Infections of the external ear canal (outer ear) by bacteria or yeast are common in dogs but not very common in cats. We call this otitis externa. The commonest cause of feline ear disease is ear mite infestation. Some cats have similar signs due to excessive wax in their ears that are not infected.
A cat with an ear infection is uncomfortable and its ear canals are sensitive. The cat shakes its head trying to get the debris and fluid out and scratches its ears. The ears often become red and inflamed and develop an offensive odour. A black or yellow discharge commonly occurs.
Ear mites can cause several of these symptoms including a black discharge, scratching and head shaking. However, ear mite infections generally occur most commonly in kittens. Ear mites in adult cats occur most frequently after a kitten carrying mites is introduced into the household. Sometimes ear mites will create an environment within the ear canal which leads to a secondary infection with bacteria or yeast. By the time the cat is presented to the vet, the mites may be gone but a significant ear infection remains.
No, careful diagnosis of the exact cause of the problem is necessary to enable selection of appropriate treatment. There are several kinds of bacteria and fungi which might cause an ear infection. Without knowing the kind of infection present we do not know which drug to use. In some cases, the ear infection may be caused by a foreign body, tumour or polyp in the ear canal. Treatment with medication alone will not resolve these problems. Also, the 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. This determination is made by the vet and must be done at the surgery.
The vet may examine the ear canal with an otoscope, an instrument that provides magnification and light. This permits a good view of the ear canal and allows him to determine whether the eardrum is intact and if there is any tumour or foreign material in the canal. When the ears are extremely painful and the cat refuses to allow ear examination, sedation or general anaesthesia may be necessary. The vet may then examine a sample of the material from the ear canal under the microscope. This is called cytology and is very important in helping the vet choose the right medication. Some cats have such a heavy build-up of debris that sedation or anaesthesia are needed to cleanse the canal and examine it completely.
The results of the otoscopic examination and cytology tell the vet. what to do. If there is a foreign body lodged in the ear canal the cat can be sedated so that 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 the use of multiple medications.
An important part of the evaluation of the cat is the identification of the underlying disease. If an underlying disease is found it can be treated. If this cannot be done the cat is less likely to have a favourable response to treatment; the cat might respond temporarily but relapse when the medication is discontinued.
Since primary ear infections are uncommon in cats should I be concerned that something else is going on?
Normal cats are very resistant to ear infections. Therefore finding otitis externa in a cat signals us to look for an underlying cause such as an ear mite infestation, an unusual shape of the ear canal or for a disease affecting the cat’s immune system.
In the cat, nearly all ear infections that are properly diagnosed and treated can be cured. However, if an underlying cause remains unidentified and untreated the outcome will be less favourable.
Closing of the ear canal occurs when an infection becomes very chronic. There are medications that can shrink the swollen tissues and open the canal in some cats. However, some cases may eventually require surgery.
It is important to get the medication into the horizontal part of the ear canal. This is best done by following these steps:-