12.3 Transmission of communicable diseases

• Communicable diseases - caused by one organism infecting another

  these infecting organisms are known as pathogens
• ports of entry

  • mouth
  • nose
  • ears
  • anus
  • vagins/penis
  • punctures
• Direct transmission

  • direct contact e.g kissing
  • inoculation e.g break in skin during sex, animal bite
  • ingestion e.g contaminated food
• Indirect transmission

  • formites e.g bedding, socks (athletes foot)
  • droplet infection e.g inhalation
  • vectors e.g mosquitos transmit malaria and water
• Transmission of pathogens between plants:

  direct

  • direct contact of a healthy plant with any part of a diseased plant e.g ring rot and tobacco mosaic virus

  indirect

  • soil contamination
  • vectors e.g wind, water, animals and humans
• Factors affecting communicable diseases in plants:

  • planting varieties of crops that are susceptible to disease
  • overcrowding
  • poor mineral nutrition
  • damp, warm conditions increase the survival of pathogens
  • climate change
• Factors affecting spread in humans:

  • human demographics e.g STI's
  • economic developments and land use
  • microbial adaption e.g HIV
  • breakdown of public health measures e.g rabies
  • climate change e.g malaria
  • international travel
  • culture e.g traditional medicine
  • overcrowding
  • poor nutrition