What is otitis externa?
Otitis externa is an infection of the external ear canal (outer ear infection). The most common cause of ear infections in cats is ear mite infestation. Outer ear infections caused by bacteria and yeast are more common in dogs than cats.
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 a bad odor. A black, brown, or yellow discharge is commonly observed.
The signs of ear infection are similar to the signs of ear mites: black discharge, scratching, and head shaking. However, ear mite infections are more common in kittens and outdoor cats. Adult cats may occasionally contract ear mites from infected kittens. Ear mites create an environment in the ear canal that often leads to a secondary bacterial or fungal infection. By the time the cat goes to the veterinarian, the mites may be gone, but a serious ear infection remains.
Can I just treat these symptoms with over-the-counter ear drops?
No, your veterinarian must diagnose the exact cause of the problem to select appropriate treatment. There are several kinds of bacteria and fungi that may cause an ear infection. Knowing the type of infection present can better direct medication choice for the most effective treatment. Sometimes, the problem is a foreign body, a polyp, or a tumor, and treatment with medication alone will not resolve these problems.
Your cat must be examined to be sure that the eardrum is intact. If the eardrum is ruptured, administration of certain medications can result in loss of hearing. Your veterinarian can detect a rupture by performing a thorough ear examination.
How are ear infections diagnosed?
Your veterinarian may examine the ear canal with an otoscope, an instrument that provides magnification and light. An otoscope gives a good view of the ear canal and allows your veterinarian to determine whether the eardrum is intact and whether a tumor or foreign material is in the canal.
If there is a lot of debris, discharge, or inflammation in the ear canal, it may not be possible to perform a thorough examination. 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.
Your veterinarian may examine a sample of the material from the ear canal under a microscope. Microscopic examination (cytology) 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 see what microorganisms are present and 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. Medication can be prescribed specifically for bacteria (antibiotics) or fungi (antifungals), and some medications combine antibiotics and antifungals with an anti-inflammatory agent.
It is important to identify any underlying disease that may have led to ear infection. If your veterinarian cannot find the underlying cause, your cat is less likely to respond positively to treatment, or they may respond temporarily and relapse when the medication is discontinued. Normally, cats are resistant to ear infections, so 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 unusually shaped ear canal, or a disease affecting your cat's immune system, such as allergies.
The ear canal may close when an infection becomes severe and chronic. Some medications may help shrink the swollen tissues and open the canal in some cats, but some cases eventually require surgery.
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 is less favorable. Several recheck examinations may be needed before the outcome is successful. Left untreated, ear infection can result in aural hematoma, in which blood vessels in the ear flap break, causing painful swelling that requires surgical treatment. Deep ear infections can damage or rupture the eardrum, causing an internal ear infection and even permanent hearing loss.
