Wag’s Chief Veterinary Advisor, Dr Tim Nuttall, on ear infections in dogs.

Introduction
Ear infections (also known as otitis externa) are very common in dogs. Prompt treatment is needed to treat the infection. However, many dogs will then need ongoing treatment to prevent recurrence.

What causes ear infections?
Ear infections are always secondary to an underlying condition. This is the primary trigger for the infection – common problems include atopic dermatitis (i.e. dog eczema), food allergies, grass seeds and ear mites (although there are many others) – figure 1.

Other problems such as long ear flaps, hairy ears and swimming etc. make ear infections more likely but rarely cause the infections by themselves. Repeated bouts of infection lead to inflammatory changes in the ear canals. These make the infections more frequent and harder to treat. Eventually, the changes become irreversible and the dogs will need a major surgical operation (a total ear canal ablation or TECA).

How is an ear infection diagnosed?
The ear will become inflamed and itchy or painful. You may also notice a discharge and smell. Your vet will examine the ear to determine the type (e.g. bacteria or Malassezia yeasts) and severity of infection. An otoscope can be used to check the ear canals and ear drum (figure 2). Cytology (i.e. examining a sample of ear discharge under a microscope) will confirm the cause of the infection and make sure that the right treatment is used (figure 3). If the ear infections keep coming back your vet will also examine your dog and do further tests looking for the underlying cause (the primary trigger). Severe cases may need x-rays or a CT scan to assess the ear canals and middle ear.

How are ear infections treated?
Most ear infections are treated with ear drops. These contain an antimicrobial to treat the bacterial or Malassezia infection and a steroid to bring down the inflammation. Severe ear infections are very painful and pain killers may be needed. Steroid tablets can be used to bring down more severe inflammation and open the ear canals. More serious cases with lots of ear discharge may need a thorough ear flush under an anaesthetic before starting the ear drops.

Will the ears need long term treatment?
It is important to remember that the most common causes of ear infections in dogs are long term conditions (e.g. atopic dermatitis and food allergies) – these can be managed but not cured. Therefore, if treatment stops once the infection has resolved they will just come back again. Just treatment the infections (i.e. ‘reactive’ therapy) leads to repeated cycles of infection and inflammation that result in the end-stage ear that needs surgery. It is important to start and maintain regular proactive therapy to prevent this.
Proactive therapy typically involves regular ear cleaning (using a ear cleaner suitable for the type of discharge in each dog) and steroid ear drops (figure 4). However, other treatment may be necessary depending on the underlying conditions in each dog.

Conclusions
Ear infections are very common in dogs. They often become recurrent and this can lead to irreversible changes that require surgery. They are always secondary to underlying factors that need diagnosing and managing. Treatment of the infection should be followed be long term measures to maintain the remission and prevent flares. However, with prompt diagnosis and treatment the prognosis is very good.

Figures
Figure 1 – An ear infection in a young dog with inflammation and swelling around the opening of the ear canal.
Figure 2 – An otoscope view of the ear canal in another dog. The ear canal is inflamed and narrowed and blocked with discharge. Part of a grass seed is just visible – this needs to be removed.
Figure 3 – Cytology from a dog with otitis externa. The peanut-shaped organisms are Malassezia yeasts. The ear drops will need to include an antifungal to be effective.
Figure 4 – The same dog as in figure 1; the infection has responded to the ear drops. However, this dog has atopic dermatitis – regular ear cleaning and steroid ear drops will be needed to maintain the improvement.