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45 Cards in this Set

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