What is an ear infection?
The simple fact is that ear infections are the number 1 reason dogs are seen at the vet. It can be extremely frustrating for the dog, the owner, and the veterinarian. I would like to go into some detail about ear infections, why the occur and what we can do to treat them.
Otitis externa, or inflammation of the external ear canal, causes numerous clinical signs in dogs and cats including: ear scratching, head shaking, redness and inflammation, odor, pain, and discharge.
One of the common mistakes of treating otitis externa is only treating the secondary causes which is what we visibly see (redness, discharge, infection, etc). Unfortunately, this does not address the primary cause.
What causes ear infections?
A helpful way to approach treating ear infections is to separate the causes into categories. There are Primary causes, Predisposing Causes, and Perpetuating causes.
Primary causes are what actually initiates inflammation of the ear canal. These can include: allergies, keratin disorders, foreign bodies, masses in the ear canal, endocrine diseases, parasites, and otitis media (inflammation of the middle ear canal). Without controlling these primary causes, otitis externa will be difficult to manage.
Predisposing factors include: conformation changes of the ear (large/floppy ears, small ear canals), increased moisture in the ear (after bathing or swimming), or a suppressed immune system. One thing to understand is that these predisposing factors do NOT result in otitis without there being an underlying problem.
Perpetuating causes are what we are commonly treating. This includes different bacteria and yeast found in the ear canal.
Diagnosing an Ear Infection
Proper diagnosis of the primary and perpetuating causes is paramount to a successful treatment. Most dogs are presented to the veterinary clinic because their owner has seen any number of the clinical signs listed above. For the rest of this section, let’s assume you are at the vet with your pet.
The vet will perform a physical exam, collect a thorough history, and likely want to run an ear cytology. The ear cytology is beneficial because it is cheap, only takes a few minutes, and can identify the presence of bacteria and yeast rather quickly. On occasion, a pet may need light sedation to have the ears thoroughly examined and the ear cytology sample collected.
The fact is that some pets do not like their ears touched at all and the ears may be too painful to examine otherwise. Do not be surprised if this is recommended. This also allows the vet to visualize the status of the ear drum as well which is important for medication selection.
Since we know that endocrine disorders can be a primary cause for otitis, the vet may also recommend running lab work to help rule out those different possibilities. Depending on the chronic nature of the otitis (occurring numerous times per year), the vet may mention running a Culture and Sensitivity test. This is where a sterile swab is used to collect a sample from the ear canal. The sample is sent to the lab where they will grow out what is on the sterile swab and test it against all the available medications to see what will work best.
This is a very useful test because we know the exact organism that is growing in the ear and know exactly which medication to use. It also helps to determine if the organism is a resistant to any medications. Unfortunately, we are seeing the number of resistant cases rising. The down side to the Culture and Sensitivity is it can be a costly test and usually takes 3-5 business days to receive results. I always recommend this for pets who have chronic otitis.
Treating Otitis Externa
Topical medications are the mainstay of treatment for otitis. Medication is selected based on cytology results. Topical medications applied directly into the ear canal have much higher concentrations than systemic medications.
Oral antibiotics and antifungals may be used depending on the chronic nature of the otitis. If the ears are very hyperplastic (thick and swollen ears), oral steroids may be used.
If an underlying disease process is determined as a primary cause, the vet will discuss the proper treatment for that disease.
Treatment for otitis can often be needed for 2-6 weeks depending on the severity and chronicity.
If there is a large amount of discharge in the ears, I prefer to do a thorough ear cleaning while the pet is in the clinic. If topical medications are going to be used, I will usually apply the first dose in the clinic as well. The next day when you are to start topical medications, there is already some improvement in the discomfort in the ear so treating the ears are much easier.
Published by Dr. Mason Romero, DVM ·