Chapter 4: Digenea – Flashcards
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Number these terms from 1-7 to describe the chronologic sequence of the life cycle of an intestinal trematode.
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1) Egg 2) Miracidium 3) Sporocyst 4) Redia 5) Cercaria 6) Metacercaria 7) Adult
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You have decided to move to the Great Lakes area of the United States to become a sheepherder. You will be a hermit, enjoying a completely self-sustained life by the edge of a lake with your sheepdog and sheep. Which of the following sets of Platyhelminthes are you most likely to contract? Why did you reject each of the other answer sets? a) Fasciola hepatica, Paragonimus westermani, Taenia solium b) Schistosoma mansoni, Echinococcus granulosus, Chlonorchis sinensis c) Fasciolopsis buski, Diphyllobothrium latum, Schistosoma japonicum d) Fasciola hepatica, Echinococcus granulosus, Diphyllobothrium latum e) Heterophyes heterophyes, Hymenolepis nana, Dipylidium caninum
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d) Possible contact with sheep-transmitted, sheepdog-transmitted, and freshwater fish-transmitted parasites. a) No contact to pigs. No contact with snails or fish hosts of Oriental lung fluke b) No contact with snails or host S. mansoni or hosts of C. sinensis c) No contact with snail hosts of S. japonicum e) No contact with snails or fish hosts of H. heterophyes
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Fasciolopsis buski (large intestinal fluke) ingestion
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Human eats metacercariae on uncooked water plant
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Clonorchis sinensis (Chinese liver fluke)
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Human eats metacercariae on uncooked fish
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Schistosoma mansoni (Manson's blood fluke)
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Cercariae penetrate skin
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Why are methods of infection and control for the blood flukes different from those for the intestinal flukes?
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blood flukes: by penetration of the skin by cercariae in fresh water. Prevention of infection requires prohibiting human feces/urine from contaminating fresh water, controlling the snail population, not entering contaminated water without protection, treating carriers with drugs, and educating the public. intestinal flukes: prevention of infection requires cooking all fish and crustaceans thoroughly, washing water plants (watercres, water chestnuts thoroughly), educating people about methods of infection and about not contaminating fresh water with human waste, treating carriers, and controlling the snail population.
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Humans can be infected with the larval stage of all except one of the following parasites. Which of these Digenea cannot develop as a viable larva in the tissues of humans?
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Bird schistosomes
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Which of the Platyhelminthes infects humans by skin penetration and has an association with bladder cancer?
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Schistosoma haematobium
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Eggs of all of the following flukes are undeveloped when passed in feces EXCEPT:
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Fasciola hepatica
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The preferred specimen for the diagnosis of paragonimiasis is:
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Sputum
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The three species of human blood flukes have as intermediate host:
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An aquatic snail
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The fluke acquired by eating contaminated vegetation is:
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Fasciolopsis buski
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Fish carrying metacercariae may transmit:
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Clonorchis sinensis
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Paragonimus westermani infection is acquired by:
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Eating infected crustacea
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Schistosoma cercariae enter the human body:
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By either b or c (by skin penetration or by in contaminated drinking water)
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The digenea infection for which bloody urine is often a symptom is:
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Schistosoma haematobium
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The fluke most commonly found in the United States is:
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Fasciola hepatica
