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notes+september+27+parasitology

notes+september+27+parasitology - Lecture 4 Schistosoma I...

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Lecture 4 - Schistosoma I. Intro A. Blood Fluke (common name) live in the veins of DH cause disease Schistosomiasis AKA bilharziasis AKA snail fever B. The species of schistosoma important in human disease S. Mansani S. haematobium S. japonicium C. 250x10^6 infections worldwide - 2nd only to malaria D. Differences between schistosmas and other trematodes 1. dioecians = separate sexes 2. habitat - live in blood vessels 3. non operculated eggs 4. no redia stage 5. no metacaria stage 6. only human trematode that is not food-borne II. Life cycle A. Egg Sh - terminal spine - looks like a leaf or teardrop Sm - lateral spine - looks like a hook on the site Sj - smaller lateral spine or knob Hatching - fresh H2O stimulates the celia of the miracidium miracidium spins -suture: line along the eggshell B. miracidium - separate sexes infects snail C. Transforms into sporocyst sporocyst produces daughter sporocyst parasitic castration can occur shistomicin peptide normally produced by snail parasite causes snail to overproduce interferes with snails neuroendocrine system snail reproductive organs get small D. No Rediae E. Cercaria I. Morphology A. Head end mouth digestive tract glands - escape plans exit snail post acetabular glands - mucus for attachment pre-acetabular glands - enzymes penetrate host skin head glands - adjust for DH environment B. Tail 2. inside DH loses tail loses glycocalyx now known as a "schistosomula"
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F. Schistosomula now it's no longer able to survive outside. gets into bloodstream migrates to lungs lives in the capillary vessels feed on red blood cells grow, develop young adults travel into systemic circulation G. Adults. migrate to hepatic portal veins in liver reach sexual maturity mate pairs migrate to the venules of the mesentery and live there 2. Morphology a. oral sucker around mouth b. ventral sucker c. no pharynx (unlike previous species) everything else has been feeding on chunky host tissue, but these feed on red blood cells. d. caecum - bifurcates but then re-joins in the posterior part of the worm to form a single caecum e. dioecious - separate exes f. sexually dimorphic - separate sexes look different male is shorter and stouter female is thinner and 15-30% longer than male g. male has gynecophoral canal (gynecophoral groove) schisto(split)soma(body) - male has a groove going down center of body thinner female lays in the groove continuous mating single sex infection studies prove female requires male to sexually mature 3. Differences between 3 species of schistosome a. size Sj male is 20mm female is 26mm Sm male is 10 mm female is 14 mm Sh male is 15 mm female is 20mm b. male tegument Sj - smooth Sm + Sh - tubercules on surface (bumps) c. females egg production Schistosoma hematomium - 30 eggs per day Schistosoma mancini - 200-300 eggs per day Schistosoma japonicum - 3500 eggs per day d. habitats of adult worms in DH all in blood vessels, but: Sh lives in veins of mesentery urinary bladder Sm lives in veins of mesentery of large intestine
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Sj lives in veins of mesentery surrounding small intestine 4. How do the adults avoid immune attack - molecular mimicry
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