Statement of the Problem

A cat was examined because of a history of biting and scratching its owners and visitors to the home.

Signalment

The cat was a 3-year-old castrated male Siamese.

History

The cat was owned by a couple and lived in a household with a spayed female Siamese cat. The owners had obtained this cat from a breeder at 8 weeks of age, and the cat had been castrated at 4 months of age. The owners reported that the cat had a bold personality as a kitten, assertively approaching any person or object, and that the cat was aggressive during play, although the owners reported they did not encourage rough play.

As an adult, the cat continued to demand affection and bit if ignored. Furthermore, the cat would occasionally approach the female owner while she was at the computer or watching television, forcefully rub its cheeks on nearby furniture, and then bite the owner on her arm or head. Although the male owner was occasionally bitten, the female owner was home most of the day and was more often the target of the cat's aggression.

The female owner's sister lived in the home for approximately 9 months, and the cat was aggressive toward her during her entire stay. The cat would on occasion trap the sister in a room by standing in the doorway while growling and lashing its tail and then lunge toward her. In addition to the male owner, the female owner, and the sister, the cat was also aggressive toward visitors to the home. The cat would jump into visitors' laps and would rub and lick the visitors' hands. However, if the visitor attempted to pet or move the cat, it would usually lash its tail and bite the visitor's hand.

The female owner reported that the cat did not move away from the hands of people and did not flatten its ears. The owners stated the cat's body position was similar during all attacks in that its ear pinnae were erect and turned to the side and, if the approach was witnessed, its head moving from side-to-side, its tail lashing at tarsal level, and its front end held low. The cat's attacks mostly consisted of bites and were sometimes accompanied by a low growl, but never hissing. This cat occasionally chased the other cat in the household, but these interactions never escalated to aggressive contact.

The cat was extremely aggressive at the veterinary clinic as well, but this behavior was characterized differently. In this setting, the cat hissed, howled, scratched, and violently thrashed with its ears flattened back on its head when manipulated by the veterinary staff.

When the cat was 18 months old, the referring veterinarian detected a grade 1 to 2 (on a scale from 1 to 5) systolic murmur and referred the cat to a local board-certified veterinary internist, who diagnosed mild idiopathic hypertrophic cardiomyopathy on the basis of results of echocardiography. For approximately 18 months prior to the present behavior consultation, the cat had been treated with atenolol, a β₁-adrenoceptor blocker (0.75 mg/kg [0.34 mg/lb] or 5 mg, PO, q 24 h), to decrease the risk of myocardial infarction and arrhythmias associated with hypertrophic cardiomyopathy. The cat reportedly did not have any clinical signs of hypertrophic cardiomyopathy, such as anorexia, vomiting, dyspnea, tachypnea, or paresis.¹

Physical Examination Findings and Laboratory Results

During the behavior consultation, the cat remained in the back of its carrier and hissed, growled, crouched with its tail tucked, and swatted when the staff attempted to remove the cat from the carrier. Because of reports¹ of arrhythmias and sudden death in cats with hypertrophic cardiomyopathy, efforts to remove the cat from the carrier were discontinued when these struggles rapidly escalated, and physical and neurologic examinations and clinicopathologic testing were not performed. However, results of a CBC and serum biochemical panel performed by the referring veterinarian 3 weeks later on a blood sample obtained after the cat was sedated were within reference limits. Thyroid hormone concentrations were not measured at this time, as the internist did not believe hyperthyroidism was likely to be associated with hypertrophic cardiomyopathy in a cat this young.

Diagnosis

A diagnosis of status aggression toward people in the home and fear-related aggression toward people at the veterinary clinic was made. Status aggression,² which has also been called status-related aggression³ and dominance aggression,⁴ refers to aggression that occurs when a cat attacks a person to control a situation,³ intentionally obstructs a person's path, or attacks when a person's guard is down.^2,3 The cat's overtly aggressive body posture and behavior during attacks on people in the home in combination with the history of an assertive temperament were considered indicative of status aggression.³ However, the cat's body posture and hissing during examinations at the veterinary clinic were indicative of fear-related aggression.^2,3 Fear-related aggression is common among cats brought to a veterinary clinic because of adverse experiences such as pain and stress caused by unfamiliar noises, smells, and other animals common in this environment.²

