Infections of the external ear canal, also called the outer ear, are common in dogs, but not very common in cats. We call this otitis externa. The Persian breed appears more prone to ear infections than other breeds of cats.
What are the symptoms of an ear infection?
A cat with an ear infection is uncomfortable; its ear canals are sensitive. It shakes its head trying to get the debris and fluid out, and it scratches its ears. The ears often become red and inflamed and develop an offensive odor. A black or yellowish discharge commonly occurs.
Don't these symptoms usually suggest ear mites?
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 and yeast (fungus). By the time the cat is presented to the veterinarian, the mites may be gone, but a significant ear infection remains.
Since these symptoms are similar and usually mean an infection, can I just come by and get some medication?
There are several kinds of bacteria and at least one type of fungus 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 or tumor 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 veterinarian and must be done in the office.
How do you find out which drug to use?
First, the ear canal is examined with an otoscope, an instrument that provides magnification and light. This permits a good view of the ear canal. This examination allows us to determine whether the eardrum is intact and if there is any foreign material in the canal. When a cat is in extreme pain and refuses to allow the examination, it must sometimes be completed under sedation or anesthesia.
The next step is to examine a sample of the material from the ear canal to determine which organism is causing the infection. This is called cytology. Examination of that material under the microscope is very important in helping the veterinarian choose the right medication to treat the inflamed ear canal.
How are ear infections treated?
The results of the otoscopic examination and cytology tell us what to do. If there is a foreign body or tick lodged in the ear canal, the cat is sedated so that it can be removed. As stated previously, some cats have such a heavy buildup of debris that sedation is needed to cleanse the canal and examine it completely. Cytologic study of debris from the ear canal dictates which drug to use. Sometimes, it reveals the presence of more than one type of infection (i.e., a bacterium and a fungus, or two kinds of bacteria); this situation usually requires the use of multiple medications.
An important part of the evaluation of the patient is the identification of underlying disease. If underlying disease is found, it must be diagnosed and treated, if at all possible. If this cannot be done, the cat is less likely to have a favorable response to treatment. Also, the cat might respond temporarily, but the infection will relapse at a later time (usually when medication is discontinued).
Since ear infections are uncommon in cats, is there something else that must be done?
Normal cats seem very resistant to ear infections, especially when compared to dogs. Therefore, finding otitis externa in a cat signals us to look for an unusual shape of the ear canal or for something that could affect the cat's immune system. There are two viruses that can cause immune system suppression. Cats with ear infections which cannot be explained should be tested for these two viruses: the feline leukemia virus and the feline immunodeficiency virus (sometimes called the feline AIDS virus). A small amount of blood is needed to test for these viruses. Diabetic cats are also known to have more frequent ear infections than other cats. The diagnosis of diabetes mellitus can be made with a blood and urine sample from the cat.
What is the prognosis?
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 favorable. A progress check may be needed before the process is completed, but we expect ultimate success. However, the presence of one of the immune suppressing viruses will complicate treatment and will have long term implications on the general health of the cat.
My cat's ear canal is nearly closed. Is that a problem?
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 will eventually require surgery.
What is the purpose of the surgery?
The surgery for a closed ear canal is called a lateral ear resection. Its purposes are to remove the vertical part of the ear canal and to remove swollen tissue from the horizontal canal. Removing the vertical canal should be successful, but removal of large amounts of tissue from the horizontal canal is more difficult. In some cases, the ear canal is surgically obliterated. This solves the canal problem, but it leaves the cat deaf on that side.
Is there anything I need to know about getting the medication in the ear?
It is important to get the medication into the horizontal part of the ear canal. This is best done by following these steps:
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