Epidemiology 1+2

Question 1

Define Epidemiology

Answer 1

• Epidemiology  the study of disease in populations (observing populations and making interferences from these observations)

Question 2

Define Veterinary Public Health

Answer 2

• Veterinary Public Health  The part played by veterinarians in human public health, relating chiefly to the recognition and control of zoonotic disease

Question 3

Define Endemic

Answer 3

Endemic - Disease commonly found in or restricted to a particular region community or group of people
R0<1

Question 4

Define R0 <1

Answer 4

Reproduction or transmissability rate <1

Average number of cases infected by primary case is less than 1

Question 5

Define epidemic

Answer 5

A level of disease in a population significantly greater than usual
R0>1

Question 6

Define R0>1

Answer 6

The average number of cases infected by a primary case is greater than 1

Question 7

Define principle of causation

Answer 7

Principles of causation – how do we know if a particular pathogen is the problem (the world is full of bugs.!)

Question 8

Give 5 points of consideration in principles of causation

Answer 8

• Time sequence – does the cause precede effect?
• Strength of association – statistical association between agent and disease?
• Biological gradient – is there a dose-response relationship?
• Consistency – is an association consistently found?
• Coherence or plausibility – is it biologically sensible?

Question 9

Describe a case control study

Answer 9

o Case-control studies
 Compare between cases aand non cases (diseased and not diseased)
 Look retrospectively at the differences in exposure to risk factors

Question 10

Describe a cohort study

Answer 10

o Cohort studies
 Look retrospectively or prospectively at individuals exposed and not exposed to risk factors and see if they develop disease

Question 11

Describe Odds Ratio

Answer 11

o Odds Ratio (OR)
 Odds of the disease in the exposed group compared with odds of the disease in the unexposed group
 Common in case-control studies
 OR>1 (risk factor associated with disease)
 OR<1 (risk factor not associated with disease)

Question 12

What measurement type is commonly used in case control studies

Answer 12

Odds ratio

Question 13

What measurement type is commonly used in cohort studies

Answer 13

Relative risk

Question 14

Describe Relative Risk

Answer 14

o	Relative risk
	Ratio of risk of disease in exposed group to risk of disease in unexposed group 
	Common in cohort studies
	RR>1 (RF associated with disease)
	RR<1 (RF not associated with disease)

Question 15

Give three methods of subtyping pathogens

Answer 15

RFLP, PCR fingerprinting, DNA sequencing

Question 16

Describe the process of pathogen subtyping

Answer 16

• Amplify targeted pieces of the pathogen’s DNA in order to determine either speciation (if unknown) or strain identification
• Compare the ‘fingerprint’ from human and animal cases and see if they are the same

Question 17

Give the triad of factors in disease control

Answer 17

The agent/pathogen
The environment
The host

Question 18

Describe disease prevention

Answer 18

Disease prevention - Avoiding disease occurrence
• Reduces the incidence and prevalence of disease
• Rule of thumb – essentially all diseases

Question 19

Describe disease control

Answer 19

Disease control – reducing the disease frequency to a tolerable level
• Reduces the prevalence of disease
• ROT  diseases that are commonly found or seen

Question 20

Describe the host element to disease control

Answer 20

• Host - Increased resistance/decrease susceptibility of host
o Modification of host resistance –> i.e. national scrapie plan
o Vaccination Strategic (e.g. emergency vaccination in an outbreak – swine flu) and Blanket (e.g. rabies and travelling pets)

Question 21

Describe the pathogen element to disease control

Answer 21

• Pathogen – Decrease pathogen population
o Decrease pathogen load - Therapeutics
o Not always effective e.g. nitazoxanide for Cryptosporidium in people
o OK at individual animal/farm level, but poor regionally/nationally
o Expensive
o ?Antimicrobial resistance & anthelmintic resistance

Question 22

Describe the environment element to disease control

Answer 22

o Restriction of host movement e.g. limited travel to Mexico during swine fever outbreak (6 day standstill in the UK for cattle and sheep movements)
o Quarantine/Isolation – e.g. norovirus - duration must exceed the incubation period of the disease
o Control of vectors – e.g. Ixodes ticks and Lyme disease
o Biosecurity – e.g. fomite control (management systems that reduce the risk of introducing infectious disease to a herd)

Question 23

Describe disease eradication

Answer 23

Disease eradication – the complete elimination of disease or disease agent from a region
• ROT  Exotoc diseases or those commonly found undergoing eradication programmes

Question 24

Describe 4 methods of disease eradication

Answer 24

• Test and removal  Animals testing positive are removed and slaughtered E.g. Bovine tuberculosis
• Pre-emptive  Animals that have been exposed to infection are slaughtered E.g. Flocks of Bernard Matthews turkeys culled because of contact with Hungarian flocks infected with avian flu in 2007
• Blanket culling  Animals on contiguous premises surrounding an infected farm are culled E.g. Killing domestic pigs in Estonia to stop African swine fever spread - 2015
• ‘Stamping out’  Combination of one of the above with other preventive measures (e.g. disinfection, burning of carcasses, dangerous contacts culled during FMD 2001 outbreak)

Question 25

Describe the 5 elements of n outbreak control plan

Answer 25

System of communications and liaison between stakeholders locally and nationally
A clear arrangement for media liaison
Arrangements for the care of patients including reducing secondary person to person spread.
Arrangements for the provision of the necessary equipment and facilities, including staff OOH
to enable the team to function adequately
A clear statement of the purpose of such a plan in the control of food related incidents

Question 26

Name a number of outbreak control teams

Answer 26

LA Environmental Health
PHE (regionally and nationally) and NHS
FSA (nationally and internationally)
APHA +/- other veterinary input
?Port Health Authority, industry and others?