Animal disease import risk analysis - a review of current methods and practice.
The application of risk analysis to the spread of disease with international trade in animals and their products, that is, import risk analysis (IRA), has been largely driven by the Sanitary and Phytosanitary (SPS) agreement of the World Trade Organization (WTO). The degree to which the IRA standard established by the World Organization for Animal Health (OIE), and associated guidance, meets the needs of the SPS agreement is discussed. The use of scenario trees is the core modelling approach used to represent the steps necessary for the hazard to occur. There is scope to elaborate scenario trees for commodity IRA so that the quantity of hazard at each step is assessed, which is crucial to the likelihood of establishment. The dependence between exposure and establishment suggests that they should fall within the same subcomponent. IRA undertaken for trade reasons must include an assessment of consequences to meet SPS criteria, but guidance is sparse. The integration of epidemiological and economic modelling may open a path for better methods. Matrices have been used in qualitative IRA to combine estimates of entry and exposure, and consequences with likelihood, but this approach has flaws and better methods are needed. OIE IRA standards and guidance indicate that the volume of trade should be taken into account, but offer no detail. Some published qualitative IRAs have assumed current levels and patterns of trade without specifying the volume of trade, which constrains the use of IRA to determine mitigation measures (to reduce risk to an acceptable level) and whether the principle of equivalence, fundamental to the SPS agreement, has been observed. It is questionable whether qualitative IRA can meet all the criteria set out in the SPS agreement. Nevertheless, scope exists to elaborate the current standards and guidance, so they better serve the principle of science-based decision-making.