Any disease that affects the nervous system and the pet's mentation can affect behaviour as can painful conditions, sensory dysfunction, altered mobility and any condition that affects urine or stool output. However, the relationship between behaviour and medicine may be more complicated. Chronic or recurrent stress and anxiety can have an impact on both health and behaviour, by affecting the hypothalamic pituitary-adrenal axis and by activation of the noradrenergic system. Some medical problems including idiopathic cystitis appear to be exacerbated by stress. Therefore prevention and treatment of anxiety and stress may be important for both the treatment of behaviour problems as well as to ensure optimum mental and physical health.

Neurological or Behavioural

A change in personality or mood, inability to recognise or respond appropriately to stimuli and loss of previously learned behaviour might be indicative of forebrain involvement. Alterations in awareness, responsiveness to stimuli and consciousness might arise from any disease that involves the brainstem or forebrain. However, altered responsiveness to stimuli can also arise from sensory decline. Diseases that affect behaviour may be intracranial (e.g., congenital, neoplasia, degenerative) or extracranial (e.g., toxin, hepatic encephalopathy, endocrinopathies, or diseases that affect brain oxygenation). Primary behavioural diseases/pathology may also exist such as compulsive, dissociative or developmental disorders.

Dermatological or Behavioural

Self-traumatic disorders including biting, chewing, licking or excessive barbering can lead to skin lesions and alopecia. Medical differentials include diseases that lead to pain or pruritus (e.g., hypersensitivity reactions, neuropathies), infections (e.g., bacterial, fungal, parasitic), endocrinopathies, tumours, or skin disorders associated with systemic diseases (e.g., hepatocutaneous syndrome). When there are no lesions other than alopecia or when signs of self-trauma are localised, then medical and behavioural causes may be particularly difficult to differentiate.

On the other hand, there may be interplay between behaviour and medicine. For example, primary dermatological conditions may be exacerbated by stress. In humans stress has been shown to increase eosinophil numbers and IgE in patients with atopic dermatitis compared to controls. In addition, stress leads to an increase in cytokines, a reduction in cortisol and the release of opioid peptides, which may potentiate pruritus. In humans, a link has also been found between stress and increased epidermal permeability, which could exacerbate atopic disease in pets that are genetically predisposed. Thus stress may effectively bring atopic patients closer to the pruritic threshold.

Diagnosis

A comprehensive behavioural and medical history is required to determine which medical problems must be ruled out as well as to formulate an effective treatment plan. For neurological signs, the diagnostic work-up should focus on the neurological examination and any laboratory diagnostics that might be indicated. Therapeutic response trials (e.g., medications for seizures or neuropathic pain), imaging studies or a neurological referral may then be indicated. For dermatological signs, the work-up should include a physical examination and laboratory tests (including endocrine testing), as well as dermatological diagnostics such as skin scrapings, fungal culture, trichogram, cytology, biopsy, or therapeutic response trials (to rule out parasites, food intolerance, pruritus and neuropathic pain).

Compulsive Disorders

Compulsive disorders can only be diagnosed by excluding those medical problems that might cause the signs. For many of the presenting complaints such as head bobbing, spinning, air snapping, pouncing upon unseen objects, pacing, freezing, or hyperaesthesia, neurological differentials must first be ruled out. For self-injurious behaviours (e.g., tail mutilation, acral lick dermatitis, flank sucking, tail mutilation), dermatological, musculoskeletal, neuro logical, infectious, immune, neoplastic, inflammatory and traumatic conditions first need to be considered.

Compulsive disorders may arise out of anxiety, conflict or frustration. Conflict occurs when the pet is motivated to perform two opposing behaviours. Frustration refers to a situation in which the pet is motivated to perform a behaviour but is not able to do so. In these situations the response might be a displacement behaviour, where the response is inappropriate or out of context with respect to the stimulus (e.g., tail chasing). Pet owners may further aggravate the problem by their responses.

Compulsive disorders are those in which the displacement behaviours are exhibited independent of the original context, have no apparent goal and have an element of dyscontrol in either the initiation or termination of the behaviour. They may be repetitive, exaggerated, sustained or so intense that they might be difficult to interrupt. Although it has been suggested that stereotypies might be a coping mechanism leading to a reduction in arousal, this is rarely the case. Compulsive disorders are generally associated with stress or anxiety and may affect physical health. There appears to be a genetic predisposition to the development of stereotypic behaviours (e.g., wool sucking in oriental breeds of cats, spinning in Bull Terriers, tail chasing in German Shepherd Dogs). Because of similarities in signs and the fact that serotonin reuptake inhibitors are effective in both pets and humans, the term compulsive or obsessive compulsive is used to describe this disorder in pets.

