Canine otitis externa refers to the inflammation of the external ear, the ear canal. Other types of canine otitis include otitis media and otitis interna, referring to inflammation of the middle and inner ear.
Canine otitis externa is relatively common amongst dogs, estimated to affect between 14-20%. All ages and breeds can develop the condition, although long-eared breeds are more susceptible. The high prevalence can be attributed to the ‘L-shaped’ ear canal of dogs, which makes natural draining of fluid difficult. Otitis externa also occurs in cats, but is fortunately much less common (around 2-10%). 1
Symptoms of Canine Otitis Externa
Dogs that develop otitis externa may produce excessive wax, and experience a thickening of the ear canal wall. These factors narrow the ear canal, making the condition worse.
See right for an example of a pruritic (itchy) ear – Image courtesy of Nottingham Vet School
Symptoms of canine otitis externa include:
- Itchy ear(s)
- Head shaking
- Painful, tender ears
- Alterations in behaviour as a result of the pain e.g. less active, depression, agression
- Discharge from the ear canal
- Bad smells emitted from the ear canal as a result of infection
- Red/pink and swollen ear(s)
- Thick and flaky skin around the outer ear and ear canal
Causes of Canine Otitis Externa
A common causes of canine otitis externa is allergies. Allergies to certain substances in the environment can cause the ear canal to become inflammed and itchy. The dog will then scratch at the ear, damaging the skin, which allows bacteria, yeast or fungi in. These microorganisms can then cause infection and symptoms such as discharge, bad smells and inflammation.
Allergies aren’t the only cause of canine otitis externa. The Merck Veterinary Manual splits possible causes into three factors. These are, primary factors, predisposing factors and perpetuating factors. These factors and examples are listed below.
These are factors that are directly responsible for the development of the condition, such as an allergy. Physical objects, such as a grass seed, can become lodged in the ear canal and cause irritation. This leads to inflammation and itchiness. Other primary factors include:
- Allergies e.g. canine atopic dermatitis or food allergies
- Parasites such as mites
- Grass seeds
Factors that make the dog more susceptible to developing canine otitis externa, such as genetic or environmental factors. Examples of predisposing factors include:
- Shape and characteristics of the ear (genetics) e.g. narrow ear canal, long ears, hairy ears
- Softened or weakened ear canal lining from swimming or frequent cleaning
- Changes in the natural microflora i.e. the ‘good bacteria’ that live naturally in the ear
- Autoimmune diseases that weaken the immune system
- Hormonal conditions that may interfere with immunity
Factors that allow the condition to continue to develop and worsen. This essentially refers to secondary infection by bacteria or other microorganisms. The ear canal becomes weakened by the dog scratching his itchy ear, which makes it easier for microorganisms to take hold and flourish. This results in infection and further inflammation, worsening the condition.
Treating Canine Otitis Externa
What we see in terms of canine otitis externa is usually the result of a secondary infection. A secondary infection is a bacterial, fungal or yeast infection that has occurred because the primary condition (otitis externa) created favourable conditions for pathogenic (harmful) microorganisms to grow. We can treat this infection, but over time, it will likely return. This is why it is important to treat the underlying cause (e.g. an allergy) first, then tackle the secondary infection.
Canine otitis externa can be painful, so examination and initial treatment should be left to your veterinarian. This is usually done under sedation or general anaesthetic.
After initial examination and diagnosis of otitis externa, your vet will likely clip the hair around the ear to improve ventilation and clean the affect ear(s). After cleaning, the ear may be flushed with antibacterial or saline solution to reduce secondary infection.
Your vet may prescribe a number of medicines including:
- Corticosteriods to reduce inflammation
- Antihistamines may also be prescribed to reduce inflammation
- An antimicrobial treatment that will be tailored to the type of infection (e.g. anti-bacteria, anti-fungal etc.)
- In more severe cases, pain medication may also be prescribed
After initial treatment by your vet, treatment will be passed over to you. A typical otitis care routine may include:
- Cleaning the ears – from daily to once or twice a week as the condition improves
- Topical antimicrobial solutions applied to the ear
- In more severe cases oral antibiotics may be given
- It is important to keep the ear canals dry and well ventilated (e.g. clipping hair around the ears)
- Apart from when cleaning, it is also important to minimise the amount of water from getting in to the ear canal. This ensures the tissue doesn’t soften, which can cause the condition to worsen
Succesful treatment of the condition can take up to 12 weeks or more depending on severity. It is important to strictly adhere to your vet’s care plan to minimise the likelihood of reinfection. Many owners will discontinue treatment if the ear looks better, which can allow reinfection.
Image Credit – Tim Simpson
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