Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/03/06 09:15:18」(JST)

wiki en

Life-history stages of the trematode flatworm Fasciola hepatica from 1911 Encyclopaedia Britannica

Trematodes or flukes are small parasitic flatworms that use vertebrates as their definitive host, and molluscs (usually freshwater snails or land snails) as their intermediate host. To accomplish this, they have several varied life cycle stages.

The life cycle of a typical digenean trematode can be thought to begin when its egg is immersed in water. Following this, a miracidium hatches, which swims to find a mollusc host. The miracidia go through several stages in the mollusc host, eventually emerging as motile cercarial larvae.^[1] The cercaria either infects vertebrates through the skin or is ingested. In its vertebrate host, the cercaria matures to an adult form, the fluke, and lays eggs that are discharged with the host feces or urine. In the presence of open water, the eggs hatch and the miracidium stage of life is reached again.

Typical life cycle stages

Metacercariae of Clinostomum phalacrocoracis in fish^[2]

Bucephalid cercaria larva from Ernst Haeckel's Kunstformen der Natur (1904): The tail's furcae give the impression of horns, hence the genus name Bucephalus meaning "ox head".

While the details vary with each species, the general life cycle stages are:

Egg – discharged either in open water or in intestine of definitive host
Miracidium (plural miracidia) – a free-living motile form, it is covered with cilia, and settles in the mollusc to become a sporocyst.^[3]
Sporocyst – an elongated sac, it produces either rediae or more sporocysts.^[4]
Redia (plural rediae) – a larval form with an oral sucker, it will produce either more rediae, or cercariae.^[4]
Cercaria (plural cercariae) – the larval form of the parasite, it develops within the germinal cells of the sporocyst or redia.^[4] A cercaria has a tapering head with large penetration glands.^[3] It may or may not have a long swimming "tail", depending on the species.^[4] The motile cercaria finds and settles in a host where it will become either an adult, or a mesocercaria, or a metacercaria, according to species.
- Mesocercaria – a cercaria little modified but resting
- Metacercaria – a cercaria encysted and resting
Adult – the fully developed mature stage, it is capable of sexual reproduction.

Deviations from the typical life cycle

Not all trematodes follow the typical sequence of eggs, miracidia, sporocysts, rediae, cercariae, and adults. In some species, the redial stage is omitted, and sporocysts produce cercariae. In some species, the cercaria develops into an adult within the same host.

Many digenean trematodes require two hosts, one (typically a snail) where asexual reproduction occurs in sporocysts, the other a vertebrate (typically a fish) where the adult form engages in sexual reproduction to produce eggs. In some species (for example Ribeiroia) the cercaria encysts, and waits until the host is eaten by a third host, in whose gut it emerges and develops into an adult.

Most trematodes are hermaphroditic, but members of the family Schistosomatidae are dioecious. Males are shorter and stouter than the females.^[3]

Representations of life cycles of several different trematode species

Life cycle stages of a digenean human parasite, Schistosoma japonicum

Life cycle stages of a digenean fish parasite, Bucephalus polymorphus

Life cycle stages of trematode species that cause "swimmer's itch"

References

^ "2. Fish Diseases (Cont'd.) 2.1.4 Parasitic Diseases". FAO of the UN Food and Agriculture Organization of the United Nations. Retrieved 18 February 2011.
^ Caffara, Monica; Davidovich, Nadav; Falk, Rama; Smirnov, Margarita; Ofek, Tamir; Cummings, David; Gustinelli, Andrea; Fioravanti, Maria L. (2014). "Redescription of Clinostomum phalacrocoracis metacercariae (Digenea: Clinostomidae) in cichlids from Lake Kinneret, Israel". Parasite. 21: 32. doi:10.1051/parasite/2014034. ISSN 1776-1042. PMC 4078730. PMID 24986336.
^ ^a ^b ^c "Schistosoma". Australian Society for Parasitology. Retrieved 19 February 2011.
^ ^a ^b ^c ^d "Glossary". VPTH 603 Veterinary Parasitology. University of Pennsylvania School of Veterinary Medicine.

