Clinical Ear Disease In Dogs, Antibiotics For Dog Ear Infection

History

The most common and earliest indication of otitis externa is itching (aural pruritus) and shaking of the head. As the otitis progresses, mild to marked exudate may develop. This is the most common point for the client to bring the pet to this animal care facility. In the history, it is important to find out if the client has been medicating the ears. Many clients will have numerous ear medications that they have tried that may or may not have been effective. Usually a client will have tried something prior to bringing the pet in. It is important to ask if a pet has had an ear infection before. Itchiness to the ears is the first sign seen in ear mite infections, foreign material and allergies. In most cases of allergic otitis, the ear pinna will be red but the ear canal will be normal. Many allergic otitis cases are seasonal in occurrence. Seborrhea, hormonal disorders, immune system diseases and glandular disorders commonly have an excessive ceruminous or scaly discharge. (Ceruminous discharge is yellowish to golden color, waxy and oily, with or without odor.) The history should include exposure to water, foreign bodies, and parasites. Does the client or groomer remove hair? Was the hair recently plucked? Have powders or other medications been used? If the ear was treated before, what was the response? Are other body locations affected by skin disease? Head shyness, Horners syndrome (paralysis of the third and lower eyelids), facial nerve paralysis (the facial nerve wraps around the ear canal and causes the face to loose feeling when paralyzed), head tilt, ataxia (falling down while walking), or pain while eating may be noted in dogs with severe otitis media or otitis interna that is associated with otitis externa.

Examination of The Ear for Disease

Otitis externa ears will have redness (erythema), swelling, scaling, crusting, hair loss (alopecia), broken hairs, head shyness, and pain. An aural hematoma may be a sign of otitis externa. Palpation of a thickened ear canal, hard, calcified ear canal, or a soft ear canal that makes squishy sounds when squeezed are signs to be noted. Presence of allergic disease on the rest of the body, feet, elbows, face, or rump is noted.

Otoscopic Examination

The otoscope cones should be kept clean and soaked in Nolvasan® or other disinfectant between patients to prevent transmission of disease. The examination of the ear canal should be done on the good ear first, then the bad ear. If the ear is very swollen and painful, anesthesia may be necessary. If the ear is so swollen that it is obvious that examination will be impossible, even with anesthesia, medications are used to reduce the inflammation for five days, then anesthesia is used to examine the ear. Notes should be placed in the file as to the findings of the examination. The type of discharge may help to indicate the type of disease:

Black, crumbly discharges is very typical of ear mites.
Dark brown, creamy, sweet-smelling discharge with itching is typical for yeast infection.
Reddened earflap with scant discharge is typical for allergies.
Golden to brown, creamy discharge (ceruminous) is typical of chronic, allergic or seborrhea or hormonal problems.
Yellow pus (purulent) discharge is typical of bacterial infection in severe chronic infections.
Red, painful, moist, ulcerated ear canals with a thin layer of whitish ooze are typical for acute moisture related to bacterial infection secondary to bathing or “swimmers ear”.

The interpretation of the normalcy of the eardrum (tympanic membrane) is difficult to assess. The membrane becomes opaque, gray, or brown due to disease and thickens, losing its characteristic fish-scale appearance.

Diagnosis of Ear Disease

A diagnosis of otitis externa is easy to make based on history and physical examination. The diagnosis of otitis media is much more difficult to make. Radiographs are sometimes indicated if disease of the middle ear is suspected. The presence of a tympanic membrane can be determined under anesthesia with a soft, red, rubber feeding tube. It is placed through the otoscope under direct visualization. If the tip of the tube stops its progression down the ear canal with the tip still visible, then the eardrum is still present. If the tip of the tube disappears, then the eardrum is gone and the tube has passed into the middle ear.

Ear Swab Stain

This is a very important diagnostic step that all patients with ear disease should have performed on them prior to medication administration. The sample should be taken with cotton-tipped applicators.

