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Cestodes

Question Answer Article
Fill in the missing words about cestodes A cestode (tapeworm) is a chain (strobila) of progressively maturing reproductive units called proglottids anchored at one end to the intestinal wall by a hold-fast organ called the scolex. Link to Answer Article
What species of Taenia occur in dogs?
  • Taenia ovis
  • Taenia hydatigena
  • Taenia pisiformis
  • Taenia multiceps
  • Taenia serialis
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Describe the features of a cysticercus
  • Fluid filled bladder, containing a single invaginated head (protoscolex) - seen as a white blob on the wall of the cyst
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In which host(s) would you expect to find the cysticercus of T. hydatigena and where in the host might it be found?
  • Sheep (mostly)'
  • Cattle
  • Pigs
  • Found in the peritoneal cavity
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What is the difference between a coenurus and a cysticercus?
  • A coenurus is a fluid filled bladder with multiples (dozens) of inverted scolices attached to the wall
  • Whereas the cysticercus has only a single inverted scolex.
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How does the distribution of hydatid cysts differ in sheep, horses and humans?
  • Sheep = most are in the lungs with smaller numbers in the liver
  • Horses = nearly all are in the liver
  • Humans = most are in the liver, with some in the lungs and a few elsewhere
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What tapeworms occur in the cat?
  • Taenia taeniaeformis
  • Dipylidium
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Why is it so difficult to prevent many cats from becoming re-infected with T. taeniaeformis?
  • The intermediate hosts are mice and other small mammals that are hunted
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Where in the host (horse) would you expect to find Anoplocephala?
  • Ileo-caecal junction
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Why are Anoplocephala eggs rarely seen on routine faecal examination?
  • They are dense structures and do not always float in the flotation media used in routine diagnosis
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Why is it so difficult to prevent grazing horses from becoming re-infected with Anoplocephala?
  • The intermediate hosts are ubiquitous free-living pasture mites
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Describe the appearance of Moniezia
  • Long tapeworm (up to 2m)
  • Segments much wider than they are long
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Why is T. solium more dangerous to human health than T. saginata?
  • If T. solium eggs get into the human small intestine, they will hatch and cysticerci can establish in the musculature and CNS. This does not happen with T. saginata.
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Trematodes

Question Answer Article
What are the most diagnostic features of the Fasciola egg?
  • Oval
  • Granular contents
  • Operculum ('trap-door') at one end
  • Double the size of a typical strongyle egg
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