Canine Ear Infections

By Margaret Muns, DVM

External ear canal disease, or otitis externa, is a very common condition in dogs. It is particularly prevalent in dogs with the long, floppy ears. Just like any other canine medical condition, external ear canal disease must be properly examined and treated from the start. Otherwise, the condition may not be resolved, and may actually become worse. If dogs have had terrible ear disease for a very long time (months to years), their ears cannot be cured by continuing to give antibiotics and hoping that they will work.

Your veterinarian should look for predisposing factors, primary causes, and perpetuating factors. The challenge is to find out what is causing the disease, and either control or eliminate it.

Predisposing Factors

Predisposing factors are conditions that greatly increase the risk of developing external ear canal disease. Conditions such as long floppy ears, excessive moisture (swimmer's ear), excessive wax production, treatment effects (irritating drugs), obstructive ear disease (polyps, tumors) and systemic disease (immune suppressing disease) must all be accounted for.

Primary Causes

Primary causes are responsible for inducing the ear disease from the start. Some primary causes are parasites (ear mites), fungal organisms, allergies, hormonal imbalances, seborrhea, foreign bodies, glandular disorders, immune mediated disease, and viral organisms.

Bacterial infection is never a primary cause of ear infections. It always shows up as secondary to an underlying problem.

Perpetuating Factors

Perpetuating factors are conditions that prevent resolution of the ear disease. Often, in very long-standing cases, there could be more than one perpetuating cause. Recognition and management of these factors are absolutely vital for controlling chronic ear disease.

In chronic dog ear disease, the most common perpetuating factors are bacteria, yeast, progressive pathological changes, and middle ear infection.

In any case of severe chronic ear disease, no drugs should be put in the ears without a proper examination. Ear cytology (examining a smear of the discharge under the microscope) doesn't tell you the underlying cause, but it is useful for detecting secondary yeast infections. It can also give you a better idea of any secondary bacterial invaders so you can use an appropriate antibiotic until the culture results come back.

Regardless of the results of the cytology, culture and sensitivity testing should be done. With these two tests, you can determine the perpetuating causes in the disease process.

Treatment

After all tests have been done, severe ear infections should be flushed out when the dog is under anesthesia. The skin lining of the ear canal must be treated, and not the wax inside. Most severe external ear infections show a ruptured ear drum and a concurrent middle ear infection. The veterinarian must clean out the wax to see if the ear drum is intact or gone, so he or she can choose the best topical drug. Some drugs and cleansers can cause damage to the middle ear the ear drum has been ruptured. With severe external ear disease, oral antibiotics are given.

To get the best chance at controlling ear infection disease, dog owners should be prepared for a long course of therapy, and practice preventative care at home to stop the disease from getting worse.

Dogs with severe chronic ear infections should have a complete medical exam to eliminate the possibility of underlying systemic disease. For example, hypothyroidism is a common underlying reason for bad ears. If atopy (an allergic condition caused by inhaled allergens) is the cause, you may need to give low doses of anti-inflammatory medicine during the season. If food allergy is the cause, then a special hypoallergenic diet may be needed. If the dog is hypothyroid (under-active thyroid), continuous thyroid therapy will be needed. In all cases, owners will need to be sure to clean the ears regularly to prevent wax build up.

Dogs that have had severe ear disease for a long period of time usually can't be completely cured. However, if the problem is approached correctly, with owner and veterinarian working closely together, you can usually achieve a controlled condition.

In cases where proper medical therapy still can't control the disease, surgical options are available. These options range from opening up the external ear canal to provide drainage (the Zepp operation), to removal of the ear canal.  

CANINE EAR INFECTIONS

How common are ear infections in dogs?

Infections of the external ear canal (outer ear) by bacteria or yeast, are one of the most common types of infections seen in dogs.  We call this otitis externa. 

Some breeds, such as Cocker Spaniels and Miniature Poodles, seem more prone to ear infections, but they may occur in any breed.

What are the symptoms of an ear infection?

A dog with an ear infection is uncomfortable; its ear canals are sensitive.  It shakes its head trying to get the debris and fluid out, and it scratches its ears.  The ears often become red and inflamed and develop an offensive odor.  A black or yellowish discharge commonly occurs.

Don't these symptoms usually suggest ear mites?