External links

Life cycle of Schistosoma mansoni

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 腸管寄生虫症 intestinal flukes
2. 住血吸虫症の疫学、病因、および臨床症状 epidemiology pathogenesis and clinical manifestations of schistosomiasis
3. 肺吸虫症 paragonimiasis
4. 肝吸虫：肝蛭症 liver flukes fascioliasis
5. 肝吸虫：Clonorchis、Opisthorchi、およびMetorchis liver flukes clonorchis opisthorchis and metorchis

English Journal

Outbreak of urogenital schistosomiasis in Corsica (France): an epidemiological case study.

Boissier J1, Grech-Angelini S2, Webster BL3, Allienne JF4, Huyse T5, Mas-Coma S6, Toulza E4, Barré-Cardi H7, Rollinson D3, Kincaid-Smith J4, Oleaga A8, Galinier R4, Foata J9, Rognon A4, Berry A10, Mouahid G4, Henneron R11, Moné H4, Noel H12, Mitta G4.
The Lancet. Infectious diseases.Lancet Infect Dis.2016 Aug;16(8):971-9. doi: 10.1016/S1473-3099(16)00175-4. Epub 2016 May 17.
BACKGROUND: Schistosomiasis is a snail-borne parasitic disease endemic in several tropical and subtropical countries. However, in the summer of 2013, an unexpected outbreak of urogenital schistosomiasis occurred in Corsica, with more than 120 local people or tourists infected. We used a multidiscipl
PMID 27197551

In vivo and in vitro effects of the herbicide Roundup® on developmental stages of the trematode Echinostoma paraensei.

Monte TC1, Garcia J1, Gentile R1, de Vasconcellos MC2, Souza J1, Braga BV1, Maldonado A Jr3.
Experimental parasitology.Exp Parasitol.2016 Jul 1;169:43-50. doi: 10.1016/j.exppara.2016.06.012. [Epub ahead of print]
The exposure of wildlife and humans to toxic residues of Roundup® through agricultural practices or the food chain has been reported since the herbicide was found contaminating rivers. Glyphosate, N-(phosphonomethyl)glycine acid, is a nonselective post-emergent herbicide and is formulated as an iso
PMID 27373431

Mobile Diagnostics Based on Motion? A Close Look at Motility Patterns in the Schistosome Life Cycle.

Linder E1, Varjo S2, Thors C3.
Diagnostics (Basel, Switzerland).Diagnostics (Basel).2016 Jun 17;6(2). pii: E24. doi: 10.3390/diagnostics6020024.
Imaging at high resolution and subsequent image analysis with modified mobile phones have the potential to solve problems related to microscopy-based diagnostics of parasitic infections in many endemic regions. Diagnostics using the computing power of "smartphones" is not restricted by limited exper
PMID 27322330

Japanese Journal

Analysis of the effectiveness of control measures against Schistosoma mekongi using an intra- and inter-village model in Champasak Province, Lao PDR

Fukuhara Kazuma,Phompida Samlane,Insisiengmay Sithat,Kirinoki Masashi,Chigusa Yuichi,Nakamura Satoshi,Matsuda Hajime,Ishikawa Hirofumi
Parasitology International 60(4), 452-459, 2011-12
… The chief characteristic of the present model is competence in dealing with the spread of infection among villages through the Mekong River in consideration of the reduction in longevity of cercariae and miracidia and their diffusion in the river. …
NAID 120004754293

P117 住血吸虫ミラシジウムの中間宿主貝への chemoklinokinesis

山内秀彦,松山拓史,青木克己
衞生動物 52(Supplement), 107, 2001-04-04
NAID 110003822155

Comparative Studies for Development of Three Different Geographic Strains of Schistosoma japonicum Cercariae in Five Subspecies of Oncomelania hupensis.

, , ,
Japanese Journal of Tropical Medicine and Hygiene 26(3), 167-171, 1998
… and 10 weeks for the Japanese and Chinese strains after exposure to 5 miracidia. …
NAID 130003975956