Host-Pathogen Interactions

Question 1

Why are infectious diseases still a problem despite vaccines, drugs and better hygiene?

Answer 1

• Newly arising pathogens
• > evolving pathogens
• > spillover from animals
• Increasing resistance to antibiotics
• Lack of vaccines for many diseases
• Unequal community access to:
• > drugs and treatment options
• > food/water hygiene

Question 2

What is the cycle of infectious disease?

Answer 2

Transmission/Contact (RESERVOIR)
Entry into body/colonisation (PORTAL OF ENTRY)
Avoid/Overcome hose defences (SUSCEPTIBLE HOST)
Growth and Spread
Damage host (symptoms and signs of disease) (PORTAL OF EXIT)
REPEAT

Question 3

How many living organisms are in/on the human body?

Answer 3

10^14

Question 4

What types of relationships exist between organisms and hosts?

Answer 4

Mutualism
Commensalism
Parasitism

Question 5

What is mutualism?

Answer 5

benefit to both

Question 6

What is commensalism?

Answer 6

benefit to one

no harm or benefit to the other

Question 7

What is parasitism?

Answer 7

benefit to one

harm to the other

Question 8

What is a pathogen?

Answer 8

an organism capable of causing damage

Question 9

What is a commensal?

Answer 9

Normal flora

an organism able to live in association with another without causing harm

Question 10

What makes a pathogen different to a commensal?

Answer 10

they can:
- gain access to
- replicate in
- persist at
normally privileged (sterile) sites within the host

Question 11

Is damage to the host is parasitism always because of the pathogen?

Answer 11

No

Immune responses to pathogens can sometimes elicit host damage that gives clinical manifestation of disease

Question 12

What is the epidemiological triad?

Answer 12

Pathogen environment host pathogen
All leading to disease

Disease results from the interaction of a pathogen with a susceptible host in an environment that brings the host and pathogen together