Ear mites can cause several of these symptoms, including a black discharge, scratching, and head shaking.  However, ear mite infections generally occur most commonly in puppies.  Ear mites in adult dogs occur most frequently after a puppy carrying mites is introduced into the household.  Sometimes, ear mites will create an environment within the ear canal which leads to a secondary infection with bacteria and yeast (fungus).  By the time the dog is presented to the veterinarian, the mites may be gone, but a significant ear infection remains.  

Since these symptoms are similar and usually mean an infection, can I just come by and get some medication?

There are several kinds of bacteria and at least one type of fungus which might cause an ear infection.  Without knowing the kind of infection present, we do not know which drug to use.  In some cases, the ear infection may be caused by a foreign body or tumor in the ear canal.  Treatment with medication alone will not resolve these problems.  Also, the dog must be examined to be sure that the eardrum is intact.  Administration of certain medications can result in loss of hearing if the eardrum is ruptured.  This determination is made by the veterinarian and must be done in the office.

How do you find out which drug to use?

First, the ear canal is examined with an otoscope, an instrument that provides magnification and light.  This permits a good view of the ear canal.  This examination allows us to determine whether the eardrum is intact and if there is any foreign material in the canal.  When a dog is in extreme pain and refuses to allow the examination, it must sometimes be completed under sedation or anesthesia. 

The next step is to examine a sample of the material from the ear canal to determine which organism is causing the infection.  This is called cytology.  Examination of that material under the microscope is very important in helping the veterinarian choose the right medication to treat the inflamed ear canal.

How are ear infections treated?

The results of the otoscopic examination and cytology tell us what to do.  If there is a foreign body or tick lodged in the ear canal, the dog is sedated so that it can be removed.  As stated previously, some dogs have such a heavy buildup of debris that sedation is needed to cleanse the canal and examine it completely. 

Cytologic study of debris from the ear canal dictates which drug to use.  Sometimes, it reveals the presence of more than one type of infection (i.e., a bacterium and a fungus, or two kinds of bacteria); this situation usually requires the use of multiple medications or a broad-spectrum medication.

An important part of the evaluation of the patient is the identification of underlying disease.  Many dogs with chronic or recurrent ear infections have allergy problems or low thyroid function (hypothyroidism).  If underlying disease is found, it must be diagnosed and treated, if at all possible.  If this cannot be done, the dog is less likely to have a favorable response to treatment.  Also, the dog might respond temporarily, but the infection will relapse at a later time (usually when ear medication is discontinued). 

What is the prognosis?

Nearly all ear infections that are properly diagnosed and treated can be cured.  However, if an underlying cause remains unidentified and untreated, the outcome will be less favorable.  A progress check may be needed before the process is completed, but we expect ultimate success. 

How important is it to treat an ear infection?

Dogs with ear infections are miserable.  Their ears are a source of constant pain resulting in head shaking and scratching.  However, that is not the only problem.  Head shaking and scratching can also cause broken blood vessels in the ear flap, requiring surgery, and chronic ear infections can penetrate the ear drum and result in an internal ear infection. 

My dog's ear canal is nearly closed.  Is that a problem?

Closing of the ear canal is another result of a chronic ear infection.  There are medications that can shrink the swollen tissues and open the canal in some dogs.  However, some cases will eventually require surgery.

What is the purpose of surgery?

The surgery for a closed ear canal is called a lateral ear resection.  Its purposes are to remove the vertical part of the ear canal and to remove swollen tissue from the horizontal canal.  Removing the vertical canal should be successful, but removal of large amounts of tissue from the horizontal canal is more difficult.  In some cases, the ear canal is surgically obliterated.  This solves the canal problem, but it leaves the dog deaf on that side.

What can be done if the ear canals are completely closed?

The most severe consequence of a chronic ear infection is total closure and hardening of the ear canal.  When this occurs, the lateral ear resection will no longer be helpful.  The appropriate surgery for this situation is an ear canal obliteration.  The entire ear canal is surgically removed.  Since severe scarring and calcification occur, this can be a lengthy surgical procedure requiring a skilled veterinary surgeon.

Is there anything I need to know about getting medication in the ear?

It is important to get the medication into the horizontal part of the ear canal.  Be aware that the dog's external ear canal is "L" shaped.  The vertical canal connects with the outside of the ear; the horizontal canal lies deeper in the canal and terminates at the eardrum.  The ear canal may be medicated by following these steps:

1)  Gently pull the ear flap straight up and hold it with one hand.

