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Institute of Medicine (US) and National Research Council (US) Committee on the Use of Chimpanzees in Biomedical and Behavioral Research; Altevogt BM, Pankevich DE, Shelton-Davenport MK, et al., editors. Chimpanzees in Biomedical and Behavioral Research: Assessing the Necessity. Washington (DC): National Academies Press (US); 2011.

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Chimpanzees in Biomedical and Behavioral Research: Assessing the Necessity.

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The task given to the committee by the NIH asked two questions about the need for chimpanzees in research: (1) Is biomedical research using chimpanzees “necessary for research discoveries and to determine the safety and efficacy of new prevention or treatment strategies?” and (2) Is behavioral research with chimpanzees “necessary for progress in understanding social, neurological, and behavioral factors that influence the development, prevention, or treatment of disease?” In responding to these questions, the committee concluded that the potential reasons for undertaking biomedical and behavioral research as well as the protocols used in each area are different enough to require different sets of criteria. However, the committee developed both sets of criteria guided by the following three principles:

  1. The knowledge gained must be necessary to advance the public’s health;
  2. There must be no other research model by which the knowledge could be obtained, and the research cannot be ethically performed on human subjects; and
  3. The animals used in the proposed research must be maintained either in ethologically appropriate physical and social environments or in natural habitats.

Ethologically Appropriate Physical and Social Environments

Chimpanzee research should be permitted only on animals maintained in an ethologically appropriate physical and social environment or in natural habitats. Chimpanzees live in complex social groups characterized by considerable interindividual cooperation, altruism, deception, and cultural transmission of learned behavior (including tool use). Furthermore, laboratory research has demonstrated that chimpanzees can master the rudiments of symbolic language and numericity, that they have the capacity for empathy and self-recognition, and that they have the human-like ability to attribute mental states to themselves and others (known as the “theory of mind”). Finally, in appropriate circumstances, chimpanzees display grief and signs of depression that are reminiscent of human responses to similar situations. It is generally accepted that all species, including our own, experience a chronic stress response (comprising behavioral as well as physiological signs) when deprived of usual habitats, which for chimpanzees includes the presence of conspecifics and sufficient space and environmental complexity to exhibit species-typical behavior. Therefore, to perform rigorous (replicable and reliable) biomedical and behavioral research, it is critical to minimize potential sources of stress on the chimpanzee. This can be achieved primarily by maintaining animals on protocols either in their natural habitats, or by consistently maintaining with conspecifics in planned, ethologically appropriate physical and social environments in facilities accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International (AZA Ape TAG, 2010; Council of Europe, 2006; NRC, 1997, 2010). Examples of appropriate physical and social environments currently accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International include primadomes or corrals with environmental enrichment, outdoor caging with access to shelter, and indoor caging.

The committee recognizes exceptions to this criterion may be warranted. For example, as a result of previously approved protocols, there are currently a few long-term research projects in which the living conditions and the relationships with humans have been idiosyncratic and integral to the protocols (e.g., studies where a chimpanzee is being taught a symbolic language and lives and/or intensely interacts with a small number of researchers). In addition, current health and prior infectious exposures might prevent social housing for particular animals in potential experiments that may need to be performed in biosafety level (BSL) 3 or 4 facilities. Therefore, while the committee encourages that animals be maintained in planned, ethologically appropriate physical and social settings or natural habitats, existing protocols should be judged on a case-by-case basis, and changes made should impose minimal physiological and psychological harm to the animals and disruption to their existing relationships with people. All future studies should conform to the need for ethologically appropriate housing.

Criteria to Assess the Necessity of the Chimpanzee for Biomedical Research

As previously discussed, the chimpanzee raises unique considerations due to the ethical issues that arise as a result of the chimpanzee’s genetic proximity to human beings. Therefore, based on the principles previously defined, the committee developed the following criteria to guide its assessment of NIH-funded biomedical research using the chimpanzee:

  1. There is no other suitable model available, such as in vitro, non-human in vivo, or other models, for the research in question;
  2. The research in question cannot be performed ethically on human subjects; and
  3. Chimpanzees are necessary to accelerate prevention, control, and/or treatment of potentially life-threatening or debilitating conditions.

