関: Echi- nococcosis

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tapeworms
tapeworms whose larvae are parasitic in humans and domestic animals

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/03/25 03:52:36」(JST)

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schematic representation of the life cycle of Echinococcus

The genus Echinococcus includes six parasite species of cyclophyllid tapeworms to date, of the family Taeniidae. Infection with Echinococcus results in hydatid disease, also known as echinococcosis.

Echinococcus is triploblastic – it has three layers – outermost ectoderm, middle mesode, and inner endoderm. An anus is absent, and it has no digestive system. Its body is covered by tegument and the worm is divided into a scolex, a short neck, and three to six proglottids. Its body shape is ribbon-like.

In humans, this causes a disease called echinococcosis. The three types of echinococcosis are cystic echinococcosis caused by E. granulosus, alveolar echinococcosis caused by E. multilocularis, and polycystic echinococcosis caused by E. vogeli or E. oligarthrus.^[1] A worm's incubation period is usually long and can be up to 50 years. Cystic echinococcosis is mostly found in South and Central America, Africa, the Middle East, China, Italy, Spain, Greece, Russia, and the western United States (Arizona, New Mexico, and California).

Echinococcosis is a zoonosis. The definitive hosts are carnivorous predators – dogs, wolves, foxes, and lions. The adult tapeworm lives in their small intestines and delivers eggs to be excreted with the stool. The intermediate hosts are infected by ingesting eggs. Sheep, goats, cattle, camels, pigs, wild herbivores, and rodents are the usual intermediate hosts, but humans can also be infected. Humans are dead-end hosts, since their corpses are nowadays seldom eaten by carnivorous predators.

The egg hatches in the digestive system of the intermediate host, producing a planula larva. It penetrates the intestinal wall and is carried by bloodstream to liver, lung, brain, or another organ. It settles there and turns into a bladder-like structure called hydatid cyst. From the inner lining of its wall, protoscoleces (i.e. scoleces with invaginated tissue layers) bud and protrude into the fluid filling the cyst.

After the death of the normal intermediate host, its body can be eaten by carnivores suitable as definitive hosts. In their small intestines, protoscoleces turn inside out, attach, and give rise to adult tapeworms, completing the lifecycle. In humans, the cysts persist and grow for years. They are regularly found in the liver (and every possible organ: spleen, kidney, bone, brain, tongue and skin) and are asymptomatic until their growing size produces symptoms or are accidentally discovered. Disruption of the cysts (spontaneous or iatrogenic e.g. liver biopsy) can be life-threatening due to anaphylactic shock.

Cysts are detected with ultrasound, X-ray computed tomography, or other imaging techniques. Antiechinococcus antibodies can be detected with serodiagnostic tests – indirect fluorescent antibody, complement fixation, ELISA, Western blot, and other methods.^[2]

Taxonomy

A phylogenetic tree has been created for several species in this genus – Echinococcus oligarthrus, Echinococcus vogeli, Echinococcus multilocularis, Echinococcus shiquicus, Echinococcus equinus, Echinococcus ortleppi, and Echinococcus granulosus.^[3] The first diverging species are the neotropical endemic species E. oligarthrus and E. vogeli. E. ortleppi and E. canadensis are sister species, as are E. multilocularis and E. shiquicus. E. canadensis is related to E. granulosus.

The origin of these parasites based on host-parasite co-evolution comparisons was North America or Asia, depending on whether the ancestral definitive hosts were canids or felids.

Echinococcus oligarthrus and Echinococcus vogeli are basal in this genus.^[4] The genus is a sister to the genus Taenia from which it diverged more than 10 million years ago. The genus Echinococcus evolved in North America in canids and began to diversify 5.8 million years ago.

Prevention

There is no vaccine against Echinococcus multilocularis. However it is possible to prevent humans from the fox tapeworm by deworming the main hosts.^[5]

