出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/05/16 20:44:45」(JST)
| Echinococcus multilocularis | |
|---|---|
| Echinococcus multilocularis isolated from a fox | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Platyhelminthes |
| Class: | Cestoda |
| Order: | Cyclophyllidea |
| Family: | Taeniidae |
| Genus: | Echinococcus |
| Species: | Echinococcus multilocularis |
| Binomial name | |
| Echinococcus multilocularis Leuckart, 1863 |
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Echinococcus multilocularis is a cyclophyllid tapeworm that, along with some other members of the Echinococcus genus (especially E. granulosus), produces the disease known as echinococcosis in certain terrestrial mammals, including wolves, foxes, jackals, coyotes, domestic dogs and humans. Unlike E. granulosus, E. multilocularis produces many small cysts (also referred to as locules) that spread throughout the internal organs of the infected animal. Ingestion of these cysts, usually by a canid eating an infected rodent, results in a heavy infestation of tapeworms.
People infected with E. multilocularis may be asymptomatic for many years. Following the asymptomatic period of this disease, commons symptoms are headache, nausea, vomiting, abdominal pain. Jaundice is rare,[1] but hepatomegaly is a common physical finding.
The life cycle of E. multilocularis involves a primary or definitive host and a secondary or intermediate host, each harboring different life stages of the parasite.
Foxes, coyotes, domestic dogs and other canids are the definitive hosts for the adult stage of the parasite. The head of the tapeworm attaches to the intestinal mucosa by hooks and suckers. It then produces hundreds of microscopic eggs, which are dispersed through the feces (Vuitton, 2009[2]).
Wild rodents such as mice serve as the intermediate host. Eggs ingested by rodents develop in the liver, lungs and other organs to form multilocular cysts. Humans could also become an intermediate host by handling infected animals or ingesting contaminated food, vegetable, and water. The life cycle is completed after a fox or canine consumes a rodent infected with cysts. Larvae within the cyst develop into adult tapeworms in the intestinal tract of the definitive host (Vuitton, 2009[2]).
Except in rare cases where infected humans are eaten by canines, humans are a dead-end or incidental host (an intermediate host that does not allow transmission to the definitive host) for E. multilocularis.
The adult parasite is a small tapeworm that is 3- 6mm long, and lives in the small intestine of canines. The segmented worm contains a scolex with suckers and hooks that enable attachment to the mucosal wall, since tapeworms do not have a digestive tract. A short neck connects the head to three proglottids, the body segment of the worm which contains the eggs to be excreted in the feces.[3]
Serological and imaging tests are commonly used to diagnose this disease. Frequently used serological tests include antibody tests, ELISA and indirect hemaglutination (IHA). Also, an intradermal allergic reaction test (Casoni test) has also been used to diagnose patients. Imaging tests include: X-rays, cat scans, MRI, and ultrasound.[1]
Alveolar echinococcosis (AE) is a highly lethal helminthic disease in humans, caused by the larval form of the parasitic tapeworm E. multilocularis. The disease represents a serious public threat in China, Siberia, and central Europe. However since the 1990s, the prevalence of the disease seems to be increasing in Europe, not only in the historically endemic areas but its neighboring regions ([4]). AE primarily affects the liver by inducing a hepatic disorder similar to liver cancer ([4]), therefore becoming extremely dangerous and difficult to diagnose. If the infection metastasizes, it may spread to any other organ and could be lethal if not treated. The most common treatment for AE is to surgically remove the parasite. Since it is difficult and not always possible to remove the entire parasite, medicine such as Albendazole is utilized to keep the cyst from growing back([2])..
Guided by the Tumor-Node-Metastasis (TNM) system of liver cancer, the European Network for Concerted Surveillance of Alveolar Echinococcosis and the World Health Organization Informal Working Group on Echinococcosis, a clinical classification system has been proposed. This classification system has been designated as the "PNM" system (P = parasitic mass, N = involvement of neighboring organs, M = metastasis). The system was developed by a retrospective analysis of records from 97 patients treated in France and Germany (2 treatment centers). Amongst other characteristics, the system takes into consideration the localization of the parasite in the liver, the extent of lesion involvement, regional involvement, and metastasis.[5]
If no specific therapy is initiated, in 94% of patients the disease is fatal within 10–20 years following diagnosis.[6]
The incidence of human infestation with E. multilocularis and disease is increasing in urban areas, as wild foxes (an important reservoir species of the sylvatic cycle) are migrating to urban and suburban areas and gaining closer contact with human populations (Vuitton, 2009[2]). Also, restocking fox enclosures for fox hunting with infected animals spreads the disease.[8] Children, health care workers and domestic animals are at risk of ingesting the cysts after coming into contact with the feces of infected wild foxes. Even with the improvement of health in developed/industrialized countries, the prevalence of alveolar echinococcosis (AE) did not decrease (Vuitton, 2009[2]). On the contrary, incidents of AE have now also been registered in eastern European countries and sporadic incidences in other European countries (Vuitton, 2009[2]).