Specific and full scientific justification for use of the chimpanzee must meet all three of the above criteria. Assessment of which uses meet these criteria should be done prospectively on a study-by-study basis. It is important that justification is substantiated and provides adequate evidence; statements such as the following would not be acceptable to the committee:

  • “The chimpanzee is immunologically, physiologically, anatomically, and/or metabolically similar to human beings.” This statement is too broad.
  • “Chimpanzees have previously been used in safety studies for this class of drug.” This statement is not specific as to the science driving the decision.

It is important to note that the committee focused its task on the type of research supported by the NIH. The committee acknowledges that biomedical research aimed at the preservation and welfare of the chimpanzee species may also necessitate use of the chimpanzee, but this research is not be supported by the NIH unless it has direct application towards advancing human health and so on its own is outside the committee’s task.

Assessing Suitability of Available In Vitro or Non-Human In Vivo Models

Continued advances over the past decade in imaging, genetics, in vitro, and in silico models, and sophisticated rodent disease models have provided scientists with more tools that could be used in place of the chimpanzee. Federal regulations require that animals selected for a protocol should be of an appropriate species and quality and that the minimum number required to obtain valid results should be used (U.S. Office of Laboratory Animal Welfare, 2002). Methods such as mathematical models, computer simulation, and in vitro biological systems should also be considered before chimpanzees are considered for research.

When assessing the necessity of the chimpanzee as a model, a more stringent process of eliminating (“deselecting”) models of species less closely related to human beings should be required, similar to the process adopted by many countries in Europe (European Union, 2010). For example, in the United Kingdom, Section 5 of the Animals Scientific Procedures Act states that the Secretary of State may not authorize any procedures where an alternative exists (Parliament of the United Kingdom, 1987). The rationale for selection of the chimpanzee as the necessary model must be supported by facts and data (Box 3). The process must be rigorous and principles for deselection must be clearly defined and consistent across institutions.

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Deselection Criteria. The following are specific examples of deselection criteria that the committee used to assess the suitability of available in vitro or non-human in vivo models. In vitro models must be deselected if specific data required can only (more...)

Assessing Whether the Research Can Be Performed on Human Subjects

As the criteria regarding necessity outline, chimpanzee research is not necessary if it can be ethically performed on humans. Standard arguments about protection of human subjects require that there be an acceptable balance of the risks and potential benefits of proposed research, that the distribution of the risks and benefits are equitable (higher risk research can be justified when the potential therapeutic benefits accrue to the subjects themselves), and that the subjects are voluntary and informed of potential liabilities during their decision making. Relevant examples of critical human health-related research that would not meet human subjects’ protection standards include trials that intentionally expose subjects to untreatable infectious diseases and exposure trials to hazardous substances that pose significant health risks without prospect of benefit.

When research on humans is justified, federal policies on protection of human subjects impose limits, including for research on subjects who cannot consent for themselves. Subparts of the federal regulations concerning research on human subjects also impose clear limits on acceptable research on children and prisoners (HHS, 2005). These include restrictions on research that poses greater than minimal risk to subjects; such research cannot be approved unless it has the potential for offsetting therapeutic benefit to the subjects themselves.

These standards and additional protective restrictions mean that more research may take place using animal models than would otherwise be the case if additional risks to human subjects were deemed acceptable.

Assessing Advancements to Treat Potentially Life-Threatening or Debilitating Conditions

The standard non-rodent and NHP species may be deselected if it can be demonstrated that forgoing the use of chimpanzees for the research in question will significantly slow or prevent important advancements to treat potentially life-threatening conditions in humans or debilitating conditions that have a significant impact on a person’s health, and thus slow or prevent important advancements for the public’s health. This assessment is based on the potential impact on human health and potential to improve well-being, which can be partially assessed by the burden of the disease or disorder. The committee notes that for emerging infectious diseases and biodefense-related threats, this information may not exist for low-probability, high-consequence threats.

