infection & response

• Communicable diseases


  • bacteria
  • viruses
  • fungi
  • protists
• Viruses reproduce


  1. Inserting their genetic material into host cells

  2. Bursting open host cells

  3. Releasing viral particles

  4. Infecting other cells
• Measles


  • Symptoms: fever, red skin rash
  • Spread: by inhalation of droplets from coughing
• Treatments


  Vaccine program
• HIV


  • Symptoms: flu-like symptoms
  • Spread: Sexual contact, exchange of bodily fluids
  • Treatments: antiretroviral drugs early on to control
• • Symptoms: mosaic pattern on leaves, not much growth
  • Spread: in soil, plants in contact with plants
  • Treatment: no treatment but good field hygiene to help prevent it

  TMV
• Bacteria


  Produce toxins that cause damage to cells and tissues
• Salmonella


  • Symptoms: fever, abdominal cramps, vomiting, diarrhoea
  • Spread: contaminated food that isn't fully cooked
  • Treatment: vaccinations, good hygiene in kitchen
• Gonorrhoea


  • Symptoms: pain when urinating, thick yellow/green discharge
  • Spread: Sexual contact
  • Treatment: barrier methods, antibiotics
• Fungi


  Grow and can penetrate the surface of plants and animals causing infection
• Rose black spot


  • Symptoms: purple or black spots on leaves
  • Spread: spores carried in wind or water
  • Treatment: fungicidal chemicals
• Protists


  Use a vector to transfer from one host to the next
• Malaria


  • Symptoms: fever, shaking
  • Spread: by mosquitoes
  • Treatment: controlling mosquito populations - bed nets and using insecticides
• Immune system


  Once a pathogen has entered the body, the role is to prevent the infection from reproducing and to destroy it
• Main components of the immune system

  • White blood cells
  • Producers of antibodies
  • Producers of antitoxins
  • Phagocytosis
• white blood cells

  Engulf and digest pathogens
• Production of antibodies


  Specific to the antigens on the surface of the pathogen
• Production of antitoxins


  Neutralise the effect of the toxin
• Vaccination


  Exposing an individual to the antigens of a pathogen in some way to trigger an immune response which results in the formation of memory cells
• If a large number of the population are vaccinated

  It is unlikely that an unvaccinated individual will become infected with the pathogen - herd immunity
• Vaccine advantages

  • Diseases that were once common are now rarely seen due to widespread vaccination
  • Epidemics can be prevented if large numbers of the population are vaccinated
• Vaccine disadvantages

  • Vaccines don't always give immunity
  • Vaccines do have side effects
• How vaccines work

  1. Introducing a small quantity of dead or inactive forms of a pathogen to the blood to stimulate the white blood cells to produce antibodies

  2. If the same pathogen re-enters the body, the white blood cells respond quickly, preventing infection
• Antibiotics


  Treat the cause of disease
• Painkillers


  Treat the symptoms of disease
• Antibiotics won't work against viruses, as they reproduce inside cells
• Antibiotics have been overused and caused the development of antibiotic resistant bacteria
• Preventing resistant bacteria


  • Avoid overuse of antibiotics (immune system will clear it up)
  • Antibiotics shouldn't be used for viral infections
  • Patients need to finish the whole course of antibiotics so all bacteria are killed and none are left to mutate to resistant strains
• Penicillin was discovered by Alexander Fleming first
• Drug development


  1. Pre-clinical testing (efficacy, toxicity)

  2. Whole organism testing (efficacy, toxicity, dosage)

  3. Clinical trials (tested on humans, including those with the disease, with a placebo used)
• Placebo


  Neither the doctor nor the patient knows if the drug is real or not
• How do pathogens spread

  • placental transfer
  • direct contact
  • sexual contact
• Digitalis made from foxglove
• Asprin made from willow bark