The application of probabilistic scenario analysis for risk assessment of animal health in international trade.

Abstract

Probabilistic scenario analysis (PSA) is a method of risk assessment that has had wide usage in many fields, including engineering, nuclear safety, and financial analysis. It is fast becoming the "gold standard" for risk assessment in many fields, including human health and the environment. It has been successfully applied in animal and plant health issues as well. PSA begins with the identification of a hazard and the development of a step-by-step scenario from some initiating event to the end point at which the hazard occurs. In PSA, the pathway leading to the end point is outlined by a model, called an event tree. Each step leading to the occurrence of the hazard is carefully outlined, called the node on the event tree. At each of these nodes, the probability of the event leading to the end point (hazard occurrence) is evaluated. The evaluation of the probability at each node may be qualitative or quantitative. The evidence used may come from standard epidemiological studies. The model can also accommodate expert opinion, anecdotal evidence, or any other information that can be verified that is pertinent to the event leading to hazard occurrence. The PSA is also quite flexible for it can be quickly revised when new data become available. With careful statement of the evidence and linkage back to bibliographic or other sources, it can provide a transparent, flexible, well-documented approach to risk assessment for animal health. Risk assessment along with regionalization is the key to healthy national herds and free international trade.