Feline Aggression: Associations with Elimination Disorders and Complex Neurochemistry
WSAVA 2002 Congress
Karen L. Overall, MA, VMD, PhD, Diplomate ACVB, ABS Certified Applied Animal Behaviorist
Psychiatry Department, University of Pennsylvania School of Medicine
Philadelphia, PA, USA


The most common feline behavioral problems involve inappropriate elimination behavior. This inappropriate behavior can take the following forms: substrate or location aversion, substrate preference for urination, defecation, or both, location preference for urination, defecation, or both, and spraying. This is one set of behavioral problems that requires a substantial medical work-up and rigorous follow-up.

1.  Aversions to substrates or location can be difficult to distinguish from preferences, and invariably lead to the cat choosing another location or substrate for elimination. Aversions become apparent because of the cat's total avoidance of the offending area or surface. In cases involving aversions that have developed in response to an horrific experience, some owners have reported that the animal will hiss, growl, slink, or piloerect when found in proximity to the substrate or area. For ultra fastidious cats, vomit or diarrhea, either their own, or a house mate's, may induce the same response. Location aversions are often coupled to fearful or painful situations, such as injuries caused by doors or torment from another cat or a child. If a cat is absolutely avoiding a specific area or substrate for elimination, they will find another until they are presented with suitable options.

2.  Substrate preferences for elimination are extremely common. This means that the cat prefers some other substrate than its litter for elimination. Although the substrate preferred is usually softer (sheets, underwear, bath mats, plastic trash bags), this does not have to be so, and some cats prefer open, reflective areas such as linoleum, wood floors, tiles, and bathtubs. This problem can develop spontaneously or be induced secondarily by a filthy environment, and may be associated with illness. A cat with cystitis or diarrhea may not be able reach the litter box and in the process of covering up the urine or feces on the carpet, discovers that they like carpeting.

3.  Location preferences require many of the same strategies as for substrate preferences, especially since many location preferences appear to be mixed substrate preferences. In a true location preference, the cat prefers one or a few areas for urination or defecation; none of these is generally its litter box. After cleaning and covering the affected area, a litter box with a litter the cat likes can be placed in the area. If the cat starts to use it, terrific. After a week or two the box can be slowly (1-2 inches per day) moved to a more appropriate area. The client should watch for relapses or sneaky elimination in new spots. Regardless, the keys to treating preferences and aversions are: excellent cleaning; prohibition of access, meeting the cat's needs and preferences, and assessment of the social situation.

4.  Spraying can be done by male or female, intact or neutered animals. Sprayed urine hits vertical surfaces and drips down, but may also be found as a long, thin, wet area, rather than a puddle if the cat stands in the middle of a horizontal surface and sprays. Very confident cats want to be seen, in which case the elevated, vibrating tail, and the movement of the body associated with kneading of the feet are all important visual signals associated with spraying. Spraying can be triggered by hormones, by the addition of a new animal, by the visitation of a strange cat to windows or sliding glass doors, by partial obstructions, by seasonal changes, and by any situation generating anxiety within the cat. Many cats will spray against the inside of covered boxes.

5.  Non-spraying marking is underappreciated in most feline households. Ancestrally and in modern times, cats use feces and urine to communicate their presence, hormonal status, frequency of visitation, and possibly health and food supply. Many substrate preferences and locations that do not resolve with standard treatment are the result of non-spraying marking. This form of marking can involve urine, in which case the urine may be deposited in many small puddles, or feces. Cats that use non-spraying marking are more covert in their behaviors and may be less certain or confident in their response to aggressive displays given by other cats.

A physical exam is essential for all cases of feline elimination disorders. This must include a complete urinalysis or fecal, a CBC, and serum laboratory evaluation. A large number of cats (estimates hover around 1/3) with substrate preferences who either do not respond, or start to respond to environmental and behavioral modification and then relapse have apparent or occult UTIs or some form of FLUTD.

