Surveillance Flashcards
Define monitoring
Continous efforts to collect data to detect changes or trends in the occourence of disease in order to inform decisisons
Define passive surveillance
Surveillance = monitoring with the view to intervene if prevalence rises above a certain theshold
Define incident
The first isolation and all subsequent isolations of the same serovar from an animal OR epidemiologiclaly distinct group of animals on a single premises wihtin a 30d period
How has salmonella incidence in humans and livestock changed over recent years?
parallell
Give an example of surveillance whre the threshold is 0
FMD
What is the target level of clinical mastitis?
30 cases/100 cows/year
How may surveillance be used?
- monitoring diseases deemed to be of importance
- checking for effectiveness of control measures
- if eradication is achieved, demonstrating freedom from infection
Give an example of a disease where the aim of surveillance is to prove freedom of disease
Brucellosis
What was the first animal disease to be officiallly declared eradicated
rinderpest
What do farm level surveillance systems focus on?
- diseases controllable by the farmer
- focus on productivity
- rely on farm records
Give egs. of monitoring/surveillance objectives at a natinoal level
- demonstrate freedom from disease (eg. brucellosis)
- outbreak detection
- diseas control/eradication
- monitor zoonoses (eg. salmonella)
- pregress of hazard reduction programmes
- detect emerging disease
Give egs. of monitoring/surveillance objectives at an industrial level
- freedom from disease
- outbreaks
- define herd health status
- monitor production diseases
- monitor zoonoses and food bourne pathogens
- document acceptable risk levels
Give egs. of monitoring/surveillance objectives at a prodcer levle
- monitor production diseases
- outbreak detection
- assure freedom from food safetly hazard
- define herd/product status
- documnet aceptable risk levels
Give egs. of monitoring/surveillance objectives at a wildlife levle
establish disease status
How may cases be defined?
- clinical criteria: suspect cases that become confirmed following lab work (lab criteria added)
- epidemiological criteria eg. FMD control: farms defined as potental cases on the bases of location with repect to infected farms or dangerous contact with infected farms
What are the varying levels of disease prevalence?
- case
- outbreak
- epidemic
- pandemic
How are incidence and prevalence different?
- incidence = rate (no. new cases/ population at risk*time at risk)
- prevalence = proportion (no. existing cases/population at risk)
Define internal and external validity
- internal : measuring what is happening on farm, valid for that farm
- external validity: extrapolating to general population
What is the difference between active and passice monitoring or surveillance? Which is more susceptable to bias?
- passive: waiting, reliant on case reporting, awareness and motivation to report [most biased]
- active: searching, surveys, testing
How does systematic error differ from random error?
- systematic error: error due to the design, implementation or analysis of the surveillance programme
- random error: due to samping variation due to a random sampe of the popuation being studeied to make inferences about the whole popuation
Give 3 types of bias
- case detection: case ascertainment
- selection bias: in surveys if participation is voluntary, if not all famrs listed in sampking frame
- information bias: case definition, diagnositc tests
How may underrerporting skew surveillance statistics?
The “clinical iceberg” means deaths, severe disease and moderate disease [likely to be admitted to hosptial] but mild disease and sub-clinical infection not often reported so no cases actually ^ than recorded.
What is important regarding defining cases for epidemiology?
deifnition must be specific so that all cases are recorded correctly
What is important following detection of a case?
Dissemination of information quickly and efficiently to those who require it
