Surveillance/Monitoring Systems Flashcards
MOSS stands for?
MOnitoring and Surveillance System
MOSS was coined by?
Salman in 2003
What is the difference between monitoring and surveillance?
- Monitoring = continuous, adaptable process of collecting data about diseases and their
determinants in a given population - Surveillance = specific case of monitoring in which control/eradication measures are
implemented
When you have a surveillance system, you need policies and rules when you find certain levels of disease. Monitoring is simply gathering data.
What are the goals of MOSS?
- Early warning of change in health status of any animal population. This is KEY.
- Provide evidence about the absence of diseases or determine extent of a disease that is
known to be present
Why is surveillance done?
- In general terms, it provides information that is critical for decision making in disease control and prevention
- How much disease is there? (Prevalence)
- What impact is this disease having on:
- Animal populations?
- Public Health?
- Farmers?
- Trade? Particularly important for economy.
- The question you can ask is, Is prevalence increasing, decreasing, staying the same?
- Where does disease occur (what populations, space, and time - what are the trends) and what are the spatial patterns and trends?
What are the qualifying terms for ‘surveillance’?
- Classified according to the collection of data:
* Active
* Passive - Classified according to the disease focus:
* Targeted surveillance, looking at a specific disease
* General, meaning we do not have a specific disease in mind - Others:
* Syndromic, related to clinical signs
* Risk-based, looking for associated risk factors
* Participatory, get general public involved as well.
Active vs. Passive has to do with?
the way the data is collected
Define active data collection.
Active data collection is the _________ recording of cases of a designated disease or a _____ of diseases for a specific goal of _______ or _________.
The population is determined by _______ and/or _____, providing each individual with a ______ (and often _____) chance of being selected
E.g. ?
–> Active
* Systematic recording of cases of a designated disease or a group of diseases
for a specific goal of monitoring or surveillance
* Population determined by location and/or time, providing each individual with a known
(and often equal) chance of being selected
E.g. survey - going out and collecting a proportion of population using random methods so we have a known probability of inclusion for each animal
Active data collection requires?
- Requires sampling design and strategies
- $$$, especially if targeted disease is rare!
- <0.1% is usually not feasible aka a rare disease; nearly impossible to find it
- Limitations of diagnostic tests (Se/Sp)
As prevalence decreases, towards eradication, 5% prevalence is high, close to eradication is very difficult to find. As prevalence decreases, sensitivity must be important so if sensitivity is low need more samples to detect disease = more money
if diagnostic test is not specific, a lot of false + pop up –> more money.
Design prevalence: immportnat in sruveillance systems because we need to determine level of disease we would expeect in a popilation if disease is present. Guidelines provided by OIE/WOAH have recs for design prevalences. We can then design a surveilance system at least tis threshold of disease in this country. If you don’t find it = disease free, if do = have disease
What is passive surveillance?
Waiting for info to come to you
Passive
* Reporting of clinical or subclinical suspect cases to the health authorities by health care professionals, at their discretion
* Validity of the system depends solely on the willingness of these professionals to secure
the flow of data
* Depends on the awareness and level of knowledge of a particular disease among veterinary practitioners and producers or owners of animals
- “Notifiable animal diseases” are typically
Passive
Notifiable animal diseases are
* ______-listed diseases (e.g. ______/_____ reportable diseases)
* While many notifiable disease should require _______ collection, many countries rely on ______ collection for a MOSS
- OIE-listed diseases (e.g. USDA/APHIS reportable diseases)
- While many notifiable disease should require active collection, many countries rely on passive collection for a MOSS
Passive methods can also be described as?
- Can also be described as the ‘secondary use of routinely collected data generated for another purpose’
- Opportunistic in nature
What are the limitations of passive methods?
- Inconsistency in the data collection for diseases
- Difficult to compare MOSS data
What is a targeted surveillance system?
Targeted
* Usually used in the context of targeting a disease
* Has been used in the context of targeting high-risk populations (Salman, 2003; see risk-
based further below)
* Uses pathogen-specific diagnostic tests
* e.g. PCR, ELISA, culture, etc.
What is a general surveillance system?
General
* Not targeted at any particular disease
* Detects new/emerging pathogens
* Uses general diagnostic techniques
* e.g. clinical exam, necropsy and histological findings
The objectives of a surveillance system can?
Objectives can change!
