Pain is an unpleasant sensation and emotional experience linked to tissue damage. Its purpose is to allow the body to react and prevent further tissue damage. it is not just about how it feels, but also how it makes you feel. And it is these unpleasant feelings that cause the suffering we humans associate with pain.
We know that animals certainly feel physical pain, but what is less clear is whether this emotional suffering that we feel can be said to be true of animals. And if it is, how we go about measuring it.
Pain is not all bad – it serves a protective function, to keep us away from further danger, to help us heal, for example by stopping us from putting weight on a sprained ankle. But if it isn’t managed effectively it can have a major negative impact on our lives inducing fear, anger, anxiety or depression – all emotions which may in turn exacerbate it.
Pain in animals
The nature of pain is perhaps even more complex in animals. How pain is sensed and the physical processes behind this are remarkably similar and well conserved across mammals and humans. There are also many similarities in pain behaviours across the species, for example they may stop socializing with people and/or other animals, they may eat less, they may vocalize more and their heart rate may rise. The capacity of animals to suffer as sentient creatures is well established and enshrined in law in many countries, however we don’t understand well how they actually experience pain.
Some aspects of the experience and expression of pain are not likely to be the same as in humans. First, animals cannot verbally communicate their pain. Dogs may yelp and you may notice behaviour change but what about your pet rabbit, cat, tortoise or horse? Animals rely on human observers to recognize pain and to evaluate its severity and impact. Without the ability to understand soothing words that explain that following surgery to repair a bone fracture, their pain will be managed (hopefully) and will subside, animals may also suffer more when in pain than we do.
For example, we know that animals and indeed birds with clinical signs of pain (limping) will choose to eat food containing pain-killing drugs (analgesics) over untreated food, and by measures of behaviour, they will improve.
Similarly many studies in a range of domestic animals have indicated that animals who have had surgery but not had adequate pain relief demonstrate behaviours reflective of pain which are alleviated when they are treated with analgesics such as morphine.
We also know that it is not just our dogs and cats that can suffer pain – there is an equally strong evidence base for the presence and negative impact of pain in sheep, cattle, pigs and horses among other species. But recognizing pain in these different species is part of the complexity associated with animal pain. Managing it in animals that we rear for food and those that we keep as companions is equally challenging.
So in order to treat and manage pain effectively we must measure it.
And there is a huge demand for these tools. The Glasgow Composite Pain Scale, a simple tool to measure acute pain in dogs and first published in 2007, has been translated into six languages. It is used in veterinary practices to measure pain to treat it effectively. It has also been used to evaluate the effectiveness of new analgesic drugs that are being developed by animal health companies. Tools to measure the impact of chronic pain, such as osteoarthritis, on the quality of life of dogs are now available and are a significant advance in managing chronic conditions.
There is now a global effort to raise awareness of pain in animals. Recently the World Small Animal Veterinary Association launched the Global Pain Council and published a treatise for vets and animal keepers worldwide to promote pain recognition, measurement and treatment. Dogs may be man’s best friend, but for all those who work with, care for and enjoy the company of animals, understanding how their pain feels is essential to improving the quality of their lives.