Medical Causes for Canine Aggression

Canine aggression can be a real problem for dog owners. No responsible dog owner wants her dog snarling and nipping at kids, friends, neighbors or other dogs. However, canine aggression is sometimes completely unavoidable, especially if you did not get your dog as a puppy. The primary causes of aggressive temperaments in dogs are inadequate socialization as puppies and genetics (some dogs have been bred to be aggressive). However, there are a number of medical conditions that can lead to aggressive behavior in dogs. If yours is normally friendly, you should take it to a veterinarian for diagnosis, should it suddenly start acting aggressive.

  1. Encephalitis

    • According to the North Carolina University College of Veterinary Medicine, encephalitis "is one of the most common causes of neurological disease in veterinary medicine." Encephalitis is essentially an inflammation or the brain and/or spinal cord. Symptoms vary, depending on the area of the brain that is affected. Behavioral changes, including various displays of aggression; loss of coordination, including imbalance; depression; seizures; head tilt; blindness; and facial paralysis are some of the most common symptoms of encephalitis. There are a variety of underlying causes of the brain inflammation, including various fungal infections, such as valley fever; tick-borne diseases, like Rocky Mountain spotted fever and Lyme disease; bacterial infections, such as meningitis; and viral diseases, like rabies and distemper. In fact, the aggression often associated with some of these diseases is actually caused by the resultant encephalitis. Autoimmune disorders have also been known to cause encephalitis. Treatment usually involves various medications, depending on the specific cause of the inflammation.

    Thyroid Dysfunction

    • Thyroid dysfunction is another common cause of aggression in dogs that has been gaining increased recognition among the veterinary community in recent years. In dogs with hypothyroidism, the thyroid gland produces too little T3 and T4 hormones, slowing down body functions; dogs with hyperthyroidism produce too many T3 and T4 hormones, speeding up body function. There are a number of causes of thyroid disorder (most commonly genetic) and, aside from unwarranted and sudden aggression, symptoms may include seizures, abnormal disobedience, extreme submissiveness, fear/nervousness, hyperventilation, unusual allergies/sensitivities, fur/skin disorders and a general change in behavior. Treatment usually involves various medications, such as steroidal, thyroidal and anti-thyroidal drugs, depending on the type of thyroid dysfunction.

    Chemical Imbalance

    • Just like humans, dogs can suffer from chemical imbalances in the brain. And just as these imbalances can cause aggression, depression and various psychotic disorders in humans, they can lead to similar conditions in canines. The most common result of a canine chemical imbalance is depression. Symptoms may include aggression, anxiety, weight loss, lack of appetite, excessive shedding and an overall change in behavior and temperament. Treatment may involve medication, such as phenobarbital, prozac and valium, as well as behavior modification treatment. Note that what appears to be a mental disorder in your dog can also be the result of unfamiliar changes in environment or ownership.