Flashcards in Surveillance Deck (41):
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
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?
Give an example of surveillance whre the threshold is 0
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
What was the first animal disease to be officiallly declared eradicated
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
- 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?
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
How may lab tests introduce bias to results?
Differing sensitivity and specificity of lab tests
How may sampling introduce bias?
Picking a non random group of subjects
What are the 2 types of farm level monitoring and surveillance?
- statutory eg. TB, Brucella
- coluntary industry led eg. JD, BVD
Define a notifiable disease
statutory requirement to report suspicion of a clinical case of disease
Define a reportable disease
statutory requirement to report a lab confirmed isolation of organisms (ie. Salmonella nad Brucella) Under Zoonoses order 1989. Report made by lab that isolated the organism from animal dervied sample.
Who should notifiable disease be reported to?
- local animal health DVM
- now APHVLA
Give 3 purposes of disease surveillance
1. monitor trends in existing diseases by comparison against a threshold
2. monitor and ID new and emerging diseases, zoonotic infections and intoxications (often threshold = 0)
3. inform defra and other stakeholders (potential risks/developing problems, directing policy and stategy)
Who carries out vet disease surveillance in the UK?
- animal owners and keepers
- livestock industry organisations
- diagnostic laboratories
- international monitoring eg. OIE, FAO, EFSA
What are VLA PM centres now known as?
Veterinary Investigation Centres
Who pays for PME of adult sheep/pig/deer?
Taxpayer subsidises, farmer pays rest
What 3 diagnostic services are available for vets in practice?
1. PM of carcasses suitable for surveillance
2. postal samples (swabs, bloods, biopsy)
3. advice on disease diagnoses and control
What use is the submission of a casrcasse for PME for national vet disease surveillance?
1. endemic disease levels
2. animal welfare issues (eg. flystrike)
3. notifiable diseases eg. Newcastle disease in pheasants, swine fever suspicions
4. novel diseases (eg shmallenburg)
5. zoonoses (HAIRS=human and animal surveillance) (eg. E . Coli)
6. chemical threats to food chain eg. car battery eaten by cows
7. ABx resistance
8. adverse reactions (eg. bluetongue vax -> abortion?)
How is scanning surveillance within APHA standardised?
- submission forms and farmfile database (single database for all pssive and active surveillance, including statutory [brucella] and emergency response [FMD, CSF] monitoring)
- accredited lab testing facitlities to ensure quality control
- standardised recording by code with specific diagnostic criteria
What is another term for scanning surveillance?
What is the downside to passive surveillance?
May miss cases - no. diagnosed cases is only the tip of the iceberg
What is targeted surveillance and when is this used?
- research into new diseases or changes in recognised diseases identified by scanning
eg. testing notifiable diseases..
> BSE in fallen stock over 48 months old
> TB (low case rate, expensive, not great test, also test healthy animals)
> Anthrax in all sudden cattle death
> FMD (blood testing during and after outbreaks)
> Brucella to assure freedom from disease
- also import testing, ABx resistnace, novel diseases, zoonoses (salmonella, campylobacter)