Supplemental Lecture (97/05/04 update) by Stephen T. Abedon (

  1. Chapter title: Arthropod Vectors
    1. A list of vocabulary words is found toward the end of this document
  2. Some Human Diseases Spread by Arthropod Vectors
    1. African trypanosomiasis
    2. arboviral encephalitis
    3. babesiosis
    4. Chagas' disease
    5. dengue fever
    6. Lyme disease
    7. epidemic typhus
    8. malaria
    9. plague
    10. relapsing fever
    11. Rocky Mountain spotted fever
    12. salmonellosis
    13. scabies
    14. tularemia
    15. yellow fever
  3. Arthropod
    1. Insect-like:
      1. Arthropods are animals with segmented bodies, exoskeletons, and jointed legs.
      2. In other words, they are insect-like things:
        1. centipedes
        2. crustaceans
        3. fleas
        4. insects
        5. lice
        6. millipedes
        7. mites
        8. spiders
        9. ticks
        10. etc.
      3. As transmitters of disease arthropods they are called vectors, arthropod vectors.
    2. Especially those arthropods that feed on blood come into intimate contact with humans and consequently can transmit disease-causing microorganism.
  4. Vector
    1. Passers of disease:
      1. Because arthropods pass disease-causing microorganisms from person to person they are know as disease vectors.
      2. There exist numerous microorganisms that have complex life cycles only in specific arthropod species.
      3. Eradication of vector-spread microorganisms often involves controlling vectors such as mosquitoes (in the case of malaria).
    2. Variations on the theme:
      1. Vectors differ in:
        1. how they transport a microorganisms
        2. whether the microorganism replicates
        3. how specific the microorganism is to its vector
  5. Mechanical vector
    1. A mechanical vector is a vector that simply carries a microorganism with no replication occurring.
    2. A house fly, for example, can pick up Salmonella spp. on its feet from feces and then deposit it on human food.
  6. Intermediate host vector
    1. Harbors asexual reproduction:
      1. Being an intermediate host vector is a level up in complexity from mechanical vector.
      2. The microorganism can replicate asexually during transport.
      3. An example is Borrelia burgdorferi (Lyme disease).
  7. Definitive host vector
    1. Harbors sexual reproduction:
      1. Being a definitive host vector is yet another level up in complexity, this time from that seen with in intermediate host vector.
      2. Here the microorganism can replicate sexually during transport.
    2. An example is Plasmodium spp. (malaria).
  8. Vocabulary
    1. Arthropod
    2. Definitive host vector
    3. Human diseases spread by arthropod vectors
    4. Intermediate host vector
    5. Mechanical vector
    6. Vector
  9. Practice questions
    1. Rocky Mountain spotted fever is an example of a disease that is transmitted by __________. [PEEK]
    2. Plague (Yersinia pestis) is transmitted by a __________. [PEEK]
      1. tick
      2. fly
      3. mosquito
      4. flea
      5. protozoa
      6. louse
  10. Practice question answers
    1. ticks
    2. iv, flea
  11. 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. 323-331.