並殖屬

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並殖科
Paragonimidae
Egg of Paragonimus westermani
科學分類
界: 動物界 Animalia
門: 扁形動物門 Platyhelminthes
綱: 吸蟲綱 Trematoda
亞綱: 複殖亞綱 Digenea
目: 斜睪目 Plagiorchiida
亞目: 住胞亞目 Troglotremata
總科: 住胞總科 Troglotrematoidea
科: 住胞科 Troglotrematidae
屬: 並殖屬 Paragonimus
Braun, 1899 [1]

見內文

並殖屬(學名:Paragonimus)是扁形动物门吸蟲綱複殖亞綱斜睪目Troglotrematidae科的一個。本屬物種多達數十個,而且部分物種之下還有亞種,彼此間要分辨也不容易,而當中有多少屬於同種異名也說不清。

在眾多物種當中,較為知名的物種是多種並殖屬肺吸蟲。部分物種是一些人畜共通傳染病的病原體,例如:肺吸蟲病。本屬物種的第一中間宿主包括有至少54個物種的淡水螺,都屬於蟹守螺總科麂眼螺總科[2]。 在人類醫學中最突出的物種是Paragonimus westermani,一種源自東亞的感染性肺吸蟲。現時本屬物種在全世界,已知約9個物種能引起肺吸蟲病[3]。這些物種存在於東亞西非北美洲南美洲[3]

形態學[编辑]

Morphology of typical Paragonimus:
AC: acetabulum (ventral sucker)
CE: cecum, EB: excretory bladder
OS: oral sucker, OV: ovary
TE: testes, UT: uterus

本屬物種的大小差異頗大,成蟲可達15毫米(0.59英寸)長、8毫米(0.31英寸)寬[4]。成蟲的體型呈卵形,有刺覆蓋厚厚的皮層。Both the oral sucker and acetabulum are round and muscular. The acetabulum is slightly bigger than the oral sucker – 0.19 mm and 0.12 mm, respectively.[4] Ovaries are located behind the acetabulum and posterior to the ovary are the testes. The seminal receptacle, the uterus and its metraterm, the thick-walled terminal part, lie between the acetabulum and the ovary.[4]

Life cycle[编辑]

The parasite passes through two intermediate hosts, an aquatic snail and a crustacean. It enters its mammalian definitive hosts when they eat infected freshwater crustaceans. Typical hosts include dogs, cats, and humans. Humans usually contract paragonimiasis when they eat undercooked freshwater crabs or crayfish, that contain live metacercariae. In the intestine, the parasite will move into the abdomen and commonly into the lungs. In the lung, the parasites encyst and cross fertilize each other. The cyst eventually ruptures in the lungs and the eggs may be coughed up or swallowed and excreted in the feces. An egg landing in fresh water hatches and releases a ciliated miracidium. A successful miracidium swims about until it finds an intermediate host, usually an aquatic snail. A crustacean in turn becomes infected by eating infected snails. The definitive host completes the cycle if it eats infected crustaceans.

Epidemiology[编辑]

Worldwide roughly 20 million people are infected with Paragonimus. Human infections are commonest in regions with many human and animal reservoir hosts plus an abundance of intermediate hosts, such as snails, crabs, or crayfish, and where in addition consumption of raw or undercooked seafood is common. Consumption of insufficiently cooked meat from infected land animal hosts, such as wild boar, commonly transmits the infection.[5]

Symptoms[编辑]

Symptoms of paragonimiasis may include abdominal pain, diarrhea, fever, and hives. If the infection remains untreated, the symptoms may peter out after only few months, but sometimes they last for decades.[6] Paragonimiasis is caused by the body's natural immune response to the worms and eggs that are present and also migrating from the intestines to the lungs.

