What is otitis?
Otitis externa is more commonly known as an outer ear infection. Infectious agents are most commonly yeast (Malassezia pachydermatis) and bacteria (e.g. Strep. intermedius, Staph. aureus) Occasionally, ear mites can also be present.
Infections lead to inflammation of the ear canal (leading to stenosis (closure of canal) and itchiness. Dogs will often shake their heads due to itch.
Infections are often secondary to a primary cause such as allergies (commonly food) and predisposing factors such as pendulous ears and chronic moisture.
Clinical signs are indicative of infection. Otoscopic examination will reveal the degree of inflammation and whether the eardrum has been affected.
Ear cytology via swab under the microscope will show the type of organisms affecting the ear so that treatment can be tailored. Culture and sensitivity may be required for chronic infections.
Determining the underlying cause is most important to prevent recurrence. Elimination diets will determine if food allergy is related to chronic cases. Treatment of environmental allergies involve oral steroids, immune modulating drugs such as cyclosporine and adjunct treatments with antihistamines and fatty acids
Topical treatment containing steroids, antibiotics and antifungals, is the mainstay of treating infections as oral antibiotics and antifungals do not penetrate the ear canal very well.
Oral steroids may be prescribed to reduce inflammation and stenosis to allow drops to be administered.
Severe cases may require surgical ear flush under general anaesthetic.
As a last resort treatment, ear resection surgery may be opted for:
Lateral ear resection involves surgical removal of part of the outer ear canal, particularly when calcification (hardening) has occurred and the above therapies are no longer effective.