関: Bilharzia、Schistosoma

WordNet

a family of Trematoda (同)family Schistosomatidae
type genus of the family Schistosomatidae: blood flukes (同)genus Schistosoma

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/09/01 21:33:15」(JST)

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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 Schistosoma, infect and cause disease in humans. Other genera which are infective to non-human vertebrates can cause mild rashes in humans.

Schistosomatids are dioecious (individuals are of separate sexes) which is exceptional with regards to their phylum, Platyhelminthes, in which most species are hermaphrodidic (individuals possess both male and female reproductive systems).

History[edit source | edit]

The eggs of these parasites were first seen by Theodor Bilharz, a German pathologist working in Egypt in 1851 who found the eggs during the course of a post mortem. He wrote two letters to his former teacher von Siebold in May and August 1851 describing his findings. von Siebold wrote a paper (published in 1852) summarizing Bilharz's findings. Bilhart's wrote a paper in 1856 describing the worms more fully and he named them Distoma haematobium. Their unusual morphology meant that they could not be comfortably included in Distoma so in 1856 Meckel von Helmsback created the genus Bilharzia for them. In 1858 Weinland proposed the name Schistosoma (Greek: 'split body') after the male worms' morphology. Despite Bilharzia having precedence the genus name Schistosoma was officially adopted by the International Commission on Zoological Nomenclature.

In 1898 all the then known species were placed in a subfamily by Stiles and Hassel. This was then elevated to family status by Looss in 1899. Poche in 1907 corrected a grammatical error in the family name. The life cycle was determined by da Silva in 1908.

Evolution[edit source | edit]

There are a number of different families of blood fluke including the Schistosomatidae. The others include the spirorchids (turtle parasites) and the sanguinicolids (fish parasites).

The Schistosomatidae are considered venous system specialists and their sister group are vascular system generalists - the Spirorchidae.

The Schistosomatidae differ from the other blood flukes in having separate sexes and homeothermic hosts. They have compensated for the reduction in potential reproductive partners by

an increased overdispersion in the vertebrate host
the reduced egg hatching time in the external environment
the formation of permanent pairs mimicking the hermaphroditic condition
the increased longevity in the definitive host
increased fecundity.

Colonization of the venous system was made possible

the evolutionary radiation into terrestrial vertebrates
the increased immunopathology associated with the high, constant body temperature of homeothermic vertebrates.

The arterial dwelling spirorchids release eggs in the direction of blood flow, resulting in a wide dissemination of eggs within the host. The lower body temperature of poikilotherms is accompanied by a seasonal nature of the immune response in these hosts resulting in a quantitatively reduced pathogenesis. Hosts that did succumb to the infection would most likely die in water where eggs could be released by predation, scavengers, or decomposition and develop successfully.

Colonization of the venous system by schistosomes required precise egg placement because their eggs are released against the blood flow. Eggs are then sequestered within the portal system (or perivesicular plexus in some species) of homeotherms which restricts egg dispersal but limits the resulting pathology to less sensitive organs. A significant number of eggs may escape into the external environment before a heavily infected host is incapacitated by, or dies from, the infection.

The first hosts of the schistosome were birds. Based on their current geographical spread the most likely place of origin of this family is Asia with subsequent spread to India and Africa.^[1]

Only one species is known to infect crocodiles - Griphobilharzia amoena. This species infects the freshwater crocodile Crocodylus johnstoni. Phylogenetic analysis shows that the genus Griphobilharzia rather than being a basal schistosome is a relation of the spirorchiids that infect freshwater turtles.^[2] It has also shown that the spirorchiids are the closest relations of the schistosoma.

An outline of the evolution of the schistosoma is now possible. The ancestral species infected freshwater turtles and the life cycle included gastropod hosts. Some of these species in their turn infected the marine turtles.^[3] At some point members of species infecting marine turtles developed the ability to infect birds - most likely waterfowl. This probably occurred somewhere in the Asian continent presumably at or near the coast. The bird species eventually developed the ability to infect mammals. This last development seems to have occurred in Gondwana between 120 million years ago and 70 million years ago.^[4]

Taxonomy[edit source | edit]

The family was created in 1926 by Stiles and Hassel for the Schistosoma, the Sanguinicolidae and the Spirochidae. It has since been divided into four subfamilies: the Schistosomatinae, the Bilharziellinae, the Denrobilharziinae and the Gigantobilharziinae. In the Gigantobilharziinae the ventral sucker is absent and the female genital pore is medial near the anterior end of the body. In the Bilharziellinae the ventral pore in the female is always posterior to the ventral sucker. Both the Bilharziellinae and the Gigantobilharziinae are found exclusively in birds while the Schistosomatinae are found in both mammals and birds. In the Denrobilharziinae both suckers are absent anmd the caecum has numerous branches. In this latter family there is one genus (Denrdobilharina) with two species (Dendrobilharzina purvulenta and Dendrobilharzina asicaticus).

