Infection and Response

• Pathogens are microorganisms that cause infectious diseases
• Pathogens are spread by:

  • Direct contact
  • Water or air
  • Vectors
• The spread of pathogens can be reduced by :

  • Simple hygienic measures (washing hands)
  • Destroying vectors
  • Isolating infected individuals
  • Giving people at risk a vaccination
• Viruses reproduce rapidly in body cells and cause damage to the cells.
• Examples of viruses:

  • Measles
  • HIV
  • Tobacco Mosaic Virus (TMV)
• Measles (Virus):

  Symptoms - Fever and red skin rash

  Spread by breathing in droplets from sneezes and coughs

  Can be avoided via vaccination
• HIV (Virus):

  Spread by sexual contact of exchange of bodily fluids (needles)

  1. Causes a flu-like illness
  2. If left untreated the virus enters the lymph nodes and attacks the body’s immune cells

  Taking antiviral drugs can delay this from happening
• Tobacco mosaic virus (Virus)

  Distinctive ‘mosaic’ discolouration pattern reduced chlorophyll content of leaves

  Affects photosynthesis and plant growth

  Dispose of affected plants
• Examples of bacterial diseases:

  • Salmonella
  • Gonorrhoea
• Salmonella (bacteria)

  • Bacteria is ingested in food that may not have been cooked properly OR prepared in hygenic conditions.

  • Cause fevers, abdominal cramps, vomiting and diarrhoea
  • Chickens in the UK are vaccinated against salmonella to control spread
• Gonorrhoea (Bacteria)

  • Spread via sexual contact
  • Thick Yellow or green discharge and pain when urinating
  • Treated with penicillin previously but now resistant strains have appeared
  • Barrier method stops bacteria being passed
• Protists:

  • Single celled organisms
  • Eukaryotic

  Example :

  Malaria
• Malaria:

  • Use mosquitos as a vector
  • Passed on when a person is bitten by mosquito
  • Reoccurring severe fever that can be fatal
  • Stop being bitten by mosquitos by kill them or using mosquito nets
• Example of fungal disease:

  • Rose black spot
• Rose black spot

  • Spread via spores from plant to plant by water or wind
  • Purple/black spots develop on leaves - turn yellow and drop early
  • Loss of leaves stunts growth due to photosynthesis being reduced
  • Treated by using fungicides and removing and destroying affected leaves
• Preventing entry of pathogen:

  • Hair on skin
  • Enzymes in tears destroy microorganisms
  • Nose traps particles containing pathogens
• Phagocytosis:

  1. Microorganisms enters the body
  2. White blood cell finds microorganism and engulfs them
  3. White blood cell ingests the microorganism
  4. The microorganism is digested and destroyed