References

^ Thompson RCA, McManus DP. Aetiology: parasites and life cycles. In: Eckert J, Gemmell MA, Meslin F-X, Pawlowski ZS editor. WHO/OIE Manual on Echinococcosis in Humans and Animals: a Public Health Problem of Global Concern. Paris: Office Internationale des Epizooities; 2001;p. 1–19
^ Wenbao Zhang, Hao Wen, Jun Li, Renyong Lin, and Donald P. McManus, Immunology and Immunodiagnosis of Cystic Echinococcosis: An Update. Clinical and Developmental Immunology, 2012, 10 pages doi:10.1155/2012/101895
^ Nakao M, McManus DP, Schantz PM, Craig PS, Ito A (2007) A molecular phylogeny of the genus Echinococcus inferred from complete mitochondrial genomes. Parasitology 134(5):713-722
^ Knapp J, Nakao M, Yanagida T, Okamoto M, Saarma U, Lavikainen A, Ito A (2011) Phylogenetic relationships within Echinococcus and Taenia tapeworms (Cestoda: Taeniidae): an inference from nuclear protein-coding genes. Mol Phylogenet Evol 61(3):628-638. doi: 10.1016/j.ympev.2011.07.022
^ Grabs A (November 2016). "How To Exterminate The Fox Tapeworm In Your Area".

UpToDate Contents

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1. エキノコックス症の臨床症状および診断clinical manifestations and diagnosis of echinococcosis [show details]
…caused by infection with the metacestode stage of the tapeworm Echinococcus, which belongs to the family Taeniidae. Four species of Echinococcus produce infection in humans; E. granulosus and E. multilocularis …
2. エキノコックス症の治療および予防treatment of echinococcosis [show details]
… Echinococcosis is caused by infection with the tapeworm Echinococcus, which belongs to the family Taeniidae. Four species of Echinococcus cause infection in humans. E. granulosus and E. multilocularis …
3. エキノコックス症の疫学および制御epidemiology and control of echinococcosis [show details]
… Echinococcal disease is caused by infection with the tapeworm Echinococcus. Four species of Echinococcus cause infection in humans. E. granulosus and E. multilocularis are the most common, causing cystic …
4. 犬からの人畜共通感染症zoonoses from dogs [show details]
…millimeters per day . Dogs and other carnivorous mammals are the definitive hosts for the tapeworm, Echinococcus granulosus The adult tapeworm inhabits the small intestine of the dog and can produce eggs that…
5. 肝嚢胞性病変の診断およびマネージメントdiagnosis and management of cystic lesions of the liver [show details]
…chemotherapy) is unknown. Echinococcal (hydatid) cysts of the liver are caused by the larval form of Echinococcus granulosus, which is usually acquired from infected dogs. These are fluid-filled structures limited …

English Journal

Molecular genotyping of Echinococcus granulosus in animal and human isolates from Egypt.

Abdel Aaty HE, Abdel-Hameed DM, Alam-Eldin YH, El-Shennawy SF, Aminou HA, Makled SS, Darweesh SK.SourceFaculty of Medicine, Ain Shams University, Abasia Square, Cairo, Egypt.
Acta tropica.Acta Trop.2012 Feb;121(2):125-8. Epub 2011 Nov 2.
Despite, Egypt is started to be considered as an emerging endemic area for cystic echinococcosis (CE), no enough data in the literature about the exact status of the genotype in both animals and humans. Therefore, the present study aims to characterize the underlying genotypes that could be responsi
PMID 22062047

Phagocyte-specific S100 proteins in the local response to the Echinococcus granulosus larva.

Basika T, Muñoz N, Casaravilla C, Irigoín F, Batthyány C, Bonilla M, Salinas G, Pacheco JP, Roth J, Durán R, Díaz A.SourceCátedra de Inmunología, Departamento de Biociencias (Facultad de Química) e Instituto de Química Biológica (Facultad de Ciencias), Universidad de la República, Montevideo, Uruguay.
Parasitology.Parasitology.2012 Jan 5:1-13. [Epub ahead of print]
SUMMARYInfection by larval Echinococcus granulosus is usually characterized by tight inflammatory control. However, various degrees of chronic granulomatous inflammation are also observed, reaching a high point in infection of cattle by the most prevalent parasite strain worldwide, which is not well
PMID 22216900

Japanese Journal

牛の肝臓にみられた小結節病巣の病理組織学的検索

日本獣医師会雑誌 69(3), 147-151, 2016
NAID 130005147263

Neglected Tropical Diseases治療薬開発研究の最新の動向

YAKUGAKU ZASSHI 136(2), 205-211, 2016
NAID 130005121470

Rapid identification of <i>Echinococcus granulosus</i> and <i>E. canadensis</i> using high-resolution melting (HRM) analysis by focusing on single nucleotide polymorphism

Japanese Journal of Infectious Diseases advpub(0), 2015
NAID 130005108467

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★リンクテーブル★

リンク元	「エキノコックス属」「包虫」「包虫属」「エキノコッカス」
拡張検索	「Echinococcus属」「Echinococcus multilocularis」