Introduction
The EU Directive and the national legislation (A(SP)A in the UK) requires you to avoid using death as an endpoint in studies. The legislation also requires you to humanely kill animals that are suffering pain or distress, if the purpose of the study has been achieved. You may also decide that you will kill animals in which unexpected or unnecessary adverse effects are detected, or this may be a requirement the Project licence.
This is best done by carefully monitoring animals and identifying signs of pain, suffering or distress, and using these to predict animals that are likely to die or experience unacceptable adverse effects.
A useful description of humane endpoints is as follows:
Humane endpoints are used to terminate research on an animal at a point where sufficient information has been gained to predict a later scientific endpoint (such as death in toxicity testing). Humane endpoints can also be used to provide an upper limit to the suffering experienced by the animals when the suffering is so great that continued use of that animal can no longer be justified.
(Morton, 1999; Hubrecht, 2014)
Developing humane endpoints
As mentioned earlier, scoresheets can be useful in determining when humane endpoints should be applied to a study. In all studies, an assessment should be made of the likely adverse effects on animals, and the actions that will be taken when these occur.
In some studies, it can be anticipated that the degree of pain, distress or suffering may gradually increase, but the anticipated outcomes are considered to outweigh the “costs” to the animals.
However, in all circumstances, an upper limit of what degree of pain or distress is permitted must be set.
If these are exceeded, even if the scientific objectives of the study have not been met, then animals must be either removed from the study and treated to alleviate their distress, or must be humanely killed.
The setting and application of these humane endpoints is not always easy, and often requires careful discussion with all of those involved with the animals. The endpoints may also need to be adjusted as a project progresses, as experience is gained with the specific animal model.
Developing endpoints is not easy, and the criteria used needs to be tailored to the particular research project.
In some studies, animals will receive an intervention as part of the study protocol that may result in recovery from a disease process, or diseases or disorders of varying severity may be induced.
It is often important to be able to differentiate these effects in order to achieve the objectives of a study, but once the required scientific goals have been attained, animals should be humanely killed.
The means of assessment and the end points to be used should be documented in the protocol for the study and on the project licence in the UK.