Donkeys are notorious for being a ‘stoical’ species. They typically do not overtly demonstrate symptoms of being in pain and discomfort. This masking behaviour is a key survival technique for many prey species. In acute scenarios, such as colic or acute musculoskeletal injury, there is an inherent risk that owners may not recognise the donkey is unwell or in discomfort until advanced stages, and vets may overlook the severity of the situation. For disease processes such as surgical colic and colitis, where prompt treatment is necessary to maximise a favourable outcome, a delay in recognition of a donkey in pain has a significant negative impact on prognosis. For chronic conditions, such as dental pathology, persistent ocular lesions and osteoarthritis, a donkey may not receive adequate analgesia and other treatment required if subtle symptoms of pain are not acknowledged.
The ability to objectively identify evidence of pain is therefore of benefit to donkey welfare, not only in recognition of acute discomfort but also for monitoring of chronic conditions, assessing quality of life, post-operative pain management and intensive care cases. Owners, vets, nurses and other clinic support staff can all be trained in the use of simple pain scoring tools. Validated pain scoring systems have been developed for horses. However, as donkeys have unique behavioural tendencies and physiology, it stands to reason that tools designed for horses may not be directly transferable to use in donkeys. Furthermore, as different sources of pain, whether acute or chronic, may result in different signs, the accuracy of objective pain scoring does not fit with a ‘one size fits all’ approach.
Facial expression based pain scales and composite pain scales have now been developed and evaluated for the scoring of acute pain in donkeys [1]. These scales used those developed for horses as their baseline, adjusting and adding further parameters using expert donkey knowledge. Results from this study indicate that acute head-related pain and colic pain are most reliably assessed using the facial pain scale, whilst acute orthopaedic pain and post-surgical castration pain are better assessed using the composite pain scale. In both scales, parameters are given a numerical score, with a higher number denoting greater evidence of pain.
The composite pain score is a multifactorial scale based on 20 parameters, scored during observations over a 5-minute period. For example, a donkey that has no audible signs of pain is given a score of 0, a donkey with audible teeth grinding and moaning more than four times in the 5-minute observation period is given a score of 3. Scores are weighted and there is a maximum score of 60. The scale includes behavioural and physiological parameters as well as responses to stimuli. Those parameters that do not require a hands-on approach are assessed first, observing the donkey from a suitable distance to avoid any effect that disturbance due to human interaction may elicit.
The facial pain scoring scale is a multifactorial scale based on 12 parameters, scored during observations over a 2-minute period. For example, ears in a normal position are scored 0, ears held in an abnormal position (hanging down or backwards) are scored 2. There is a maximum score of 24.
Inter-observational reliability has been demonstrated for both scales. Whilst there are clear limitations, repeated use of the scales by trained observers provides an objective data set which is clinically applicable. Elevated scores should promote discussion of why that score is present – is the donkey in pain, why and what is the response to any treatment administered? For hospitalised patients, scores that are increasing are an immediate alert that a treatment plan may need adjusting.
Work is underway to evaluate scoring systems for assessment of chronic pain in donkeys. The availability of validated scales will be welcome to those vets and owners caring for not only geriatric donkeys, but any donkey with a chronic health condition. In a study [2], researchers constructed a chronic pain score, which is an amalgamation of composite and facial pain scoring scales. The study demonstrated good inter-observational reliability between well trained, previously inexperienced observers. The choice to amalgamate two scoring scales arose because pilot work indicated that donkeys experiencing pain from chronic conditions may show changes in facial expressions akin to those found in donkeys in acute pain, whilst demonstrating behavioural changes that are quantifiable using the composite pain scale. Validation of this chronic pain scale will be of major benefit to those monitoring the health and welfare of any donkey living with a chronic health condition. It is hoped that the regular use of chronic pain scale scoring will assist treatment monitoring and will be a welcome inclusion to a quality of life assessment toolkit.
References
1. van Dierendonck, M.C., Burden, F.A., Rickards, K. and van Loon, J.P.A.M. (2020) Monitoring acute pain in donkeys with the Equine Utrecht University Scale for Donkeys Composite Pain Assessment (EQUUSDONKEY-COMPASS) and the Equine Utrecht University Scale for Donkey Facial Assessment of Pain (EQUUS-DONKEY-FAP). Animals 10(2), 354.
2. van Loon, J.P.A.M., de Grauw, J.C., Burden, F., Vos, K.J., Bardelmeijer, L.H. and Rickards, K. (2021) Objective assessment of chronic pain in donkeys using the donkey chronic pain scale (DCPS): A scale-construction study. Vet. J. 267, 105580.