cycles of some digeneans include only two hosts, the second being a vertebrate. In these groups, sexual maturity occurs after the cercaria penetrates the second host, which is in this case also the

definitive host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

. Two-host life cycles can be primary (there never was a third host) as in the

Bivesiculidae Bivesiculidae is a family of trematodes 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 t ...

, or secondary (there was at one time in evolutionary history a third host but it has been lost). In three-host life cycles, cercariae develop in the second intermediate host into a resting stage, the ''metacercaria'', which is usually encysted in a

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble ...

of host and parasite origin, or encapsulated in a layer of tissue derived from the host only. This stage is infective to the

. Transmission occurs when the definitive host preys upon an infected second intermediate host. Metacercariae excyst in the definitive host's gut in response to a variety of physical and chemical signals, such as gut pH levels, digestive

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on ...

, etc. Once excysted, adult digeneans migrate to more or less specific sites in the definitive host and the life cycle repeats.

Evolution

The evolutionary origins of the Digenea have been debated for some time, but there appears general agreement that the proto-digenean was a parasite of a mollusc, possibly of the mantle cavity. Evidence for this comes from the ubiquity of molluscs as first intermediate hosts for digeneans, and the fact that most aspidogastreans (the sister group to the Digenea) also have mollusc associations. It is thought that the early trematodes (the collective name for digeneans and aspidogastreans) likely evolved from rhabdocoel

turbellaria The Turbellaria are one of the traditional sub-divisions of the phylum Platyhelminthes (flatworms), and include all the sub-groups that are not exclusively parasitic. There are about 4,500 species, which range from to large freshwater forms mor ...

ns that colonised the open mantle cavity of early molluscs. It is likely that more complex life cycles evolved through a process of terminal addition, whereby digeneans survived predation of their mollusc host, probably by a fish. Other hosts were added by the same process until the modern bewildering diversity of life cycle patterns developed.

Important families

Digenea includes about 80 families.Olson P. D., Cribb T. H., Tkach V. V., Bray R. A. & Littlewood D. T. J. (2003). "Phylogeny and classification of the Digenea (Platyhelminthes: Trematoda)". ''International Journal for Parasitology'' 33(7): 733–755. They are listed below, organised by order. Digenea *

Diplostomida Diplostomida is an order of trematodes in the subclass Digenea. It is synonymous with Strigeida Poche, 1926. Families Order Diplostomida *Suborder Diplostomata **Superfamily Brachylaimoidea Joyeux & Foley, 1930 *** Brachylaimidae Joyeux & Foley ...

**Suborder Diplostomata ***Superfamily Brachylaimoidea Joyeux & Foley, 1930 **** Brachylaimidae Joyeux & Foley, 1930 **** Leucochloridiidae Poche, 1907 ***Superfamily Diplostomoidea Poirier, 1886 **** Brauninidae Wolf, 1903 **** Cyathocotylidae Mühling, 1898 **** Diplostomidae Poirier, 1886 **** Proterodiplostomidae Dubois, 1936 **** Strigeidae Railliet, 1919 ***Superfamily Schistosomatoidea Stiles & Hassall, 1898 **** Aporocotylidae Odhner, 1912 ****

Schistosomatidae Schistosomatidae is a family of digenetic trematodes with complex parasitic life cycles. Immature developmental stages of schistosomes are found in molluscs and adults occur in vertebrates. The best studied group, the blood flukes of the genus ...

Stiles & Hassall, 1898 ****

Spirorchiidae Spirorchiidae is a family of digenetic trematodes. Infestation by these trematodes leads to the disease spirorchiidiosis. Spirorchiids are mainly parasites of turtles. It has been synonymised with Proparorchiidae Ward, 1921, Spirorchidae Stun ...

Stunkard, 1921 *

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, or ...

**Apocreadiata ***Apocreadioidea Skrjabin, 1942 ****

Apocreadiidae Apocreadiidae is a family of parasitic worms in the class Trematoda. Characteristics Members of the family are characterised by having extensive vitelline (yolk producing) follicles, eye-spot pigment dispersed in the front half of the body, a ro ...

