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  • GekkoVet Team

Pain and neurological problems - causes behind an animal's aggression

The aggressive behavior of a pet is often draining for both the owner as well as for the animal itself. The aggression should always be taken seriously, as it may be reflecting an underlying serious issue. An aggressive animal can cause danger to the surrounding individuals, as well as to the animal itself.

There are several possible factors behind the aggressiveness of an animal: physical pain, neurological syndromes, and disorders, fear, stress, anxiety, genetic problems, defensive behavior, maternal instincts, conflict situations as well as a wide variety of learned behavioral patterns. In this article, the main focus is on aggression caused by physical pain and neurological problems.

An aggressive animal is angry, threatening, anxious, and often scared. The animal uses aggression to defend itself against something dangerous or unpleasant. An aggressive dog might growl, bark, reveal its teeth and bite. The dog might freeze or crouch at first; this might be followed by an attack. An aggressive cat on the other hand might hiss and grimace with a hunched back and a lifted tail, simultaneously pressing its ears against its head. The cat’s pupils are dilated and when approached, it might try to scratch and bite. Both cats and dogs raise their hair when they express anger. An aggressive animal tries to make itself look as big and powerful as possible.

Why does physical pain cause aggressive behavior in animals?

An animal in pain is often more alert and anxious than normal. Concurrently, the animal is weaker, and cannot defend itself in a dangerous situation like a healthy animal could. An aggressive behavior helps the animal to keep away the people and other animals it considers to be threatening. The animal strives to avoid touching and moving. Physical pain has also been proven to decrease the amount of serotonin activity in the central nervous system, increasing aggressive behavior. Pain can also increase earlier, pre-existing aggression.

The physical pain behind aggressiveness may be acute or chronic. For example, traumatic pain, toothache, tumors, gastrointestinal pain, as well as pain in the musculoskeletal system are known to be the cause of a wide variety of behavioral problems in animals, including aggression. In dogs, for instance, chronic pain in the hips, knees, and back can cause aggressiveness. Cats suffering from constipation often experience stomach aches, which can be connected to increased peeved behavior. Cats that are in pain might try to scratch their owners when petted. In the case of localized pain (for example, joint pain), the animal might suddenly attack when the painful area is touched.

The pain that is causing aggression can be confirmed by imaging as well as with different physical examinations. When the pain is treated, the aggressiveness of the animal decreases. Correspondingly, as the pain relief stops, the aggressiveness of the animal returns. When pain is suspected to be the cause of the belligerent behavior, avoid touching the painful part and take the animal to a veterinary clinic for an examination. It is important to remember that in the case of prolonged pain, the aggressiveness might not diminish automatically with pain relief; the animal may have already learned certain behavioral patterns. In this case, the help of a professional trainer is most likely needed.

Neurological problems

Some neurological problems and diseases are able to cause aggressive behavior in animals. According to multiple studies, some epileptic dogs display aggressiveness as a defense mechanism - however, this is relatively rare. Additionally, a viral disease called canine distemper (CD), as well as tumors of the central nervous system may cause aggression in animals. Dogs who experience anxiety and stress may also show angry and aggressive behavior. The aggressiveness is often justified when it comes to a stressful situation: the animal feels threatened and defends itself. An anxious animal, however, is afraid of a threatening situation that has not yet occurred. The aggression of an anxious animal is not based on a real danger and does not protect the animal. In this case, the aggression should be eliminated.

