Chapter 6 - Emergence/Re-emergaence of pathogens and vaccines

Question 1

Contrast emerging and re-emerging pathogens

Answer 1

Emerging:
- a disease caused by a newly identified or previously unknown agent
- a disease that has existed in other species but whose incidence in humans has increased in the past two decades, either locally or internationally.

Re-emerging:
- a disease that reappears after a significant decline in its incidence
- Re-emerging diseases were once controlled but have increased to a level that causes significant health issues.

Question 2

Provide two examples of new pathogens

Answer 2

1. AIDs disease from the HIV agent 1981
2. COVID-19 from the SARS-CoV-2 agent 2019

Question 3

Provide two examples of re-emerging pathogens

Answer 3

1. Ebola fever disease from the Ebola Virus agent 1976
2. Dengue fever disease from the Dengue virus agent 1943

Question 4

State the difference between an epidemic and a pandemic

Answer 4

Epidemic - A widespread occurrence of an infectious disease in a restricted geographical area in a particular area
Pandemic - An outbreak of a disease that occurs over a wide geographical area that affects a high proportion of the population

Question 5

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

Answer 5

• There is no isolation of nations which can help reduce the spread of infection between individuals
• Pandemics would occur if these infections affected people all around the same geographical area

Question 6

State the impact of European (infectious disease) arrival on Indigenous populations

Answer 6

• Bringing over new infectious diseases that are emerging in Australia
• highly infectious for Indigenous people because they have never been exposed to those pathogens before

Question 7

Explain why diseases introduced by Europeans had such a large impact on Indigenous Australians

Answer 7

They have never been exposed before

Question 8

Describe physical methods to identify pathogens

Answer 8

Cell size, shape, anaerobic/aerobic, x ray, crystallography electron microscopy

Question 9

Describe immunological methods to identify pathogens

Answer 9

ELISA

Question 10

Describe molecular methods to identify pathogens

Answer 10

Probes, fingerprinting

Question 11

Describe how pathogens can be transmitted between individuals

Answer 11

Direct contact - touching, exchanging fluids
Indirect contact - aerosol, surfaces, food/water
Vector - Insects

Question 12

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

Answer 12

Prevention - clean water, wash hands, safe sex, insect nets, etc.
Vaccination - Reduce the number of hosts and long-term immunity
Medication - Treat the person to reduce transmission
Surveillance - Monitor outbreaks
Modification of environment - Drain ponds sprays, mosquito nets (vector control)
Improving infection control standards (sterilization of surfaces/objects, masks, quarantine, etc.

Question 13

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

Answer 13

• breaking the transmission cycle
• developing treatments and vaccines
  targeting prevention efforts

Question 14

Describe 3 ways that antibiotics work

Answer 14

• interference with the cell wall synthesis
• inhibition of protein synthesis
• interference with nucleic acid synthesis

Question 15

Describe 3 ways that antivirals work

Answer 15

• block entry of the virus into the host
  cell
• block fusion of the virus with host cell
• prevent replication of the viral genome

Question 16

Why are antibiotics not effective in treating viral infections?

Answer 16

• Antibiotics are only effective in bacteria-infected cells
• To treat virally infected cells you would need to use antivirals

Question 17

State what is in a vaccine

Answer 17

• a weakened part of the antigen so that it can bind to the antibodies present in the immune body cells

Question 18

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

Answer 18

Hepatitis B vaccine - from birth to every two months until 6 months
Measles, Mumps, Rubella (MMR) vaccine - 12 and 18 months
Pneumococcal Conjugate Vaccine (13vPCV - Prevenar 13) - every two months from birth up to 6 months

Question 19

Explain how vaccines provide long-term immunity

Answer 19

• vaccines contain a weakened version of the live virus or bacteria
• T helper cells will signal the production of more B + T cells which can only target the presented cell
• clonal expansion creating memory cells will allow faster attack on the antigen if the virus is re-exposed/re-infects the body

Question 20

Explain why booster shots are needed for some vaccines

Answer 20

• Yearly vaccines are needed to expose the body to ‘new’ diseases to develop immunity by memory cells
• New antibodies can be created so

Question 21

Explain why diseases such as Influenza need new vaccines each year

Answer 21

• Viral infections such as the Flu (Influenza) need new vaccines because they can mutate and create new strands where previous vaccines will not be able to cure new strains
• Creation of new and different antibodies will target the new strains from mutations

Question 22

Define herd immunity

Answer 22

Resistance to the spread of an infectious disease within a population that is based on pre-existing immunity of a high proportion of individuals as a result of previous infection or vaccination.

Question 23

State two reasons that prevent some people from being vaccinated

Answer 23

1. Medical contraindications or allergies
2. Religious/personal beliefs

Question 24

Explain how herd immunity protects the unvaccinated

Answer 24

Herd immunity protects the unvaccinated by reducing the likelihood of exposure to the disease.

Question 25

Describe a monoclonal antibody

Answer 25

• Artificially produced antibodies that bind to one specific type of antigen
• produced in the laboratory by stimulating the production of B Cells in mice injected with a specific type of antigen

Question 26

Describe how monoclonal antibodies are made

Answer 26

1. antigen into the organism
2. B Cells which produced antibodies against antigen X
3. Constantly divide are added to the separate B cells
4. B cells fuse with tumour cells to form cells called hybridomas
5. required antibodies against antigen X can be harvested

Question 27

Describe 3 ways in which monoclonal antibodies can act to treat cancer

Answer 27

• Block the growth of blood vessels to a tumour
• Attach to the cancer cells to stimulate destruction
• Block signals for cancer cell reproduction/growth

Question 28

Describe what an autoimmune disease is

Answer 28

A disease that attacks all cells including your self cells

Question 29

Explain how monoclonal antibodies can be used to treat autoimmune diseases

Answer 29

• produces autoantibodies - antibodies attack their cells - T and B cells inappropriately activated
  E.g per 1 diabetes, multiple sclerosis, rheumatoid arthritis