Proceedings for Pain Management and Humane Endpoints

Canadian Council on Animal Care Guidelines on: Choosing an Appropriate Endpoint in Experiments Using Animals in Research Teaching and Testing

James H Wong, DVM
Canadian Council on Animal Care
Ottawa, Canada

The Foreword to Volume 1 of the Guide to the Care and Use of Experimental Animals which states:

Every ethical and conscientious society must concern itself with the humane care and use of all animal life. It is a particular responsibility of all individuals who work with animals in research, teaching, testing and production to ensure that the care given is always optimal. Unnecessary stress must be avoided and numbers of animals used should be kept to the scientifically-acceptable minimum. The term 'experimental animal' includes any vertebrate that is separated from its natural environment and used in research, teaching and testing.

In the application of ethical guidelines for the use of laboratory animals, it is apparent that the scientist has the primary responsibility and must become increasingly aware of how and why animals are being used.

In Canada we have been subject to virtually the same rise in social concern regarding animal experimentation as has occurred in the United States and have indeed seen social consciousness raised on animal issues.

The scientific community, responded to these by forming a Special Committee of the National Research Council of Canada (NRC) to evaluate the concerns and make recommendations in dealing with them. The committee concluded in 1966 that Canada did not require legislation and that the objective of achieving optimal animal care could best be achieved by a voluntary approach. It recommended the development of a program of voluntary control under the direction and supervision of an independent body which would have the freedom to develop standards and guidelines pertaining to all aspects of animal care and use and which could respond quickly and effectively to public concerns as well as changing needs within the scientific community.

In 1968 the Canadian Council on Animal Care was founded under the aegis of the Association of Universities and Colleges of Canada (AUCC). It has since been incorporated. A private non-profit corporation, it maintains a totally independent position which enables it to carry out its mandate without bias or undue influence. The Council's terms of reference were made purposely broad and simple. Its mandate is "to work for the improvement of animal care and use on a Canada-wide basis." More specifically, the terms of reference include the making of recommendations for improvements in the procurement and production of experimental animals, the facilities and care of experimental animals and the control over experiments involving animals.

CCAC Guidelines

The Council's original guidelines for the care and use of experimental animals have subsequently been revised and published in a two volume Guide to the Care and Use of Experimental Animals and addenda. These guidelines are under constant revision in order to reflect changing priorities in the scientific community as well as public concerns. Volume 1 of the Guide was revised in 1993. In addition, guidelines have been developed on various issues such as protocol review, transgenic animals and choosing appropriate endpoints. The CCAC guidelines are developed to assist Institutional Animal Care Committees in their local oversight of animal based research teaching and testing.

CCAC guidelines are developed in response to current and emerging needs of the research community, advances in laboratory animal care and in conjunction with the needs of the assessment program. The CCAC establishes a subcommittee composed of experts knowledgeable and experienced on the topic to be covered by the guideline. This committee is then responsible for providing a draft guideline including references. CCAC guidelines are prescriptive, rather than descriptive and are justified through reference to published literature.

The draft document is circulated widely to experts in the area, CCAC constituents likely to be affected by the guidelines and council members for review and comments. When revisions have been completed, the final draft is placed before council for approval.

CCAC Guidelines on: Choosing an Appropriate Endpoint

CCAC guidelines on: choosing an appropriate endpoint was accepted by council in June 1998. They were developed by an ad hoc subcommittee on endpoints of the CCAC Guidelines committee.

The CCAC policy statement Ethics of Animal Investigation states:

"Animals must not be subject to unnecessary pain or distress. The experimental design must offer them every practical safeguard, whether in research, in teaching or in testing procedures..."
(Ethics of Animal Investigation, CCAC, 1989)

The purpose of the CCAC guideline on: choosing an appropriate endpoint in experiments using animals for research, teaching and testing is to assist Animal Care Committee members and investigators in fulfilling their ethical responsibilities in minimizing pain and distress in experimental protocols.

The term "Endpoint" is defined as the point at which an experimental animal's pain and/or distress is terminated, minimized or reduced, by taking actions such as killing the animal humanely, terminating a painful procedure, or giving treatment to relieve pain and/or distress.