The swab is placed into the ear canal and twirled to acquire a representative sample of the exudate from the ear canal.
The material on the swab is gently rolled (not smeared) onto a microscope slide.
The slide is labeled on the same side as the sample.
The slide is passed through a flame three to four times to “heat-fix” the material on the slide. This step is important because it melts the wax from the cells, yeast and bacteria allowing stain uptake.
The slide is cleaned of soot with a tissue and dipped into the light blue fixative solution of the Diff-Quick® stain five times, followed by the red stain for five dips, followed by the dark blue stain for five dips.
The slide is then gently rinsed under a trickle of tap water and allowed to drip dry on a paper towel.
The dry slide is examined under low and high power, as well as oil immersion lenses, for cytological evidence of the disease process.

Examination of the ear swab will identify any cocci and rod bacteria, yeast cells, inflammatory cells and the epithelial cells that line the ear canal. Yeast can be seen in up to thirty-nine percent of the normal dogs. Our rule of thumb is that unless there are more than five yeast cells per high power field, then yeast is not the primary cause of the illness. The presence of neutrophils suggests that inflammatory by-products are being released into the ear and an ear flushing is needed to remove these toxins.

Culture and Sensitivity

Culture and sensitivity is a test performed by an outside laboratory. We send the laboratory a sample of ear exudate. They grow the bacteria that are present in the ear and then test them for which antibiotic will kill these bacteria. This test is not necessary unless an ear swab shows neutrophils or other inflammatory cells in the presence of bacteria. The primary indication of a culture and sensitivity is in chronic ear infections of the middle ear in which systemic drugs are planned.

Therapy for Ear Disease

The first and most important part of therapy is an accurate diagnosis. Many clients will ask for ear medications without wanting to have the pet examined. Veterinarians at other clinics may have prescribed medications for them in the past without a diagnosis. It is rarely acceptable to look into an ear canal with an otoscope and decide the therapeutic recommendations. Ear disease is a part of every day veterinary practice with one in five patients suffering from some form of this malady. This condition is too important to the veterinary practice to take it casually. Veterinary clients rarely take ear disease casually and neither should you. Proper management of ear disease can substantially affect the entire veterinary practice. Diagnostic and therapeutic protocols for each of the common presentations of ear disease are given to aid in this process. By following these protocols, the chances of a cure to the ear problem on the first attempt are more likely. This early success requires early, aggressive diagnostic and therapeutic action but will result in a healthier pet, a happier client and a better veterinary practice.

Many clients upon presentation will assume that their pet has ear mites and needs ear mite medications. These clients may be upset when you do not immediately comply with their wishes. These clients need to understand the complexities of managing ear canal disease and all the possible causes of their pet’s problem.

Treatment of ear disease relies on the client’s ability and compliance with medication instructions. A client with a fractious, painful dog will not likely medicate the ears. Frequent, no-charge rechecks are made to monitor response to therapy. We try to let the client know what is expected of them for treatment and that it does not cost them extra to have us re-evaluate their efforts.

Another important aspect of therapy involves cleaning of the ear canal. Many times this requires sedation or some form of restraint. For cases with minimal restraint and an intact eardrum, proparacaine 0.5% can be used to deaden the ear canal. (This is a solution called “Ophthaine®” for eye exams.)

Cleaning of The Ear Canal

This step cannot be skipped if the ear treatment is to be successful. If middle ear disease is present, then cleaning of the tympanic bulla is also needed. Cleaning is valuable for several reasons:

Promotes effective therapy.
Allows examination of the ear canal that may have been blocked by the exudate.
Reduces cellular toxins in the ear that cause inflammation.
Removes foreign bodies.
Removes wax and debris which can inactivate medications.
Removes wax and debris that protect bacteria and yeast from medications.

