Introduction

• Feline aggression is not a unitary topic. Cats can exhibit numerous kinds of aggression which have been classified as follow:
  • Aggression due to lack of socialization Lack of appropriate socialization and/or habituation.
  • Play aggression.
  • Intercat aggression Aggression: intercat.
  • Territorial aggression.
  • Fearful aggression Aggression: fear.
  • Maternal aggression.
  • Redirected aggression Aggression: towards people.
  • Predatory aggression.
  • Assertion / status-related / impulse control aggression.

Pathogenesis

Etiology

• The etiology of feline aggression can be understood - as is true with all behavioral diagnoses - at a number of levels.
• The easiest of these for the clients to understand is the phenotypic one involving social interaction and provocation.
• The extent to which any cat is susceptible to provocation involves a complex interaction between genomic response surfaces, molecular and neurochemical flexibility, and neuroanatomical arousal.
• We do not understand this interaction for any behavioral diagnosis at present.

Predisposing factors

General

• Because the extent to which cats are outgoing v. withdrawn is greatly influenced by their paternal genetic contribution, fear aggression, fears, and learned aggressions that may develop as a result of fears could be lessened by breeding only friendly, outgoing male cats.
• This is practical in cattery situations, but unlikely in most other situations.

• Lack of early handling and exposure of kittens to new environments and people has an adverse effect on the extent to which cats can be influenced and adapt their responses in the future.
• It is possible that early handling, particularly that which occurs between 2 and 7 weeks, affects brain development and neurochemical effects on cells in specific regions of the brain.
• Such effects have been established for rodents, and are also likely to be important in cats since they have not been selected to be 'domesticated'. Part of the domestication process would have involved an expansion of these sensitive periods.
• Cats that are taught by their mothers to catch prey will likely exhibit predatory behavior later in life.  This learned response may not extend to aberrant behavior, like predatory aggression.
• Cats that are undernourished as kittens and those born to queens who were severely undernourished when pregnant have been shown to be more reactive, less calm, and more impaired in social learning.  The extent to which such nutritional concerns provide a fertile ground for the development of feline aggression has not been established, but may warrant serious thought.
• Underlying physical disease usually makes most animals more reactive and cats are no exception.
• The link between behavior and physical health is a complex one that is not sufficiently emphasized in most veterinary practices.
• Many of the immunosuppressive viral agents also exert non-trivial effects on brain development, memory, and certain types of behavior.
• These interactions are seldom explored, although FIV has been associated with increased reactivity in cats. Such reactivity could lead to a number of the aggressive conditions discussed.

Pathophysiology

• We know so little about true behavioral pathology that we can only guess at the numerous underlying contributory factors to feline aggression.
• Because cats have been used as models for many human brain conditions (eg epileptic kindling) we actually know a lot about changes that occur subsequent to chronic stimulation.
• The amygdala is the region of the brain that is most often associated with the development and execution of fearful responses and behaviors.
• Cell bodies and ganglia within the amygdala give rises to nerve tracts to diffuse regions of the brain stem and the brain cortex.
• In cats, responses to stimulation are quick, act to recruit other cells and brain regions, and are prolonged for a considerable amount of time after the stimulus is discontinued.
• The hypothalamus in cats responds to stimuli in a region-dependent manner, and recruitment of firing neurons depends on where the largest stimulus is.
• Accordingly, active biting attacks and quiet predatory attacks with real prey items involve different parts of the hypothalamus.
• The extent to which cellular and molecular learning, or long-term potentiation, is involved in these triggered responses has not been investigated in cats.
• However, the patterns of behavior suggest that such processes act to change neurochemistry with each repeated exposure wherein the cat reacts, so that threshold levels are changed, and other social patterns altered.
• In the absence of definitive pathological information the best advice practitioners can give to clients is to treat cats with aggression early and often, learn to recognize the signs of the aggression so that help can be sought early, and avoid behaviors and situations that could encourage aggressive responses.
• This dialog should occur at the time of the kitten appointments, and veterinarians should emphasize that it is because we know so little that early reliance on non-specific signs and potentially worrisome behaviors becomes critical.

• We don't know enough about these conditions at any level other than the phenotypic one, which is not helpful for understanding most pathophysiology.
• Laboratory experiments have show that stimulation of the ventromedial hypothalamus [VMH] provokes active defense behaviors in cats whereas lesioning the VMH increases frank aggression post-lesion.
• Stimulation of the lateral hypothalamus [LH] provokes predatory attack whereas lesion the LH results in a decrease in aggression or its abolition.
• Given these findings, understanding the neural circuitry and it's molecular associations involved in feline aggression should be research focus.
• Now that we have the ability to use molecular probes, functional imaging, and post-mortem immunohistochemistry our emphasis should be on understand the mechanism underlying our phenotypic diagnoses.

Timecourse

• With the exception of the aggressions that develop early due to lack of early learning and exposure (eg aggression due to lack of socialization, play aggression), the vast majority of feline aggressions develop at social maturity and are more specific manifestations of anxiety disorders.
• The hallmark of social maturity in all species that have been studied involves complex brain neurochemical changes that are disruptive and then settle into the individual's characteristic 'pattern' at the end of this period.
• The period of social maturity is separate from the period of sexual maturity but sexual hormones likely have some interactions with those that are changing during social maturity.
• A rough approximation of the age at which social maturity occurs in cats is 2-4 years.
• This estimate fits well with data on free-ranging cats that indicate in resource-rich environments, sub-adult cats 18 + months of age remain with their family groups and help with other young, rather than breeding independently. 
• The onset of an anxiety disorder is almost impossible for the client to recognize because the behavior may not be viewed as aberrant or troublesome, and the pattern is not clear.
• Accordingly, most anxiety disorders are recognized only when fully formed so it is almost impossible know the true timecourse.
• That said, some anxiety disorders develop quickly and abruptly, and some develop as if by accumulation.
• This gross observation suggests that various genetic response surfaces comprise the population, and the extent to which environmental stimuli interact with these increases the variability. Once established, these conditions do not improve on their own, and the earlier the intervention in the development of any pathology involving aggression, the more likely treatment is to be shorter.  Once fully established, the reversal of learned behaviors becomes a real challenge, and treatment that minimally involves management is lifelong.

Epidemiology

• The population dynamics have largely been discussed earlier.  However, clients need to be reminded that the population that they must address is that of their entire household, and one cat with an anxiety-related condition, particularly if aggression is involved, can dysregulate all relationships, not just those involving the cats.
• By watching such relationships, the clients are likely to detect changes earlier.

Diagnosis

Treatment

Prevention

Outcomes