The CCAC's general guideline for selecting an appropriate endpoint states:

"In experiments involving animals, any actual or potential pain, distress, or discomfort should be minimized or alleviated by choosing the earliest endpoint that is compatible with the scientific objectives of the research. Selection of this endpoint by the investigator should involve consultation with the laboratory animal veterinarian and the animal care committee."

Assessment of Pain and Distress

Morton & Griffiths (1985) laid the groundwork for developing a set of observations for assessing pain, distress and discomfort in laboratory animals, based on evaluating five aspects of an animal's condition:

  1. changes in body weight (and related changes in food and water intake);
  2. external physical appearance;
  3. measurable clinical signs (e.g., changes in heart rate, in respiratory rate, and in their nature);
  4. changes in unprovoked behavior; and,
  5. behavioral responses to external stimuli.

It is important to be aware of the characteristic behavior of the species under observation. Animals such as non-human primates, rodents, rabbits and some livestock may not show many behavioral changes even when in severe pain. In addition, strain variations must be considered. It is, therefore, imperative that the investigator/observer understand these characteristics prior to setting endpoints.

Morton & Griffiths (1985), and Sanford, et al. (1986), focussed attention on the need for more objective assessments of the pain and/or distress that may occur in an animal in the course of biomedical research. Efforts at refining the scoring of clinical signs have continued since 1985 (Morton, 1990; Morton & Townsend, 1995; Workman, et al, 1998, for example). More detailed observational checklists have been proposed for some specific scientific procedures, including: endotoxin administration in mice (Townsend & Morton, 1994); monoclonal antibody production in mice (Morton, 1997); cancer research (Workman, et al, 1998).

Information on the general signs of pain and/or distress for the various animal species commonly used in biomedical research are readily available (CCAC, 1993; Sanford, et al, 1986; Wallace, et al, 1990). Of these signs, significant weight loss may be one of the more important signs of deterioration in the animal's condition (reflecting a change in food and water consumption). Weight loss in these circumstances must always be compared to the appropriate control animal. Body condition scoring charts, which are available for domestic livestock, and dogs and cats, may be useful for evaluating chronic weight loss in experimental animals in specific studies.

Hypothermia can also be an important indicator of a deteriorating condition in the animal, when it occurs in specific disease or toxic states. For example, Wong, et al. (1997) found that a decrease in body temperature (below 32°C) of mice infected with an influenza virus was predictive of mortality. Soothill, et al. (1992) found that in mice infected with bacteria, hypothermia of 34°C was predictive of mortality. Thus, in specific experimental cases, the point at which the body temperature of an experimental animal drops to a specified temperature could be set as the endpoint at which euthanasia is recommended.

Pilot Studies

The use of preliminary or pilot experiments can be very useful in determining endpoints (Olfert, 1995; Browder, 1995, Everitt & Griffin, 1995), particularly when the effects of the treatment on the animals are unknown. A pilot study, using a small number of animals, may help determine the morbidity, time course of effects, and frequency of observations required to set an earlier endpoint. A pilot study can also provide an indication of the variance of responses between treatment groups, which can then be used to estimate group sizes more accurately for the main study. Conducting a pilot experiment also provides the opportunity for all persons to become experienced with the expected signs and symptoms.

Specific guidelines have been developed that address the frequency and responsibility for observations as well as competency assurance for those monitoring the animals.

Frequency

Based on previous knowledge, during critical periods of the experiment and at the onset of adverse reactions, a minimum of two or three observations should be made daily. The frequency of the observations should increase depending on the potential for increasing pain and/or distress.

The frequency with which affected animals should be observed must be determined for each study. The required frequency of, and interval between, observations will depend on the expected or known time course of the condition.

The appropriate monitoring schedule should be established by the investigator in consultation with the veterinarian, and approved by the ACC in its consideration of the protocol.

Responsibility

With respect to setting and determining endpoints, the responsibility(ies) of each individual should be clearly defined, and a clear chain of reporting established. The ultimate authority for euthanasia must rest with the veterinarian, supported by the animal care committee.