Cleaning Agents (Ceruminolytic Agents)

These chemicals break down the wax so that it can be flushed from the ear canal. The most effective ceruminolytic agent that we have found is carbamide peroxide. This product releases oxygen when it is used resulting in a foaming reaction that helps dislodge particles from the ear canal. Dioctyl sodium sulfosuccinate (DSS) is also a commonly used ear cleaning agent that does not foam but will effectively break the ear wax apart so that it can be flushed out. CLEAR-X® contains both DSS and carbamide peroxide and has been effectively used to clean ears with minimal adverse reactions. EPI-OTIC is an extremely well-tolerated, highly-efficient ear cleanser. Salicylic Acid associated with the surfactant/wax solvent system facilitates the removal of cellular debris and excessive wax as weal as drying the ear canal. PCMX in association with EDTA helps to restore the microbial balance in the ear canal, while the inclusion of monosaccharide has a soothing effect as well as limiting the binding of bacteria to the skin surface.

The ear cleaner should be applied 5 to 15 minutes prior to ear flushing. Gentle massage increases the effectiveness. If the ear flush is to be done as an outpatient with the client present, we generally have the client massage the ear canals while the doctor or technician prepares the sedation and other equipment for the ear flush. A ruptured eardrum does not preclude the use of these products but it does mandate that thorough flushing be done to leave no trace of the medication in the ear after cleaning.

Cleaning Techniques

The first principle of medicine is “do not harm” and this applies to ear disease in general and therapeutic flushing in particular. Flushing is necessary if therapeutic success is the goal, yet ear flushing can cause many problems if not done with care and consideration for the delicate structures of the ear. Care is taken to avoid damage to the eardrum if it is intact and care is taken to avoid damage to the delicate structures of the middle ear if the eardrum is not intact.

If the pet is sedated, an appropriate anesthesia release form is signed by the owner of the pet.
An ear swab is taken for cytological examination as described earlier.
The ceruminolytic agent is placed in the ear canal and massaged for five to fifteen minutes.
A warm solution of Betadine® or Nolvasan® diluted 10:1 with tap water is made (resulting in a tea-colored solution when Betadine® is used). Use Betadine® if the eardrum is suspected to be ruptured because Nolvasan® is toxic to the auditory nerve.
A rubber-bulb syringe is used to flush the ear canal. The bulb syringe is placed with the tip along one side of the ear canal as to allow water to escape while flushing. This allows back flow and prevents excessive pressure to the eardrum. If water drips from the nose of the pet while flushing is done, then the eardrum is ruptured.
The syringe is used to aspirate the cleaning solution and flush into the ear canal several times.
The ear is then aspirated free of water for examination. The eardrum is tested for patency (to detect a hole) with a soft, red, rubber tube placed through the otoscope speculum. While observing the tip of the tube, pass it into the ear canal. If the tip of the tube disappears, it is in the middle ear and the eardrum is ruptured.
Additional application of the ceruminolytic solution may be necessary if there is still wax or debris blocking the eardrum.
A soft, red, rubber feeding tube and syringe is used to flush the debris from the middle ear. Flushing solution in, and aspirating it out, is very effective.
Ear curettes or cerumin loops are used through the otoscope to retrieve large chunks that cannot be flushed out or to scrape the middle ear free of lodged debris.
Alligator forceps can also be used to remove hair, foreign objects and plugs of debris if necessary.
The ear canal is suctioned and flushed with water as a final rinse, then suctioned and dried gently with cotton swabs.

Other instruments have been used in the past such as Water-Piks® and Frazier® suction apparatus as used in humans, but these become contaminated and are difficult to keep sterile from patient to patient.

Drying Agents

After the ear is clean, drying agents and other medications may be placed in the ear canal. Most contain isopropyl alcohol as well as one or more of the following: boric acid, benzoic acid, sulfur, or silicone dioxide. CLEAR-X® Treatment Dryer is excellent for this purpose. Other products include , and Epi-Otic®. These products can also be used at home for “swimmers ear” and as an ear deodorizer.

