Epidemiology 1+2 Flashcards
Define Epidemiology
• Epidemiology the study of disease in populations (observing populations and making interferences from these observations)
Define Veterinary Public Health
• Veterinary Public Health The part played by veterinarians in human public health, relating chiefly to the recognition and control of zoonotic disease
Define Endemic
Endemic - Disease commonly found in or restricted to a particular region community or group of people
R0<1
Define R0 <1
Reproduction or transmissability rate <1
Average number of cases infected by primary case is less than 1
Define epidemic
A level of disease in a population significantly greater than usual
R0>1
Define R0>1
The average number of cases infected by a primary case is greater than 1
Define principle of causation
Principles of causation – how do we know if a particular pathogen is the problem (the world is full of bugs.!)
Give 5 points of consideration in principles of causation
- 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?
Describe a case control study
o Case-control studies
Compare between cases aand non cases (diseased and not diseased)
Look retrospectively at the differences in exposure to risk factors
Describe a cohort study
o Cohort studies
Look retrospectively or prospectively at individuals exposed and not exposed to risk factors and see if they develop disease
Describe Odds Ratio
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)
What measurement type is commonly used in case control studies
Odds ratio
What measurement type is commonly used in cohort studies
Relative risk
Describe Relative Risk
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)
Give three methods of subtyping pathogens
RFLP, PCR fingerprinting, DNA sequencing
Describe the process of pathogen subtyping
- 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
Give the triad of factors in disease control
The agent/pathogen
The environment
The host
Describe disease prevention
Disease prevention - Avoiding disease occurrence
• Reduces the incidence and prevalence of disease
• Rule of thumb – essentially all diseases
Describe disease control
Disease control – reducing the disease frequency to a tolerable level
• Reduces the prevalence of disease
• ROT diseases that are commonly found or seen
Describe the host element to disease control
• 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)
Describe the pathogen element to disease control
• 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
Describe the environment element to disease control
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)
Describe disease eradication
Disease eradication – the complete elimination of disease or disease agent from a region
• ROT Exotoc diseases or those commonly found undergoing eradication programmes
Describe 4 methods of disease eradication
- 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)
Describe the 5 elements of n outbreak control plan
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
Name a number of outbreak control teams
LA Environmental Health PHE (regionally and nationally) and NHS FSA (nationally and internationally) APHA +/- other veterinary input ?Port Health Authority, industry and others?
