by Barry B. Burtis D.V.M.
Long, short, droopy, erect, fluffy and folded - dog ears come in all shapes and sizes. Trouble is these wonderful, often unique, appendages are often the source of problems for dogs. In a previous column there was a discussion of some of the predisposing factors that lead to the development these problems. This time the focus will be on some of the primary causes ear infections and then some perpetuating factors that can result in recurring ear infections.
There are a few skin parasites that can cause ear infections. The most common one is the ear mite, Otodectes cynotis. It's probably a bit more common to see cats with an ear mite infection than dogs. Ear mites spread from an infected individual. Often their own mother or other animals contacted early in life will be the source of infections for young kittens or puppies. Ear mites spend their entire life cycle - adult, egg and young adult - within the ear canal. Living off tissue fluids and cells in the ear canal these microscopic insects cause tremendous irritation and discomfort. At the same time, the reaction they cause in the ear canal allows secondary bacteria infection to occur. Demodex, Sarcoptic and Notoedric mites are more likely to infect the skin of the ear pinna.
Dermatophytosis is a fungus infection. More commonly known as ringworm, it is an infectious agent that can cause ear infection as well as skin infections. Autoimmune diseases are a group of diseases where the body's immune system fails to recognize normal body cells and begins to attack them in a fashion normally reserved for invading organisms or foreign cells. Lupus is an example of such a disease. It, as well as, several other autoimmune diseases that primarily affect the skin, can be a cause of ear infection.
There are a number of hypersensitivity disorders that can cause inflammation in the ear. In my opinion, they are probably the most common cause for ear infections in dogs. We often lump the three most common hypersensitivities - atopy, food allergy, and contact allergy - together and call them skin allergies. Sometimes ear infections are the only manifestation of allergic disease, sometimes ear problems are only a part of more generalized skin disorders. Regardless, controlling the hypersensitivity will be the only way of resolving the ear problems.
There are also several hormonal disorders that can be associated with ear problems. They can cause changes in the amounts of keratin in the skin or epidermis and as a result predispose to ear trouble. An under active thyroid, adrenal gland disorders, and sex hormone imbalances are examples of hormone disorders of this kind.
Polyps in the ear canal, cancers or foreign bodies are all things that can obstruct the ear canal and lead to ear infections. Fortunately, none of these are common problems for dogs and cats.
Now for some of the things that can keep ear problems going or cause them to recur. If for some reason an infection with yeast or bacteria develops in an ear, it will be important to identify it and make sure it is eliminated. If for some reason that is not accomplished, the ear problem will not be resolved. Antibiotics are usually very effective against bacterial infections, but yeast infections can be more difficult to deal with. It is necessary to make the location less favourable for the growth of yeast. This usually requires good cleaning and control of wax or greasy conditions in the ear canal. Occasionally, other measures against yeast infections will be required. Barry Burtis is a local companion animal veterinarian. Past Pet Tales can be found at www.baycitiesanimalhospital.