Supplemental Lecture (97/05/04 update) by Stephen T. Abedon (abedon.1@osu.edu)

  1. Chapter title: Multicellular Parasites
    1. A list of vocabulary words is found toward the end of this document
  2. Some Human Diseases Caused by Multicellular Parasites
    1. ascariasis
    2. hookworm
    3. hydatidosis
    4. neurocysticercosis
    5. paragonimiasis
    6. pinworm
    7. schistosomiasis
    8. tapeworm
    9. trichinosis
    10. anisakiasis
  3. Parasite [parasitism]
    1. Small, intimate injurer:
      1. Parasitism is an intimate association between one organisms (the parasite) and a second organism (the host) in which the parasite derives benefits and the host is injured in some way.
      2. Usually a parasite is considered to be something smaller than the host and therefore capable of parasitizing only one host at a time.
  4. Helminths
    1. Parasitic worms:
      1. Helminths are eucaryotic, multicellular animals that are mostly parasitic of other animals.
      2. They live in a large variety of tissues, though many are specialized to single tissues such as muscle, vein, brain, or intestine.
      3. Many have complex life cycles that reach an apex in some which must pass through as succession of well defined hosts.
      4. May be devided into:
        1. flatworms (platyhelminths)
        2. tapeworms (cestodes)
        3. flukes (trematodes)
        4. roundworms (nematodes)
    2. Characteristics:
      1. Generally helminths:
        1. have a degenerative digestive tract and instead may absorb digested nutrients directly from their host
        2. have degenerate nervous systems
        3. do not locomote under their own power well if at all
        4. have a physiology dominated by their reproductive system
      2. Some helminths are dioecious while others are hermaphrodites, some may self-fertilize while others are obligate outcrossers.
  5. Platyhelminths [flatworm]
    1. A platyhelminths is a flatworm helminth.
  6. Cestodes [tapeworm]
    1. A cestodes is a tapeworm platyhelminth.
    2. Intestinal parasite:
      1. Cestodes are intestinal parasites.
      2. They attach at one end to the wall of their host but otherwise do not absorb nutrients using a specialized organ.
  7. Trematodes [flukes]
    1. Fluke platyhelminths:
      1. Trematodes are fluke platyhelminths.
      2. Flukes are flatworms with:
        1. flattened bodies
        2. a ventral sucker
        3. an oral sucker
  8. Nematodes [roundworm]
    1. Roundworms:
      1. Nematodes are roundworms.
      2. Roundworms are cylindrical helminths, tapered at each end, which contain a complete digestive system
      3. Nematodes do not have nearly as complex life cycles as do platyhelminths.
      4. For some nematodes the egg is infective while for others it is the larva that are infective.
  9. Vocabulary
    1. Cestodes
    2. Helminth
    3. Human diseases caused by multicellular parasites
    4. Nematodes
    5. Parasite
    6. Platyhelminth
    7. Trematode
  10. Practice Questions
    1. No entry.
  11. Practice Question Answers
    1. No entry.
  12. References
    1. Tortora, G.J., Funke, B.R., Case, C.L. (1995). Microbiology. An Introduction. Fifth Edition. The Benjamin/Cummings Publishing, Co., Inc., Redwood City, CA, pp. 317-323.