It is possible that there is a common pathophysiology, that neurotransmitters vary between presenting complaints, or that there may be changing involvement as the problem progresses. Beta-endorphins, dopamine and serotonin have all been implicated.

When presented with a cat that has hair loss or licking, the diagnostic work-up should begin with an examination, anal gland expression, blood and urine testing and a viral profile. A dermatological evaluation, including a trichogram, fungal culture, skin scraping and possible biopsy would also be indicated. Assuming no abnormal findings, a therapeutic trial of a parasiticide and a food trial of 8 weeks' duration, followed by a steroid-response trial might be the only practical way to differentiate pruritus from a behavioural cause. Using this protocol in 21 cases presented for psychogenic alopecia, 76.2% had a medical aetiology, 9.5% were compulsive and 14.3% were combined medical and behavioural. A combination of adverse food reaction and atopy (six cases) was the most common diagnosis. Some cats had atopy, parasitic hypersensitivity or an adverse food reaction alone. Although histopathology indicated an inflammatory response for most medical cases, some cats with histologically normal skin had a medical cause.

For acral lick dermatitis (ALD) in dogs, a physical examination, blood and urine screening and a dermatological work-up, including a skin scraping, fungal culture, cytology and biopsy may all be indicated. When diagnostic tests do not reveal the underlying cause, therapeutic trials with antibiotics, pain medication, anti-inflammatory drugs, parasiticides and/or food trials may be necessary. In some cases complete resolution can be achieved with long-term antibiotic therapy alone, indicating that, even if the original cause was behavioural, infection was the maintaining factor. Owner supervision and preventive mechanisms such as bandaging or E-collars may also be necessary to allow the lesions to heal. In one of our cases, a mast cell tumour was misdiagnosed as ALD for over 2 years. In a recent publication, six dogs presumed to have ALD were diagnosed with lymphoblastic lymphoma, irritation from a Kirschner pin, furunculosis, a mast cell tumour, leishmaniasis and sporotrichosis.

Tail mutilation and hyperaesthesia in cats may also be a conflict-induced or compulsive disorder requiring a diagnostic work-up similar to ALD and psychogenic alopecia. In addition, neurological disorders (central, spinal) and neuropathic pain are also a consideration.

Treatment of Compulsive Disorders

Behavioural management combined with drug therapy is required for the successful control of most compulsive disorders. As a general rule, pets with compulsive disorders should receive a more structured and stimulating daily routine. Some pets may be particularly sensitive to inconsistency or lack of predictability in their daily schedule or in their interactions with their owners. Therefore the daily routine should include regular sessions of social interaction with people (in the form of training, play and exercise) or with other pets. Owners might be encouraged to focus on play that simulates the normal activities of the species or breed, e.g., pulling carts, retrieving, mousing. Following social interaction and training, scheduled periods of inattention may help the pet learn to expect and accept spending time alone. At these times it can be useful to have a favoured bedding area, and to provide a variety of enrichment and chew toys (feeding and foraging toys). In fact working for some or all of the daily food is an important component of treatment for most compulsive disorders.

Training should encourage behaviours that are desirable rather than punishing behaviours that are undesirable. Casual and inconsistent owner interactions should be replaced by a programme of predictable rewards where the owners ensure that all rewards including affection, toys and food are only given for behaviours that are incompatible with the compulsive disorder (e.g., resting on a mat, playing with a favoured toy). A leash and head halter or a harness for cats can be used to prompt the desired response as well as to inhibit, disrupt or prevent undesirable behaviour.

Clomipramine or a selective serotonin reuptake inhibitor, such fluoxetine or paroxetine, are usually the first drugs of choice for compulsive disorders. After 4-6 weeks, if there is insufficient response and no adverse effects, a higher dose may be needed.

References

1.  Hewson CJ, Luescher UA, et al. Efficacy of clomipramine in the treatment of canine compulsive disorder. Journal of the American Veterinary Medical Association 1998; 213: 1760-1765.

2.  Luescher UA. Diagnosis and management of compulsive disorders in dogs and cats. Veterinary Clinics of North America Small Animal Practice 2003; 33: 253-267.

3.  Virga V. Behavioral dermatology. Veterinary Clinics of North American Small Animal Practice 2003; 33: 231-251.

4.  Waisglass SE, Landsberg GM, et al. Underlying medical conditions in cats with presumptive psychogenic alopecia. Journal of the American Veterinary Medical Association 2006; 228: 1705-1709.