Home Ear Flushing

Many dogs have chronic skin disorders such as seborrhea, bacterial pyoderma, Demodex and so on. Most of these pets also have chronic otitis externa as well. The client is usually instructed to wash the pet twice weekly which can put the ears at greater risk of infection. These pets benefit from ear flushing as a part of their overall care. Therefore, dogs with chronic allergies and seborrhea that require frequent bathing should have their ears flushed by the owners at the same time. Clear-X® is placed in the ear while bathing and allowed to soak. After the pet is lathered, the ears are flushed with a 50/50 mixture of white vinegar and water. Detergents should not be used for home flushing as rinsing may not be complete and irritation will result. The debris from the ears is rinsed away when the shampoo for the coat is rinsed. At the end of the bath, the ears are given a final rinse and a drying solution is applied. Do not encourage cotton swabs or cotton balls except on the outer portions of the ear.

Ear cleaners are used for ears that are not clinically showing problems. The ears might have been waxy or dirty on examination and a preventative measure is indicated to reduce inflammation and wax production. They might be helpful with ears with a mild odor, but they are not for treatment of clinical otitis externa. These cleaners include Epi-Otic.

Medications used for Ear Disease

It is the general rule for ear medications to be formulated to control multiple causes of ear disease. Almost all ear infection medications for dogs contain an anti-inflammatory medication, an anti-fungal medication and an anti-bacterial medication. This rationale tempts us to use these products in the absence of an accurate diagnosis. Using medications that are formulated for each case would treat ear disease more effectively.

Corticosteroids

These medications are “steroids” and have potent anti-inflammatory effects. They reduce itching and decrease exudation and swelling. These compounds also cause atrophy of wax producing glands, reduce scar tissue formation and proliferative changes associated with hyperplastic otitis externa. Therefore, most ear treatments contain glucocorticoid or steroids. It has recently been shown, however, that products that contain triamcinolone acetonide (Panalog®) and dexamethasone (Tresaderm®) are absorbed internally and can cause adrenal suppression if given on a chronic basis. Treated dogs had liver enzyme elevation and reduced adrenal function. Long-term glucocorticoid therapy is better achieved with hydrocortisone, which is less likely to produce these effects. Powerful steroid action may be necessary for a short period in allergic diseases and Synotic® contains a very potent steroid for this purpose but it should not be used on a long-term basis. Systemic corticosteroids are also used in injectable form to reduce inflammation initially so the ear is easier to treat.

Antibiotics

The use of other antibiotics for dogs that are not already contained in proprietary ear treatments can be very effective in the therapy of ear disease. Mixing ear medications for each patient based on a good diagnostic work-up is more accurate. Systemic (oral or injectable) antibiotics are also useful in ear disease and include Primor®, trimethoprim-sulfa, cephalexin, and Baytril®.

Anti-fungal

Otomax® and Mometamax® contain clotrimazole which is effective against yeast. Older combination ear medications such as Panalog® and Tresaderm® contain nystatin, which is reported to kill yeast (Malassezia), yet these medications do not seem to be as effective as claimed. We can also use human Lotrimin to mix with our ear preparations for anti-yeast activity that works well. Nolvasan® also helps kill both bacteria and yeast and is commonly used. Ketoconazole is a systemic medication that may be used orally at (5-10 mg/kg q 12-24 h) for yeast infections that are present in the middle ear. There are newer anti-fungal preparations used for vaginal yeast infections in women that can also be used for resistant yeast infections in pets.

Parasiticidal

Ear mite disease is best controlled with Acarex® (ivermectin 1%). Do not use the other common ear mite medications because they tend to be irritating and do not kill other secondary infections that may be present. The treatment schedule for ear mites involves applying Acarex® – drops in each ear; then repeat in two weeks. At the beginning and end of each treatment period flea baths are done to kill mites that may be on the external coat.

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Clinical Ear Disease in Dogs