Feline aggression: associations with elimination disorders: Categorization of feline aggression is similar to that of canine aggression; differences in the manifestation of the aggressions may be attributable to differences in mating behaviors and differences in social hierarchies. The most common feline aggression diagnosis that is co-morbid with elimination diagnoses is intercat aggression, which may also be accompanied by redirected aggression in multi-cat households. True territorial aggression or behavior may be accompanied by marking as a normal aspect of feline behavior.

Intercat aggression: When considered a descriptor of normal feline behavior, intercat aggression is most commonly seen between toms. In most wild, feline social systems, few males mate with most of the females. The skewed sex ratio in the breeding population is induced and maintained by vigilance and aggression on the part of the males. There is an additional olfactory component of spraying and non-spraying marking that contribute to the rank aggression. The aggression is classic and involves flattened ears, howling, hissing, piloerection, threats using eyes, teeth, and claws in combat. Early neutering (prior to 12 months of age) decreases or prevents fighting by 90%.

The form of intercat aggression that is pathological and with which most clients are concerned is more commonly based on conflicts within social hierarchies than it is with sex. Cats begin to become socially mature some where between 2 and 4 years of age. At this time, some cats may begin to challenge others. Problems arise when one cat will not accept lack of engagement by another cat. Responses include passive aggression (staring and posturing), active aggression, and marking. Cats that consider themselves as more equal are less likely to participate in overt aggression-expect covert aggression. Intercat aggression is extremely complex, often subtle, and under-appreciated.

Heuristic model for thinking about phenotypic patterns of feline aggression-Potential axes:

 Overt vs covert aggression

 Active vs passive aggression

 Offensive vs defensive aggression

Sample scenarios:

 Overt, passive, offensive aggression: confident cat staring when another enters room

 Overt, passive, defensive aggression: less confident cat leaving room or backing up and withdrawing into smaller space, tail tucked vocalizing

 Covert, passive, defensive aggression: vanquished or less confident marking with mystacial glands in boundary areas or areas from which cat had been displaced

 Covert, active, offensive aggression: vanquished or less confident marking with urine or feces in boundary areas or areas from which cat had been displaced

 Overt, active, offensive aggression: chase and attack using teeth and accompanied by vocalization by resident cat toward new cat in environment

 Overt, active, defensive aggression: attack or response using hitting and or swatting while leaning back or avoiding further pursuit

 Covert, active, defensive aggression: withdrawal and marking of restricted area by victim cat

 Covert, passive, offensive aggression: displacement or theft of "bully" or higher ranking cat's toys, bed, food, or hidden copulations (?), accompanied by non-elimination pheromonal marking

Drugs that may prove useful: Benzodiazepines, while humanly abusable, can be excellent drugs for some cats who have joint elimination / aggression problems because of underlying non-specific anxiety that results in a decrease in outgoing behavior in the affected cat. Clients should be advised to watch for any signs associated with hepatopathies, although these are extraordinarily rare. The exact mechanism of action of the benzodiazepines (e.g., diazepam, chlordiazepoxide, clorazepate, lorazepam, alprazolam, and clonazepam) is poorly understood. Calming effects may be due to limbic system and reticular formation effects. Compared with barbiturates, cortical function is relatively unimpaired by benzodiazepines. All benzodiazepines potentiate the effects of GABA by increasing binding affinity of the GABA receptor for GABA and increasing the flow of chloride ions into the neuron, affecting primarily GABAA receptors. Binding of diazepam is highest in the cerebral cortex compared with the limbic system and midbrain, which are, in turn, higher than the brainstem and the spinal cord, paralleling that of GABAA receptors. At low dosages, benzodiazepines act as mild sedatives, facilitating daytime activity by tempering excitement. At moderate dosages they act as anti-anxiety agents, facilitating social interaction in a more proactive manner. At high dosages they act as hypnotics, facilitating sleep. Ataxia and profound sedation usually only occur at dosages beyond those needed for anxiolytic effects. Note that the duration of action of the parent compound, diazepam, and its intermediate metabolite, nordiazepam (N-desmethyl diazepam) in cats is 5.5 h and 21 h, respectively.

