External Ear Infection (External Otitis) in Dogs
External otitis is an infection of the ear canal. The ear canals are delicate structures and are easily infected. Eighty percent of infections occur in breeds with long, dropped ears. This is a function of lack of air circulation; open, erect ears dry out more easily than dropped ears and therefore provide less favorable conditions for bacterial growth.
Many factors contribute to the development of external otitis. Some breeds (such as the Chinese Shar-Pei) are predisposed because of narrow or stenotic ear canals. Other breeds may be predisposed because they have an abundance of hair that blocks the circulation of air. Many dogs with allergic skin diseases, particularly canine atopy and food hypersensitivity dermatitis, are predisposed to ear infections as part of the generalized skin response. Similarly, dogs with primary and secondary seborrhea often have ear canal involvement characterized by a buildup of yellowish oily wax that provides an excellent medium for bacterial growth. Foreign bodies such as grass seeds and foxtails, and growths in the ear canal, are other predisposing causes. Ear mites can precede bacterial otitis.
Iatrogenic causes of infection include using cotton-tipped applicators to clean the deep recesses of the ears, allowing water to get into the ears during bathing, excessive and improper cleaning of the ears, and a grooming routine that calls for plucking or clipping hair in the external ear canals.
Signs of external otitis are head-shaking and scratching and rubbing at the affected ear. The ear is painful. The dog often tilts or carries her head down on the painful side and cries or whines when the ear is touched. An examination reveals redness and swelling of the skin folds. There usually is a waxy or purulent discharge with a bad odor. Hearing can be affected.
Ceruminous otitis occurs with primary seborrhea. There is an extensive buildup of oily, yellowish wax in the ear canals, which provides an excellent medium for bacteria and yeast. Treatment is directed toward control of the seborrhea. Regularly cleaning the ear canal may be necessary until this problem is controlled.
Bacterial otitis, in its acute form, is usually caused by Staphylococci. The discharge is moist and light brown. Chronic infections usually are caused by Proteus or Pseudomonas bacteria. The discharge is generally yellow or green, although there are exceptions. More than one species of bacteria may be involved, which complicates antibiotic treatment.
Yeast or fungal infections may follow antibiotic treatment of bacterial otitis. Yeast infections also occur commonly in dogs suffering from atopic dermatitis, food hypersensitive dermatitis, and seborrheic skin diseases. A brown, waxy discharge with a rancid odor is sometimes seen, or a very red, inflamed, moist ear with minimal discharge. These infections tend to persist until the underlying disease is controlled.
Treatment: Because external ear infections often progress to the middle ear, it is extremely important to take your dog to a veterinarian as soon as you suspect an ear problem. Veterinary examination of the deep portions of the ear canal using an otoscope is the most important step in making the diagnosis and planning the treatment.
Otoscopic examination cannot be attempted if the canal is dirty and filled with wax and purulent debris. First, the ear must be cleaned. This may require sedation or anesthesia.
It is essential to know whether the eardrums are intact, since it is not safe to medicate the ears with certain medications if the drums are perforated. It is also important to be sure the problem is not caused by a foreign body or tumor. A specimen of waxy material is taken with a cotton-tipped applicator, rolled onto a glass slide, and examined under the microscope looking for bacteria, yeast, ear mites, and any other predisposing factors. Your veterinarian may need to do a culture and sensitivity test on the discharge, especially if this is a recurring problem. A correct and definite diagnosis of the cause helps to determine the most appropriate and best treatment.
The first step in treatment is to clean and dry the ear canals. This requires ear-cleaning solutions, a syringe, an ear curette, and cotton balls. It should be done at the veterinary clinic. Cleaning creates a less favorable environment for bacteria to grow and allows the medication to treat the surface of the ear canal. Medication can't penetrate the debris in a dirty ear.
Follow-up care at home involves medicating the ear with a preparation prescribed by your veterinarian. If the ear continues to produce wax and exudate, a cleansing and flushing solution such as Oti-Clens or Epi-Otic, and/or a drying solution such as ClearX or Panodry, may be recommended. These solutions are used immediately before medicating the ear with an antibiotic or antifungal medication. Topical and/or oral corticosteroids may be recommended to control pain and decrease swelling and inflammation. Some dogs may need oral antibiotics as well for severe infections.
Bacterial infections that continue to progress produce thickening and narrowing of the ear canal and chronic pain. These ears are difficult to clean and treat. Asa last resort, your veterinarian may advise a surgical procedure called an ear resection that reestablishes air circulation and promotes drainage.
This article is excerpted from “Dog Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.
Copyright © 2007 by Howell Book House. All rights reserved.
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