A study by veterinary parasitologists from Purdue University indicated that the disease is spreading throughout the Midwestern United States, where it was previously rare or nonexistent. Additionally, the disease has extended its range in Europe in the last few decades [1]. Still the infection is fairly rare. Between 1982 and 2000 a total of 559 cases were reported throughout Europe [2].
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| リンク元 | 「蠕虫」「寄生虫症」「多包条虫」 |
| 蠕虫類 | 病原体名 | 病名 | 感染経路 | 寄生部位 | 症状 | 診断 | 治療 | |
| 線虫類 | Ancylostoma duodenale | ズビニ鉤虫 | 鈎虫症/十二指腸虫症 | F型幼虫経口感染、経皮 | 空腸上部 | 皮膚炎、若菜病、貧血 | 飽和食塩水浮遊法、遠心沈降法 | pyrantel pamoate、鉄剤 |
| Necator americanus | アメリカ鉤虫 | |||||||
| Strongyloides stercoralis | 糞線虫 | 糞線虫症 | F型幼虫経皮感染 | 小腸上部 | Loffler症候群 | 糞便塗沫、普通寒天平板培養による R型、F型幼虫の検出 |
thiabendazole, ivermectin | |
| Enterobius vermicularis | 蟯虫 | 蟯虫症 | 虫卵経口感染 | 盲腸～大腸 | 夜間の掻痒、不眠、情緒不安定 | 肛囲検査法「柿の種」 | pyrantel pamoate | |
| Ascaris lumbricoides | 回虫 | 回虫症 | 虫卵経口感染 | 小腸孵化→門脈→ 肺発育→食道嚥下→小腸 |
Loffler症候群。急性腹痛 | 糞便虫の虫卵の証明 | pyrantel pamoate | |
| Toxocara canis | イヌ回虫 | 幼虫移行症 | 生後1-2ヶ月の感染犬の 糞から経口感染 |
なし | 幼虫移行症→失明 | 免疫診断 | 治療法無し？ | |
| Wuchereria bancrofti | バンクロフト糸状虫 | フィラリア症/糸状虫症 | アカイエカ | リンパ系 | 急性期：リンパ肝炎、リンパ腺炎を伴う熱発作(filarial fever) 慢性期：乳糜尿、リンパ管瘤、陰嚢水腫、象皮病 |
急性期：夜間のmicrofilariaの検出 慢性期：特有の症状を考慮 |
diethylcarbamazine & ivermectin | |
| Brugia malayi | マレー糸状虫 | |||||||
| Dirofilaria immitis | イヌ糸状虫 | アカイエカ | なし | 幼虫移行症→肺血管閉塞→胸部X線画像銭形陰影 | ||||
| Gnathostoma spinigerum | 有棘顎口虫 | 顎口虫症 | ドジョウ、雷魚、ヘビの生食 | 消化管壁貫通→皮下移動による腫瘤や線状皮膚炎 | 移動性腫瘤、皮膚爬行疹 雷魚やドジョウの生殖の問診 免疫血清診断 |
なし | ||
| Gnathostoma hispidum | 剛棘顎口虫 | |||||||
| Gnathostoma doloresi | ドロレス顎口虫 | |||||||
| Gnathostoma nipponicum | 日本顎口虫 | |||||||
| Anisakis simplex, larva | アニキサス幼虫 | アニサキス症 (1)胃アニサキス症、 (2)腸アニサキス症、 (3)異所性アニサキス症 |
経口感染 終宿主：クジラ、イルカ。 中間宿主：オキアミ。 待機宿主：サバ、ニシン、アジ、タラなど |
胃や腸 | (1)急激な上腹部痛"胃けいれん" (2)腹痛、急性虫垂炎、イレウス様。劇症型と緩和型がある (3)腹腔内の炎症性肉芽腫 |
胃内視鏡検査 | 内視鏡による虫体摘出 | |
| Pseudoterranova decipiens | ||||||||