Tricyclic antidepressants (TCAs) act to inhibit serotonin and norepinephrine re-uptake, and can be useful for some cats that spray, some who are averse to or anxious about their litter box, and cats who are experiencing anxiety about heir social situation. Drugs of choice include amitriptyline and its active intermediate metabolite, nortriptyline, and clomipramine. There are three major effects of TCAs that vary in degree depending on the individual drug: (1) sedation, (2) peripheral and central anticholinergic action, and (3) potentiation of CNS biogenic amines by blocking their re-uptake presynaptically. Knowledge of intermediate metabolites can be important: animals experiencing sedation or other side effects with the parent compound may do quite well when treated with the intermediate metabolite, alone. For example, cats that become sedated or nauseous when treated with amitriptyline may respond well when treated with nortriptyline at the same dose since the former has 2x the NE-re-uptake effect of the latter.

Partial 5-HT1A/B agonists (e.g., buspirone) have few side effects, do not negatively affect cognition, allow rehabilitation by influencing cognition, attention, arousal, and mood regulation, and may aid in treating aggression associated with impaired social interaction.

The SSRIs (fluoxetine, paroxetine, sertraline, and fluvoxamine) are derivatives of TCAs. These drugs have a long half-life, and after 2-3 weeks plasma levels peak within 4-8 hours. Since these drugs act to induce receptor conformation changes-an action that can take 3-5 weeks-treatment must continue for a minimum of 6-8 weeks before a determination about efficacy can be made. Most of the SSRI effects are due to highly selective blockade of the re-uptake of 5-HT1A into pre-synaptic neurons.

Newer treatments involving a synthetic analogue of feline cheek gland secretions (e.g., pheromones) (FeliwayTM) show some promise for spraying that either has recently started and is related to the introduction of a new individual (human or animal), or to disruptions in the colony scent. No double-blind studies have been conducted, and the need for such studies is more critical in this situation than in those involving some oral medications because the mechanism of action is unknown, but appears to be relatively general. One peer-reviewed study that has examined the use of Feliway for the treatment of spraying, found that in many cases there was a statistically significant reduction in spraying, but few to no cats stopped spraying all together. In some cases the concomitant use of pheromonal agents and anti-anxiety medications may produce a quicker resolution than would be produced by either alone.

Useful medications (brand names are those in the US):

1.  Diazepam (Benzodiazepine; Valium) 0.2-0.4 mg / kg po q. 12-24 h for the victim, primarily, to make more outgoing and friendlier; for the aggressor if aggression is secondary to anxiety about interaction and increased friendliness will help

2.  Amitriptyline (TCA; Elavil) 0.5-1.0 mg / kg po q 12-24 h for the victim or aggressor with non-specific anxiety

3.  Nortriptyline (TCA; Pamelor) 0.5-1.0 mg / kg po q 12-24 h for the victim or aggressor with non-specific anxiety and sedation with amitriptyline

4.  Clomipramine (TCA; Clomicalm) 0.5 mg/kg po q 24 h for the victim or aggressor with more specific anxiety

5.  Buspirone (NSA; BuSpar) 0.5-1.0 mg / kg po q 12-24 h for the victim, only; may make more outgoing and situation resolves with some overt aggression

6.  Fluoxetine, paroxetine (SSRI; Prozac, Paxil) 0.5 mg/kg po q 24 h for more specific anxieties involving outburst (fluoxetine) and social (paroxetine) anxieties


References are available on request.

Speaker Information
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Karen L Overall, MA, VMD, PhD, Diplomate ACVB, ABS
Certified Applied Animal Behaviorist
Psychiatry Department
University of Pennsylvania School of Medicine
Philadelphia, PA, USA

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