Part 1: History / Introduction
Part 6: Pain in the Avian Species (Please scroll down)
Part 8: Quality-of-Life Issues
Part 6: Pain in the Avian Species
Recognizing Avian Pain
All animals are capable of perceiving and transmitting pain stimuli. Even though they are unable to express their pain verbally, they convey their discomfort emotionally through their body language. Birds know there is no survival advantage to displaying their pain outwardly; however, birds perceive and respond to noxious stimuli in the same way other animals and mammals do.
Because of their reluctance to demonstrate pain, birds are often undertreated for it. Most bird owners and many practitioners find it difficult to determine the presence and severity of the bird’s pain. Birds held in a hospital setting often experience an even higher level of pain and anxiety due to isolation in an unfamiliar place and separation from their families.
Scientific information concerning appropriate therapies and dosages for birds is lacking in much of the literature; as a result, many practitioners do not have the knowledge needed to adequately treat pain in their avian patients. When assessing avian pain, the clinician must consider the age, species, gender, and environment of his patient. He must also determine the source of this pain and whether there exists a concurrent illness which could be affecting the pain level.
When a bird experiences pain, some of the normal behaviors are usually changed or absent. These include:
Decreased social interactions: Perching away from other birds, decreased grooming of self or other conspecifics (birds of its own species), decreased interactions with owner.
Guarding behavior. Change in posture to protect a painful area, decreased activity
Increased aggression toward conspecifics or owner
Grooming behavior at painful site or generalized, feather-destructive behaviors, self-mutilation
(For complete Quality of Life and Pain Assessment questionnaires, please see Part 9 of this series.)
Some behaviors are obvious, but others may be more subtle. Interactions with the owner may occur less often than usual, and antisocial behaviors might begin to take place. Guarding behavior, during which the bird attempts to protect the painful area, is usually displayed. The bird may become aggressive, scream, or bite when handled. An increase or decrease in preening may take place, and this may lead to feather-picking and self-mutilation, particularly over the area of discomfort. It has been observed that distracting the bird from itself reduced the severity of pain.
Physiology of Avian Pain
The physiology of avian pain first involves the peripheral nerves (nociceptors) detecting the noxious stimulus, or painful event, whether it be mechanical, thermal, or chemical. The nerves must then transmit the impulses to the dorsal root of the spinal cord, where they are modulated (changed) and projected to the brain for central processing of the information. The brain then determines the perception of the noxious stimuli. (Pain perception in birds is considered to be the same as in mammals.)
Compared to mammals, birds are less sensitive to lower temperatures and have a higher threshold to high temperatures, possibly because their body temperatures are higher. Therefore, they have a wider range of thermal tolerance than mammals.
As stimulus intensity increases, the number of nerve responses increases. Peripheral nerve sensation increases when inflammation is added to a normally painful stimulus. Cell damage and leakage lead to central sensitization, and the increase in excitability of the spinal cord over a long period of time triggers hyper-sensitization of a wide range of neurons that don’t respond under normal circumstances, such as the C-Fibers. These only activate during periods of extreme pain.
This has led physicians and veterinarians to conclude that the earlier analgesics are given, the better the pain control will be. If analgesics are given before the painful even (e.g., surgery) is performed, rather than after the start of neuro-stimulation, the spinal excitability can be suppressed. The earlier pain is treated, the less total analgesia is needed, both during and after surgery. In studies using pigeons, birds receiving analgesia before surgery recovered faster than those receiving it only during and after surgery.
Treatment of Pain
Identifying the cause of pain and site of tissue damage in birds is challenging, but it is necessary in order to select the correct analgesic drugs and supportive care. Drug therapy is used to resolve the injury or disease and to decrease the peripheral pain signals leading to the brain. In some cases, the patient’s pain and other symptoms may need to be treated before the cause of the pain is known and a diagnosis is reached. In such cases, the choice of analgesic drugs will need to be conservative.
Both physicians and veterinarians have, in the past several decades, learned that the use of multimodal analgesia is more effective than the use of a single drug. Combining analgesics which work by different mechanisms can augment the pain relief. Many times, administering two or more analgesics produces a synergistic effect; the medications work together to diminish the pain. Combining drugs reduces not only the amount of the drugs used, but the side effects of each drug.
A patient undergoing surgery will receive:
A local anesthetic (such as lidocaine) at the incision site,
An opioid administered directly before and after surgery, and
An NSAID (non-steroidal anti-inflammatory) given during surgery and for several days following the procedure.
Giving the painkiller before the surgery will lessen the need for stronger opioids during and after the surgery by dampening the nociceptive pain messages being sent to the brain. Often, the patient will receive adjunctive drugs, such as tranquilizers, to reduce anxiety, thus enhancing the effects of the analgesia. The avian patient also needs supportive care during and after the traumatic event; he needs to be kept warm, dry, and clean. A separate area just for birds should be part of the clinic, since the sounds and smells of other animals, particularly predators like dogs and cats, can disturb the bird and heighten its anxiety, thus lowering the effect of the analgesic drugs. Gentle, soothing human contact is essential.
Paul-Murphy J. Pain management for the Pet Bird. In: Handbook of Veterinary Pain Management. Ed. James Gaynor, William Muir III. Mosby, Inc 2009