Ear infections are one of the most common reasons why dogs and less frequently cats are brought to the veterinarian. Ear infections, also called otitis, can be divided into three different categories: otitis externa, media and interna, which refer to infection of the external, middle and inner parts of the ear respectively. Bacteria, yeast, and mites are the organisms that are most typically involved in these infections, but in many cases, an underlying disorder such as an allergy or anatomic abnormality plays a large role in the development of the condition.
Dog's with otitis externa, which is the most common form of ear infection, scratch their ears and shake their heads and often have red skin and discharge around the openings to their ear canals. Most cases of otitis media develop because infection of the outer ear extends through the eardrum and into the middle ear. Symptoms are similar to those observed with otitis externa but may also include neurologic abnormalities affecting various parts of the face. If the infection moves even deeper into the ear, otitis interna develops, and the animal may develop a head tilt, circling, abnormal eye movements and difficulty walking. One or both ears may be involved in all three forms of otitis. A veterinarian will diagnose and differentiate between otitis externa, media and interna by observing the animal's symptoms, examining the ears with an otoscope and sometimes taking x-rays of the skull. To determine which microorganisms are involved, the veterinarian will usually take a small sample of the discharge from the ear and examine it under a microscope.
Treatment for ear infections includes cleaning out the affected ear(s), topical and/or systemic medications that kill bacteria, yeast or mites, and sometimes corticosteroids to relieve itching and inflammation. When the deeper structures of the ears are involved, surgery to drain infected material or the long-term use of oral antibiotics may be necessary. Otitis often returns after treatment stops unless the underlying conditions that promoted the development of the infection are also dealt with.
Written by: Jennifer Coates, DVM
Last reviewed: October 2, 2008