Ear disease (Otitis externa)

Otitis externa (OE) is a common inflammatory disorder of the external ear canal - the tubular part of the ear going down to the eardrum. It can also include the pinna - the outside flap of the ear. It occurs when the cells which line the canal become inflamed and thickened. This usually results in increased wax production, which then changes the conditions in the ear canal and predisposes to infection from bacteria and yeasts. It can affect one or both ears, and be either acute (sudden onset) or chronic (long term).

Otitis externa in its acute form can be simple and uncomplicated. However, chronic and recurring otitis can have a range of underlying factors.

There are certain primary factors which directly cause inflammation of the canal. These include parasites (such as the ear mite Otodectes cyanotes), allergic disease (food allergies, environmental allergies and contact hypersensitivities), endocrine disease such as hypothyroidism, foreign bodies such as grass seeds, and various types of cancer of the ear. Underlying allergies - especially atopy) is the most common cause of otitis externa in dogs.

Perpetuating factors are those which do not directly cause inflammation but exacerbate the disease and cause further problems even if the main cause is treated. The main perpetuating factor is infection. Bacteria such as Staphylococcus and Pseudomonas and yeasts such as Malassezia are common. If the infection spreads to the middle ear (past the eardrum), this can cause otitis media - and also recurrent otitis externa.

There are some dogs who are more at risk of otitis externa due to the conformation of their ears. Breeds of dog with pendulous ears, such as Basset Hounds and Beagles, are more prone to developing otitis, as are breeds with V-shaped dropped ear carriage. Dog breeds with erect ears have a much lower risk.

Brachycephalic breeds such as Pugs and French Bulldogs are also more likely to develop otitis.

As otitis externa is a common problem for dogs with allergies, those breeds who are predisposed to atopic dermatitis are also predisposed to OE.

There is evidence that exposure to moisture, such as those dogs who regularly swim, are more likely to develop OE. It has also been found that obese dogs are more at risk of otitis. Some dogs appear to produce more cerumen (wax) than others in their ears, which can be a risk factor.

Signs of otitis externa include:

One or both ears may be affected. The symptoms may come on very suddenly or develop more slowly.

Otitis externa is often clearly visible on a physical examination by a vet. They may well use an ‘otoscope’ - a piece of equipment with a light to look down your dog’s ear canal - to see the extent of the inflammation, any signs of infection or foreign bodies and to see if the tympanic membrane (ear drum) can be seen.

Your vet may well take a sample of the cells inside the ear canal using a swab to look at under a microscope and to send away to see what bacteria or yeasts can be cultured. If your dog has severe otitis and is very sore, they may need some sedation for a full examination to take place.

Treating otitis usually relies upon treating the current inflammation and on finding and managing any underlying disease or conditions.

Firstly, the ears may require anti-inflammatories, painkillers and/or antimicrobials, (antibiotics and/or antifungals) depending on what is found on diagnosis. Often, topical ear drops are used which can contain a combination of medications, but some cases will require oral medications as well. It may be recommended that the ears are flushed under anaesthesia or sedation if they are very infected. In some cases, temporary implants (‘wicks’) may be used to help dry up the ear canal, or antiparasitic medications may be used to kill any ear mites.

Management of underlying causes is important as well. If allergies are suspected, treatment of these is crucial to managing ongoing otitis.

In the most severe cases, where medical management has been ineffective, surgery to open out the ear canal (Lateral Wall Resection), or even remove the whole of the diseased and chronically inflamed tissue (Total Ear Canal Ablation, or TECA) may sometimes be needed.

It can be difficult to prevent otitis. Ensuring that there is no underlying cause, and initiating treatment if there is a predisposing reason is crucial. Dogs who are prone to waxy ears may benefit from routine ear cleaning with a veterinary recommended ear cleaner. Swimming can lead to ear infections, so avoidance of water may be indicated if your dog is prone to otitis. Regular checks of the ears is important as early disease is much more easily managed.