Chapter 6: Disease Challenges and Strategies

Question 1

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Define new and re-emerging disease

Answer 1

• Emerging diseases are caused by newly identified or previously unknown pathogens
• Re-emerging diseases involve the reappearance of a pathogen after being absent in a population for a significant period of time

Question 2

Provide examples of new and re-emerging pathogens

Answer 2

• New pathogens → COVID-19 and HIV
• Re-emerging pathogens → Ebola and cholera

Question 3

State the difference between an epidemic and a pandemic

Answer 3

• An epidemic is a local outbreak of infectious disease
• A pandemic is a widespread outbreak of infectious disease (present in at least 2 World Health Organisation regions)

Question 4

Explain why living in a globally connected world increases the likelihood of pandemics

Answer 4

• Greater mobility (e.g. air travel) in the globally connected world allows pathogens to be exported from one country to another through infected passengers

Question 5

Explain the impact of European arrival on Indigenous populations

Answer 5

• Many Aboriginal Australians died due to infectious diseases that were introduced by Europeans
• Australia is geographically isolated
• Prior to European arrival there was little interaction between Europeans and Indigenous Australians
• Western diseases were unknown, so Indigenous populations had no immunity against them (high susceptibility and rapid spread of new infectious disease)

Question 6

Explain and list physical methods used to identify pathogens

Answer 6

• Physical methods involve identifying pathogens based on size and shape
• X-ray crystallography → determines structure of viruses
• Electron microscopy → obtains images that allow viruses to be distinguished from one another

Question 7

Explain and list immunological methods used to identify pathogens

Answer 7

• Immunological methods involve the diagnosis of pathogens based on the presence of specific antigens or antibodies
• ELISA (enzyme linked immunosorbent assay) → allows for the diagnosis of disease by detecting specific antigens or antibodies
• MAB (monoclonal antibodies) → designed to have a specific antigen binding site
• Immunofluorescence → uses an antibody with a fluorescent marker to bind to and detect specific antigens or antibodies in serum

Question 8

Explain and list molecular methods used to identify pathogens

Answer 8

• Molecular methods involve identifying a pathogen by examing genetic material using DNA or RNA
• PCR (polymerase chain reaction)
• Gel electrophoresis
• Sequencing

Question 9

Explain and list phenotypic methods used to identify pathogens

Answer 9

• Phenotypic methods involve identifying observable traits or features in bacteria
• Gram staining
• Observing growth

Question 10

Explain the immunological process of ELISA

Answer 10

• Wells on a tray are coated with an antigen specific to the disease being tested
• Antibodies specific to a particular antigen is added to each well
• Antibodies bind to the antigen in the wells
• The wells are then washed to remove any unbound antibodies
• The substrate for the enzyme is added, leading to a colour change if an antigen-antibody complex has formed (this indicates a positive test)

Question 11

Describe how pathogens can be transmitted between individuals

Answer 11

• Direct transmission involving direct person-to-person contact
  
  • E.g. kissing or sexual contact
• Indirect transmission that does not involve person-to-person contact
  
  • E.g. inhaling airborne particles such as uncovered sneezes, contact with contaminated objects or ingestion of contaminated food
• Vectors that are a form of indirect transmission
  
  • E.g. organisms such as fleas and mosquitos that carry pathogens and spread them to other organisms via bites or droppings on food

Question 12

Explain how a disease that starts in a small population can spread around the world within a few weeks or months

Answer 12

• Asymptomatic people can spread the disease before they start showing symptoms
• People are very mobile and are able to travel large distances quickly by car, train and plane
• Some animals such as birds (for avian flu) can fly long distances, carrying pathogens between countries
• High population density increases the likelihood for diseases to spread
• Some countries may have poor sanitation/quarantine conditions and hence are unable to effectively isolate infected individuals from the community

Question 13

Describe control measures to prevent or limit the spread of infectious disease (PVMSI)

Answer 13

• Prevention strategies such as hand washing, using clean water and having safe sex, etc.
• Vaccination to reduce the number of hosts
• Medication to reduce transmission
• Surveillance which involves monitoring outbreaks
• Improving infection control standards such as sterilization of surfaces, masks, quarantine, etc.

TIP: Preventing Viruses Means Staying Informed.

