Animal, vegetable, or ...? A case study in using animal-health monitoring design tools to solve a plant-health surveillance problem

Abstract

Biosecurity managers are often responsible for designing the surveys that are used to demonstrate pest absence from a region or country. This design process involves determining the number of locations to measure and choosing the locations from which survey information is collected (the sampling plan) as well as the number of units within each location that will be sampled (sample size). The choice of sampling plan may be influenced by prior information about the locations and by their spatial distribution. Sample size is influenced by the effectiveness of the testing method, the confidence interval required and the available budget. Biosecurity managers who do not have the time or skills to design appropriate surveys would benefit from applying pre-existing tools or templates to determine the sampling plan, the sample size and the level of resources needed to meet the survey requirements to ensure market access. Unfortunately such tools have not been developed specifically for plant-health applications, despite their development and widespread use in animal health surveillance. We show how EpiTools, a set of web-based tools developed to support survey designs for estimating disease prevalence or demonstrating free dom from diseases in animal herds, is equally applicable in the plant-health context. In this chapter we demonstrate the use of several of the statistical functions provided in EpiTools by designing a citrus canker surveillance strategy for the Northern Territory.