Ear Infections/Otitis Externa
A dog’s ear canal has both vertical and horizontal canals. This anatomy, as well as floppy ears, can predispose a dog to ear infections because it is difficult to move debris upward out of the vertical canal. Moisture and hair can also hold debris within the canal. This debris, made of ear wax, skin oil, skin cells, and other organic matter, feed bacteria and yeast that are normally found within the ear canal and on the skin, causing an infection. Itchy dogs with allergies to food or environmental allergens can be more prone to ear infections, because the ears are just an extension of the skin.
Signs that your dog may have an ear infection include shaking the head or scratching the ears or behind the ears. You may also see visible discharge inside one or both ears or smell a yeasty odor. A severe infection can potentially progress to the inner ear and cause a head tilt, loss of balance, and abnormal eye changes. A dog who frequently shakes its head due to an infection can get an aural hematoma, where a blood vessel within the ear pinna (flap) bursts causing a buildup of blood that makes the ear flaps swell.
Treatment of Infection
One of the most important aspects to treating an ear infection is the cytology. We take a sample of the ear discharge from each ear, place it on a slide, stain the sample, and examine it under a microscope. This allows us to see if the infection is bacterial or yeast in nature or both. It also allows us to quantify the infection. This is important for two reasons:
- So we can use the appropriate medication to treat the infection – with an antibiotic for a bacterial infection, an antifungal for a yeast infection, or a combination of the two. Depending on the severity of the infection, we may also need to add in oral antibiotics as well as topical. One type of resistant bacteria can form a biofilm that makes topical medications unable to reach the bacteria. We can see evidence of this on cytology and make sure we use a medication to dissolve the biofilm prior to starting antibiotics.
- So we can make sure the infection has completely cleared before stopping therapy. If you stop too soon, the weak organisms may die, but the stronger ones persist thus become resistant to the medication. Also, it is not uncommon for an infection to start out bacterial only to change to a yeast infection after the bacteria has been cleared, or vice versa.
Sometimes dogs have recurrent or chronic bacterial ear infections that do not go away with treatment or return as soon as medications are finished. In these cases we recommend an ear culture to determine the exact type of bacteria that is present to find the appropriate antibiotics to use. We send a sample out to the lab, where the discharge is placed on a petri dish to grow the bacteria to identify it. It is then subjected to different classes of antibiotics to determine the sensitivity.
In rare cases, some chronic ear infections cannot be fully resolved with medical therapy. These can be referred for surgery to either open the canals or to remove the canals completely in order to provide relief to the pet.
It is always best for your pet to never let their infection become chronic. If you think they have signs of an ear infection, please contact your veterinarian immediately and follow up with a recheck to make sure the infection has resolved completely.