Ear Canal Infection (Bacterial Otitis Externa) in Cats
Bacterial infections in the ear canal are frequently caused by scratches to the skin or cat bites. Some begin in an ear canal that contains excessive amounts of wax, cellular debris, or foreign material. Ear mite infections are often the cause of bacterial otitis.
Signs of an infected ear canal are shaking the head, scratching at the affected ear, and an unpleasant odor. The cat may tilt or carry her head down on the painful side and exhibit tenderness when the ear is touched. Examination reveals redness and swelling of the skin folds of the ear canal. There may be an excess amount of wax or a purulent discharge. There is often an unpleasant odor associated with the discharge.
An otoscope is needed to examine the deeper portions of the ear canal and look for a foreign body or other cause of chronic infection. This is best left to a qualified professional-your veterinarian or a veterinary technician.
Bacterial infections that progress over a long period produce thickening and reddening of the ear canal with considerable discomfort and pain. Treatment is prolonged. Inflammatory polyps and tumorlike masses may develop and block the ear passages. Surgery then becomes necessary to open the ear and promote drainage.
Treatment: The first step is to determine the cause. Mild cases-those without excessive discharge but perhaps associated with a dirty ear or the buildup of wax-may be treated at home after they have been diagnosed by a veterinarian.
Remove crusts and serum with a cotton ball soaked in an ear-cleaning solution obtained from your veterinarian, being careful not to push the debris deeper into the canal. If there is a buildup of wax, instill a special wax-dissolving agent to soften the debris and make it easier to remove. Afterward, dry the ear canals with a cloth or cotton ball and apply an antibiotic ear medication.
If the ear is extremely painful, you may need to leave your cat at the veterinary clinic for sedation and a thorough cleaning. A swab of the discharge may be examined under the microscope to look for the cause of the problem. Also, your veterinarian may take a sample for a culture and sensitivity test, especially if your cat has recurrent infections, to determine the best choice of antibiotic therapy. Some cats will need oral antibiotics as well as topical ones.
Clip the cat's nails to minimize injuries from scratching at the ear.
Yeast of Fungal Otitis Externa
The prolonged use of topical antibiotics alters the natural bacterial flora in the ear canal, which improves conditions for the growth of yeast and fungi. A yeast otitis may therefore develop as a secondary problem in a cat with a long-standing bacterial or ear mite infection, or a food allergy. Malassezia pachydermatis is the most common culprit, including in cases of otitis related to food allergies and atopy.
Signs and symptoms of a yeast infection are not nearly as pronounced as the infection caused by bacteria. The ear is inflamed and painful, but less so. Sometimes the ear will simply be red and moist in appearance. The discharge is dark and waxy but not purulent. A rancid odor is characteristic.
Yeast and fungus infections tend to recur, and treatment is often prolonged.
Treatment: Your veterinarian may want to do a swab to look at cells from the ear to determine the exact cause of the problem and to determine whether the problem has cleared, because stopping treatment beforehand (not just at the remission of signs) frequently results in relapse. Topical medications may need to be supplemented with oral medications.
Treatment is similar to the treatment for bacterial otitis, except that an antifungal agent (such as nystatin or thiabendazole) is used. Panolog, which contains nystatin, is effective against the yeast Candida albicans. Tresaderm, which contains thiabendazole, is effective against Candida and most other common yeast invaders. Miconazole solutions are commonly prescribed as well.
This article is excerpted from “ Cat Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.
Copyright © 2008 by Delbert Carlson, DVM, and James M. Giffin, MD. All rights reserved.