* e.g. targeted surveillance for BSE in the US and Canada was designed to demonstrate freedom, but ended up finding cases
How types of surveillance systems overlap
General active = syndromic surveillance
Risk-based surveillance
* Where you Intentionally _______ toward sub-populations
* _______ risk of disease = much better probability of finding disease
* Population is stratified according to _____/_____ risk factors
* Strata are not sampled proportional to their _____!
* Increased efficiency = ___ $
- Where you Intentionally biased toward sub-populations
- Higher risk of disease = much better probability of finding disease
- Population is stratified according to known/hypothesized risk factors
- Strata are not sampled proportional to their size!
- Increased efficiency = ↓ $
Three types of risk factors can be used for risk-based surveillance:
1) Causal factors for disease - risk factors that cause disease
* e.g. Age group more susceptible to disease, farms with lower biosecurity
2) Factors caused by the disease
* e.g. Clinical signs appearing with disease
3) Non-causal factors that may be associated with disease; not commonly used
* e.g. smaller farms… maybe associated with employees working in multiple sites (…reduced biosecurity)
Syndromic surveillance
- Syndromes = a group of clinical signs associated with diseases
- trying to cut out the time
- trying to get it at the lab submission level; without knowing outcome, just trying to see if there are more clinical signs in a given population.
based on the clinical signs that you can gather from labs submission levels or other facilities and that it’s a general and active form of surveillance to look for trends
What is participatory surveillance?
Participatory surveillance
* Growing trend
* Involving the public in the collection of disease information
* Usually in a digital format (an app on a smart phone)
* “Putting the ‘public’ in public health”
* People on the street or at the farm level have a lot of information
about certain diseases or syndromes
* Common in rural areas (e.g. Africa and Asia)
* Apps also educate ‘para-vets’ as they enter data
Evaluating a MOSS involves ?
Trying to understand the probability a surveillance system will detect a disease.
In order to truly understand a surveillance system’s efficacy, you need to understand the?
Population coverage = Proportion of the population that is included in the surveillance system
* Census = every animal in the population
* Sample = sub-sample of the population
* Think back to sampling class…
* Are you properly representing the target population?
* The rarer the disease, the more you need to sample and the better the diagnostic sensitivity needs to be
Schematic representation of a MOSS for determining ‘freedom from disease’
Historically, in order to determine freedom of disease a country would conduct?
repeated surveys and conduct all the tests to ensure no disease presence/eradicate disease if found.
If to demonstrate to not have disease for trade country would have to do a one off survey.
With time, way of thining shifted –> each survey is a chain of islands -> weight of evidence –> continued freedom in further years if one year the country did not have disease. only thing counteracting: any given time there is the probability that the disease can be introduced.
FYI
How do you determine if a country has a legitimate SPS measure?
- Is the disease you are concerned with exotic or endemic?
WOAH - Risk Assessment
1. Release assessment (Pathogen “[Formally called] Entering” your country and leaving exporting country)
- Estimate likelihood of the imported commodity being infected/contaminated
* What factors need to be considered here?
2. Exposure assessment (“Establishing”) - Relates to importing country
- Describe the biological pathway(s) necessary for exposure of animals and humans
* What factors need to be considered here?
3. Consequence assessment (Now that it is in the country, want to know how it spreads “[Formally called] Spreading”)
- Estimate the likelihood of potential consequences
4. Risk estimation (This is the outcome/product of risk assessment - your best guess after doing steps 1-3)
- Compilation of the results obtained from the Risk Assessment (Release, Exposure, and Consequence)
- If estimated risk is ‘non-negligible’ = actual hazard aka you need to deal with it and put SPS measures in place.
same factors for 1 and 2
Factors for 3:
Direct – in the animal (population)
1. Morbidity and mortality
2. Production losses
3. Animal welfare
Indirect
1. Economic
- Costs of control and eradication or surveillance
- Potential trade losses
2. Environmental
- Amenity values
- Social, cultural and esthetic conditions
We are looking at what is the risk of the human contracting S. enteriditis post interaction
Define Negligible.
Cost and losses/consequences?
Description?
Event would be virtually unlikely to occur
Anything right of the line is?
Non-negligible
This is where politicians or govt. officials need to implement SPS measures.
This is only looking at the probability of an event
Anything of the right line is?
Non-negligible
Risk estimate looks at overall estimate so both the overall probability of an event and the consequences of an event.
Non-linear relationship