2)  Apply a small amount of medication into the vertical part of the ear canal while continuing to keep the ear flap elevated.  Hold this position long enough for the medication to run down to the turn between the vertical and horizontal canal.

3)  Put one finger in front of and at the base of the ear flap, and put your thumb behind and at the base.

4)  Massage the ear canal between your finger and thumb.  A squishing sound tells you that the medication has gone into the horizontal canal.

5)  Release the ear and let your dog shake its head.  If the medication contains a wax solvent, debris will be dissolved so it can be shaken out. 

6)  If another medication is to be used, apply it in the same manner.

7)  When all medications have been applied, clean the outer part of the ear canal and the inside of the ear flap with a cotton ball soaked with a small amount of rubbing (isopropyl) alcohol.  Do not use cotton tipped applicators to do this as they tend to push debris back into the vertical ear canal.

Now HEAR This!

I once had a pet owner complain that she had been treating her dog for what she thought were ear mites (a parasite found in the ear) for weeks and had not been successful at resolving the problem. Upon examination of her dog's ear canal, I found several pieces of spear grass embedded near the ear drum and gently extracted them. All the ear mite medication in the world would not have re-solved the problem.

To understand the dog's ear problems better, we must initially understand that the dog's ear canal is anatomically different than that of the human ear. Unlike the human ear, the dog's ear has two compartments. Beginning at the opening of the ear canal, the vertical canal travels downward towards the dog's jaw. Then it makes a 45 degree turn and travels horizontally towards the ear drum. This makes visualization and treatment of the entire canal more difficult. Also, as a rule, most breeds have a much longer ear canal than humans. These differences predispose the dog's ear to infection as well as make treatment more difficult.

Dogs with long, pendulous ears, such as Cocker Spaniels, Labrador Retrievers, Basset Hounds and Irish Setters, certainly are more predisposed to ear problems than those breeds with short, erect ears. As the ear folds, it covers the ear canal and prohibits air from entering and drying the canal. The result is a moist, warm ear canal that is a perfect environment for organisms to grow.

Parasitic Problems

Inflammation of the ear canal, or otitis externa, can be caused by a number of factors, such as parasites, microorganisms, foreign bodies, tumors, and underlying dermatological (skin) disease. Ear mites are parasites that often can cause otitis externa. However, the incidence is much lower than often thought. In my experience, less than 10 percent of all ear problems in dogs that I have treated are the result of ear mites. Ticks and fleas are other examples of parasites commonly found in canine ear canals.

Ear mites can be problematic, however. An elderly gentleman once explained that he thought his dog was "going crazy." He said his old setter would sleep by the fireplace. Suddenly it would jump up yelping and begin to run around the room in circles. After several minutes of hysterical commotion, the dog would lie down again and go back to sleep.

After pondering the situation, I examined the dog's ears and found a heavy infestation of ear mites. It appeared that as the heat from the fire warmed the dog's ear canals, the mites would became agitated and began to move around. As the old setter would run around the room, the ears would cool down and the mites would stop their activity. Then the dog would return to the fireside.

An important point to remember is that ear mites are parasites. Therefore, for your dog to have ear mites, it must have had direct contact with another pet infested with ear mites. So if your veterinarian diagnoses one animal in your house with ear mites, it is best to have all of your animals examined for possible infestations.

Dastardly Yeast Infections

The most common cause of canine ear problems that I see is caused by microorganisms, particularly yeasts. Malassezia pachydermatitis usually is the culprit, and it loves to proliferate in warm, moist environments such as the dog's ear canal.

Owners will notice the dog shaking its head or scratching at its ears. A good sniff near the ears usually verifies a problem, as most infectious otitis ears are quite pungent. Certain bacteria such as Staphylococci, Streptococci, E coli, and Pseudomonas spp also can cause infections in the dog's ear, and in many cases both bacteria and yeast are present. If the infection persists, the ear canal will become inflamed and often discharge a purulent exudate, a pussy substance.

Your veterinarian usually will take an ear swab and examine it under a microscope to determine the exact cause of the infection. This will enable a specific treatment plan to resolve the problem. Often, treatment will include flushing the ear canal with an antimicrobial solution and drying agent. An anti-inflammatory injection is then administered to reduce swelling and relieve the pain. The appropriate topical medication also will be dispensed for further treatment by the pet owner. Remember, all ear infections are not caused by the same microorganism; therefore, treatment without proper examination is strictly guessing.