Skrjabin, 1942 **Bivesiculata ***Bivesiculoidea ****

Yamaguti, 1934 **Bucephalata ***Bucephaloidea Poche, 1907 **** Bucephalidae Poche, 1907 ****

Nuitrematidae Nuitrematidae is a monotypic family of trematodes in the order 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 f ...

Kurochkin, 1975 ***Gymnophalloidea Odhner, 1905 ****

Botulisaccidae Botulisaccidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Botulisaccus'' Caballero y C., Bravo-Hollis & Grocott, 1955 References Plagiorchiida {{Trematoda-stub ...

Yamaguti, 1971 ****

Fellodistomidae Fellodistomidae is a family of trematodes belonging to the order Plagiorchiida. References Plagiorchiida Trematode families {{Trematoda-stub ...

Nicoll, 1909 **** Gymnophallidae Odhner, 1905 **** Tandanicolidae Johnston, 1927 **Echinostomata ***Echinostomatoidea Looss, 1902 ****

Calycodidae Calycodidae is a family of trematodes belonging to the order 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 ...

Dollfus, 1929 ****

Cyclocoelidae Cyclocoelidae is a family of trematodes in the order 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 signifi ...

Stossich, 1902 ****

Echinochasmidae Echinochasmidae is a family of trematodes in the order Plagiorchiida. Genera *''Echinochasmus ''Echinochasmus'' is a genus of trematodes in the family Echinochasmidae. Species *''Echinochasmus cohensi'' Rao, 1951Rao, N. S. K. (1951). ''Ec ...

Odhner, 1910 ****

Echinostomatidae Echinostomatidae is a family of trematodes in the order Plagiorchiida, first described in 1899.Fuhrmann, O. (1928). ''Zweite Klasse des Cladus Platyhelminthes: Trematoda''. Berlin & Leipzig: Kükenthal's Handbuch der Zoologie. Subdivisions Th ...

Looss, 1899 ****

Eucotylidae Eucotylidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Eucotyle'' Cohn, 1904 * '' Neoeucotyle'' Kanev, Radev & Fried, 2002 * '' Paratanaisia'' Teixeira de Freitas, 1959 * '' Tamerlania'' Skrjabin, 1924 * '' Tan ...

Cohn, 1904 ****

Fasciolidae Fasciolidae is a Family (biology), family of Trematoda, trematodes and includes several parasites involved in the veterinary and medical sciences, which cause the disease Fasciolosis. Fasciolidae is divided into five genus, genera by Olson et al. ...

Railliet, 1895 ****

Himasthlidae Himasthlidae is a family of trematodes in the order Plagiorchiida. Genera *''Acanthoparyphium ''Acanthoparyphium'' is a genus of flatworms belonging to the family Himasthlidae. The species of this genus are found in Australia and Japan. Spe ...

Odhner, 1910 ****

Philophthalmidae Philophthalmidae is a family of trematodes in the order 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 signi ...

Looss, 1899 ****

Psilostomidae Psilostomidae is a family of trematodes belonging to the order 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 fe ...

Looss, 1900 ****

Rhytidodidae Rhytidodidae is a family of trematodes belonging to the order 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 ...

Odhner, 1926 ****

Typhlocoelidae Typhlocoelidae is a family of trematodes belonging to the order 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 f ...

Harrah, 1922 **Haplosplanchnata ***Haplosplanchnoidea Poche, 1925 ****

Haplosplanchnidae Haplosplanchnidae is a family of flatworms belonging to the order Plagiorchiida. Genera Genera: * '' Discocephalotrema'' Machida, 1993 * '' Haplosplanchnoides'' Nahhas & Cable, 1964 * '' Haplosplanchnus'' Looss, 1902 References {{Taxonbar, ...

Poche, 1926 **Hemiurata ***Azygioidea Lühe, 1909 **** Azygiidae Lühe, 1909 ***Hemiuroidea Looss, 1899 ****

Accacoeliidae Accacoeliidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * ''Accacladium'' Odhner, 1928 * ''Accacladocoelium'' Odhner, 1928 * ''Accacoelium'' Monticelli, 1893 * ''Odhnerium'' Yamaguti, 1934 * ''Orophocotyle'' Looss, ...

