Chronic Ear Problems in Dogs
Dr. Rosanna Marsalla
Take a complete history that includes information concerning the age of onset, progression of the disease, and response to previous treatments.
The identification of the underlying disease responsible for the chronic ear disease is of crucial importance. In order to do this it is important for your veterinarian to:
Perform a thorough physical examination of the ears to detect the presence and condition of tympanic membrane, the severity of changes in the ear canal, and also the rest of the body to detect signs of concurrent skin or internal disease
Examine the ear discharge under the microscope to identify the organisms that are perpetuating the infection. Bacterial culture may be necessary in cases that have been treated by numerous drugs with only moderate improvement, because some of the bacteria tend to become rapidly resistant to commonly used antibiotics.
Treat the secondary infections aggressively. Antibiotics and antifungal drugs may be prescribed for extended periods of time, up to two months, in cases in which the infection has progressed in the deep part of the ear canal (otitis media). This happens in over 80 percent of cases of animals with chronic ear disease.
Thoroughly clean the ear canals. Topical therapy is vitally important for successful management of otitis. Ear flushing under sedation or general anesthesia is required in most cases to remove the discharge that is present in the deep part of the ear (bulla). Failure to remove this material will result in poor response to treatment and relapse of infection as soon as therapy is discontinued. Wax, oil, and cellular debris may be irritating, prevent medication from contacting the canal epithelium, and produce a favorable environment for microorganisms to proliferate and inactivate certain antibiotics.
Regular cleaning at home is an important part of the therapy. Several products can be used.
A mixture of vinegar and water (1/10) is a good degreasing solution to remove wax (cerumen) and dry the excessive moisture in the ear canal. The liquid should be applied gently in the canal, the ear massaged to allow breakage of the cerumen and cotton balls used to remove the cerumen and wipe out the excess liquid. Extreme care should be used when mechanically cleaning the ears. The use of cotton applicators should be avoided or limited as they may cause rupture of the tympanic membrane. Also powders should not be applied in the canal as they build up, predisposing the ears to the development of secondary infections.
Several products are available on the market and they should be used as directed by a veterinarian as some of them may interfere with the efficacy of the topical medications. These products are usually classified as either ceruminolytic or drying agents. Gentle massage improves their effect. Most of these products are contraindicated with a ruptured ear drum. However, frequently the condition of the ear drum cannot be determined until after the canal has been cleaned. In those cases the probability of ear toxicity may be decreased by flushing with water after the application of such agents.
Inhalant allergy is extremely common in dogs and is the most common underlying cause for recurrent otitis externa. Clinical signs are initially seasonal. Progressive worsening with time is also typical. At least 50 percent of these dogs have bilateral otitis externa. In up to 5 percent of cases, otitis may be the only complaint. These dogs tend to have itchy feet, itchy face and itchy ears. They are predisposed to secondary skin and ear infections that tend to recur after treatment unless the underlying allergy is well controlled.
Food allergy. Over 20 percent of these cases start with just otitis externa and ear disease is present in 80 percent of the cases. It should be considered as a top differential for otitis externa in any dog less than one year of age. Food allergy, however, can occur at any age and may mimic clinical signs of inhalant allergy. These animals tend to have recurrent skin and ear infections unless the underlying allergy is identified and addressed.
Foreign bodies. Plant material (fox tails) dirt, sand, impacted wax, loose hair and dried medications are frequently responsible for ear infections. In most cases this is a unilateral otitis, which means it only affects one ear.
Diseases of keratinization, such as primary seborrhea of cocker spaniels. Follicular casts and scales are found on physical exam and secondary skin infections occur commonly as the excessive amount of lipids is an optimal medium for bacteria and yeast to proliferate.
Endocrine disorders. Hypothyroidism and Cushing's disease are the most common endocrine diseases that can cause otitis externa. If a middle-aged dog keeps relapsing with otitis externa and is not itchy, then endocrine disease should be considered as a possible underlying cause.
The ear mite (Otodectes cynotis). In dogs, the incidence is controversial but most veterinarians agree that it is responsible for 5 to 10 percent of cases. In recurrent cases it is possible that others in contact with animals can act as asymptomatic carriers. It is hypothesized that hypersensitivity may induce severe inflammation that is sometimes seen in some cases, especially when few or no mites are found.