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  1. Describe the difference between sexes in schistosomes
    • males shorter/stouter
    • males have gynecophoric canal to house female
    • males have 5-9 testes depending on spp
    • cirrus is absent
    • *NOTE - copulation is continuous
  2. Where causes damage in a schistosome infection?
    Eggs: they are spined, penetrate the vein wall, and often get lodged in other areas of the body
  3. Describe the general life cycle of a schistosome
    • Eggs: hatch in freshwater
    • *NOTE - no operculum
    • Miracidium: swims and enters snail host
    • transforms into sporocyst
    • Sporocysts: produce 2nd generation of migratory sporocysts
    • move to digestive gland or gonads
    • produce more sporocysts OR cercaria
    • *NOTE - redia absent
    • Cercaria: leave the sporocyst via birth pore
    • exits snail tissues using escape glands
    • penetrate mamalian skin using penetration glands
    • *NOTE - schistosome cercaria have FORKED tail
    • *NOTE - no 2nd intermediate host
    • *NOTE - no metacercaria
    • schistosomula: enters peripheral circulation, taken to right side of heart
    • feeds on RBCs in pulmonary capillaries
    • move back to heart and into systemic circulation
    • attain sexual maturity in hepatic portal veins
    • Paired worms migrate to preferred location
  4. How does schistosomula physically differ from cercaria?
    • removal of tail
    • smaller size due to excretion from glands
  5. How many infections worldwide of schistomiasis?  Details about "who" gets infected
    • >250 million (~5% of world population)
    • 500-600 million exposed to schistosomiasis
    • S. japonicum is most serious disease in China
    • Men infected 9:1
    • Mostly occurs <30 years of age
    • vulnerable groups: farmers in irrigation water, fishermen in streams, children playing in water, women washing clothes in streams
    • *NOTE - human feces in water is most important factor
  6. What is cercarial dermatitis?
    • AKA swimmer's itch
    • Cercariae of nonhuman blood flukes attack humans
    • cannot enter blood stream, destroyed by immune system
    • released materials cause inflamation
    • common in northern US lakes
  7. Describe the progression of schistosomiasis (in phases)
    • Initial phase: 4-10 weeks after infection
    • migration from lungs to hepatic portal system
    • fever, allergies, abdominal pain, hepatosplenomegaly, diarrhea
    • Intermediate phase: 2 months - several years after infection
    • Bloody stools (S. japonicum, S. mansoni)
    • Hematuria, dysuria (S. haematobium)
    • caused by passage of spined eggs
    • Final phase: most serious phase
    • severe intestinal, renal, and hepatic pathology
    • caused by rx of host to eggs
    • eggs lodged in venuoles cause inflammation, and lead to pseudotubercles which may block circulation
    • Hepatosplenomegaly
  8. Is there a vaccine for schistosomes?
    • No
    • Schistosomes practice molecular mimicry VERY early in schistosomule stage
    • effective vaccine would require knowledge of initial penetration and immediate vaccination
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2014-11-12 19:47:49
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