Odhner, 1911 **** Bathycotylidae Dollfus, 1932 ****

Derogenidae Derogenidae is a family of trematodes belonging to the order Plagiorchiida. Subdivisions Derogenidae contains 22 genera arranged in two subfamilies, with one being unassigned. * Subfamily Derogeninae Nicoll, 1910 ** ''Derogenes'' Lühe, 1900 ** ' ...

Nicoll, 1910 **** Dictysarcidae Skrjabin & Guschanskaja, 1955 **** Didymozoidae Monticelli, 1888 **** Gonocercidae Skrjabin & Guschanskaja, 1955 **** Hemiuridae Looss, 1899 ****

Hirudinellidae Hirudinellidae is a family of flatworms belonging to the order Plagiorchiida. Genera: * ''Botula ''Botula'' is a genus of mussels in the family Mytilidae Mytilidae are a family of small to large marine and brackish-water bivalve mollusc ...

Dollfus, 1932 ****

Isoparorchiidae Isoparorchiidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Isoparorchis'' Southwell, 1913 References Plagiorchiida {{Trematoda-stub ...

Travassos, 1922 ****

Lecithasteridae Lecithasteridae is a family of trematodes belonging to the order Plagiorchiida. Genera Genera: * '' Acanthuritrema'' Yamaguti, 1970 * '' Aponurus'' Looss, 1907 * '' Assitrema'' Parukhin, 1976 References {{Taxonbar, from=Q10556135 Plagior ...

Odhner, 1905 ****

Ptychogonimidae Ptychogonimidae is a family of 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 occu ...

Dollfus, 1937 ****

Sclerodistomidae Sclerodistomidae is a family of trematodes belonging to the order 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 ...

Odhner, 1927 ****

Sclerodistomoididae Sclerodistomoididae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Sclerodistomoides'' Kamegai, 1971 References Plagiorchiida Trematode families {{trematoda-stub ...

Gibson & Bray, 1979 ****

Syncoeliidae Syncoeliidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Copiatestes'' Crowcroft, 1948 * '' Otiotrema'' Setti, 1897 * '' Paronatrema'' Dollfus, 1937 * '' Syncoelium'' Looss, 1899 References {{Taxonbar, from= ...

Looss, 1899 **Heronimata ***Heronimoidea Ward, 1918 ****

Heronimidae Heronimidae is a family of digenean trematode parasites consisting of a single genus with a single species.Pearson, J. C. (1992). On the position of the digenean family Heronimidae: an inquiry into a cladistic classification of the Digenea. ''Sys ...

Ward, 1918 **Lepocreadiata ***Lepocreadioidea Odhner, 1905 ****

Aephnidiogenidae Aephnidiogenidae is a family of trematodes in the order Plagiorchiida. Genera *''Aephnidiogenes'' Nicoll, 1915Nicoll, W. (1915). The trematode parasites of north Queensland. III. Parasites of fishes. ''Parasitology'', 8(1), 22–41. *''Austroh ...

Yamaguti, 1934 **** Deropristidae Cable & Hunninen, 1942 ****

Enenteridae Enenteridae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Enenterageitus'' Huston, Cutmore & Cribb, 2019 * '' Enenterum'' Linton, 1910 * '' Koseiria'' Nagaty, 1942 * '' Neoenenterum'' Bilqees & Khatoon, 2004 * '' ...

Yamaguti, 1958 ****

Gorgocephalidae Gorgocephalidae is a family of 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 occu ...

Manter, 1966 **** Gyliauchenidae Fukui, 1929 ****

Lepidapedidae Lepidapedidae is a family of trematodes belonging to the order Plagiorchiida. Genera Genera: * '' Allolepidapedon'' Yamaguti, 1940 * '' Bulbocirrus'' Yamaguti, 1965 * '' Gibsonia'' Gaevskaya & Rodyuk, 1988 References {{Taxonbar, from=Q2132 ...

