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45 Cards in this Set
- Front
- Back
Definition of flukes
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Parasitic flatworms that reproduce sexually in humans (or other DEFINITIVE hosts) and multipy asexually in snails (obligatory INTERMEDIATE host)
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What is the difference between blood flukes and tissue flukes
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Blood flukes have separate male and female forms, tissue flukes are hermaphroditic
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Oriental liver fluke is this type of fluke
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Tissue fluke (hermaphroditic)
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What are the three important schistosomes of humans
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Mansoni, haematobium, japonicum
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These are the blood flukes
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Schistosomes
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Route of infection of schistosomes
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Penetration of human skin by free-swimming cercariae
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What are cercariae
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The free-swimming, fresh water form of Schistosomes
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Site of maturation of schistosomes
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Lungs, and then hepatoportal system
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Cercariae are the free-living forms of this worm
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Schistosomes (mansoni, haematobium, japonicum)
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Mature mated pairs of these schistosomes enter mesenteric venules
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S. mansoni, S. japonicum
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Mature mated pairs of this schistosome enters the bladder venules
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S. haematobium
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Site of egg-laying of Schistosomes
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Mesenteric venules (S. masoni, S. japonicum), or bladder venules (S. haematobium)
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How are schistosome eggs released into the environment?
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Urine (S. haematobium), feces (S. masoni, S. japonicum)
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Site of egg-hatching of Schistosomes
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Fresh water
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Define the ciliated stage of Schistosomes
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This is the stage of the Schistosome right after it hatches, which infects snails and multiplies extensively to yield many cercariae
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Infective stage of Schistosomes
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Ciliated stage infects the intermediate host (snail) where they mature to cercariae, which infect the definitive host (human)
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Diagnostic stage of Schistosomiasis
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Egg in feces, urine or rectal biopsy
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Description of S. mansoni egg
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Large lateral spine
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Description of S. japonicum egg
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Small lateral spine
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Description of S. haematobium egg
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Large terminal spine
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Signs and symptoms of schistosomiasis
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Fever, flu-like sx, HSM, LAD, eosinophilia; respiratory sx, urticaria; hematuria, bloody vomit
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Pathogenesis of schistosomiasis
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Caused by immune response to eggs in various tissues
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Lifespan of schistosome eggs
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They can live for decades in the human host
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These worms cloak themselves in human antigens to avoid immune response
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Schistosomes
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How many eggs does the female schistosome produce daily?
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One thousand (1,000)
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Incubation period of schistosomiasis
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3-6 weeks
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Infection by this worm is characterized by granuloma formation, especially in the liver
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Schistosome
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Blood flow is compromised by the immune response to this worm's eggs
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Schistosome
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Pipestem fibrosis is a feature of this worm infection
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Schistosomiasis
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Complications of pipestem fibrosis
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Portal HTN, esophageal varices, hepatomegaly, sometimes splenomegaly
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Sites where schistosome eggs can deposit
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Liver, lungs (via portal-systemic circulation, which bypasses the liver), CNS vasculature
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This worm's eggs can deposit in the CNS vasculature where they can cause severe damage
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Schistosome
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Eggs of this worm can cause chronic UTI's and bladder tumors
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Schistosoma haematobium
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Complications of this worm infection includes cancer
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Schistosoma haematobium's eggs can induce bladder tumors
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Complications of this worm infection includes hydronephrosis
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Schistosoma haematobium
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Complications of this worm infection includes reduced ability of bladder expansion
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Schistosoma haematobium, due to calcification of eggs
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Bloody vomit or hematuria can notably be caused by this worm infection
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Schistosomiasis
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Africa and Middle East
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Schistosoma haematobium
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China, Japan, Southeast Asia
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Schistosoma japonicum
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Northern Africa, Arabia, South America, Caribbean islands
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Schistosoma mansoni
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T/F: Momentary contact with fresh water can cause schistosomiasis
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False. Momentary contact with fresh water will almost never result in worm burdens great enough to cause sx.
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Treatment of schistosomiasis
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Praziquantel
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Swimmer's itch
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Schistosome dermatitis
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Cause of swimmer's itch
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Cercariae of schistosomes of which humans are the ACCIDENTAL host; their DEFINITIVE host is birds or other mammals. Cercariae penetrate the skin and die, causing itchy dermatitis.
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Geographic distribution of swimmer's itch
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Worldwide, fresh or salt water depending on the species of snail (human schistosomes live in fresh water only)
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