When Is an Infection Not an Infection?

Ken Tudor, DVM
Updated: May 22, 2015
Published: March 07, 2013
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We veterinarians are a simple lot. Rather than take the time to fully explain complicated medical conditions we resort to simplistic explanations. These are often misleading or confusing for owners. Two great examples are recurrent ear "infections" in dogs and recurrent bladder "infections" in cats.

Calling something an infection generally implies a bacterial cause (sometimes fungal). It also implies that with the proper antibiotics (or antifungals) the problem will resolve. No wonder owners are confused when they return to the veterinary office repeatedly with their dogs for treatment of smelly and painful ears and their cats’ inappropriate or frequent urination.

Owners deserve a better explanation that these are chronic medical conditions that are not curable short term but manageable long term.

Ear Problems in Dogs

In humans ear infections are very common in children. Infections take place in the middle ear in back of the eardrum. They are associated with respiratory infections like flu or colds or other bacterial infections from the nose and sinuses. The connection of the nose and throat area to the middle ear, called the Eustachian tube, allows bacterial migration to the middle ear to cause the infection.

Although bacterial middle and inner ear infections do occur in dogs, the most common ear problem in dogs is in the ear canal, which is called otitis externa. These do not occur because of an invasion of bacteria to the ear canal. Rather they result from a breakdown in normal canal cell immunity that allows the overgrowth of bacteria and fungus that are normal inhabitants of the ear canal.

Ear mites and foreign objects (foxtails, grass awns) can cause ear problems but are resolved with proper treatment or removal. Animals with food or environmental allergies, certain skin conditions, or other immune mediated diseases are the most affected. Certain breeds with narrowed or ear canal abnormalities are also chronically troubled. Floppy ears and swimming are often cited as risk factors but are weak explanations. Perky eared dogs and non-swimmers are equally afflicted, while millions of swimming dogs have no ear problems. In fact, the microscopic hairs of the ear canal, called cilia, beat in synchronous waves to expel water or other liquids from the ear.

It is these allergic, immune, or anatomical problems that are the cause. Ear medications that control bacterial and fungal growth resolve the symptoms but don’t address the cause. That is why ear problems recur. If the underlying cause cannot be identified or resolved, veterinarians need to offer treatment programs that manage the condition without creating unreasonable expectations of curing the problem.

Bladder Problems in Cats

Many cat owners are familiar with recurrent bladder problems or cystitis in their cats. These pets exhibit repeated bouts of inappropriate urination or frequent, poor productive trips to the litter box. Occasionally owners will observe blood in the cat’s small urinary deposits.

Some of these cats produce crystals or stones that cause bladder irritation and the resulting symptoms. Most affected cats suffer from a chronic inflammation of the bladder called interstitial cystitis. This condition is believed to be an immune disorder similar to what occurs in women.

With the exception of a small percentage of cats with struvite crystals or stones, cystitis in cats is not associated with bacterial infections. The actual causes for the various types of cystitis are still not known. Although risk factors have been identified with crystal or stone forming cats, interstitial cystitis is still a mystery. Antibiotics will not "cure" these problems. In fact nothing will "cure" most cases of feline cystitis. Even the management of cystitis with dietary intervention, supplements, and various drugs is not universally successful. Owners should be alerted to this reality.

Dr. Ken Tudor

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