A new approach (CSA-Score) to assessing the cumulative overall stress load in the case of animal experiments and even beyond

In laboratory animal science, severity assessment has been mandatory by European law since 2013. Various severity assessments have been created for many single manipulations. However, when multiple harmful interventions or stressors occur simultaneously or repeatedly, the cumulative overall severity is difficult to capture objectively, often leading to significant underestimation. We propose a new scoring system (CSA-Score) that makes it possible to visualise cumulative stress loads. The main features of the CSA-Score are, that severity measures of multiple stressors must not be simply added together. Moreover, the highest individual stress load forms the basis for the cumulative score. All further stressors must be added in a weighted manner. The developed scoring system is based on four different aspects, namely the definition of the (1) highest individual stress load, the assessment of (2) parallel and (3) serial occurring stress loads and the consideration of a (4) baseline stress load. From these four different aspects, a cumulative overall stress load can then be determined through score allocations. We propose that this scoring system will be highly effective in objectively depicting cumulative stress load and covert burden and therefore leading to a more realistic overall severity assessment.