As a rule, the parasites begin to cause the symptoms about three weeks after ingesting live metacercariae. After about eight weeks, they begin to produce eggs in the lungs. Some patients develop brain damage if parasites establish in the brain and produce eggs. The brain damage commonly causes headache, vomiting, and seizures.[3] Untreated cerebral paragonimaisis commonly results in death from increased intracranial pressure.

Treatment[编辑]

Praziquantel has been used to effectively treat paragonimiasis by separating the tegument. An effectively complete rate of cure may be expected after three days of treatment if there has not been too much permanent damage, such as from intracranial effects.[7] Other medications can also be used such as bithionol, niclofan, and triclabendazole with high cure rates.

Prevention[编辑]

Thorough cooking of an infected crustacean kills all stages of the parasite. Crab meat should not be eaten raw, even if pickled, because the pickling solution often fails to kill all the parasites. Utensils and cutlery boards should be cleaned thoroughly before and after food preparation.[3]

屬與物種[编辑]

並殖科包括下列各個屬及各物種:

並殖屬 Paragonimus
狸殖屬

參考文獻[编辑]

  1. ^ M. Braun. Über Clinostomum Leidy. Zoologischer Anzeiger. 1899, 22 (603): 489–493 (德语). 
  2. ^ 2.0 2.1 G. M. Davis, C. E. Chen, Z. B. Kang & Y. Y. Liu. Snail hosts of Paragonimus in Asia and the Americas. Biomedical and Environmental Sciences. 1994, 7 (4): 369–382. PMID 7535537. 
  3. ^ 3.0 3.1 3.2 3.3 Gary W. Procop. North American paragonimiasis (caused by Paragonimus kellicotti) in the context of global paragonimiasis. Clinical Microbiology Reviews. 2009, 22 (3): 415–446. PMC 2708389. PMID 19597007. doi:10.1128/CMR.00005-08. 
  4. ^ 4.0 4.1 4.2 Imelda Vélez, Luz E. Velásquez and Iván D. Vélez. Morphological description and life cycle of Paragonimus sp. (Trematoda: Troglotrematidae): causal agent of human paragonimiasis in Colombia. Journal of Parasitology. 2003, 89 (4): 749–755. JSTOR 3285872. PMID 14533686. doi:10.1645/ge-2858. 
  5. ^ Karin Leder; Peter F Weller. Paragonimiasis. UpToDate. [15 May 2014]. 
  6. ^ Paragonimiasis (lung fluke) (PDF). August 2006 [8 December 2011]. (原始内容 (PDF)存档于2011年12月11日). 
  7. ^ Nawa Yukifumi. Re-emergence of paragonimiasis. Internal Medicine. 2000, 39 (5): 353–354. PMID 10830172. doi:10.2169/internalmedicine.39.353. 
  8. ^ 中国科学院动物研究所. 会同并殖吸虫. 《中国动物物种编目数据库》. 中国科学院微生物研究所. [2009-04-16]. (原始内容存档于2016-03-05). 
  9. ^ 中国科学院动物研究所. 卫氏并殖吸虫伊春亚种. 《中国动物物种编目数据库》. 中国科学院微生物研究所. [2009-04-16]. (原始内容存档于2016-03-05). 
  10. ^ 中国科学院动物研究所. 勐腊并殖吸虫. 《中国动物物种编目数据库》. 中国科学院微生物研究所. [2009-04-16]. (原始内容存档于2016-03-05). 
  11. ^ 中国科学院动物研究所. 四川并殖吸虫. 《中国动物物种编目数据库》. 中国科学院微生物研究所. [2009-04-16]. (原始内容存档于2016-03-05). 
  12. ^ 中国科学院动物研究所. 卫氏并殖吸虫四川亚种. 《中国动物物种编目数据库》. 中国科学院微生物研究所. [2009-04-16]. (原始内容存档于2016-03-05). 
  13. ^ 中国科学院动物研究所. 云南并殖吸虫. 《中国动物物种编目数据库》. 中国科学院微生物研究所. [2009-04-16]. (原始内容存档于2016-03-04).