Question 14

Explain why identifying the host or reservoir is important in controlling the spread of disease

Answer 14

• Transmission occurs when a pathogen leaves its reservoir (habitat) or host (organism that can be infected) and enters a susceptible host
• By identifying these areas, preventative measures can be placed to control the spread

Question 15

Define and describe ways that antibiotics work

Answer 15

• Antibiotics are substances, that in low concentrations, kill or inhibit the growth of bacteria
• Penicillin inhibits cell wall synthesis in bacteria
• Sulfanilamide competitively inhibits enzyme activity in bacteria
• Rifampin and quinolones inhibit nucleic acid synthesis

Question 16

Describe ways that antivirals work

Answer 16

• Antivirals are substances that are used to treat viral infections (actively replicating viruses)
• Prevent the entry of viruses
• Prevent replication of the viral genome
• Prevent synthesis of specific viral proteins

Question 17

Describe why antibiotics are not effective in treating viral infection

Answer 17

• Because they inhibit the growth of/kill bacteria rather than viruses
• They inhibit cell wall synthesis, bacterial reproduction or protein synthesis
• Viruses are non cellular and are therefore unnaffected by antibiotics

Question 18

Define and state what is in a vaccine

Answer 18

• A vaccine is a substance containing live attenuated antigens that elicit an immune response
• A vaccine contains live attenuated pathogens that cannot cause disease

Question 19

Suggest reasons for why vaccination rates may be lower in a region

Answer 19

• Less education about the importance of vaccines
• Less accessibility to vaccines due to cost
• Lack of medical staff who can administer vaccines
• Lack of mandatory vaccination laws

Question 20

Give examples of 3 vaccines that are on the Australian vaccination schedule and the age at which they are given

Answer 20

• Hepatitis B → preferably within 24 hours of birth
• Meningococcal → 12 months
• Human papillomavirus (HPV) → 12-13 years

Question 21

Explain how vaccines provide long-term immunity

Answer 21

• Vaccines initiate an immune response that results in the production of memory cells
• These memory cells remain in the lymphatic system and can initiate a stronger and more rapid immune response should reinfection with the same specific antigen occur

Question 22

Explain why booster shots are needed for some vaccines

Answer 22

• Booster shots help retain a memory of the pathogen and maintain the number of memory B cells and antibodies
• Inactivated vaccines (compared to live attenuated vaccines) produce a weaker immune response where immunity lasts for a shorter period of time
• As a result, they need to be administered more than once in order to maintain immunity against a disease

Question 23

Explain why diseases such as influenza need new vaccines each year

Answer 23

• Some diseases can mutate into new strains
• Antibodies produced by previous vaccines will fail to work against the new strain as they cannot bind to the mutated antigens
• Therefore, vaccines must be developed in order to adapt to mutatations as humans would have no immunity to the new strains

Question 24

Define herd immunity

Answer 24

• Herd immunity involves the indirect protection from infection of unvaccinated people by being surrounded by people who are vaccinated
• 95% should be vaccinated for herd immunity to occur
• Protection is created by the presence of immune individuals
• Protection is received by unvaccinated individuals

Question 25

State the advantages and disadvantages of herd immunity

Answer 25

• Advantages
  
  • Protects vulnerable individuals who cannot be vaccinated
  • Reduces the spread of diseases
• Disadvantages
  
  • Relies on very high vaccination rates (difficult for poor countries to achieve)
  • Potential for outbreaks if herd immunity is not maintained or if immunity wanes over time

Question 26

List reasons that prevent some people from being vaccinated

Answer 26

• Weak immune systems (immunocompromised)
• Being too young or too old for specific vaccinations
• Lack of access to hospitals or medical staff that can administer vaccinews

Question 27

Explain how herd immunity protects the unvaccinated

Answer 27

• Unlikely that vaccinated individuals become infected and pass it on to unvaccinated people
• If the large majority of a population is immune, the disease will not get the chance to spread which reduces the risk for those who cannot be vaccinated

Question 28

State reasons for why a newborn child may be less susceptible to an infectious disease

Answer 28

• They are protected by their mother’s antibodies passed down through the placenta or through breast milk (passive natural immunity)
• Less exposure to the virus due to limited human contact

Question 29

Discuss the ethics of refusing to be vaccinated

Answer 29

• Respecting an individual’s autonomy (by honouring their feelings, needs and decisions) is a fundamental ethical principle. People have the right to make decisions about their own bodies, including whether or not they wish to be vaccinated.
• However, respecting the rights and well-being of vulnerable populations is equally important. Individuals who cannot get vaccinated due to age or immunodeficiency disorders rely on herd immunity to receive protection against infection. Therefore, refusing vaccination without a valid medical reason may jeopardize the health of these individuals and could be seen as a lack of respect for their well-being.

