Qualitative risk analysis in animal health: A methodological example

Risk analysis can be performed following either a quantitative or a qualitative approach. Both methodologies are linked to the same theoretical rules. Once the potential hazard has been identified, the qualitative risk assessment is carried out by combining the probabilities of occurrences of the events (emission and exposition) in the presence of a hazard, and its consequences. The probability of an event can be evaluated by combining the probabilities of the different parameters. Within the frame of global expertise, the necessity of realizing collegial risk evaluations, sometimes when only few data are available and within a short amount of time, leads us to work on a standardised method for a qualitative approach. The process of global qualitative risk appreciation is completed by adding support to the rationalisation of the estimation step. It has been proposed that each parameter be evaluated with the help of all available information and that an evaluation of the probability of occurrence of each of these can be realized individually to yield a given level of probability (null, negligible, low, moderate, high) or an interval between two levels (for example: 'negligible to low'). The combination of probabilities and of intervals was carried out using a table that was tested and evaluated through the following risk assessment: qualitative risk evaluations of the transmission of (a fever to humans in France. Both the advantages and the limitation of this approach are also presented.