There are 12 genera in this family. Of these 7 infect birds: the others infect mammals including humans. There are about 100 known species in this family. The largest genus within the family Schistosomatidae is the Trichobilharzia with over 40 species.

The genera are:

Subfamily Bilharziellinae
- Genus Bilharziella - birds (Setophaga pensylvanica, ducks)

Subfamily Denrobilharziinae
- Genus Dendritobilharzia - birds (ducks, swans)

Subfamily Gigantobilharziinae
- Gigantobilharzia - birds (Spinus tristis tristis)

Subfamily Schistosomatinae
- Allobilharzia - birds (Cygnus cygnus)
- Austrobilharzia - birds (mainly waterfowl)
- Bivitellobilharzia - mammals (elephants)
- Heterobilharzia - mammals (raccoons)
- Microbilharzia - birds (Larus canescens)
- Ornithobilharzia - mammals (cattle, cats)
- Schistomatium - mammals (rodents)
- Schistosoma - mammals including humans
- Trichobilharzia - birds (mainly waterfowl)

Orientobilharzia differ from Schistosoma only in the number of testes. The four species in this genus have recently (2012) been moved to the genus Schistosoma on the basis of morphology and molecular studies.^[5] The genus name should now be regarded as a junior synonom of Schistomsoma.

The genera Bivitellobilharzia and Schistosoma form a clade in this family. Austrobilharzia and Ornithobilharzia are the closest relations of this clade.

Heterobilharzia and Schistomatium form a separate clade indicating that adaption to mammalian hosts has occurred at least twice. The species in these genera are found in North American mammals suggesting that transmission occurred via birds with subsequent transmission to mammals.

The genus Griphobilharzia which infects reptiles has been shown to be a member of the spirorchiid family whose other members infect freshwater turtles.^[2] Like the spirorchiids and unlike the schistomes Griphobilharzia preferentially inhabits the arterial system rather than the venous. This genus was originally grouped with the schistosoma on the basis of the existence of two sexes and other morphological features.

Notes

Sinobilharzia is a genus that is no longer considered valid

References[edit source | edit]

^ Lockyer AE, Olson PD, Ostergaard P, Rollinson D, Johnston DA, Attwood SW, Southgate VR, Horak P, Snyder SD, Le TH, Agatsuma T, McManus DP, Carmichael AC, Naem S, Littlewood DT (2003) The phylogeny of the Schistosomatidae based on three genes with emphasis on the interrelationships of Schistosoma Weinland, 1858. Parasitology 126(Pt 3):203-224
^ ^a ^b Brant SV, Loker ES (2005) Can specialized pathogens colonize distantly related hosts? Schistosome evolution as a case study. PLoS Pathog 1(3): e38. doi:10.1371/journal.ppat.0010038
^ Snyder SD (2004) Phylogeny and paraphyly among tetrapod blood flukes (Digenea: Schistosomatidae and Spirorchiidae). Int J Parasitol 34(12):1385-1392
^ Beer SA, Voronin MV, Zazornova OP, Khrisanfova GG, Semenova SK (2010) Phylogenetic relationships among schistosomatidae. Med Parazitol (Mosk) 2010 (2):53-59
^ Aldhoun JA, Littlewood DT (2012) Orientobilharzia Dutt & Srivastava, 1955 (Trematoda: Schistosomatidae), a junior synonym of Schistosoma Weinland, 1858. Syst Parasitol 82(2):81-8. doi: 10.1007/s11230-012-9349-8

External links[edit source | edit]

Information portal for NSF funded research on avian schistosome diversity

English Journal

Two avian schistosome cercariae from Nepal, including a Macrobilharzia-like species from Indoplanorbis exustus.