As a pet owner, it is important to know that persistent or recurring ear infections in a dog commonly are manifestations of other concurring disease processes. Allergies and hypothyroidism are good examples. Systemic allergies often cause dermatitis and itching in the ear canal, which predispose self-trauma and subsequent ear infection. Hypothyroidism may manifest itself as increased thickness of the skin and continual release of exudate in the ear canal, which favors an environment for otitis externa.

Practicing Proper Ear Care

Proper ear care for the dog can often prevent recurring infection. Dogs with a history of ear disease require routine cleaning of the canals. I recommend plucking all hair that grows in the canal. Hair impedes air flow into the canal that tends to keep the canal dry. Common household tweezers or forceps work well and usually are well tolerated by the dog. Be careful not to grasp the skin of the canal. After hair removal, flush the ear canals with a commercial ear cleaner. These products can be found at most veterinarian clinics or pet shops. After flushing, gently massage the base of the ears to distribute the solution around the normal ear folds.

Most ear cleaners have several functions. They not only clean the ear canal but also have an agent for liquefying exudate, drying the ear canal, and changing the pH (acidity) in the canals. Most microorganisms prefer an environment that is alkaline; therefore, most ear preparations have an acid base. Frequency of treatment will vary among individuals, but once a week during the warm months is a good rule of thumb for those dogs that have had problems with infected ears. Also, any time your dog is bathed or enters the water, an ear cleaning solution should be administered immediately afterward. This preventative is similar to what humans do to ward off "swimmer's ear." Dogs without a history of ear problems may be treated with an ear cleanser after bathing.

It is not wise to use cotton tip applicators in the ear canal. This can be quite painful to the dog. Also, I don't recommend using alcohol in a dog's ear. Alcohol will dry the ear, but if there is inflammation or small scratches in the canal, the alcohol will burn and cause tremendous pain and further inflammation. If you must use a product from the shelf at home, use white vinegar diluted 50:50 with water.

Good preventative ear care can eliminate needless trips to your veterinarian and save a lot of discomfort for your dog. Watch your dog carefully for scratching at its ears or shaking its head. Have your groomer check for an ear problem each time you take your dog in, and at home take the time to check your dog's ears for redness, odor or the presence of exudate. If you determine there is a problem with your pet's ears, don't wait. Let your veterinarian do a thorough examination and direct specific treatment before the problem worsens.

Canine Ear Checklist

You may need to take your dog to the vet for a thorough examination if it:

• Shakes its head or scratches its ears
• Lives with other pets with parasitic infestations
• Exudes a pungent odor from its ears
• Has long, pendulous ears
• Lives in a humid environment
• Loves to swim or bathe
• Has a history of recurring ear infections

Dr. Thomas has been a practicing veterinarian in Lewisville, Texas, for 15 years. He has written numerous articles about pet health published in several magazines and newspapers. This article was published in Dog World magazine, November 1996 edition.

CANINE EAR INFECTIONS

How common are ear infections in dogs?

Infections of the external ear canal (outer ear) by bacteria or yeast, are one of the most common types of infections seen in dogs.  We call this otitis externa. 

Some breeds, such as Cocker Spaniels and Miniature Poodles, seem more prone to ear infections, but they may occur in any breed.

What are the symptoms of an ear infection?

A dog with an ear infection is uncomfortable; its ear canals are sensitive.  It shakes its head trying to get the debris and fluid out, and it scratches its ears.  The ears often become red and inflamed and develop an offensive odor.  A black or yellowish discharge commonly occurs.

Don't these symptoms usually suggest ear mites?

Ear mites can cause several of these symptoms, including a black discharge, scratching, and head shaking.  However, ear mite infections generally occur most commonly in puppies.  Ear mites in adult dogs occur most frequently after a puppy carrying mites is introduced into the household.  Sometimes, ear mites will create an environment within the ear canal which leads to a secondary infection with bacteria and yeast (fungus).  By the time the dog is presented to the veterinarian, the mites may be gone, but a significant ear infection remains.  

Since these symptoms are similar and usually mean an infection, can I just come by and get some medication?

There are several kinds of bacteria and at least one type of fungus which might cause an ear infection.  Without knowing the kind of infection present, we do not know which drug to use.  In some cases, the ear infection may be caused by a foreign body or tumor in the ear canal.  Treatment with medication alone will not resolve these problems.  Also, the dog must be examined to be sure that the eardrum is intact.  Administration of certain medications can result in loss of hearing if the eardrum is ruptured.  This determination is made by the veterinarian and must be done in the office.