Training

All persons responsible for making observations of the animals, from which an endpoint will be determined, should be competent in evaluating the normal physiology, behavior and body condition of the animals under observation, and the anticipated specific changes from normal.

The role of the ACC is vital in establishing the structure to ensure that the earliest endpoints consistent with producing reliable data are considered, identified, and used. This is a joint responsibility with the investigator and the veterinary staff.

For some specific areas of biomedical research and testing, more detailed guidelines for selecting an appropriate endpoint are provided. In particular, endpoint guidelines for animals used in monoclonal antibody production, cancer research, toxicology, infectious disease studies, and pain research specifically. However, it may be necessary to develop observation checklists for other areas using the expertise of the attending laboratory animal veterinarian and the oversight of the ACC.

Monoclonal Antibody Production in Rodents

Guideline: That as long as rodents continue to be used for monoclonal antibody production, the following endpoints be established:

Cancer Research

Guideline: For all cancer research in animal models, endpoints should be established that minimize the potential for pain and/or distress in the animals.

Some recommended endpoints are:

Acute toxicity testing

Guideline: Before a protocol that includes safety/efficacy/toxicity testing with death as an endpoint for regulatory purposes can be accepted by the institution's animal care committee, there must be clear, written documentation obtained by the investigator from the appropriate regulatory agency that the proposed test is a necessary part of the submission for licensing/approval. The investigator must also demonstrate to the animal care committee that an alternative in vitro test will not be acceptable to the regulatory agency, and that this testing has not been previously done elsewhere.

Chronic toxicity studies and studies in aging

Guideline: Before a protocol that requires holding animals to an age close to or beyond the median survival age specific to the species or strain (e.g., chronic toxicity studies, carcinogenicity testing, or aging studies) is approved by the institution's animal care committee, the investigator in collaboration with the veterinary staff must establish the endpoint criteria for euthanasia of the animals, the persons responsible for monitoring the animals' condition, and the authority of the persons who will make the decision to euthanize.

Pain Research

Guideline:

Infectious Disease Studies, Vaccine Trials, etc.

Guideline: For all infectious disease research, including virulence tests in animal models, endpoints should be established that minimize the potential for pain and/or distress in the animals.

Specific Animal Models with the Potential for Significant Levels of Pain and/or Distress:

Guideline: Any pain and/or distress, or deficits in function that negatively affect the animal's well-being, not scientifically "necessary" for the study, should be alleviated or minimized. Cost or convenience should not deter from this. Further, as soon as the study is complete, the pain and/or distress should be alleviated through treatment or euthanasia.

Some animal models have inherent or induced functional deficiencies with the potential for pain and/or distress. There is a responsibility to attend to the special needs of these animals, beyond the care provided to normal animals. Animal models with inherited deficits (distressed phenotypes), transgenic animals, ischemia or seizure models, stereotaxic manipulations, are some examples of the kinds of laboratory animals for whom this recommendation is made.

Conclusion

All those involved in the use of animals for research, teaching and testing; ACC members, investigators and their research staff, the laboratory animal veterinarian and the animal health technicians, have responsibilities for the humane care and use of experimental animals. In working with investigators to establish appropriate endpoints, the ACC should ensure that the appropriate criteria are used by the principal investigator to determine the endpoint. Through the use of observational checklists and animal condition scoring systems, the most objective, and more humane, endpoints can be identified. Responsibilities for observing and monitoring the animal's condition must be clearly delineated. Persons involved in establishing and validating endpoints in invasive experiments are encouraged to present and publish these data, to support efforts at continually refining the animal use practices that occur in biomedical research.

Acknowledgement

The CCAC wishes to recognize the efforts of those persons serving on the ad hoc Subcommittee on Endpoints: Dr Ernest Olfert (co-chair), Dr Jag Bhasin (co-chair), Dr Richard Latt, Dr Eileen Macallum, Dr Kathy McCutcheon, Dr Don Rainnie, Dr Michael Schunk, Dr Gilly Griffin (CCAC Liaison).

CCAC Website: Visit the CCAC website at www.ccac.ca for all published CCAC guidelines and program descriptions.

References