At the start of the assessment view the animal from a distance and note its natural appearance and undisturbed behaviour. Next, as you approach the animal it should take notice of you and interact in some way. The nature of that interaction can be used to assess whether the animal is responding normally. Finally a detailed clinical examination can be carried out making appropriate clinical measurements (such as body weight).
If there is no deviation from the normal, for each parameter score 0. If there is mild deviation score 1, moderate deviation score 2, and substantial deviation score 3. If three is scored more than once, give an extra 1 to each, making a maximum score of 20.
The use of such a system encourages regular close observation of the animal, leading to improved standards of animal care. If the animal is found to be deteriorating then actively consider euthanasia before the experimental end point is reached. It is vital to remember to re-score the animal after giving analgesics or other treatments to ensure that the drugs have had the desired effect and the animal’s condition has improved. Specific scoring systems have been devised to examine many species and types of experiments in order to define an intervention point such as provision of analgesia or carrying out of euthanasia, such as the Mouse Grimace Scale14.
Frequency of assessments
The frequency of use of the scoring system to assess the animal will depend on when signs are expected to occur and the length of time that they will persist. For example, in a toxicity study the early signs are likely to be due to the primary effects of a substance on a particular tissue or cell, which depends on the physical and chemical characteristics of the test substance. Secondary effects occur after the compound has been taken into the body and undergone metabolism in the cells. The effects of this may occur at cellular level, organ level or affect the whole animal and may be manifested in a variety of physiological and behavioural effects. Tertiary effects may not be related directly to the interaction of the compound itself within the body; for example, if a compound induces diarrhoea the animal may become dehydrated if it does not drink, and it is the dehydration which will cause the death of the animal. Signs that occur shortly before death may be due to the secondary effects of the substance but are more likely to be due the tertiary effects. Carcinogenicity studies may involve a necessary assessment of tertiary effects and provide needed experimental data, but the majority of toxicity studies are to determine the primary and secondary effects; the tertiary effects provide little additional information. The combination of the type of clinical signs and their duration can be used to assess the severity of the procedure and the intensity of suffering of the animal. The observations should therefore be frequent enough to identify any animals that are showing the defined set of signs of distress to enable euthanasia to be carried out in a timely manner. It is also scientifically useful to collect as much data as possible on clinical signs and any unobserved animal deaths will represent lost information on the compound under test and a reduction in the quality of the scientific information yielded.
Development of welfare assessment systems
In practice, scoring systems can be valuable tools in keeping the harm to animals in biomedical research to a minimum. However, the system outlined in Figure 4.1 is very general. Many research projects produce changes in just one organ system, and a general scoring system such as the one described here may not be sensitive enough to pick up specific indicators of poor welfare in these cases. To overcome this the parameters are modified to include only those specific changes which are anticipated in the particular project. Pilot studies are important to develop these more specific assessment sheets and it may be necessary to modify the chosen system as the experiment progresses. The list of clinical signs to be assessed for a particular scientific procedure should be developed through experience and to a large extent will be unique to the specific husbandry system, the species or strain and to the specific experiment.
A scheme of scoring clinical signs for recognition and assessment of adverse effects on animals during scientific procedures has been shown to have a number of benefits, including the following.
- Closer observation of animals by all staff at critical times in the experiment. This increases awareness of the potential adverse effects and allows for the appropriate use of methods of alleviation.
- Subjective assessments are avoided and opinion is both more structured and more evidence-based, thus promoting more fruitful dialogue between scientists and animal care staff.
- Providing assistance with making a valid harm/benefit analysis in the justification of a procedure.
- Consistency in scoring is increased.
- Combinations of signs can be used to indicate the overall severity of the procedure and the continued assessment will determine the effectiveness of any therapies given to alleviate the adverse effects.
- The assessment will allow retrospective review of procedures to assess which experimental models cause the least pain and distress. This will therefore help to further refine procedures in the future, to develop better systems of animal care, yielding better science and better animal welfare.
- The use of scoring systems assists with the training of new personnel in how to assess adverse effects on animals.
There are various components to the objective assessment of an animal’s welfare, as follows.