Devkota R1, Brant SV2, Thapa S3, Loker ES2.Author information 1Center for Evolutionary and Theoretical Immunology (CETI), Department of Biology, University of New Mexico, NM, USA. Electronic address: rdevkota@unm.edu.2Center for Evolutionary and Theoretical Immunology (CETI), Department of Biology, University of New Mexico, NM, USA; Division of Parasitology, Museum of Southwestern Biology, University of New Mexico, USA.3Small Mammals Conservation and Research Foundation, New Baneshwor, Kathmandu, Nepal.AbstractAs part of a global survey of schistosomes, a total of 16,109 freshwater snails representing 14 species were collected from lakes, ponds, rivers, rice fields and swamps mostly in the Terai region of southern Nepal. Only two snails were found to harbor avian schistosome cercariae even though Nepal is well known for its rich avian diversity. One schistosome infection was from an individual of Radix luteola and on the basis of phylogenetic analyses using 28S rDNA and cox1 sequences, grouped as a distinctive and previously unknown lineage within Trichobilharzia. This genus is the most speciose within the family Schistosomatidae. It includes 40 described species worldwide, and its members mostly infect anseriform birds (ducks) and two families of freshwater snails (Lymnaeidae and Physidae). The second schistosome cercaria was recovered from an individual of Indoplanorbis exustus that was also actively emerging a Petasiger-like echinostome cercaria. Although I. exustus is commonly infected with mammalian schistosomes of the Schistosoma indicum species group on the Indian subcontinent, this is the first specifically documented avian schistosome reported in this snail. Both cercariae reported here are among the largest of all schistosome cercariae recovered to date. The I. exustus-derived schistosome clustered most closely with Macrobilharzia macrobilharzia, although it seems to represent a distinct lineage. Specimens of Macrobilharzia have thus far not been recovered from snails, being known only as adult worms from anhingas and cormorants. This study is the first to characterize by sequence data avian schistosomes recovered from Asian freshwater habitats. This approach can help unravel the complex of cryptic species causing cercarial dermatitis here and elsewhere in the world.
Parasitology international.Parasitol Int.2014 Apr;63(2):374-80. doi: 10.1016/j.parint.2013.12.009. Epub 2013 Dec 22.
As part of a global survey of schistosomes, a total of 16,109 freshwater snails representing 14 species were collected from lakes, ponds, rivers, rice fields and swamps mostly in the Terai region of southern Nepal. Only two snails were found to harbor avian schistosome cercariae even though Nepal is
PMID 24369339

Sharing schistosomes: the elephant schistosome Bivitellobilharzia nairi also infects the greater one-horned rhinoceros (Rhinoceros unicornis) in Chitwan National Park, Nepal.

Devkota R1, Brant SV1, Thapa A2, Loker ES1.Author information 1Center for Evolutionary and Theoretical Immunology (CETI), Department of Biology, University of New Mexico, New Mexico, USA.2Biodiversity and Environmental Management, NOMA Program, Central Department of Botany, Tribhuvan University, Kirtipur, Kathmandu, Nepal.AbstractBecause the digenetic trematode fauna of Nepal is poorly known, we began to search for schistosomes in and around Chitwan National Park (CNP) of southern Nepal. Both domestic and wild Indian elephants (Elephus maximus) are present, and we found one of two dung samples from wild elephants and 1 of 22 (4.5%) dung samples from domestic elephants to be positive for schistosome eggs. The morphology of the eggs and both cox1 and 28S sequences derived from the eggs/miracidia were consistent with Bivitellobilharzia nairi, reported here for the first time from Nepal. Also, 7 of 14 faecal samples from the Asian or greater one-horned rhinoceros (Rhinoceros unicornis) contained viable eggs indistinguishable from those of B. nairi. This identification was confirmed by comparison with both cox1 and 28S sequences from B. nairi eggs/miracidia derived from Nepalese and Sri Lankan elephants. This represents the first sequence-verified identification of a schistosome from any species of rhinoceros, and the first verified occurrence of a representative of Bivitellobilharzia (a genus of 'elephant schistosomes') in mammals other than elephants. Our work suggests that elephants and rhinos share B. nairi in CNP, even though these two members of the 'charismatic megafauna' belong to unrelated mammalian families. Their shared life style of extensive contact with freshwater habitats likely plays a role, although the snail intermediate host and mode of definitive host infection for B. nairi have yet to be documented. This report also supports Bivitellobilharzia as a monophyletic group and its status as a distinct genus within Schistosomatidae.
Journal of helminthology.J Helminthol.2014 Mar;88(1):32-40. doi: 10.1017/S0022149X12000697. Epub 2012 Oct 31.
Because the digenetic trematode fauna of Nepal is poorly known, we began to search for schistosomes in and around Chitwan National Park (CNP) of southern Nepal. Both domestic and wild Indian elephants (Elephus maximus) are present, and we found one of two dung samples from wild elephants and 1 of 22
PMID 23113960

Gigantobilharzia melanoidis n.sp. (Trematoda: Schistosomatidae) from Melanoides tuberculata (Gastropoda: Thiaridae) in the United Arab Emirates.

