Abstract
Surveillance is the collection, analysis, and dissemination of information to support prevention and mitigation of pest and pathogen impacts across natural and managed health systems. Surveillance provides an informational foundation for the risks posed by the organism, current status of the outbreak, directing limited resources, and effectiveness of management actions within the context of a response. Each response may have a series of management goals to accomplish over time and the information needs to support each goal will vary. Surveillance must be appropriately designed to align with the response goal and be well supported by risk assessment information on the biology of the invasive pest/pathogen, biology of the host or host system, pathways of introduction and spread, types and magnitude of impact, etc. This chapter proposes a generalized framework as a starting place for designing surveillance schemes using core design factors and how to effectively narrow parameterization of these factors within the context of a response goal.
TopIntroduction
Surveillance may be defined as an organized system of sample design data collection and reporting intended to gather information about a hazard within a certain likelihood in a timely manner. Plans describing complete surveillance systems are often developed to address multiple objectives for a single hazard and include hazard background, budget details, and communication plans in addition to one or more surveillance schemes. Here we focus on designing surveillance schemes for a single objective. In the previous chapter, we were introduced to the concept of surveillance for the early detection of plant and animal pests and diseases, which we collectively define in this chapter as “hazards”. As the previous chapter states, the objective of early detection is to find the hazard before it becomes established, resulting in ecologic and economic harm to the agricultural or ecological system. However, this chapter focuses on surveillance after the initial detection and the application of biological knowledge to guide that surveillance (i.e., risk-based surveillance). Unlike early detection, there may be multiple post-detection response goals and the surveillance designed to support those response activities will need tailoring for each goal. Also, there may be multiple surveillance activities that occur simultaneously. It is not possible to adequately cover all aspects of surveillance design in a single chapter, nor is it realistic to propose a prescriptive guide that fits all situations. Thus, the intent of this chapter is to illustrate the critical thinking skills of the design process, define a set of core factors to consider in each scheme, and describe how to rapidly adapt a scheme to any post-detection hazard response situation for plant, animal, or ecological health systems. While this chapter provides a common set of core factors and discusses how each varies according to objective, the overarching tenet is the same: the purpose of surveillance design is to support the post-detection goal(s) and narrow the focus such that collection of information is optimized for the response goals for the hazard.
The chapter begins with the context of how surveillance occurs within a set of response activities (Figure 1). Once a hazard is detected, the responding agency, department, or program will have a high-level mission to accomplish regarding the hazard (e.g., pest or pathogen eradication). The response implemented depends on a number of variables, including previous experience with a similar type of hazard, expected consequences of the hazard, point of entry, first-detection numbers, susceptible hosts, at-risk livelihoods, ecosystems, and businesses, knowledge of environmental conditions for survival and spread, and resources available. Because of the large number of variables, no response will be the same for different hazards or even for different incursions of the same hazard. Each response will have multiple distinct goals with activities tailored to achieve each goal.
Figure 1. Conceptual diagram of the structure of a response following first detection and the relationship of surveillance within the context of a response
Surveillance does not directly achieve a response goal. Surveillance has its own objectives aligned to the response goal (Table 1) and provides supporting information to the overall response such as guiding the response activities or estimating success of the response goal. The design of a surveillance scheme will depend on the upstream choices (Figure 1) and existing information. It is the complexity of response goals and uniqueness of activities that imply a need for both agility and flexibility when designing surveillance. Response scenarios are primarily used for fast spreading, high-consequence hazards to illustrate how different response goals drive different surveillance objectives. Not all these response goals and the associated surveillance objectives are necessary with every new introduction. There are also response goals and surveillance objectives not listed in Table 1 here that may be appropriate for certain hazards.
Key Terms in this Chapter
Population of Interest: The population upon which a study is based, is actively being managed, or from which inference is being drawn.
Control Zone: A buffered around and inclusive of the infested/infected area within which surveillance and control operations occur. The control zone ensures that the hazard is contained if it spreads beyond the infected/infested zone.
Case Finding (Also Delimitation): Detection of the occurrence of a hazard within an ecological system with the intent to detect geographic boundaries.
Consequences: Social, economic, and biological impacts incurred from a hazard.
Business Continuity: Ensuring that an organization’s critical functions are not interrupted or that the business-critical functions will be quickly restored to operational status.
Subpopulation: A fraction of a population which has common characteristics of interest in the study.
Delimitation (Also Case Finding): Detection of the occurrence of a hazard within an ecological system with the intent to detect geographic boundaries.
Risk Assessment: Evaluation of the risk associated with a hazard.
Free Zone: Area outside of the control zone which is considered hazard-free and not actively (or perhaps intensively) surveyed.
Surveillance: An organized system of sample design and collection, testing, and reporting intended to collect information about a hazard with a certain likelihood or level of precision in a defined period of time.
Scope: The geographic extent and populations potentially at risk from a hazard.
Outbreak: The occurrence of a case or cases in excess of what would normally be expected in a defined community.
OIE: World Organisation for Animal Health (formerly the Office International des Epizooties).
Target: The subpopulation or sublocation potentially affected differentially by the hazard, and from which information needs collection.
Susceptible: A (host) population or subpopulation at risk of becoming affected by a hazard.
Host-Hazard System: The biology and interactions between two distinct organisms, a pest or pathogen (hazard) and the host (plant or animal) upon which the hazard sustains itself, and the impact of those interactions within an ecological context.
Confidence Level: Probability that the true parameter value falls within the estimated interval.
Hazard Freedom: Achievement and maintenance of eradication of a hazard.
Sensitivity: True positive rate, the probability of detecting a hazard when it is present.
Stable Health Status: Health metrics of interest for a population (disease prevalence, population size, birth rate, growth rate, milk production, etc.) maintain a steady rate with a normal level of random fluctuation over a sustained period of time.
FAO: Food and Agriculture Organization of the United Nations.
Infected or Infested Zone: A buffered area around presumptive or confirmed positive detections of a hazard. Infected may reference pathogen-based hazards whereas infested may reference hazards that are insect pests or weeds.
Monitoring: The collection of information for the purpose of assessment of the progress and success of a land use (or fishery management) plan. Monitoring is used for the purpose of enforcement and of revising the original plan, or to gather information for future planning.
Risk: A combination of the likelihood of occurrence and the consequences of the occurrence.
Eradication: Elimination of a hazard to a known detectable level such that mitigations are no longer required.
Scheme: Collection of factors, risk information, and other parameterizations that make up a surveillance design for a particular objective.
Specificity: True negative rate, the probability of not detecting a hazard when it is absent.
Production facility: A licensed premise, business, or foreign manufacturing site where any step in preparing agricultural products occur.
Case: A detection that is suspect, presumptive positive, or confirmed positive for the hazard itself or for host exposure to the hazard. Some forms of detection (such as environmental samples) may indicate potential of the hazard but are not indicative of active spread.
Target Analysis: An approach that provides the structure of first making the strategic decisions related to identifying the target (who or what) and goal (desired outcome) and then making sound operational decisions that guide surveillance to the right place (where), right time (when) and right tools (how).
IPPC: International Plant Protection Convention.
Risk-Based Surveillance: The application of risk analysis to inform which health hazards and outcomes matter most, the result of which (risk) is used to prioritize and resource surveillance activities to efficiently achieve the surveillance goal.
Hazard: A biological agent with the potential to cause an adverse effect in natural or agricultural ecosystems.
Likelihood: The chances of a hazard or some other event occurring.
Prevalence: Proportion of hosts affected by a hazard.
Exposure: Contact of a host or host system with a hazard.