Infectious and Non-infectious diseases

• Disease is any condition that impairs or intefers with the normal function of the body
• Infectious disease (communicable/transmissable) describes a disease that can be transmitted from host to host by pathogens
• Types of Pathogens

  • Prion
  • Virus
  • Bacteria
  • Protozoa
  • Fungi
  • Macro-parasite
• Modes of Transmission:

  • Horizontal (Direct, Indirect, Vectors, Contamination)
  • Vertical (Transplacental, Vaginal Birth, Breast-feeding)
• Robert Koch's Postulates:

  1. Micro-organisms must be present in the diseased
  2. Micro-organisms can be isolated form diseased and grown independently
  3. When a health organism is in contact with pure culture it must develop the same symptoms as the original sick organism
  4. Isolate and regrow the micro-organism from the newly infected organism
• Louis Pasteur disapproved the theory of spontaneous generation
• Transmission of Pathogens:

  ADAPTATIONS FACILITATING ENTRY

  • Cell wall degrading enzymes
  • Toxins
  • Effector proteins
  • Adhesion of host cells
  • Extremophiles
• Transmission of pathogens

  ADAPTATIONS FACILITATING TRANSMISSION BETWEEN

  • Reservoirs
  • Vectors
  • Protective Covering
  • Rapid species evolution