Communicable diseases

Communicable diseases

1. Pathogens

   • Microorganisms that cause communicable disease
   • Bacteria
     • Prokaryotic cells which are 1/100 th the size of normal cells and can cause disease
     • They make you feel ill by producing toxins
       • These toxins cause cell and tissue damage
         • Makes you feel ill
     • E.g. Salmonella, gonorrhoea
     • They reproduce very quickly and split into two under the right conditions with the correct amount of nutrients every 20 minutes by binary fission
       • The rate of division of affected by
         • Oxygen levels
         • pH levels
         • Environmental conditions
       • They reproduce the best under moist, warm conditions
   • Viruses
     • They are not living cells and they are 1/100 th the size of a bacterium.
     • They consist of genetic material enclosed in a protein coating
     • They make you feel ill by invading your cells
       • They then use the cells machinery,chemicals, to replicate producing many copies of themselves
         • These copies break out of the cells releasing new viruses
           • Causes cell damage
             • Makes you feel ill
     • They can't reproduce on their own, they need a host cell
     • E.g. HIV, TMV, measles
   • Protists
     • Eukaryotes that are often unicellular which may cause disease
     • E.g. Malaria
     • Spread by animal vectors with carry the pathogen and transfer it to another organism which gets the disease
     • Often carried by parasites
       • E.g. Mosquitos
   • Fungi
     • They are unicellular or multicellular microorganisms which may cause disease
     • E.g. Athletes foot, rose black spot
     • They often have hyphae
       • Hyphae are thread like structures on the surface of a fungus
         • Hyphae spread the disease as they produce spores
           • Can be carried by air and water spreading the pathogen
         • Hyphae also spread disease by penetrating surfaces such as the skin of a human or the body of a plant

2. Spread of disease

   • Air
     • Fungal, bacterial and viral spores can be carried from one plant or animal to another in the air, spreading the disease
     • Droplet infection in humans is when you cough or sneeze and droplets containing infection are released and are then inhaled by others spreading the disease
       • E.g. Influenza
     • Some diseases can be spread by bring carried by the air and the inhaled
   • Wtaer
   • Direct contact
     • Some diseases can be spread by touching contaminated surfaces such as the skin

3. Preventing infection

4. Fungal diseases

5. Viral diseases

6. Bacterial diseases

7. Protist diseases

8. Human defence systems

9. Plant defence systems