Animal owners and veterinary professionals have a responsibility to recognise pain, disease and suffering in canines as stated in the Animal Welfare Act 2006 (Legislation.gov.uk, 2020). Assessing pain in animals can be challenging as it is frequently measured indirectly through behavioural assessment using factors such as posture, expression and aggression. Physiological factors such as heart rate and cortisol levels can also be measured however this is more invasive (McGowan, 2008). Behavioural changes are typically correlated with new onset pain, aggression in canines presented as the leading behavioural problem identified in clinic representing 52.28% of all cases referred (Fatjo et al., 2007; Muir et al., 2004).

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A study by Hsu and Son (2010) found a positive correlation using the “canine behavioural assessment and research questionnaire” between pain sensitivity and expression of aggressive behaviours in dogs, often aggression was triggered by the anxiety of feeling pain. This experiment could be biased as it was based on questionnaires completed by owners, individuals may perceive behaviours differently however the rating scale provided helps to minimise bias. Further research carried out through interviews supports this study, research completed on a selection of dogs presented at a veterinary clinic with new or worsening pain-related aggression, the prevailing cause identified was Hip Dysplasia (HD) (66%).

 

It is estimated that 17.7% - 19.7% of dogs have some degree of HD (Rettenmaier et al., 2005). Typically dogs displayed aggressive behaviour when coming into contact with someone or when asserting dominance over an item e.g. a toy. Diseases causing chronic pain such as HD were identified as a significant risk factor in the development of aggressive behaviours (Camps et al., 2012). The sample size in for this project was limited, however the results achieved are reliable due to confirmation of disease through diagnostic techniques and comprehensive interviews carried out by a trained behaviourist. In a case study by Mills et al., (2020) a dog was presented with new onset aggression over rewards, was not willing to walk and was opposed to handling. Aggressive behaviour increased when attempting to put a harness on the dog, upon x-ray the animal was diagnosed with bilateral hip dysplasia. This confirms results from other investigations that conditions causing chronic pain correlate with the onset of aggression.

 

In recent years more consideration has been placed on the effects that chronic pain has on animal quality of life, this is challenging to measure. It relates to an animals ability to be able to cope with its situation in a positive or negative manner and the effect that external factors induce. Chronic pain often results in reduced exercise, pain related aggression and reduced social interaction all of which significantly impact quality of life (Belshaw and Yeates, 2018). This suggests that animal welfare is impacted negatively by chronic pain, and can be measured by a number of changes to behaviour. Furthermore Dawson et al., (2016) distributed a survey to veterinarians and researchers focused on animal welfare influences, it was found that they also considered chronic pain significantly influences canine welfare.

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In conclusion using aggression as a behavioural measure of chronic pain in the assessment of poor welfare is relatively simple as the signals are easy to measure, in addition it is reliable due to the strong correlation seen between onset of aggressive behaviours and diagnosis of conditions associated with pain. However aggression alone is not a substantial source for identifying animal welfare and quality of life in relation to chronic pain, partially due to the challenge of assessing severity. Other considerations should be made and indicators used to make a successful assessment.

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References

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Animal Welfare Act 2006 (S.I. 2007/499) LONODN: TSO Ltd.

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Belshaw, Z. and Yeates, J. 2018. Assessment of quality of life and chronic pain in dogs. The Veterinary Journal. 239, pp. 59–64. https://doi.org/10.1016/j.tvjl.2018.07.010

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Camps, T., Amat, M., Mariotti, V.M., Le Brech, S., Manteca, X. 2012. Pain-related aggression in dogs: 12 clinical cases. Journal of Veterinary Behaviour. 7 (2), pp. 99–102. https://doi.org/10.1016/j.jveb.2011.08.002

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Dawson, L., Dewey, C., Stone, E., Guerin, M., Niel, L. 2016. A survey of animal welfare experts and practicing veterinarians to identify and explore key factors thought to influence canine and feline welfare in relation to veterinary care. Universities federation for animal welfare. 25 (1), pp. 125–134. https://doi.org/10.7120/09627286.25.1.125

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Fatjo, J., Amat, M., Mariotti, V.M., de la Torre, J.L.R., Manteca, X. 2007. Analysis of 1040 cases of canine aggression in a referral practice in Spain. Journal of Veterinary Behaviour. 2 (5), pp. 158–165. https://doi.org/10.1016/j.jveb.2007.07.008

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Hsu, Y. and Sun, L. 2010. Factors associated with aggressive responses in pet dogs. Applied Animal Behaviour Science. 123 (3-4), pp. 108–123. https://doi.org/10.1016/j.applanim.2010.01.013

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McGowan, C. 2008. Animal physiotherapy: assessment, treatment and rehabilitation of animals. 2nd ed. West Sussex: Wiley-Blackwell.

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Mills, D.S., Demontigny-Bédard, I., Gruen, M., Klinck, M.P., McPeake, K.J., Barcelos, A.M., Hewison, L., Van Haevermaet, H., Denenberg, S., Hauser, H., Koch, C., Ballantyne, K., Wilson, C., Mathkari, C.V., Pounder, J., Garcia, E., Darder, P., Fatjó, J., Levine, E. 2020. Pain and Problem Behaviour in Cats and Dogs. MDPI Animals. 10 (318), pp. 1-20. https://doi.org/10.3390/ani10020318

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Muir, W.W., Wiese, A.J., Wittum, T.E. 2004. Prevalence and characteristics of pain in dogs and cats examined as outpatients at a veterinary teaching hospital. Journal of the American Veterinary Medical Association. 224 (9), pp. 1459–1463. https://doi.org/10.2460/javma.2004.224.1459

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Rettenmaier, J.L., Keller, G.G., Lattimer, J.C., Corley, E.A., Ellersieck, M.R. 2005. Prevalence of canine hip dysplasia in a veterinary teaching hospital population. Veterinary Radiology & Ultrasound. 43 (4), pp. 313–318. https://doi.org/10.1111/j.1740-8261.2002.tb01010.x