Yamaguti, 1958 **** Lepocreadiidae Odhner, 1905 ****

Liliatrematidae Liliatrematidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Liliatrema'' Gubanov, 1953 References Plagiorchiida {{Trematoda-stub ...

Gubanov, 1953 **Monorchiata ***Monorchioidea Odhner, 1911 ****

Lissorchiidae Lissorchiidae is a family of flatworms belonging to the order Plagiorchiida. Genera Genera: * '' Alloplagiorchis'' Simer, 1931 * '' Asaccotrema'' Sokolov & Gordeev, 2019 * '' Asymphylodora'' Looss, 1899 References {{Taxonbar, from=Q5032528 ...

Magath, 1917 **** Monorchiidae Odhner, 1911 **Opisthorchiata ***Opisthorchioidea Braun, 1901 **** Cryptogonimidae Ward, 1917 ****

Heterophyidae Heterophyidae is a family of intestinal trematodes in the order Plagiorchiida. Description: "Tegument covered by spines. Oral sucker not armed or armed by cyrcumoral spines. Pharynx presented. Genital synus presented. Ventral and genital suck ...

Leiper, 1909 ****

Opisthorchiidae Opisthorchiidae is a family of digenean trematodes. Opisthorchiidae have cosmopolitan distribution. The most medically important species in the family Opisthorchiidae are '' Clonorchis sinensis'', '' Opisthorchis viverrini'', and '' Opisthorchis ...

Looss, 1899 **Pronocephalata ***Paramphistomoidea Fischoeder, 1901 ****

Cladorchiidae Cladorchiidae is a family of trematodes belonging to the order Plagiorchiida. Genera Genera: * '' Allassostoma'' Stunkard, 1916 * '' Allassostomoides'' Stunkard, 1924 * '' Alphamphistoma'' Thatcher & Jégu, 1996 References {{Taxonbar, fro ...

Fischoeder, 1901 **** Mesometridae Poche, 1926 ****

Microscaphidiidae Microscaphidiidae is a family of flatworms belonging to the order Plagiorchiida. Genera Genera: * '' Angiodictyum'' Looss, 1902 * '' Curumai'' Travassos, 1961 * '' Denticauda'' Fukui, 1929 References {{Taxonbar, from=Q5032148 Platyhelmin ...

Looss, 1900 ****

Paramphistomidae Paramphistomidae is a family of trematodes 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 wherei ...

Fischoeder, 1901 ***Pronocephaloidea Looss, 1899 ****

Labicolidae Labicolidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Labicola'' Blair, 1979 References Plagiorchiida {{trematoda-stub ...

Blair, 1979 ****

Notocotylidae Notocotylidae is a family of trematodes 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 t ...

Lühe, 1909 ****

Nudacotylidae Nudacotylidae is a family of trematodes belonging to the order 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 fe ...

Barker, 1916 ****

Opisthotrematidae Opisthotrematidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Folitrema'' Blair, 1981 * '' Lankatrema'' Crusz & Fernand, 1954 * '' Lankatrematoides'' Blair, 1981 * '' Moniligerum'' Dailey, Vogelbein & Forrester, ...

Poche, 1926 ****

Pronocephalidae Pronocephalidae is a family of trematodes belonging to the order Plagiorchiida. Genera Genera: * '' Adenogaster'' Looss, 1901 * '' Astrochis'' Poche, 1925 * '' Buckarootrema'' Platt & Brooks, 2001 References {{Taxonbar, from=Q5033367 Pla ...

Looss, 1899 ****

Rhabdiopoeidae Rhabdiopoeidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Faredifex'' Blair, 1981 * '' Haerator'' Blair, 1981 * '' Rhabdiopoeus'' Johnston, 1913 * '' Taprobanella'' Crusz & Fernand, 1954 References {{Taxonba ...

Poche, 1926 **Transversotremata ***Transversotrematoidea Witenberg, 1944 **** Transversotrematidae Witenberg, 1944 **Xiphidiata ***Allocreadioidea Looss, 1902 ****

Acanthocolpidae Acanthocolpidae is a family of trematodes belonging to the order 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 fe ...