Criteria for Use of the Chimpanzee in Comparative Genomics and Behavioral Research

As previously discussed, research using the chimpanzee raises unique ethical issues because of its genetic proximity to human beings and highly developed cognitive and social skills. Therefore, based on the principles previously defined, the committee developed the following criteria to guide its assessment of NIH-funded comparative genomics and behavioral research using the chimpanzee:

  1. Studies provide otherwise unattainable insight into comparative genomics, normal and abnormal behavior, mental health, emotion, or cognition; and
  2. All experiments are performed on acquiescent animals, in a manner that minimizes pain and distress, and is minimally invasive.

Specific and full scientific justification for the continued and future use of the chimpanzee must meet the above criteria, as well as the housing/maintenance requirements described earlier in the document. This assessment should be applied prospectively on a study-by-study basis.

Assessing the Objectives of the Project

The review of research projects on a study-by-study basis must demonstrate that the primary objective of the research is to provide otherwise unattainable, specific insight into human evolution, normal and abnormal behavior, mental health, emotion, or cognition. Research may be either basic or applied, but must be consistent with the mission of the NIH “to seek fundamental knowledge about the nature and behavior of living systems and the application of that knowledge to enhance health, lengthen life, and reduce the burdens of illness and disability” (NIH, 2011).

The committee recognizes that most behavioral research differs fundamentally from biomedical research in the sense that mental or behavioral disorders (with few exceptions) cannot be modeled explicitly using chimpanzees. This is because the naturally occurring prevalence of such disease is likely to be low if compared to what is observed in human populations, thus precluding reasonably sized studies using chimpanzees. Some conditions (e.g., depression or post-traumatic stress syndrome) may be inducible in chimpanzees, but likely only using procedures that would be judged unacceptably invasive. This is especially true inasmuch as other animals, including other nonhuman primates, have been used to model these disorders. It is for the forgoing reasons that the majority of comparative genomics or behavioral studies using chimpanzees have focused on continua of behavioral and developmental phenomena from normal to abnormal, taking advantage of similarities in behavioral and brain complexity that mark chimpanzees and humans apart from virtually all other species.

Assessing Animal Acquiescence and Distress

Comparative genomics and behavioral research should only be performed on acquiescent animals and in a manner that minimizes distress to the animal. Evidence of acquiescence includes situations in which animals do not refuse or resist research-related interventions and that do not require physical or psychological threats for participation. In addition, only minimally invasive protocols should be performed. Examples of minimally invasive procedures include behavioral observation and the introduction of novel objects to the living area. In performing some comparative genomics or behavioral research, it also may be necessary to temporarily isolate an animal from its social group to perform behavioral tasks or for anesthesia. It is anticipated that anesthesia may be necessary for noninvasive imaging studies, the collection of biological samples (including blood, skin, adipose, or muscle) that do not involve surgical invasion of body cavities, the implantation of radio transmitters to measure autonomic nervous system function or physical activity, and the use of biosensors for recording central nervous system responses in freely moving animals. Whenever possible, anesthesia for comparative genomics or behavioral purposes should coincide with scheduled veterinary examination. Research on elderly or infirm animals in particular should take full advantage of anesthesia performed as part of routine veterinary care. It is recognized, however, that some study protocols may require that animals be anesthetized apart from veterinary examinations. The annual occurrence of such episodes of anesthesia should be minimized in number and the length of time the animals are sedated, consistent with accepted veterinary practice, including post-procedure analgesia as required. In all instances, anesthesia protocols should be designed to ensure that effects on the central nervous system or other organs are transient, and anesthesia for research purposes only should be avoided when possible in elderly or infirm animals. When animal protocols for anesthesia are not available, protocols used for human patients under similar circumstances may guide the choice of procedures.

Finally, when temporary removal from the social group is required for behavioral manipulation or anesthesia, animals must be handled in a manner that minimizes stress. Successful strategies have included positive reinforcement training that allows animals to be called by name or otherwise enticed to leave their habitual setting to engage in research procedures.

Copyright © 2011, National Academy of Sciences.
Bookshelf ID: NBK91454
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