1.2 Types of surveillance

Surveillance systems can be classified as either passive or active, based on how the data are obtained.

Active surveillance is ‘the investigator-initiated collection of animal health-related data using a defined protocol to perform actions that are scheduled in advance. Decisions about whether information is collected, and what information should be collected from which animals, is made by the investigator’ (Hoinville, 2013). In the context of AMR surveillance in animals, the investigator can be any stakeholder in charge of the surveillance system: this is often the competent authorities, such as national veterinary services. Active surveillance involves the use of surveys and active testing for data collection in healthy animals and animal products. Data collection of samples and information can take place at farms, abattoirs, markets or retail.

Passive surveillance is ‘the observer-initiated provision of animal health-related data (e.g. voluntary notification of suspect disease) or the use of existing data for surveillance. Decisions about whether information is provided, and what information is provided from which animals, is made by the data provider’ (Hoinville, 2013). In other words, passive surveillance relies on data that has been collected for other purposes. This is usually data from animals with symptoms of disease, including results of microbiological culture and antimicrobial susceptibility testing (AST) of isolates from diagnostic samples and other associated information provided, such as clinical information.

These data are obtained when farmers or practitioners send clinical samples to diagnostic laboratories and AMR tests are performed to choose an appropriate treatment. The main reason for generating the data is to improve animal health and profitability of the farmer; however, this system provides data to monitor resistance, and is particularly useful in LMICs where there is a lack of resources needed for active surveillance. Because passive surveillance relies on the voluntary actions of farmers and animal health providers to report the occurrence of disease, the data obtained will be dependent on their motivation and awareness and will contain some degree of bias.

Enhanced passive surveillance is an observer-initiated provision of animal health-related data with active investigator involvement; for example, by actively encouraging producers to report certain types of disease, or actively following up suspect disease reports.

Other types of surveillance

Sentinel surveillance can be defined as ‘the repeated collection of information from the same selected sites or groups of animals (e.g. veterinary practices, laboratories, herds or animals) to identify changes in the health status of a specified population over time. These sentinels should act as a proxy for the larger population of interest; they may be selected on the basis of risk but can also be selected randomly or on the basis of convenience or compliance’ (Hoinville, 2013).

In many countries, the capacity and resources to implement a full-scale surveillance system may not yet be available. In these cases, collecting data through point prevalence surveys, or cross-sectional studies, can be used as a less resource-intensive way to collect AMR data.

Syndromic surveillance ‘uses health-related information (clinical signs or other data) that might precede (or may substitute for) formal diagnosis. This information may be used to indicate a sufficient probability of a change in the health of the population either to deserve further investigation or to enable a timely assessment of the impact of health threats which may require action. This type of passive surveillance is not usually focused on a particular hazard, so can be used to detect a variety of diseases or pathogens-including new (emerging) diseases. This type of surveillance is particularly applicable for early-warning surveillance’ (Hoinville et al., 2013).

Activity 3: The surveillance systems in your country

Timing: Allow about 5 minutes

Thinking about the surveillance activities you have identified in your setting, can you think of a surveillance system in food-producing animals, livestock or aquaculture? Is it a passive or active surveillance system?

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Discussion

You may want to consider particular activities that you engage with at your workplace that fit with the descriptions in the section above. You may want to discuss this with the lab manager or your supervisor.

Surveillance systems in LMICs are likely to be passive; that is, based on reporting of clinical findings.

  • Consider the surveillance objectives below and decide whether active or passive surveillance would be most appropriate in each scenario.

    Controlling an endemic bacterial disease in animals or fish

    • a. 

    Active surveillance


    b. 

    Passive surveillance


    The correct answer is a.

  • Active surveillance would be most appropriate in this scenario, because activities can be designed to target the specific endemic disease that that you wish to control within a population.

  • Monitoring changes in trends of AMR in animals.

    • a. 

    Active surveillance


    b. 

    Passive surveillance


    The correct answer is b.

  • Passive surveillance would be most appropriate in this scenario, because you are interested in general trends rather than a specific target species or resistance type, but it requires farmers and veterinarians to regularly submit samples to laboratories. Designing an active surveillance system to monitor general trends in AMR would require a lot of resources.

  • Investigating the public health risk of AMR E. coli in meat products.

    • a. 

    Active surveillance


    b. 

    Passive surveillance


    The correct answer is a.

  • Active surveillance would be most appropriate in this scenario, because activities can be designed to target the products and organism of interest in order to investigate the risk to public health.

  • Detecting the emergence of novel types of resistance among bacterial pathogens.

    • a. 

    Active surveillance


    b. 

    Passive surveillance


    The correct answer is b.

  • Passive surveillance would be most appropriate in this scenario, because there is no specific target and data would be obtained following the reported occurrence of disease. This would be an example of early warning surveillance.

1.1 Monitoring and surveillance to address the AMR challenge

1.3 AMR surveillance data