Lühe, 1906 ****

Allocreadiidae Allocreadiidae is a family of flatworms belonging to the order Plagiorchiida. Genera The family includes about 40 genera, including: * '' Acanthocreadium'' Mikailov, 1969 * '' Acrolichanus'' Ward, 1917 * ''Allocreadium ''Allocreadium'' is a ...

Looss, 1902 ****

Batrachotrematidae Batrachotrematidae is a family of trematodes in the order Plagiorchiida. Genera The following genera are described severally, and by Rizvi, ''et al.'' (2012):Rizvi, A. N., Bursey, C. R. & Bhutia, P. T. (2012). Three new species of Digenea (Ba ...

Dollfus & Williams, 1966 ****

Brachycladiidae Brachycladiidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * ''Balanorchis'' Fischoeder, 1901 * ''Brachycladium'' Looss, 1899 * ''Campula'' Cobbold, 1858 * ''Cetitrema'' A.S.Skrjabin, 1970 * ''Hunterotrema'' Mclntosh, ...

Odhner, 1905 ****

Opecoelidae Opecoelidae is a family of trematodes. It is the largest digenean family with over 90 genera and nearly 900 species, almost solely found in marine and freshwater teleost fishes.Bray, Rodney A., Cribb, Thomas H., Littlewood, D. Timothy J. & Waesc ...

Ozaki, 1925 ***Gorgoderoidea Looss, 1901 ****

Callodistomidae Callodistomidae is a family of 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 occ ...

Odhner, 1910 **** Dicrocoeliidae Looss, 1899 ****

Gorgoderidae Gorgoderidae is a family of trematodes 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 t ...

Looss, 1899 ***Haploporoidea Nicoll, 1914 **** Atractotrematidae Yamaguti, 1939 ****

Haploporidae Haploporidae is a family of trematodes in the order Plagiorchiida. Genera The genera are organised by their subfamily. *Chalcinotrematinae Overstreet & Curran, 2005 **'' Chalicinotrema'' Texeira de Freitas, 1947 **'' Paralecithobotrys'' Teixe ...

Nicoll, 1914 ***Microphalloidea Ward, 1901 ****

Diplangidae Diplangidae is a family of 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, ...

Yamaguti, 1971 ****

Exotidendriidae Exotidendriidae is a family of 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 occu ...

Mehra, 1935 ****

Faustulidae Faustulidae is a family of trematodes belonging to the order Plagiorchiida. Genera Genera: * '' Allofellodistomum'' Yamaguti, 1971 * '' Antorchis'' Linton, 1911 * '' Bacciger'' Nicoll, 1914 References {{Taxonbar, from=Q10494373 Plagiorc ...

Poche, 1926 **** Microphallidae Ward, 1901 **** Pachypsolidae Yamaguti, 1958 ****

Phaneropsolidae Phaneropsolidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * ''Microtrema Opisthorchiidae is a family of digenean trematodes. Opisthorchiidae have cosmopolitan distribution. The most medically important species in ...

Mehra, 1935 **** Pleurogenidae Looss, 1899 ****

Prosthogonimidae The Prosthogonimidae are a family of trematodes. They are part of the huge of the suborder Xiphidiata in the order Plagiorchiida. The adults of these parasites occur in the bursa of Fabricius, caecum, cloaca, liver, oviduct and sometimes eve ...

Lühe, 1909 ****

Renicolidae Renicolidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Nephromonorcha'' Leonov, 1958 * '' Renicola'' Cohn, 1904 References Plagiorchiida {{Trematoda-stub ...

Dollfus, 1939 **** Zoogonidae Odhner, 1902 ***Plagiorchioidea Lühe, 1901 ****

Auridistomidae Auridistomidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Auridistomum'' Stafford, 1905 * ''Patagium The patagium (plural: patagia) is a membranous body part that assists an animal in obtaining lift when gl ...

Lühe, 1901 ****

Brachycoeliidae Brachycoeliidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Brachycoelium'' Dujardin, 1845 * '' Brachycoelium'' Stiles & Hassall, 1898 * '' Cymatocarpus'' Looss, 1899 * '' Parabrachycoelium'' Pérez-Ponce de Leo ...

