Module 7 - biology

• Response of a named Australian plant to a named pathogen

  1. Practical and/or second-sourced investigation

  2. Example: Eucalyptus Trees and Protozoa (Water Mould)

  3. Water mould destroyed trees in WA

  4. Mould was in soil and attaches to roots to absorb nutrients

  5. Jarrah roots show where water mould activity has damaged the tree

  6. Jarrah tree more resistant to pathogen, has healthy roots with increased lignin development

  7. Lignin protects the cell wall of plant from damage by pathogens

  8. PAL (phenylalanine ammonia lyase) is an enzyme associated with lignin production caused by the presence of a pathogen
• Physical and chemical changes in host animal cells and tissues in response to pathogens

  • Passive innate barrier or first line of defense are physical barriers preventing pathogen entry
  • No energy is required from the body for the barriers to function
  • Examples: Skin, Mucous Membrane
  • Skin is a large physical barrier protecting cells from pathogens, waterproof to prevent pathogen growth
  • Mucous membrane on respiratory and digestive tracts produces mucous to trap pathogens
  • Saliva contains enzymes to break down pathogens
  • Microbes on membranes produce chemicals that hinder pathogen growth
• Pathogens


  Agents that can cause infectious disease
• Infection


  • Examples not provided
• Innate Immune Response


  • Immediate response to pathogens
• Types of Immune Cells

  • Neutrophils
  • Eosinophils
  • Basophils
  • Monocytes
  • Lymphocytes
• Neutrophils


  Most abundant white blood cell, first responder to pathogens, phagocytose and digest pathogens
• Eosinophils


  Respond to allergies and parasitic infections, do not directly attack pathogens but secrete chemicals to kill them
• Basophils


  Initiate inflammatory responses by releasing chemicals like histamine, similar to mast cells but circulate in blood
• Monocytes


  Large phagocytic cells, differentiate into macrophages and dendritic cells to continue pathogen digestion and antigen presentation
• Lymphocytes


  Part of the adaptive immune response, responsible for specific recognition and destruction of pathogens
• Macrophages remain in tissue and phagocytose pathogens, dendritic cells present antigen fragments to lymphocytes
• Innate Immunity 


  What an organism is born with , does not differentiate between pathogens (non-specific).
• What is a dendritic cell?

  Antigen presenting cell that inform the fight against invasive pathogens while enforcing tolerance to self and harmless environmental antigens.
• Pathogen


  A biological agent that can cause disease or illness in a host
• Modes of transmission (direct/infectious)

  • Direct contact
  • Exchange of fluid
  • Airborne
• Modes of transmission (indirect)

  • Airborne
  • Contamination
  • Vector
• Non-infectious diseases


  Cannot be transferred
• Infectious diseases


  Transferred, caused by pathogen
• Transmission types

  • Indirect transmission
  • Direct transmission
• Epidemic

  Widespread occurrence of an infectious disease in a community at a particular time
• Investigating the transmission of a disease during an epidemic

  1. Affects great no. of people/animals

  2. Spreads to new areas
• Pandemic

  Epidemic on a global scale
• EIV (Equine Influenza virus)


  • Symptoms: fever, watery nasal discharge, cough, lack of appetite, muscle pain
  • Highly contagious
  • Spreads directly (body fluids) and indirectly (humans contaminate)
• Management of EIV


  1. Lockdown

  2. Quarantine
• Future control of EIV


  1. Restrict horse importations

  2. Strict biosecurity measures

  3. Educate, biosecurity training
• Methods of transmission


  • Airborne
  • Arthropod
  • Biological
  • Contact
  • Developmental
  • Fecal-oral
• Airborne transmission

  • 10-20 feet, droplets, dust
• Arthropod transmission

  • Insect, biological vector, carry pathogen, multiply within
• Biological transmission

  • Colostral, intrauterine, testis, breastfeeding
• Contact transmission

  • Direct
• Fecal-oral transmission

  • Infectious faeces
• Epidemic


  Outbreak of an infectious disease that spreads rapidly and affects a large number of people in a population at the same time
• Pandemic


  Epidemic that spreads across multiple countries or continents
• Ebola


  • Severe, often fatal
  • Transmitted from animal to human (direct transmission)
  • Prevents immune response, causes cell death
  • No vaccination
• There is currently no cure or treatment for Ebola
• Prevention and control of Ebola

  1. Thoroughly cooking meat

  2. Avoid human-to-human transmission by wearing personal protective equipment

  3. Maintain good hygiene practices

  4. Refrain from unprotected sex
• Ebola has a high fatality rate of around 50%
• Ebola is transmitted from bats to humans, and can then spread between humans through direct contact with bodily fluids
• Factors that affect disease transmission include population density, population mobility, host exposure and susceptibility, and public health infrastructure