Assessment of distress varies in relation to the species, husbandry conditions, and experimental protocol employed as well as with each individual animal, and is most effectively achieved by the collection of multiple behavioral and physiological parameters and the use of a team approach that includes researchers, veterinarians, and animal caretakers/technicians. While the most reliable distress measures are the clinical signs previously described, identification and interpretation of these results depends on a solid foundation of knowledge of animal behavior and may likely require special training of relevant personnel.

Distress evaluation becomes crucial in two contexts: (1) when the research protocol calls for the animals’ exposure to stressful situations known to produce distress; and (2) when any animal unexpectedly shows signs of distress. In the first case, the experimental protocol approved by the Institutional Animal Care and Use Committee (IACUC) generally includes procedures and decision algorithms for distress management. The appropriate intervention will be informed by the stressor’s duration and intensity as well as some of the animal’s individual characteristics (e.g., species, age, gender). In the second case, additional assessments and monitoring may be necessary.

Once an animal has shown initial signs of distress, there should be immediate communication between the primary investigator, the veterinarian, and the animal care staff to determine whether the distress is related to the study (whether anticipated or unanticipated) or further investigation into its cause is required. The discussion should also include potential interventions (see Chapter 4) and their effects on the objectives of the research project, as they may introduce unknown variables into the study. Options may include removal of the animal from the study population or euthanasia, depending on the severity and prognosis of the distress insult. It is essential to maintain a collaborative relationship and dialogue between those responsible for the care and welfare of the animal throughout the assessment.

The next step is to identify the etiology or trigger of the distress episode by performing a thorough examination of the animal and its environment. The investigation should begin by obtaining information regarding the animal’s species, strain, age, gender, and reproductive status. An effective examination should account for species-related differences among natural behaviors, learning abilities, and levels of intelligence, in addition to the ways animals use their senses and communicate. Some species, strains, or breeds are predisposed to certain behavioral problems or have certain behavioral phenotypes, or an individual animal’s characteristics may affect both the development and alleviation of its distress.

Physical examination and appropriate diagnostic tests for all distressed animals can help determine whether an underlying medical condition is the primary cause of distress. A review of the medical and investigator records

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