module 4 - disease

• Health


  Free from disease, physical and mental and social well-being, good nutrition, suitably housed
• Disease


  A condition that impairs normal functioning of the body, a departure from good health caused by a malfunction of the mind or body
• Communicable diseases


  Diseases that can spread between people
• Non-communicable diseases


  Diseases that cannot be spread
• Pathogen


  An organism (e.g. bacteria, viruses, fungi) that causes disease
• Parasite


  An organism (e.g. tapeworms, roundworms) which lives in or on another living organism (host) and causes harm to the host organism it infects
• Benefits of parasitism


  Nutritional, warmth, protection or a means of transmission
• Replication of viruses


  1. Virus binds to receptor on host cell

  2. Viral nucleic acid enters cell

  3. Viral nucleic acid takes over cell metabolism

  4. Viral nucleic acid is replicated

  5. Protein coats are manufactured

  6. Whole virus particles are made

  7. Viral particles are released when cell bursts
• Communicable diseases


  • Tuberculosis (TB)
  • Bacterial meningitis
  • Ring rot (potatoes, tomatoes)
  • HIV/AIDS (human)
  • Influenza (animals)
  • Tobacco Mosaic Virus (plants)
  • Malaria
  • Potato/tomato late blight
  • Black sigatoka (bananas)
  • Ringworm (cattle)
  • Athlete's foot (humans)
• Bacteria


  Prokaryotes that either damage cells directly or release toxins which damage cells
• Tuberculosis (TB)


  Pathogen is Mycobacterium tuberculosis and M. bovis which infect lungs
• Bacterial meningitis


  Pathogen is Neisseria meningitidis which infects the meninges-membranes in the brain making them swell
• Bacterial ring rot


  Pathogen is Clavibacter michiganensis which lives in the vascular tissue causing these tissues to blacken
• Viruses


  Invade cells, take over cell metabolism, replicate using host cell, manufacture protein coats, release new viral particles
• HIV/AIDS


  Pathogen is HIV which infects helper cells compromising the immune system
• Influenza


  Infects the respiratory system
• Tobacco Mosaic Virus


  Infects plants
• Protoctista


  Often parasitic organisms
• Malaria


  Pathogen is Plasmodium, vector is Anopheles mosquito
• Potato/tomato late blight


  Pathogen is Phytophthora infestans
• Fungi


  Saprotrophs that release enzymes which digest tissue in plants resulting in decay, and form hyphae under skin in animals releasing spores causing irritation
• Black sigatoka


  Fungal disease of bananas
• Ringworm


  Fungal disease of cattle
• Athlete's foot


  Fungal disease of humans
• Means of transmission of animal and plant communicable pathogens

  • Direct contact
  • Indirect contact
  • Food and water
  • Airborne droplets
  • Insect bites
• Pathogen

  An organism (e.g. bacteria, viruses, fungi) that causes communicable diseases
• Parasite

  An organism (e.g. tapeworms, roundworms) which lives in or on another living organism (host) and causes harm to the host organism it infects
• Droplet diseases

  • Tuberculosis (TB), influenza
• Diseases transmitted by water

  • Cholera, salmonella food poisoning
• Diseases transmitted by contact

  • HIV/AIDS, chlamydia
• Diseases transmitted by an insect vector

  • Malaria, rabies
• HIV is described as a retrovirus because it has RNA and an enzyme called reverse transcriptase which converts RNA to DNA
• Pathogens


  • Mycobacterium tuberculosis
  • M. bovis
  • Streptococcus pneumoniae
  • Neisseria meningitidis
  • Clavibacter michiganensis
  • Plasmodium
  • Phytophthora infestans
  • Tinia pedia
• Forms of indirect transmission

  • Fomites - inanimate objects such as bedding and cosmetics
  • Droplet infection - any infection that makes you cough or sneeze
  • Vectors - something that transmit disease eg. Rat fleas and bubonic plague
  • Spores

  
• Malaria transmission by mosquito vector

  1. Mosquito sucks blood containing gametes

  2. Plasmodium develops and enters salivary glands of mosquito

  3. Mosquito bites person and plasmodium enters blood stream

  
• Wind and water can carry spores
• Overcrowding

  Facilitates easier transmission of diseases
• Poor nutrition


  Weakens the immune system and makes people more susceptible to disease
• Climate change can cause malarial parasites to develop quicker in mosquitoes and increase the lifespan of mosquitoes, leading to increased malaria transmission

  
• Factors that can increase the transmission of communicable diseases in plants

  • Planting varieties that are susceptible to disease
  • Over-crowding
  • Poor mineral nutrition
  • Damp, warm conditions
  • Climate change - increase rainfall and wind