Introduction
The way an animal behaves depends on three key factors. Its genetic predisposition, learning from previous experiences and the particular environment it is in at the time. None of these factors acts in isolation, so all need to be taken into consideration.
Understanding fear and anxiety is important not only when managing patients in the veterinary clinic setting but also assisting clients with their dogs and cats outside the clinic environment.
Apart from behavioural problems, such as separation anxiety and noise phobias, the underlying reason for many cases that present in general practice with recurrent medical problems, such as vomiting, diarrhoea or skin problems, may also be anxiety related.
The Brain and Behaviour
The amount of knowledge about brain function and how it helps us to understand behaviour has grown significantly in the last decade or so.
The central nervous system is our main area of concern when considering the behaviour of our patients. The three areas of the brain are the cerebrum, cerebellum and brain stem. The cerebellum is primarily concerned with the coordination of movement.
Although the brain stem is critical for maintaining life, it is not our main area of interest when it comes to addressing problems related to anxiety, fear or stress.
The cerebrum is the area of the brain that is of primary interest with respect to behavioural problems in pets. The cerebral cortex is involved in problem solving and logical thought processes. This is important when a pet has to learn a new behaviour.
The contrasting part of the cerebrum is the emotional centre called the limbic system. Highly arousing experiences are inclined to activate the limbic system. Owners will often describe the difficulties they experience with their dog when they are highly aroused, such as when they begin to react by barking when they see another dog. They often describe this as the dog not listening to them and often interpret this behaviour as disobedience or dominance.
However, when the dog or cat is in a highly emotional state, the limbic activation is high. At this time, the ability for the dog or cat to think clearly is compromised. When limbic activation is high, cortical activation is low. When the dog or cat is experiencing fear or stress, the limbic system (the emotional brain) will override the cortical system (the thinking logical brain).
The arousal levels and emotional content associated with experiences can also be important in how these experiences influence future behaviour. The most memorable events in life tend to be highly emotional moments. One highly distressing event can have a really marked effect on a pet's future behaviour. For instance, some dogs become distressed when left alone after the house has been broken into in their owner's absence.
Anxiety, Fears, and Phobias
Although the terms anxiety and fear are often used interchangeably, they are not the same. Fear is related to the specific behaviours of escape and avoidance, whereas anxiety is the result of threats that are perceived to be uncontrollable or unavoidable (from the animal's perspective). Both fear and anxiety may be adaptive in some circumstances whereas phobias are maladaptive.
Although the specific genes have not been identified yet, a genetic predisposition for many anxiety disorders has been established in people. The prefrontal cortex, amygdala and limbic system, and hypothalamus (hypothalamic-pituitary-adrenal axis) are thought to be involved in the regulation of fear.
Serotonin, noradrenaline, dopamine and GABA are all involved in the development of fear and anxiety. The neurotransmitter serotonin has been identified as a mediator of fear and anxiety. This is why medication is used in managing many behaviour problems that involve fear or anxiety.
Stress or anxiety may be manifest in many ways. Some behaviours that may be exhibited are changes in:
Appetite (e.g., a decrease in appetite or pica)
Grooming (usually increased)
Elimination (e.g., urination or defecation)
Social interactions (e.g., vocalisation, increased or decreased contact)
Physical activity (e.g., increased or decreased)
Effects of Fear, Anxiety, and Stress on Mental and Physical Health
Acute and chronic stress can impact on both health and behaviour. Stress is an altered stated of homeostasis which can be caused by physical or emotional factors that trigger psychological, behavioural, endocrine and immune effects that are designed to handle stress. Response to stress will vary between individuals and may be affected by breed, early experience, sex, age, health, and the pet's behavioural profile.
In dogs and cats, exposure to mild stressors and handling early in life stimulates hormonal, adrenal and pituitary systems that result in animals that perform better in problem solving tasks, have greater resistance to disease and can better withstand stress later in life. However, excessive stress is not helpful. Acute fear and anxiety can lead to a decrease in appetite or anorexia, diarrhoea, vomiting or colitis. With chronic anxiety, such as when moving homes, when a new pet is introduced into the home, or with the loss of a human or pet in the family, there may be more profound effects on behaviour and health. In cats, prolonged anorexia can have serious hepatic consequences. Pica, polyphagia, and polydipsia may also be stress induced.
Thus, not only can health affect behaviour but behaviour can affect health. Therefore, improving or resolving any underlying stress and anxiety can be essential to the health and welfare of the pet.
The first component of the stress response is the HPA axis, in which the hypothalamus releases corticotropic-releasing hormone (CRH), which stimulates the release of ACTH. The second component is the sympathetic-adrenal-medullary system, which releases noradrenaline and adrenaline.
Noradrenaline is associated with sensitization and fear conditioning. In cats, a transient hyperglycemia is often reported. A recent study found higher plasma levels of dopamine and 5-HT in pets with stress compared to controls. Increases in dopamine may enhance aggressive behaviour and lead to an increase in stereotypic and grooming behaviours.
Prolactin levels may also be elevated in fearful and anxious pets with higher prolactin levels in dogs with chronic stress, stereotypic behaviours, fear aggression and autonomic signs, while lower levels of prolactin were associated with acute fearful and phobic events. Therefore, there can be marked differences in the effects of acute and chronic stress on health and behaviour.
If stress is persistent or chronic, there is continued stimulation of the HPA axis and an increase in cortisol with depression of the catecholamine system, leading to alterations in the immune system and possible development of stress-related diseases. Stress has also been shown to be a contributing or aggravating factor in gastrointestinal diseases, dermatologic conditions, respiratory and cardiac conditions, behavioural disorders and a shortened lifespan in dogs.
Cats with FIC have altered bladder permeability during stress when compared to cats in an enriched environment. Cats receiving MEMO (multimodal environmental modification) had a significant reduction in FIC, respiratory disease, fearfulness, and nervousness and less inflammatory bowel disease and aggression. In a placebo-controlled study, there were less bouts of FIC when a Feliway® diffuser was installed.
A dog or cat that is highly stressed is likely to exhibit some or all of the following signs:
Dilated pupils
Tense muscles
Hypervigilance ("on the alert"; "watching for danger")
Raised hackles
Tight lips
Panting
Flattened or "helicopter" ears
Lowered tail that may be wagging in a short arc
Displacement activities
Hyperactivity or stillness
Vocalising
Drooling
Possible urination/defaecation/expression of anal glands
Baring of teeth, lunging or biting
Sniffing
Grooming
Obviously, the context the dog or cat is in at the time and assessing the whole animal is very important in making an assessment. For example, dogs or cats may have dilated pupils and be panting because they are in a dark, warm room.
The longer that anxiety-related conditions are unrecognised and untreated, the more complex they become and potentially the more difficult they are to treat. Treatment usually involves behaviour modification techniques, the use of psychotropic medications as well as environmental modification. Medications that influence serotonin metabolism, such as the selective serotonin reuptake inhibitors (SSRIs) and the tricyclic antidepressants (TCAs) have been used in the treatment of anxiety-related disorders. Anxiolytic medication (e.g., benzodiazepines) has also proved useful in some cases in combination with TCAs and SSRIs, especially if the pet has phobias or experiences exhibits panic attacks. The use of the synthetic pheromone analogue products Feliway® and AdaptilTM can also be useful in managing anxiety disorders.
Conclusion
The role of the veterinary practitioner should be to educate clients about the impact of stress and fear on pets as well as provide opportunities for puppies and kittens to be exposed to a variety of stimuli in a nonthreatening manner such as Puppy Preschool® and Kitten Kindy®. Already stressed and anxious pets may need referral to a veterinary behaviourist.
References
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