Question 30

Define immunotherapy

Answer 30

• Immunotherapy is a disease treatment that involves either stimulating or repressing the immune response
• E.g. monoclonal antibodies

Question 31

Explain monoclonal antibodies

Answer 31

• Monoclonal antibodies are artificially produced antibodies that bind to one specific type of antigen
• They are produced in the laboratory by stimulating the production of B lymphocytes in mice upon injection of a specific type of antigen

Question 32

Explain how monoclonal antibodies are produced

Answer 32

• A mouse is injected with an antigen
• This stimulates an active immune response involving the production of the mouse’s B cells, which produce antibodies against the antigen
• The spleen of the mouse is removed, placed in a culture medium and its cells are separated
• B cells fuse with tumour cells to form hybridomas
• Hybridoma cells divide repeatedly and identical copies of each individual hybridoma cell are produced
• Clones are screened to identify cells that produce the required antibodies against the antigen
• The antibodies can then be collected and purified

NOTE: Plasma cells are short lived while myeloma (tumour) cells are immortal.

Question 33

List the advantages and disadvantages of monoclonal antibodies

Answer 33

• Advantages
  
  • Highly specific (only binds to specific antigens and does not affect healthy cells)
  • Can be standardised world-wide
  • Consistent quality
• Disadvantages
  
  • High cost of production
  • Limited availability
  • Potential side effects

Question 34

Describe ways in which monoclonal antibodies can act to treat cancer

Answer 34

• Attach to the cancer cell to stimulate its destruction
• Block the growth of blood vessels to a tumour
• Block signals for cell reproduction
• Take chemotherapy drugs directly to the cancer
• Make it easier for immune cells to detect cancer cells

NOTE: They can be used in the treatment of rheumatoid arthritis as they play a role in reducing inflammation.

Question 35

Explain and provide examples of autoimmune diseases

Answer 35

• An autoimmune disease is when the body’s immune system attacks its own cells
• They occur when autoantibodies are produced or when T/B cells are inappropriately activated
• Multiple sclerosis → immune system attacks the myelin sheath that protects nerves
• Type 1 diabetes → immune system mistakenly attacks and destroys pancreatic tissues and cells

Question 36

Explain how monoclonal antibodies can be used to treat autoimmune diseases

Answer 36

• Bind to cytokines to prevent B-cell signalling and activation
• Bind to T cells, stopping their movement to the brain/spinal cord and attacking the myelin sheath
• Bind to IgE to prevent allergies

Question 37

Define cancer

Answer 37

• Cancer is a disease in which cells divide uncontrollably, forming an abnormal mass of cells called a tumour

Question 38

Explain the difference between immunotherapy and chemotherapy when treating cancer

Answer 38

• Chemotherapy acts directly on tumour cells → including healthy cells which can cause side effects such as hairloss and fatigue
• Immunotherapy acts on the patient’s immune system → can have fewer side effects but may not be effective for all cancer patients
• Immunotherapy offers the potential for long-term control against cancer by retaining a memory
• Chemotherapy generally works quicker compared to immunotherapy

NOTE: Chemotherapy is NOT an example of immunotherapy. They are two separate treatments.

Question 39

Outline strategies that may used to increase vaccination rates in Indigenous Australians

Answer 39

• Community elders could be educated to provide a trusted source of information to the Indigenous community
• Vaccination programs can be directly held in Indigenous communities
• Media campaigns, including Indigenous Australians, can be created to promote vaccination

Question 40

Define virulence

Answer 40

• Virulence refers to the severity of disease caused by a pathogen

Question 41

Explain how MAbs block signals for cell division

Answer 41

• Growth factors bind to receptors on cancer cells, signalling them to divide
• In cancerous cells, the receptor is over-expressed, resulting in uncontrollable division
• MAbs can bind to these receptors, blocking them from receiving signals from growth factors (slowing/preventing the growth of the cancer)

NOTE: Healthy tissues receive signals from growth factors for normal cell replacement.

Question 42

Explain how MAbs deliver anticancer or radioisotopes to cancer cells

Answer 42

• MAbs can be joined with a radioisotope particle, delivering it to cancer cells
• The antibody links to its target antigen on the cell
• This causes the radioisotope to emit radiation, destroying the cancer cell

Question 43

Explain how MAbs signal immune cells to attack cancer cells

Answer 43

• MAbs can bind to antigens on cancer cells, acting as markers that make them more visible to the immune system
• This attracts immune cells to attack the cancer cells

Question 44

Explain how MAbs can stop the growth of new blood vessels to cancers

Answer 44

• Cancer cells require oxygen and nutrients to grow
• They release growth factors (hormones) that signal the growth of blood vessels (provide oxygen and nutrients)
• MAbs can bind to growth factors, preventing the growth of new vessels

Question 45

State how sterile conditions can be achieved in a hospital

Answer 45

• Flaming, steaming, boiling or autoclaving medical equipment
• Using antibacterial handwash
• Using disposable gloves