Veterinarians in general practice are just about guaranteed to see at least a few dogs every week suffering from ear problems. Why is this so common? Multiple predisposing factors and the anatomy of the canine ear canal create the “perfect storm” for inflammation and infection to occur.
Although several different diseases can affect the external ear canal, they all tend to produce pretty much the same symptoms: head shaking and ear scratching +/- redness and discharge within the ear canal. Given their generic nature, one cannot rely on a dog’s symptoms to disclose the underlying cause of the problem.
Honing in on the diagnosis typically requires two steps, both performed by a veterinarian. First, the entire length of the external ear canal is visualized using an instrument called an otoscope. This rules out the presence of a mass or foreign body and confirms that the eardrum has not been ruptured. A torn eardrum will require alteration of normal ear cleaning procedures and the types of medications used. A successful otoscopic exam can be a difficult if not impossible task on a dog with a painful ear filled with discharge. Sedation or even anesthesia may be required.
The second diagnostic step is examination of discharge from the ear canal under the microscope, looking for bacteria, yeast, or mites. If allergies are at play, inflammatory cells may be the only finding. The most appropriate medication is chosen on the basis of these findings.
This article will discuss the different types of ear canal disease dogs develop. The next article in this series will provide pointers for dealing with dogs who tend to be repeat offenders.
Allergic ear disease
Any dog can suffer from allergies, but some breeds are particularly predisposed. Terriers of all types are notorious allergy sufferers along with Dalmatians, Lhasa Apsos, Shar Peis, Bulldogs, and Labrador Retrievers. Unlike humans who develop stuffy noses, dogs with allergies tend to have itchy skin and/or inflammation within their ear canals. This ear inflammation invariably leads to secondary bacterial or yeast infections. In fact, for some allergic dogs recurrent ear infections may be their one and only symptom.
Dogs can develop allergies to things in their environment (the dog’s version of hay fever) or to ingredients in their food. Anti-inflammatory medications can be used in the ear, but true resolution of this ear problem relies on successful treatment of the underlying allergy. This may involve dietary trials, skin testing to determine responses to environmental allergens, and/or treatment with medication to control the allergic response. Other medication will be needed if the allergy has given rise to a secondary bacterial or yeast infection (see below).
Bacteria are normal residents on the skin surface as well as within the external ear canals. It is when these “normal bacteria” overpopulate or different types of bacteria set up housekeeping that an ear infection arises.
Bacterial infections are most commonly treated with topical antibiotics (placed directly within the ear canal). Rarely are oral antibiotics necessary. Initial flushing (cleaning) of the ear canal may be performed to remove as much discharge from the ear canal as possible, but only if it is known with certainty that the eardrum is in tact (ear flushing should not be done at home without approval and instruction from a veterinarian).
A culture to identify the type of bacteria present along with antibiotic sensitivity testing may be warranted for dogs with recurrent infections or when there is a lack of response to the antibiotic prescribed. Bacterial ear infections are rarely contagious from dog to dog.
Malassezia pachydermatis is the technical name for the yeast that normally lives within a dog’s ear canal. Symptoms of infection occur when these microorganisms proliferate in response to underlying factors such as allergies or moisture.
Yeast infections are treated with initial ear cleaning (if the eardrum is in tact) and medicated eardrops or ointment to reduce the yeast population back down to their normal numbers. Sometimes, an oral antifungal medication is prescribed. Yeast infections are not contagious from dog to dog.
Whereas mites are one of the most common causes of ear disease in cats, they are a relatively uncommon cause in dogs. Mange mites (demodex and sarcoptes) cause skin disease that can involve the ears. The true “ear mite” that affects only the ears is Otodectes cyanotis. These microscopic critters are highly contagious between dogs and cats. They march around within the ear canal biting, laying eggs, and generally wreaking havoc. A cure is accomplished by removal of excess debris from the ear canal in conjunction with a topical mite killing medication and/or use of a systemic anti-parasite product. All dogs and cats within the household should be treated simultaneously.
The most common foreign body that makes its way into a dog’s ear canal is a plant awn referred to as a foxtail. If you live west of the Mississippi, your dog may be exposed to them during the late spring and summer months. Once in the ear canal, the foxtail’s barbs along with the slope of the ear canal prevent the darned thing from being dislodged, no matter how much head shaking the poor dog does.
Ticks sometimes migrate down into the ear canal where they become a “foreign body” until mealtime is over and they climb back out. Other foreign objects I have removed from doggie ears include nonfoxtail types of plant material, dirt, sand, hair, and an occasional “something or other” dropped in the ear canal by a curious child.
Keep in mind that gravity will carry the vast majority of foreign bodies down into the ear canal beyond view from the surface. Their removal is best accomplished by a veterinarian. An otoscope is used for visualization and a snare or an instrument called an “alligator forceps” is used to remove the foreign body. Even the best-behaved dogs may require sedation or anesthesia for this procedure. On occasion, a foreign body manages to perforate the eardrum. If a foreign body is not removed it almost invariably incites a secondary infection.
Masses and polyps occasionally arise within the ear canal. It is usually the secondary infection they cause that first attracts attention. Ear canal masses can be malignant or benign- a biopsy is necessary for this differentiation. Removal of the growth is typically necessary to fully alleviate symptoms. Surgery may be needed, depending on the size and location of the mass.
Have your dogs suffered from any of these ear canal diseases? If so, how were they treated? What worked well and what didn’t?
Diplomate, American College of Veterinary Internal Medicine
Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
Author of Your Dog’s Best Health: A Dozen Reasonable Things to Expect From Your Vet
Spot’s Blog: http://www.speakingforspot.com/blog