Intro to Epidemiology

Question 1

Epidemiology

Answer 1

study of distribution and determinants of disease in specified populations and the application of this study to control health problems

Question 2

Epidemiology focus on groups or individuals

Answer 2

groups

Question 3

Purpose of epidemiology

Answer 3

ID determinants and describe disease distribution

Question 4

Veterinary epidemiology

Answer 4

investigates disease, productivity, and welfare in animal populations

Question 5

Why care about Epi?

Answer 5

evidence based veterinary medicine

provide tools for research
evaluate research
integrate research into practice

Question 6

Clinical epidemiology approach

Answer 6

-focus on individual (PE, Ddx, Diagnostics..)

-success depends on
known disease & correct Dx

Question 7

Epidemiological Approach

Answer 7

Focus on groups
describe population with and without disease
look for differences in groups
ID factors
Apply measures
Success without knowing etiology

Question 8

John Snow

Answer 8

removed the pump handle

found Cholera outbreak

Question 9

Descriptive Epidemiology

Answer 9

describe disease (CANNOT infer causality)
characteristics, amount, distribution 

Describes what in terms of
who, when, where

Question 10

Analytical Epidemiology

Answer 10

determine assoc. of exposure and outcome in population and how strong association is
(why)

Ultimate goal is determine if exposure factor = disease

Question 11

the What?

Answer 11

health/ production/ welfare issue of concern
case definition
example: retained placenta in cows

Question 12

the Who

Answer 12

Age, gender, breed, production type (feedlot/ shelter)

Question 13

When : time?

Answer 13

changing or stable rates of disease
clustered in time or evenly distributed
single point / intermittent exposure
seasonal variation

Question 14

Where : place?

Answer 14

geographically restricted or widespread
relation to food/ water supply
clustered or even distributed
one room or whole barn

Question 15

Association

Answer 15

Dependent
relationship of two measured dependent quantities
- exposure changes and so does amount of disease

Independent (not associated)
- when exposure changes, nothing happens to the
amount of disease

Question 16

Exposure

Answer 16

any potential determinant of disease or health status

May or May not de determinant

Question 17

Outcome

Answer 17

result or response

Question 18

Fundamental axiom of disease

Answer 18

disease are NOT random

disease have causal and preventive factors that can be ID

Question 19

Cause vs Cause of disease

Answer 19

cause = brings about an effect or result

cause of disease = does not only mean cause

     - dz is complex with many causes 
     - event, condition, character playing an essential roles in producing disease occurrence

Question 20

Koch’s Postulates if microbes

Answer 20

1. always found in individuals with disease
2. not found in healthy animals
3. can be isolated in pure culture from disease individual
4. pure microbe produces same disease in healthy animal
5. can be re-isolated from #4

Question 21

Web of Causation

Answer 21

describes modern disease problems where presence or absence of disease is not just a matter of presence/ absence of pathogens

Question 22

Epidemiological Triad

Answer 22

host, agent, environment

Disease results form interaction of agent and susceptible host in an environment that supports transmission of agent from source to host

Question 23

Ken Rothmans (Rothman’s Pies)

Answer 23

general model for representing components causes resulting in disease

Question 24

Rothmans Pies

Sufficient Cause

Answer 24

each complete pie is a set of component causes that is sufficient to cause disease

Question 25

Rothman’s Pies

Component cuase

Answer 25

-any one of the component causes of a sufficient cause
(each piece of pie) A - J slices

-not all component causes need to be present in every
sufficient cause

Question 26

Rothman’s Pies

Necessary cause

Answer 26

component cause that is member of every sufficient cause

slice A is necessary in every pie

Question 27

Simple cause model of Anthrax

Answer 27

susceptible cattle
Bacillus anthracis spores in soil

DOESNT EXPLAIN OUTBREAK

Question 28

Sufficient cause of Anthrax

Answer 28

susceptible cattle
Bacillus anthracis spores in soil
excess winter snow and spring rain\
hot, dry summer

Question 29

Anthrax Sufficent causes with necessary and component causes?

Answer 29

Necessary cause = spores in soil

components
   spore in soil
   susceptible cattle, sheep, bison, ...
   spores in forage
   excess snow and spring rain
   dry summer

Question 30

Rothman Model

Answer 30

completion of sufficient cause is synonymous with occurrence of disease (not diagnoses)

component causes can act far apart in time

a. block action of component cause
b. blocks completion of the sufficient cause
c. preventing disease occurrence by that pathway

Question 31

How to prove Rothmans model

Answer 31

Does association = Causality

Question 32

Associations measured can be results of what?

Answer 32

1. exposure truly causes outcome
2. random error
3. systematic error (bias, confounding)

Question 33

Bradford Hill criteria

Answer 33

temporal relationship 
          (cause before effect)
assoc. strength 
does- response relationship
            (more exposure = more disease) ??
replicate findings?
biological plausibility
             (does it make sense) 
consider alternate explanations
cessation of exposure 
              (does dz go away when exposure goes away)
specificity of assoc.
consistency