Infections of the external ear canal or outer ear caused by bacteria and yeast are more common in dogs than cats. Outer ear infections are called otitis externa. The most common cause of feline otitis externa is ear mite infestation.
What are the clinical signs of an ear infection?
Ear infections cause pain and discomfort, and the ear canals are sensitive. Many cats will shake their head and scratch their ears, attempting to remove the debris and fluid from the ear canal. The ears often become red and inflamed and may develop an offensive odor. A black, brown, or yellow discharge is commonly observed.
Don't these signs usually suggest ear mites?
Ear mites can cause several signs, including a black discharge, scratching, and head shaking. However, ear mite infections generally occur in kittens and outdoor cats. Ear mites in adult cats occur most frequently after a kitten with ear mites is introduced into the household.
Sometimes, ear mites will create an environment within the ear canal that promotes the development of secondary infection with bacteria or yeast. By the time the cat is presented to the veterinarian, the mites may be gone, but a serious ear infection remains.
"Sometimes, ear mites will create an environment within the ear canal that promotes the development of secondary infection with bacteria or yeast."
Since these symptoms are similar, can I just buy some ear drops?
No, careful diagnosis of the exact cause of the problem is necessary to enable the selection of appropriate treatment. Several kinds of bacteria and fungi may also cause an ear infection. Without knowing the kind of infection present, it is not possible to know which drug to use. Sometimes, a foreign body, tumor, or polyp in the ear canal may cause an ear infection. Treatment with medication alone will not resolve these problems. Your cat must be examined to be sure that the eardrum is intact. Administration of certain medications can result in loss of hearing if the eardrum is ruptured.
How are ear infections diagnosed?
Your veterinarian may examine the ear canal with an otoscope, an instrument that provides magnification and light. This gives a good view of the ear canal and allows your veterinarian to determine whether the eardrum is intact and if there is a tumor or foreign material in the ear canal. If there is a great deal of debris, discharge, or inflammation within the ear canal, performing a thorough examination may not be possible. If this is the case, or if the ears are extremely painful and your cat refuses to allow ear examination, sedation or general anesthesia may be necessary.
"...if the ears are extremely painful and your cat refuses to allow ear examination, sedation or general anesthesia may be necessary."
Your veterinarian may examine a sample of the material from the ear canal under a microscope. Microscopic examination is essential to choose the right medication to treat the inflamed ear canal. Culture and susceptibility tests are often used in severe or chronic ear infections to ensure your cat receives the right medication.
How are ear infections treated?
The otoscopic examination and cytology results tell the veterinarian how to treat your cat. If a foreign body is lodged in the ear canal, your cat can be sedated so it can be removed. Specific medication can be prescribed for bacteria or fungi; sometimes, more than one type of infection is identified, and this situation requires multiple medications; however, some medications combine both antibiotics and antifungal treatments with an anti-inflammatory agent.
An important part of the evaluation is the identification of an underlying disease. If this cannot be done, your cat is less likely to respond positively to treatment, or she may respond temporarily and relapse when the medication is discontinued.
Normally, cats are very resistant to ear infections. Therefore, if your cat develops otitis externa, especially if it recurs, it is necessary to look for an underlying cause, such as an ear mite infestation, an unusual shape of the ear canal, or a disease affecting your cat's immune system, such as allergies.
Closing of the ear canal occurs when an infection becomes severe and chronic. Some medications may help shrink the swollen tissues and open the canal in some cats. However, some cases may eventually require surgery.
See the handout “Applying Ear Drops to Cats” for a step-by-step guide on administering medication to your cat’s ears.
What is the prognosis?
Nearly all ear infections in cats that are diagnosed and treated can be cured. However, if an underlying cause remains unidentified and untreated, the outcome will be less favorable.