Once you have recognised signs of poor health or welfare, you need to take corrective action. This requires that you determine the underlying cause of the problem. Although this may be directly related to your research procedure, it could be a result of the housing or husbandry conditions.
Pain, distress or suffering can also be caused by spontaneous disease. This can be caused by infectious agents or have non-infectious causes. Some strains of laboratory rodents have a high incidence of conditions such as hydrocephalus, arthritis, kidney disorders and skin disease.
Once you know what the cause of the problem is, you can consider treatment, and the use of anaesthetics or analgesics to minimise any pain or distress.
Scientific goals
It is important that you consider carefully the scientific goals of the study.
It may not be possible, for example, to give some veterinary treatments if they would interfere with the specific experiment, and in these circumstances if your treatment options are limited, you may have to humanely kill the animal.
When injuries due to fighting or other welfare problems are noticed, it’s also helpful to review the study protocol and husbandry methods to see if something could have triggered the problem.
For example, putting mice into new groups when a study commences can trigger fighting. Fights can also occur if some animals are removed from a group because of the design of the study. Fighting is more common in some strains of mice, and more common in males than females.
Discussing these issues with the animal welfare officer (NACWO in UK) and facility veterinarian (NVS in UK) can often help prevent similar problems in the future.
Anaesthetics & analgesics
In some circumstances, anaesthetics, analgesics and other agents (e.g. anti-anxiety agents), can be used to minimise pain or distress.
For example, an anaesthetic could be given to avoid the need for physical restraint that an animal might find distressing. Anaesthetics can also be used to prevent pain during a brief procedure. Analgesics can be given to prevent pain after a procedure, and can be given for prolonged periods if needed.
Anti-anxiety drugs
If a procedure causes mild distress, but anaesthesia needs to be avoided, anti-anxiety drugs such as diazepam can be used.
In some circumstances, it may be preferable to use positive reinforcement training to familiarise an animal to the procedure and motivate it to accept any restraint or other distressing component.
Direct & indirect causes of pain and distress
In their book “Principles of Humane Experimental Technique”, Russell and Burch described both direct and indirect causes of pain and distress, and explained how we need to consider both causes in order to refine our experiments as much as possible.
Indirect causes include factors such as poor caging conditions, poor environmental conditions, and spontaneous diseases. Fighting, which commonly occurs in groups of mice is another indirect cause of pain and distress.
Direct causes are factors directly related to the research procedures, for example ill-health caused by experimentally induced disease, or adverse effects associated with growth of experimental tumours
Treatment summary
To summarise, when preventing and treating pain and distress we should aim to do the following:
- Optimise animal housing conditions, provide environmental enrichment and careful and expert handling and restraint.
- Provide additional warmth, fluids and nutritional support when this is needed, for example when animals are recovering from surgery or other stressful experimental procedures.
- If a procedure is not painful, but requires physical restraint of the animal, it may be preferable to use light anaesthesia – for example when imaging animals or taking blood samples.