Pathogens & Transmission of Disease

• Health is the state of complete physical, mental and social wellbeing
• Disease is a departure from good health as part of the body or mind isn't able to function at maximum efficiency causing identifiable symptoms
• Diseases can be acute (e.g, food poisoning) and symptoms appear quickly
• Diseases can be chronic (long-term) with symptoms that last for months/years. E.g, AIDS or tuberculosis
• Bacteria are prokaryotic single cells that reproduce rapidly by binary fission
• Bacteria cause disease by producing toxins (in blood plasma and tissue fluid) or waste products
• Bacteria also cause disease by damaging cells.
• Bacteria cause disease in plants by causing the death of vascular tissue (xylem & phloem)
• Diseases caused by bacteria include:

  • Tuberculosis
  • Meningitis
  • Ring Rot (potatoes and tomatoes)
• Virus- Infectious microbe consisting of genetic material (DNA or RNA) surrounded be a protein coat (capsid)
• Viruses are 20nm-400nm and can take on different shapes
• Viruses cause disease by:

  • Invading host cells
  • Inserting their genetic information into the hosts' DNA
  • Cells manufacture more copies of the virus causing cell damage and results in feeling ill
• Diseases caused by viruses include:

  • AIDS (HIV)
  • Influenza (Flu)
  • Tobacco mosaic virus - plants
• Fungi in ANIMALS: Microsporum species live in the skin and send out reproductive hyphae which grow to the skins surface and release spores (causes redness)
• Fungi in PLANTS: Fungi live in vascular tissue in plants. Hyphae release extracellular enzymes which digest surrounding tissues and cause decay. Leaves shrivel and die, fruit roots blacken and decay
• Protoctists are single-celled eukaryotic organisms that form a diverse group. Many have features similar to animal cells
• Protoctists cause disease by:

  • Entering host cells
  • Feeding on the contents of cells
• Diseases caused by protoctists include:

  • Malaria (humans)
  • Tomato/potato late blight