Otitis

Introduction

Otitis externa means inflammation of the external part of the ear. The external part of the ear extends from the tympanic membrane (ear drum), along the ear canal to the ear pinna (ear flap). While we often see patients with ear infections, otitis externa does not always mean an infection in the ear is present. However, the presence of an ear infection is very common and can prevent the ear disease from resolving. In order to understand how otitis externa can be treated and managed, it is important to know that this is a multifactorial disease, meaning that many factors contribute to the disease process and these underlying factors must be addressed, especially for chronic or recurrent bouts of otitis externa.

Causes

There are numerous causes and factors of otitis externa, and in many cases, a combination of these are involved in your pet’s ear disease.

The primary causes are those responsible for initiating the inflammatory process in the ear. The most common primary causes include:

  • Allergies (atopic dermatitis, adverse food reaction, contact allergy)
  • Endocrine diseases
  • Ectoparasites (ear and skin mites)
  • Foreign bodies (grass seeds)
  • Keratinisation disorders (diseases of the skin lining the ear canal)
  • Masses within the ear (polyps, cysts, tumours).

Other factors that contribute to otitis externa may predispose the ear to disease or may prevent the ear disease from resolving. Examples of other factors include but are not limited to pendulous ears, narrowed ear canals, moisture within the ears, secondary bacterial and yeast infections and middle ear disease.

Clinical signs

Clinical signs of otitis externa include scratching at the ears, shaking the head, painful ears, red and inflamed ear pinna, discharge in the ear and malodour. The most common presentation that vets see is when the ear is infected which is often when the ear has discharge, is red and painful and can have a bad smell. Depending on what organisms are present the discharge may be a thick brown waxy discharge or a purulent (pus) discharge.

Diagnostic tests

Diagnostic tests are performed to help identify some of the causes and factors that may be involved in your pet’s ear disease.

An otoscope can be used to look into your pet’s ear. A lot of information can be obtained from this simple test –  changes to the ear canal such as redness and narrowing, foreign bodies and masses within the ear can be visualised, the ear drum can be assessed and the amount of discharge within the ear can be determined.

A sample of the discharge present in the ear is usually taken with a swab and viewed under a microscope. This enables your vet to determine what type of organisms (if present) have proliferated in your pet’s ear and to help guide treatment.

Further tests to help identify the primary condition include blood tests, skin tests, food trials and even using an otoscope while your pet is under general anaesthetic.

Treatment

Successful treatment of otitis externa relies on identification of all causes and factors contributing to your pet’s ear disease and implementing a management plan for these. This is especially important for chronic or recurrent ear infections, as failure to control the underlying inflammation will lead to repeated flares of otitis externa and possible secondary infections.

Treatment will be individual for each patient and a plan will need to be made with your veterinarian.

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