Dr Liz Rowland
Have you noticed your dog scratching his ears, rubbing or shaking his head, or a strange odour coming from one or both ears? He could have an infection.
What causes ear infections in dogs?
There are a number of factors that contribute to the development of ear infections in dogs. In veterinary literature, they are classified as:
- Predisposing factors such as genetic conformation of the ear (hairy ears, pendulous ears), moisture in the ears from swimming or a humid environment, or an underlying systemic illness;
- Primary factors, the most important of which is allergies (atopy), parasites (such as ear mites), foreign bodies (such as grass seeds);
- Secondary factors, which are the things that actually create disease in the ear, such as bacteria and fungus/yeast; and
- Perpetuating factors, which develop as a result of the ear infection and interfere with its treatment, such as thickened or narrowed ear canals or ear drum rupture.
An ear infection occurs when predisposing and primary factors cause damage to the delicate lining of the ear canal. The ears usual cleaning mechanism breaks down and wax and exudate accumulate. Bacteria and yeast organisms thrive in this environment, allowing them to proliferate.
The result is inflammation (redness, swelling, pain, heat) and significant discomfort for your pet. When your pet scratches, they further damage the lining of the ear canal and introduce opportunistic bugs, resulting in a vicious cycle of inflammation and infection.
In my experience, ear infections are more common in certain breeds of dog (especially poodle or poodle mixes, though they can affect any breed), those with hairy ear canals, those with atopy (environmental allergies) and those that go swimming. They are also more likely in summer due to the heat, humidity and high pollen counts.
What happens if we don’t treat?
Infected ears do not get better by themselves.
The dog’s external ear is made up of an ear flap (pinnae), horizontal and vertical ear canal (see diagram below). Left untreated, external ear infections (otitis externa) can perforate the tympanic membrane (ear drum) and extend into the middle and/or inner ear, resulting in significant pain and sometimes neurological signs such as a head tilt.
What can be done?
If you notice your dog scratching, rubbing or shaking his ears, or you notice an odour or unusual redness the pinnae (external skin of the ear), book him/her in for a check up. Your vet will perform an otoscopic examination to evaluate the ear canal. They will then take a swab of the waxy discharge to evaluate under the microscope for evidence of fungal or bacterial overgrowth.
If infections are recurrent or are not responding to typical therapies, a sample may be sent for a culture (to grow the bug) and sensitivity (to work out what treatments will be effective), as it may be a resistant organism requiring a more specific treatment protocol.
Depending on the severity of the infection, treatment may include:
- Topical antibiotic/antifungal ear drops. Most of these products are applied either twice a day or once a day for a period of 7-10 days;
- Oral antibiotics / antifungals, in more severe cases, especially if there is a suspicion of middle ear involvement;
- Flushing of the ear canal under general anaesthetic if the ears have significant exudate that will affect treatment efficacy; and
- Surgery to remove non-healing parts of the ear canal in severe, chronic cases, especially those with middle or inner ear involvement.
We will generally recommend a recheck at the end of the treatment protocol to ensure that the infection has resolved.
What if my dog won’t let me treat his ears?
There is a new product on the market called Osurnia® which can help treat ear infections in difficult patients. It is essentially a topical antibiotic / antifungal gel that is applied once into the affected ear and then once a week later. We offer this new product at VetHQ and have had a lot of success.
How can you prevent ear infections?
Keeping the ears clean and dry is important. This means using a ear cleaner for dogs (available over the counter), especially if there is a build up of waxy material and after swimming. These products help the wax to migrate out of the ears and help to dry them out. If you’re not sure how to do this, book in with one of our lovely nurses to show you how.
Ear cleaning is a bit of a balancing act as over-vigorous cleaning can damage the delicate lining of the ear canal and actually predispose to infection. Once a week is generally enough for most dogs.
Removing hair from your dogs ears is contentious. Some seem to benefit from this, however there is risk of causing trauma to the ear canal. Do only where really necessary.
Treating underlying allergies can also help to reduce ear infection recurrence.
Looking at your dog’s ears occasionally, and being aware of the signs of ear infections (scratching, rubbing, abnormal odour, dark waxy discharge, redness or swelling of the pinnae) will also mean you can treat before it becomes a major problem.
Diagram 1: A typical canine ear. Note the vertical and horizontal canals, ear drum and its association with the middle ear.
Diagram 2: A healthy ear on the right and an infected ear on the left.