echinococcus

　

WordNet

1. 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）』「2015/05/14 17:29:54」(JST)

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This article is about the organism. For the infection, see Echinococcosis.

Echinococcus
Scientific classification
Kingdom:	Animalia
Phylum:	Platyhelminthes
Class:	Cestoda
Order:	Cyclophyllidea
Family:	Taeniidae
Genus:	Echinococcus

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 mesoderm, 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. A worm'sincubation 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; humans are dead-end hosts. 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.

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.

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. 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. 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.

References

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
• 2. エキノコックス症の治療および予防 treatment of echinococcosis
• 3. エキノコックス症の疫学および制御 epidemiology and control of echinococcosis
• 4. 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
• 5. 犬からの人畜共通感染症 zoonoses from dogs

English Journal

• Chemoprophylactic and therapeutic efficacy of thymol in murine cystic echinococcosis.

• Maggiore M1, Pensel PE2, Denegri G2, Elissondo MC3.
• Parasitology international.Parasitol Int.2015 Oct;64(5):435-40. doi: 10.1016/j.parint.2015.06.005. Epub 2015 Jun 19.
• Cystic echinococcosis is a zoonotic disease caused by the larval stage of the cestode Echinococcus granulosus. The drugs commonly used against cystic echinococcosis are benzimidazoles. Unfortunately, 20%-40% of cases do not respond favorably to such chemotherapy. Consequently, the search of new ther
• PMID 26096310

• The first report of human-derived G10 genotype of Echinococcus canadensis in China and possible sources and routes of transmission.

• Yang D1, Zhang T2, Zeng Z3, Zhao W1, Zhang W4, Liu A5.
• Parasitology international.Parasitol Int.2015 Oct;64(5):330-3. doi: 10.1016/j.parint.2015.05.001. Epub 2015 May 9.
• Cystic echinococcosis (CE) is one of the most important parasitic zoonoses. 10 distinct genotypes, designated G1-G10 genotypes of Echinococcus granulosus sensu lato (s.l.), have been split into 4 species: Echinococcus granulosus sensu stricto (s.s.) (G1-G3), Echinococcus equinus (G4), Echinococcus o
• PMID 25967082

• Neotropical echinococcosis caused by Echinococcus vogeli in a 6-year-old child: the second case report in humans in French Guiana.

• Debourgogne A, Blanchet D, Fior A, Umhang G, Simon S, Aznar C.
• Paediatrics and international child health.Paediatr Int Child Health.2015 Sep 10:2046905515Y0000000054. [Epub ahead of print]
• Human polycystic echinococcosis is a parasitic infection caused by the larval stage of Echinococcus vogeli which occurs in rural areas of Central and South America. Abdominal echinococcosis caused by E. vogeli is reported for the first time in a child, a 6-year-old boy in French Guiana. The diagnosi
• PMID 26355940

Japanese Journal

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

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

• Cystic Hydatidosis of the Rib–Case Report and Review of the Literature

• Annals of Thoracic and Cardiovascular Surgery 21(5), 492-495, 2015
• NAID 130005104678

• Cystic Hydatidosis of the Rib–Case Report and Review of the Literature

• Annals of Thoracic and Cardiovascular Surgery advpub(0), 2015
• NAID 130005072779

Related Links

• Echinococcus: MedlinePlus Medical Encyclopedia

Echinococcus is common in: Africa Central Asia Southern South America The Mediterranean The Middle East In the United States, the disease is very rare. But it has been reported in California, Arizona, New Mexico ...

• echinococcusの意味 - goo辞書 英和和英

echinococcusとは。意味や和訳。[名詞] 〔病理〕 エキノコックス，包虫：サナダムシの幼生が哺乳類の体内で示す1型. - 80万項目以上収録、例文・コロケーションが豊富な無料英和和英辞典。

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