Updated 15 January 2015

The health clues in your dog's behaviour

Many cases of behavioural problems in dogs have a medical origin.


The Chappell family was puzzled: Why was their house-trained mixed poodle, Molly, now wetting her bed during the night? Ten-year-old Molly had never done this before, making it seem like the once well-mannered canine suddenly decided to misbehave.

"We couldn't understand why Molly was forgetting her house-training," recalls Stan Chappell, who lives in Vienna, US. "It was frustrating - especially for my wife, who ended up having to launder Molly's wet bedding every morning."

What the Chappells didn't realise was that Molly's bed-wetting wasn't a house-training issue at all. "Many cases of behavioural problems have a medical origin," says Dr Andrew Luescher, a veterinary behaviourist and director of Purdue University's Animal Behaviour Clinic in West Lafayette, US.

Here are some common apparent canine behavioural problems and their possible medical causes:

Aggression. Pain or discomfort can prompt a dog to become grumpy toward people or other pets. For example, an older dog that develops arthritis may snap when touched in a newly-painful area. "This happens in people, too - you're much more likely to snap at your spouse or co-worker if you have a headache or feel crummy," points out Dr Karen Sueda, a veterinary behaviourist who practices at West Los Angeles Animal Hospital.

Pain isn't the only physical trigger of aggression. Experts also cite seizures, low levels of thyroid production, brain tumours and liver disease as possible causes of aggression. Another cause of aggressive behaviour could be the loss of sight or hearing. For example, a dog that becomes deaf may snap or bite if surprised by a person or animal approaching it from behind.

Compulsive behaviour. A dog whose behaviour appears to be compulsive and/or harmful, such as excessively licking one spot, biting their fur or other forms of self-mutilation, or constant head shaking, may simply be trying to deal with discomfort on the skin or in the ears. "Many of the behaviours that are directed to the self…are due to dermatological disease," notes Luescher. "And repetitive behaviour may be caused by neurological disease."

House soiling. "Of all the cases that I see, house-soiling is probably the most common problem that has a primary medical origin," says Sueda. Endocrine [hormonal] and kidney disease may increase a dog's need to eliminate. Additionally, older dogs that develop arthritis or spinal cord disease may suddenly find it more difficult to use stairs or the dog door to go outside and eliminate.

Other causes of house soiling can be as simple as a urinary tract infection, or as complicated as an older dog developing a condition called canine cognitive dysfunction syndrome, which is very similar to Alzheimer's disease in humans.

Because behaviour problems - particularly behavioural changes - in dogs often have physical causes, it's important for any pet exhibiting unwanted behaviour to be examined by a veterinarian, saysSueda. Generally, if the causes of the behaviour are eliminated, the behaviour itself will cease.

That's what happened with the Chappells' bed-wetting dog. When the behaviour persisted, the family took Molly to her veterinarian for an examination. The veterinarian explained that as spayed female dogs like Molly grow older, they lose oestrogen. The lower supply of oestrogen then leads to a loss of muscle tone in the urinary tracts in these dogs. The result, all too often, is that such dogs wet their beds during the night.

Molly's veterinarian prescribed a short course of a synthetic hormone called diethylstilbestrol (DES) to replace her lost oestrogen. The medicine did the trick. Chappell reports, "After that, Molly never wet her bed again." In this case, as for many others, the good dog seemingly gone bad was really just a sick puppy needing appropriate medical treatment.

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