Guidelines on severity assessment and classification of genetically altered mice and rat lines

Genetic alteration of laboratory rodents may affect their welfare. In compliance with EU Directive 2010/63, potentially harmful phenotypes must be characterised and their effects reduced to what is strictly necessary for the experiment.

These guidelines have been published in Laboratory Animals. In addition to background information on severity classification, they include examples of the classification of the symptoms in a range of disorders: lethal factors, behavioural disorders, alterations of the skin and coat, diseases of the sensory organs, neurological diseases, diseases of the immune system, cardiovascular and haematological diseases, diseases of the respiratory tract, metabolic diseases, reproductive diseases, cancer, renal diseases and alterations of the locomotor system.
The Guidelines also include Recommendations on the number of animals required to evaluate an increase in harmful phenotypes in mouse and rat lines, and a large number of literature references.

Many of the authors of these guidelines are members of the Working Group of Berlin Animal Welfare Officers, and reflect the Group's initial experiences in defining the severity degrees of genetically altered lines. Line-specific properties, varying manifestation of symptoms and institution-specific housing conditions must be taken into account when the severity degree is selected.

Many more resources for planning and conducting animal research and testing can be found in the PREPARE guidelines.