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General issues of Vaccine
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General issues of Tropical med.
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General issues of Travel med.
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Trematode (fluke, distoma)
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schistosoma is distinct from other trematoda
- trematode中schistosomaは他のtrematodeと異なる特徴を持つ
schistosoma |
other trematode
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transmitted to human by percutaneous invasion of cercariae |
transmitted to human by oral ingestion of metacercariae
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male and female separated 雌雄別体 |
hermaphrodite雌雄同体
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does not require 2nd intermediate host (no metacercariae stage) |
requires 2nd intermediate host
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Schistosoma japonicum
- Katsurada Fujiro found 26 May 1904 from a cat in Yamanashi(水腫腸満)
- Fujinami Kan found 30 May 1904 from a murder victim in Katayama, Hiroshima(片山病)
- found egg in 1904 in Saga(奇病)
pathogenesis
- adult female paired by male migrate to messenteric vein from portal vein and lay eggs into messenteric venule, which are secreted from messenteric venule to intestinal lumen
- eggs also reach urinary bladder or genital tract and generate inflammation, followed by necrosis of tissue and perforation to intestine, resulted in extracorporeal distribution of egg via stool
- eggs are also distributed in liver and cause inflammation resulting in cirrhosis
- inflammation is exclusively due to egg
- adult pairs do not cause disease per se
co-infection
- HIV
- Typhoid
- Salmonella typhi has crossover antigenicity with Schistosoma and makes immune-tolerance against Schistosoma infection
- Also Salmonella hide between male and female schistosomes in the gynecophoric canal
- HepB/C
treatment
- praziquantel was discovered only in mid-1970s in Germany
- praziquantel only kills adult schistosoma
control
- only way to control is eliminate intermediate hosts, snails - Oncomelania nosophora 宮入貝