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Aggressive Dogs and Pain, What's the Connection?

Aggressive dogs and pain

Aggressive dogs may be frightening, but there's a reason for their "mad dog" behavior. A new study highlights the connection between aggressive behavior in dogs and pain, and the information may help you take steps to resolve aggression in your dog.

Why some dogs are aggressive

Behavioral problems in dogs, especially if they are aggressive toward people, are often the reason why otherwise healthy dogs are euthanized. Typically, the exact cause of the dogs' aggressive actions are not known.

Aggression in dogs may have a genetic component, and this possibility has been explored in a number of studies. One, from the Norwegian School of Veterinary Science and published in BMC Veterinary Research, looked at the connection between canine aggression and genes that are involved in neurotransmission (sending signals between neurons), such as serotonin and dopamine, which play a critical role in behavior.

Other factors can result in aggression, including how a puppy was handled after birth including being taken early from the litter, weaning age, experiences during a puppy's socialization stage, exercise, diet, and how a dog is trained and disciplined. However, another significant factor can be the presence of pain that has never been diagnosed or treated, which was explored in a recent study.

Aggression in dogs study
Twelve dogs (11 males, 1 female) of different breeds (Giant Schnauzer, Irish setter, Pitbull, Dalmation, 2 German Shepherds, Neopolitan Mastiff, Shih-tzu, Bobtail, Catalan Sheepdog, Chow-chow, Doberman) and all with aggression problems reported by their owners were evaluated by members of the department of Animal and Food Science at the Autonomous University of Barcelona.

All twelve dogs were determined to have aggression caused by pain, with hip dysplasia being the most common cause (8 of 12). But there were differences in the characteristics of the aggression, including the targets of their attacks, whether they were impulsive, and position.

For example, the researchers found that dogs who were already aggressive for other reasons before they began experiencing pain attacked their owners more often and intensely when food was taken away, when they had to move from their resting area, or when they were made to do something. These dogs were aggressive in the same or nearly same circumstances as dogs who were already aggressive.

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However, the study's lead author, Tomas Camps, noted that "dogs that had never been aggressive before the onset of pain began to behave in this way in situations when an attempt is made to control them." Researchers also discovered that these dogs were more likely to attack without warning (e.g., they did not growl before striking).

Therefore the researchers explained that "if the pet is handled when in pain, it will quickly act aggressively to avoid more discomfort without the owner being able to prevent it."

Hip dysplasia is a hereditary and degenerative bone condition associated with abnormal joint structure and lax muscles, connective tissue, and ligaments that are supposed to support the joint. Over time, the abnormalities cause the two bones within the joint to separate (called subluxation), resulting in pain and limping. One or both hips can be affected.

Canine hip dysplasia usually affects large dogs, but it can be found in dogs of any size and in purebred dogs as well as mixed breeds. In fact, an evaluation of hip dysplasia in more than 120 dog breeds conducted by the Orthopedic Foundation for Animals shows that while Bulldogs topped the list (dysplasia present in 72.1%), they were followed by Pugs (66%), with Dogue de Bordeaux and Otterhounds in third and fourth place, respectively (56.7%, 51.1%).

St. Bernards were number 7 (46.8%), while Rottweillers were number 30 at 20.3% and German Shepherds hit the list at number 40 and 19%. The relatively small Cardigan Welsh Corgi is more likely to experience hip dysplasia (19.7%) than a German Shepherd.

The results of this new study indicate that pain associated with hip dysplasia plays an important role in the risk of dogs becoming aggressive. There's a connection between aggressive dogs and pain, and pet owners may prevent or reduce this problem if painful conditions such as hip dysplasia are diagnosed and treated early.

Camps T et al. Pain-related aggression in dogs: 12 clinical cases. Journal of Veterinary Behavior: Clinical Applications and Research 2012; 7(2): 99-102
Orthopedic Foundation for Animals
Vage J et al. Differential gene expression in brain tissues of aggressive and non-aggressive dogs. BMC Veterinary Research 2010 Jun 16; 6:34

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