Other possible causes of the owner-directed aggression that were considered included fear-related aggression, redirected aggression, petting-induced aggression, play aggression, and aggression related to underlying medical conditions. Although clients are often unaware of stimuli that may have originally caused redirected aggression, the cat's history of rough play and an assertive personality from a young age made a diagnosis of redirected aggression unlikely. Play aggression is characteristic of young cats, but the targets of aggression for the cat described in the present report were often stationary, and the cat did not exhibit the pouncing or hopping that is typical of play aggression.^2–4 In the home, the cat never displayed defensive postures, such as a crouched body position, flattened ears, or arched back, associated with fear-related aggression.^2–4 Lethargy and anorexia have been associated with hypertrophic cardiomyopathy and atenolol administration, but not aggression, and the cat's behavior did not change after drug treatment was started. Although decreased cerebral blood flow may cause altered mentation,¹ echocardiography revealed negligible cardiac outflow obstructions.

Other possible causes of the visitor-directed aggression that were considered included territorial aggression, fear-related aggression, and petting-induced aggression. The cat's body posture and biting were not indicative of fear. Territorial aggression could not be ruled out, in that the cat was overtly aggressive and forcefully bunted its head against visitors' hands, possibly as a marking behavior. However, cats with territorial aggression typically have a history of lunging at people³ and urine marking.¹ In contrast, this cat had no history of urine spraying or house soiling and was not aggressive toward visitors until they reached to pet him. Aggression in response to petting is characteristic of petting-induced aggression, but the cat would become aggressive during any manipulation by a visitor, not just petting, and the cat would allow petting by the owners.

Treatment

The owners were advised that for safety purposes, the cat should be placed in a separate room behind a closed door while visitors were present. The owners were also instructed to place a bell on the cat's collar to help prevent the cat from sneaking up on them. Laundry baskets and blankets were suggested as methods to contain the cat during aggressive episodes. A program of training the cat to earn rewards was outlined.¹ Specifically the cat was trained to respond to sit, touch (a finger tip), and up (jumping up on a chair) commands, with a clicker used as a secondary reinforcer.²

The owners were advised to give the cat a command as a response substitution if an attack appeared imminent.² Furthermore, response substitution was suggested as a means of changing the cat's underlying motivation toward visitors. That is, the cat was clicker-trained to respond to a “place” command by going to a special cat bed. When visitors arrived, one of the owners was to give the cat the bed command, while the other owner let the visitors into the house. The cat was to be ushered into another room if it could not be strictly supervised, preferably while wearing a harness. Once the cat was reliably obeying commands for the owners, visitors would then be allowed to ask the cat to obey commands for treats, but visitors were never to pet the cat.

To address the fear-related aggression at the veterinary clinic, the owners were asked to use a protocol for systematic desensitization and counter-conditioning during which the cat was exposed to the clinic in a controlled and gradually more intense fashion.⁵ To aid in attenuating the cat's aggression, treatment with fluoxetine, a selective serotonin reuptake inhibitor (0.75 mg/kg or 5 mg, PO, q 24 h), was recommended once results of clinicopathologic testing were available. Concentrations of the neurotransmitter serotonin are often low in aggressive animals, and although no studies have been published pertaining to its use in cats with human-directed aggression, it has been effective in the treatment of other behavioral problems in cats and in the treatment of aggression in other species.⁶

Follow-up

Four weeks after the behavior consultation, a follow-up conversation revealed that the cat had been receiving the fluoxetine for 1 week with no adverse effects and had responded well to the clicker training. No aggressive episodes had occurred since the consultation, but the cat had not been allowed in the same room with visitors during this period.

Eight weeks after the behavior consultation, the owners reported a dramatic improvement in the cat's aggression. The owners engaged in several minutes of training throughout the day, and now, when visitors came to the door, the cat would immediately go to its special bed in the living room for a treat. The cat would obey commands from visitors and had not shown any aggression toward visitors to the home. The owners had not commenced desensitization and counter-conditioning at the veterinary clinic.

Six months after the behavior consultation, the owners reported that behavior improvements in the home had been maintained. However, they still had not attempted desensitization and counter-conditioning at the veterinary clinic.