Detecting animal pain is critical if refinement is to be successfully implemented when using animals in science.
Species and individual responses to pain are variable; therefore, it is essential that veterinary staff evaluating animals for pain understand typical species responses and individual behaviours. This includes recognizing changes in the normal behaviour and appearance of the animal.
Diagnosis of pain in animals is seldom made on the basis of a single observation or laboratory value. It is subjective and dependent on a combination of a clinical examination; familiarity with species, breed, and individual behaviour; knowledge of the degree of pain associated with particular procedures or illnesses; and recognition of the signs of discomfort and pain.
Clinical Signs of Pain
Clinical signs (observable without handling the animal) that may indicate pain in terrestrial species include:
Other clinical signs, requiring the animal to be handled, that may indicate pain include: increases in heart rate, respiratory rate and body temperature, and elevations in blood glucose, corticosteroid and catecholamine concentrations.
Regardless of the clinical signs demonstrated, if there is any doubt that an animal may be experiencing pain, then a trial treatment with analgesics should be initiated.
Fish have the potential to experience pain, and manipulations that provoke stress or avoidance/escape behaviour may be causes of distress. Fish respond to noxious stimuli (stimuli that are damaging or potentially damaging to normal tissue, such as mechanical pressure, extremes of temperature and corrosive chemicals) with altered behavioural, physiological and hormonal parameters.
Many fish species are prey animals and are genetically predisposed not to exhibit signs of injury or pain, therefore the recognition and evaluation of pain in fish is not simple.
Clinical signs of pain in fish include:
Other signs that are indicators of acute stress and that may be indicative of pain include changes in corticosteroid and catecholamine levels, as well as increases in plasma glucose and lactic acid.
Regardless of the clinical signs demonstrated, if there is any doubt that a fish may be experiencing pain, then a trial treatment with analgesics should be initiated.
This section was adapted from the ACVA position paper on the treatment of pain in animals and the CCAC guidelines on: the care and use of fish in research, teaching and testing.
For more information on pain assessment, the following resources may be useful.
Reference list organized by species