Looss, 1899 ****

Cephalogonimidae Cephalogonimidae is a family of trematode parasites characterized by a genital pore located anterior to the oral sucker, at the apex of the body.Bray, R. A., Gibson, D. I., & Jones, A. (2008). ''Keys to the Trematoda, Volume 3''. CAB Internation ...

Looss, 1899 ****

Choanocotylidae Choanocotylidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Auriculotrema'' Platt, 2003 References Plagiorchiida {{Trematoda-stub ...

Jue Sue & Platt, 1998 ****

Echinoporidae Echinoporidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Echinoporus'' References {{trematoda-stub Plagiorchiida ...

Krasnolobova & Timofeeva, 1965 **** Encyclometridae Mehra, 1931 **** Leptophallidae Dayal, 1938 ****

Macroderoididae Macroderoididae is a family of trematodes belonging to the order Plagiorchiida. Genera Genera: * ''Alloglossidium'' Simer, 1929 * ''Alloglyptus'' Byrd, 1950 * ''Allomacroderoides'' Watson, 1976 References

{{Taxonbar, from=Q5014116 Plag ...

McMullen, 1937 ****

Meristocotylidae Meristocotylidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Meristocotyle'' Fischthal & Kuntz, 1964 References Plagiorchiida {{Trematoda-stub ...

Fischthal & Kuntz, 1981 ****

Ocadiatrematidae Ocadiatrematidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * '' Ocadiatrema'' Fischthal & Kuntz, 1981 References Plagiorchiida Trematode families {{Trematoda-stub ...

Fischthal & Kuntz, 1981 ****

Orientocreadiidae Orientocreadiidae is a family of trematodes belonging to the order Plagiorchiida. Genera: * ''Macrotrema ''Macrotrema caligans'' is a species of swamp eel native to Peninsular Malaysia and the Mae Nam Chao Praya basin in Thailand. The male ...

Yamaguti, 1958 **** Plagiorchiidae Lühe, 1901 **** Styphlotrematidae Baer, 1924 **** Telorchiidae Looss, 1899 **** Thrinascotrematidae Jue Sue & Platt, 1999 **** Urotrematidae Poche, 1926

Human digenean infections

Only about 12 of the 6,000 known species are

infectious An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dis ...

to humans, but some of these species are important

disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

s afflicting over 200 million people. The species that infect humans can be divided into groups, the schistosomes and the non-schistosomes.

Schistosomes

The Schistosomes occur in the

circulatory system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

of the definitive host. Humans become infected after free-swimming cercaria liberated from infected snails penetrate the skin. These dioecious worms are long and thin, ranging in size from 10 to 30 mm in length to 0.2 to 1.0 mm in diameter. Adult males are shorter and thicker than females, and have a long groove along one side of the body in which the female is clasped. Females reach sexual maturity after they have been united with a male. After mating the two remain locked together for the rest of their lives. They can live for several years and produce many thousands of eggs. The four species of schistosomes that infect humans are members of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

'' Schistosoma''.

Non-schistosomes

The seven major species of non-schistosomes that infect humans are listed below. People become infected after ingesting metacercarial cysts on plants or in undercooked animal flesh. Most species inhabit the human gastrointestinal tract, where they shed eggs along with host feces. ''Paragonimus westermani'', which colonizes the lungs, can also pass its eggs in saliva. These flukes generally cause mild pathology in humans, but more serious effects may also occur.

References

Notes

* Gibson, D.I., Jones, A. & Bray, R.A. (2002). ''Key to the Trematoda, vol.1'' * Littlewood D.T.J. & Bray R.A. (2001) ''Interrelationships of the Platyhelminthes.'' * Yamaguti, S. (1971). ''Synopsis of digenetic trematodes of vertebrates.'' Keigaku Publishing Co., Tokyo.

External links

Cambridge University Schistosome Research GroupFishdisease.net
{{Taxonbar, from=Q132650 Protostome subclasses