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  • 1. Introduction to Risk Analysis
  • 2. Terminology and Uncertainty in Pest Risk Analysis
  • 3. Types of Pest Risk Analyses
• Topics
  • 1. PRA Initiation Points
  • 2. Organism PRA
  • 3. Pathway PRA
  • 4. Commodity PRA
  • 5. Lesson Summary
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  • Glossary
  • Acknowledgements

Lesson 3: Types of Pest Risk Analyses

Topic 1: PRA Initiation Points

At the beginning of this lesson, we learned that the key to harmonization of plant health issues is the use of terms and definitions that are clearly understood and agreed upon by the entire phytosanitary community. ISPM No. 5, Glossary of Phytosanitary Terms, is an IPPC reference standard that promotes harmonization and improves communication and understanding of plant health issues among the contracting parties. ISPM No. 5 is updated annually to add, remove, revise, or further clarify terms and definitions important to all plant protection activities, including pest risk analysis.

When conducting PRA, an analyst is faced with thousands of potential pests, hundreds of potential host commodities, and an unlimited number of possible trade scenarios. It is therefore not surprising that specific information on a particular pest or its association with a commodity is often lacking, resulting in varying levels of uncertainty. However, regulatory decisions are still necessary, even when our uncertainty is high. Extrapolation and expert judgment can be used to describe and, in some cases, quantify uncertainty in pest risk analysis. The PRA process should handle uncertainty in predictable and scientifically defensible ways that are responsive to the needs of decision makers. 

When Should PRA be Conducted?

Recall that according to the SPS Agreement and the IPPC, we must use international standards or PRA to justify the phytosanitary measures applied to reduce, manage, or eliminate risk. As such, conducting PRA to assess and manage the risks of agricultural commodities moving in international trade is one of the most common uses of PRA. However, PRA can also be used by an NPPO to support plant health decisions that have little to do with trade, such as informing domestic activities like surveillance programs and eradication, containment, or management programs. The need for a PRA may arise because an NPPO is considering a change in (domestic or international) regulatory policy. For example, an NPPO may decide to revise its requirements (entry, movement, etc.) for a particular type of commodity. An NPPO may need to evaluate a new pest that might be introduced or was already introduced into a country. If the concern is that a new pest might be introduced, the country may wish to determine if specific regulatory action may be needed to prevent its introduction. If the pest was already introduced into that country, the NPPO may wish to determine whether the pest should be under official control (containment or eradication). In both of these instances, a PRA would provide the scientific justification for the proposed actions.

Let’s examine some of these types of PRA more closely.

These different types of PRAs vary in complexity, depending on the nature of the problem, the audience, and the availability of scientific and other information to support the analysis. PRAs may use a variety of methods and processes to analyze risk. Methods may be qualitative or quantitative and may include mapping and geographic information systems. The methods selected will largely depend on the type of PRA and the scope of the problem, the data available, and the expected outcomes in terms of level of detail, available time for analysis, and the audience for the PRA.

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