Rabies, also called hydrophobia, is a life-threatening disease caused by a rabies virus. Rabies mainly spreads in the canids and bats, but it can infect any mammal, including humans. In rabies, the virus travels through the animal’s nervous system, causing inflammation in the spinal cord and the brain. The most common symptoms of rabies are different neurological disturbances, including aggressiveness, irritability, convulsions, as well as disturbances in consciousness and cognition. A rabid animal may behave unexpectedly and aggressively, and try to bite the people, animals, and objects surrounding it. The animal often salivates excessively, and the consistency of the saliva can be foamy. The rabies virus is secreted in the saliva and spreads via biting. Additionally, to the aggressive form of rabies, the disease may also be displayed in a paralytic form. In this form, the muscles of the animal are paralyzed, starting from the muscles of the neck and chin, making it difficult to swallow and keep the mouth closed. The paralysis quickly spreads to the entire body. Both forms of rabies lead to death if the signs and symptoms have already appeared. In some cases, the disease has been successfully eliminated, when the treatment was started before the signs became apparent. A vaccination against rabies exists, and it is an effective way to prevent the disease.

How is an aggressive animal treated?

Before starting the treatment, it is important to inspect the cause of the animal’s aggression, so that a proper treatment method can be applied. The first step is to take the animal to a veterinary clinic. An animal that suffers from physical pain is treated with painkillers. The cause of the pain should be solved and removed. In neurological issues, a combination of medication, as well as behavioral training, is used; however, neurological problems are always dealt with on a case-by-case basis. Try to avoid every action that triggers the aggressive behavior in your pet, until you receive professional help. It is also good to remember that when handling the animal, the safety of the owner as well as the veterinary staff is always the number one priority: the veterinarian might sedate the animal or use a muzzle on it. Aggressive cats may be sedated and examined in a cage. These measures are always attempted to be carried out as rapidly as possible, without causing harm or unnecessary stress to the animal.

The aggressive behavior of a pet can be overwhelmingly exhausting and even dangerous for the people surrounding it. Because handling the animal is often quite difficult, the lives of both the pet and the owner become burdensome. For example, going out for a walk or implementing the necessary treatment measures may become impossible to accomplish. One should never answer to the animal’s aggression with anger - this will often make the situation even worse and reinforce the unwanted behavior in the future.

The aggressive behavior of a pet should always be taken seriously, even if it would not cause immediate harm. For example, an aggressive but small dog could easily be kept under control. However, the aggression could be manifested by a serious, underlying issue. An aggressive animal can cause danger to the surrounding individuals, as well as to the animal itself. Nonetheless, it is good to remember that there is a time and a place for aggression - it is within the animal’s natural instinct to defend itself against a threat. Aggressiveness becomes a problem when it shows up in situations where it is not needed, or towards individuals that will not cause harm to the animal.


Camps, T., Amat, M., and Manteca, X. (2019). A Review of Medical Conditions and Behavioral Problems in Dogs and Cats. Animals: an open access journal from MDPI, 9(12), 1133.

Candini, D., Biasato, I., Dell'Armelina Rocha, P. R., Grego, E., Capucchio, M. T., and Vercelli, C. (2017). How Behavioral Changes Can Indicate Serious Cerebral Pathology: A Case Report of Concomitant Olfactory Neuroblastoma and Distemper Virus Encephalitis in a Swiss Shepherd Dog. Veterinary sciences, 4(3), 42.

Frank D. (2013). Aggressive dogs: What questions do we need to ask?. The Canadian veterinary journal = La revue veterinaire canadienne, 54(6), 554–556.

Landsberg, G. M. and Denenberg, S. (2014). Behavioral Problems of Dogs. The Merck veterinary manual. Whitehouse Station, NJ, Merck & Co., Inc.

Mills, D. S., Demontigny-Bédard, I., Gruen, M., Klinck, M. P., McPeake, K. J., Barcelos, A. M., Hewison, L., Van Haevermaet, H., Denenberg, S., Hauser, H., Koch, C., Ballantyne, K., Wilson, C., Mathkari, C. V., Pounder, J., Garcia, E., Darder, P., Fatjó, J., and Levine, E. (2020). Pain and Problem Behavior in Cats and Dogs. Animals: an open access journal from MDPI, 10(2), 318.

Rupprecht, C. E. (2018). Rabies in Dogs. The Merck veterinary manual. Whitehouse Station, NJ, Merck & Co., Inc.


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