Schuster RK1, Aldhoun JA, O'Donovan D.Author information 1Central Veterinary Research Laboratory, PO Box 597, Dubai, United Arab Emirates, moniezia@zedat.fu-berlin.de.AbstractDelicate filamentous schistosomatids detected in the intestinal veins of experimentally infected chickens are here described as a new parasite species, Gigantobilharzia melanoidis, and details of its life cycle are given. It is the first complete description of a schistosome species that uses Melanoides tuberculata as an intermediate host. Apharyngeate ocellate brevifurcate cercariae found in 65 out of 950 M. tuberculata collected in a pond in Al Aweer, United Arab Emirates were used as infection material. The new species can be distinguished from the other species of the genus by the following combination of characters: caecal reunion in males situated anterior to seminal vesicle, a very short gynecophoric canal (gynecophoric canal length/body length ratio lower than 0.05) supported by 12-14 thickened bands. Cercariae of G. melanoidis can be distinguished from other Gigantobilharzia cercariae described in the literature based on the combination of these characters: flame cell formula 2[3 + 3 + (1)] = 14 and relatively longer tail stem in relation to body (tail stem length/body length ratio = 2). Under laboratory conditions at a temperature between 24 and 26 °C, M. tuberculata started to shed cercariae 7 weeks after exposure to miracidia. The prepatent period of G. melanoidis in experimentally infected chicken lasted between 43 and 49 days. The parasite inhabits the blood vessels mainly of the small intestine. Sections of adult worms and eggs were also found in histocuts of parenchymatous organs. Results of phylogenetic analysis corroborated that G. melanoidis is a distinct species; however, they also confirmed that the genus Gigantobilharzia is in need of revision and in future might be split into several genera.
Parasitology research.Parasitol Res.2014 Mar;113(3):959-72. doi: 10.1007/s00436-013-3728-1. Epub 2013 Dec 10.
Delicate filamentous schistosomatids detected in the intestinal veins of experimentally infected chickens are here described as a new parasite species, Gigantobilharzia melanoidis, and details of its life cycle are given. It is the first complete description of a schistosome species that uses Melano
PMID 24322292

Japanese Journal

Allobilharzia visceralis gen.nov., sp. nov. (Schistosomatidae-Trematoda) from Cygnus cygnus (L.) (Anatidae)

Parasitology international : official journal of the Japanese Society of Parasitology 55(3), 179-186, 2006-09-01
NAID 10018772293

Description and surface topography of the cercaria of Austrobilharzia sp. (Digenea : Schistosomatidae)

Parasitology international : official journal of the Japanese Society of Parasitology 53(1), 11-21, 2004-03-01
NAID 10013330590

The phylogeny of the Schistosomatidae based on three genes with emphasis on the interrelationships of Schistosoma Weinland, 1858

Parasitology 126, 203-224, 2003-03
NAID 120001728763

Related Pictures

★リンクテーブル★

リンク元	「住血吸虫属」「Bilharzia」「住血吸虫科」

「住血吸虫属」

Schistosomatidae
	Egg of Schistosoma mansoni
Scientific classification
Kingdom:	Animalia
Phylum:	Platyhelminthes
Class:	Trematoda
Order:	Strigeidida
Superfamily:	Schistosomatoidea
Family:	Schistosomatidae; Poche, 1907

　　[★]

ラ: Schistosoma、Bilharzia
同: シストソーマ属、Schistosoma属
関: 住血吸虫、住血吸虫科 Schistosomatidae; Bilharzia　Bilharzia属、ビルハルジア属、ビルハルジア; 住血吸虫症

「Bilharzia」

　　[★]

ビルハルジア、住血吸虫属、ビルハルジア属、Bilharzia属

関: Schistosoma、Schistosomatidae

「住血吸虫科」

　　[★]

ラ: Schistosomatidae
関: 住血吸虫、住血吸虫属

[Lockyer2003-1] Lockyer AE, Olson PD, Ostergaard P, Rollinson D, Johnston DA, Attwood SW, Southgate VR, Horak P, Snyder SD, Le TH, Agatsuma T, McManus DP, Carmichael AC, Naem S, Littlewood DT (2003) The phylogeny of the Schistosomatidae based on three genes with emphasis on the interrelationships of Schistosoma Weinland, 1858. Parasitology 126(Pt 3):203-224

[Brant2005-2] Brant SV, Loker ES (2005) Can specialized pathogens colonize distantly related hosts? Schistosome evolution as a case study. PLoS Pathog 1(3): e38. doi:10.1371/journal.ppat.0010038

[Snyder2004-3] Snyder SD (2004) Phylogeny and paraphyly among tetrapod blood flukes (Digenea: Schistosomatidae and Spirorchiidae). Int J Parasitol 34(12):1385-1392

[Beer2010-4] Beer SA, Voronin MV, Zazornova OP, Khrisanfova GG, Semenova SK (2010) Phylogenetic relationships among schistosomatidae. Med Parazitol (Mosk) 2010 (2):53-59

[Aldhoun2012-5] Aldhoun JA, Littlewood DT (2012) Orientobilharzia Dutt & Srivastava, 1955 (Trematoda: Schistosomatidae), a junior synonym of Schistosoma Weinland, 1858. Syst Parasitol 82(2):81-8. doi: 10.1007/s11230-012-9349-8

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案内

Schistosomatidae