Victims of redirected aggression do not necessarily need to make contact with the cat. For example, an aroused cat may charge and attack a person who is across the room and paying no attention to it. Such attacks are often intense, sudden, and uninhibited. Multiple bites and severe injuries are common. Attacks may seem unprovoked because the arousing stimulus was present when the owner was not around, and the pet remained in a high state of arousal. Families are often unsettled about the apparent unpredictability of the aggression, thinking that their cats have "gone mad."

Diagnosing redirected aggression requires identifying the arousal stimulus associated with aggressive displays. A good history is key to identifying this stimulus. Get a detailed description of the problem and of other incidents of aggression or extreme fear in the pet's past. Since cats may stay in a high state of arousal for long periods after stimulus exposure, the owner may not know what stimulus caused the attacks. A history of aggressive incidents may lead to a list of likely stimuli. It is reasonable to suspect redirected aggression when two cats that have always gotten along suddenly begin fighting for no apparent reason.

Treatment. Treatment involves removing the cat's access to the stimulus or modifying its response to the stimulus. If the cat becomes highly aroused when it goes outdoors, keep the cat indoors. If it becomes aroused watching outdoor cats through the windows, remove the cat's access to the windows. Intact male cats may pay less attention to cats visiting their territories after they are castrated. Medication (fluoxetine, paroxetine [Table 2]) may help reduce an animal's response to stimuli. Desensitization and counterconditioning may be helpful as well. This approach is more successful when the stimulus is a nonsocial, environmental noise rather than an unfamiliar cat in the territory.

When the aggression is directed toward another pet in the home, the cats should be separated until the level of arousal diminishes, which could be several hours to a week or more. The cats should be gradually reintroduced as if they were new pets in the home. Medication (fluoxetine, paroxetine [Table 2]) for the aggressive cat or in some cases for both cats may be beneficial, and Feliway can also help the cats relax.

It's important that owners understand what causes the aggression, how to recognize the arousal signs, how to prevent situations that lead to aggressive arousal, and how to handle an aroused cat. When a cat is in a high state of arousal, the ideal way to respond is to leave it in a darkened room, avoid contact, and close the door. If the cat must be handled, thick leather gloves, a fish net, or a large towel may be used for protection.

The decision whether to keep the cat should be based on the frequency and severity of the attacks and on family members' ability to recognize and control the arousing stimuli and to recognize and avoid the aroused cat. If some people in the household cannot avoid the aroused cat, serious consideration should be given to removing the pet from the home or euthanizing it, especially those cats that charge their victims or bite uninhibitedly.

Petting-induced aggression

Some cats that are not fearful, in pain, or exhibiting any of the other emotional states described in this article bite while being petted. This problem can be disconcerting for the family. Such cats often seek attention, crawl into laps, or rub against legs and seem to enjoy the initial physical contact. But after a certain amount of petting occurs, the cats suddenly bite and run off. It seems that these cats have a threshold for how much physical interaction they can tolerate and cannot communicate that they have had enough in an acceptable manner. However, an observant owner knows when a cat is about to bite since the cat usually shows signs, including fidgeting, tail twitching, tenseness, leaning away, flattened ears, horizontal retraction of the lips, and hissing.