Epidemiologic Triad

Question 1

what is the underlying principle of epidemiology?

Answer 1

disease does not occur randomly in a population

Question 2

describe the epidemiologic triad

Answer 2

1. agent
2. host
3. environment

helps us:
-describe current status of disease
-look for patterns
-comparison between groups
-describe changes over time
-establish causation

Question 3

what are agent factors?

Answer 3

1. types of agents:
   -biological: bacterial, viral, parasites, fungi, prion
   -physical: floods, wildfires
   -chemical
2. infectivity
3. pathogenicity
4. antigenicity
5. virulence
6. mode of transmission

Question 4

what are host factors?

Answer 4

1. susceptibility to infection: genetics, vaccination status, prior/current disease, age, stressors (transport, exercise)
2. shedders:
   -healthy animals may shed infectious agents
   -stress may induce shedding

Question 5

what are environmental factors?

Answer 5

1. heat
2. humidity
3. wind
4. stocking density
5. water quality
6. ventilation: barn, arena