How do you find out which drug to use?

First, the ear canal is examined with an otoscope, an instrument that provides magnification and light.  This permits a good view of the ear canal.  This examination allows us to determine whether the eardrum is intact and if there is any foreign material in the canal.  When a dog is in extreme pain and refuses to allow the examination, it must sometimes be completed under sedation or anesthesia. 

The next step is to examine a sample of the material from the ear canal to determine which organism is causing the infection.  This is called cytology.  Examination of that material under the microscope is very important in helping the veterinarian choose the right medication to treat the inflamed ear canal.

How are ear infections treated?

The results of the otoscopic examination and cytology tell us what to do.  If there is a foreign body or tick lodged in the ear canal, the dog is sedated so that it can be removed.  As stated previously, some dogs have such a heavy buildup of debris that sedation is needed to cleanse the canal and examine it completely. 

Cytologic study of debris from the ear canal dictates which drug to use.  Sometimes, it reveals the presence of more than one type of infection (i.e., a bacterium and a fungus, or two kinds of bacteria); this situation usually requires the use of multiple medications or a broad-spectrum medication.

An important part of the evaluation of the patient is the identification of underlying disease.  Many dogs with chronic or recurrent ear infections have allergy problems or low thyroid function (hypothyroidism).  If underlying disease is found, it must be diagnosed and treated, if at all possible.  If this cannot be done, the dog is less likely to have a favorable response to treatment.  Also, the dog might respond temporarily, but the infection will relapse at a later time (usually when ear medication is discontinued). 

What is the prognosis?

Nearly all ear infections that are properly diagnosed and treated can be cured.  However, if an underlying cause remains unidentified and untreated, the outcome will be less favorable.  A progress check may be needed before the process is completed, but we expect ultimate success. 

How important is it to treat an ear infection?

Dogs with ear infections are miserable.  Their ears are a source of constant pain resulting in head shaking and scratching.  However, that is not the only problem.  Head shaking and scratching can also cause broken blood vessels in the ear flap, requiring surgery, and chronic ear infections can penetrate the ear drum and result in an internal ear infection. 

My dog's ear canal is nearly closed.  Is that a problem?

Closing of the ear canal is another result of a chronic ear infection.  There are medications that can shrink the swollen tissues and open the canal in some dogs.  However, some cases will eventually require surgery.

What is the purpose of surgery?

The surgery for a closed ear canal is called a lateral ear resection.  Its purposes are to remove the vertical part of the ear canal and to remove swollen tissue from the horizontal canal.  Removing the vertical canal should be successful, but removal of large amounts of tissue from the horizontal canal is more difficult.  In some cases, the ear canal is surgically obliterated.  This solves the canal problem, but it leaves the dog deaf on that side.

What can be done if the ear canals are completely closed?

The most severe consequence of a chronic ear infection is total closure and hardening of the ear canal.  When this occurs, the lateral ear resection will no longer be helpful.  The appropriate surgery for this situation is an ear canal obliteration.  The entire ear canal is surgically removed.  Since severe scarring and calcification occur, this can be a lengthy surgical procedure requiring a skilled veterinary surgeon.

Is there anything I need to know about getting medication in the ear?

It is important to get the medication into the horizontal part of the ear canal.  Be aware that the dog's external ear canal is "L" shaped.  The vertical canal connects with the outside of the ear; the horizontal canal lies deeper in the canal and terminates at the eardrum.  The ear canal may be medicated by following these steps:

1)  Gently pull the ear flap straight up and hold it with one hand.

2)  Apply a small amount of medication into the vertical part of the ear canal while continuing to keep the ear flap elevated.  Hold this position long enough for the medication to run down to the turn between the vertical and horizontal canal.

3)  Put one finger in front of and at the base of the ear flap, and put your thumb behind and at the base.

4)  Massage the ear canal between your finger and thumb.  A squishing sound tells you that the medication has gone into the horizontal canal.

5)  Release the ear and let your dog shake its head.  If the medication contains a wax solvent, debris will be dissolved so it can be shaken out. 

6)  If another medication is to be used, apply it in the same manner.

7)  When all medications have been applied, clean the outer part of the ear canal and the inside of the ear flap with a cotton ball soaked with a small amount of rubbing (isopropyl) alcohol.  Do not use cotton tipped applicators to do this as they tend to push debris back into the vertical ear canal.