| Trichinella spiralis | 旋毛虫 | 旋毛虫症 | 経口感染 豚肉、クマ肉の生食 |
(1)成虫侵襲期：下痢、腹痛 (2)幼虫筋肉移行期：顔面浮腫、心筋障害など (3)幼虫被嚢期：全身浮腫、衰弱 |
急性期：ステロイド 殺虫：mebendazole | |||
| 鞭虫症 | 盲腸 | 慢性下痢、腹痛、異食症、貧血 | セロファン重層塗沫法、 ホルマリンエーテル法 |
mebendazole | ||||
| Spirurin nematode larva | 旋尾線虫 | 旋尾線虫幼虫 | ホタルイカの生食 | なし | 皮膚爬行疹、イレウス様症状 | 予防：-30℃24時間。 生食には-30℃4日間以上 |
摘出 | |
| 吸虫類 | Shistosoma japonicum | 日本住血吸虫 | 日本住血吸虫症 | 糞便虫の虫卵→ミラシジウム→ ミヤイリガイ体内でセルカリア→ 人畜の皮膚より浸入→循環系→ 門脈に寄生 |
門脈 | (1)潜伏期：侵入部の掻痒性皮膚炎。肺移行期：咳、発熱 (2)急性期：虫卵の門脈系寄生、産卵。住血吸虫性赤痢。 (3)慢性期：虫卵の肝、脳などの塞栓。肝硬変。脾腫、腹水 |
糞便虫の虫卵の検出。 直腸粘膜層掻爬法、 肝穿刺による組織内虫卵の検出。 補助診断として免疫血清学的検査。 |
praziquantel |
| Paragonimus westermani | ウェステルマン肺吸虫 | 肺吸虫症/肺ジストマ症 | 経口感染 淡水産のカニ、イノシシ肉の生食 |
肺 | 痰、咳、胸痛、時に喀血 | 痰や便の虫卵検査、 胸部写真、 断層写真で明らかな虫嚢。 免疫学血清検査 |
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| Paragonimus miyazakii | 宮崎肺吸虫 | 肺 | 気胸、胸水貯留、膿胸、好酸球増加 | praziquantel | ||||
| Clonorchis sinensis | 肝吸虫 | 肝吸虫症/肝ジストマ症 | 経口感染 虫卵→(マメタニシ:セルカリア)→ セルカリア→(魚:メタセルカリア)→ 摂取→(ヒト:成虫)→虫卵 |
胆管 | 胆汁流出障害による肝障害→肝硬変 | 糞便、胆汁(十二指腸ゾンデ法)。 肝吸虫卵の検出。CT像。エコー検査。 |
praziquantel | |
| 横川吸虫症 | 淡水魚(アユ、フナ、ウグイ、シラウオ)の生食 | 小腸粘膜 | 下痢、腹痛 | 糞便虫の虫卵 | praziquantel | |||
| 条虫類 | Taeniarhynchus saginatus | 無鉤条虫 | 腸管条虫症 | 経口感染。中間宿主：ウシ | 小腸 | 無症状。下痢。 広節裂頭条虫感染では悪性貧血。 |
糞便虫の虫卵と体節により診断 | praziquantel。 有鉤条虫の場合はガストログラフィン。 有鉤条虫の駆虫の際、 虫体を破壊しない →虫体の融解による嚢虫症 |
| Taenia solium | 有鉤条虫 | 経口感染。中間宿主：ブタ | ||||||
| Diphyllobothrium latum | 広節裂頭条虫 | 経口感染。中間宿主：サケ、マス | ||||||
| 日本海裂頭条虫 | 経口感染。中間宿主：サケ | |||||||
| 腸管外条虫症 | ||||||||
| 有鉤嚢虫症 | 有鉤条虫の虫卵の経口摂取 | 皮下、筋肉内 脳、脊髄、眼球 |
皮下、筋肉内：小指頭大の無症状腫瘤 脳、脊髄、眼球：Jacksonてんかん。痙性麻痺など |
皮下の虫嚢 | 外科的摘出。 成虫寄生がなければ、praziquantel, albendazole + ステロイド | |||
| Echinococcus granulosus | 単包虫 | 包虫症/ エキノコックス症 (単包虫症) |
終宿主：イヌ、キツネなど。 中間宿主：ヒト、ブタ、野ネズミなど。 終宿主の糞便虫の虫卵を中間宿主が接種して発症 |
肝、肺、まれに脳、腎、筋肉 | 肝寄生：肝部疼痛、満腹、時に黄疸、下肢浮腫 肺寄生：胸部圧迫感、胸痛、咳、血痰、時に喀血 |
肝や肺の嚢胞形成から疑う。 早期に診断に皮内反応→ CT、エコー→ 生検。免疫血清学的診断法 |
外科的切除。 albendazoleの長期投与 | |
| Echinococcus multilocularis | 多包虫 | 包虫症/ エキノコックス症 (多包虫症) | ||||||