PROVET HEALTHCARE INFORMATION

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OTITIS EXTERNA

Note for Pet Owners:
This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Topics on this Page:

Description
Cause
Breed Occurrence
Signs
Complications

Diagnosis
Treatment
Prognosis
Long-term problems

Description
Otitis externa is inflammation of the outer ear canal.

Cause
There are many primary causes of otitis externa including :

Allergies

Atopy - one of the commonest causes of otitis externa
Food hypersensitivity (80% of affected cats and dogs reported to have otitis)
Contact hypersensitivity

Autoimmune disorders

Pemphigus foliaceous

Diseases of glands in the skin

Hyperplasia of glands reported in Cocker Spaniels

Foreign objects in the ear canal

Grass awns
Excessive hair
Sand, soil, water

Fungi

Dermatophytes

Generalised diseases of keratinisation

Primary idiopathic seborrhoea
Hormonal disorders - hypothyroidism, sex hormone imbalances

Parasites

Ear mites (eg otodectes cynotis) - one of the commonest causes in cats (50%) and dogs (10%)
Flies, ticks and fleas - seen abroad - not in the UK

Viruses

Canine distemper virus has been implicated

Other causes
- Eosinophilic infiltration of the pinna

Breed Occurrence
Animals with narrow auditory canals and flop ears are more likely to develop otitis externa than others. Cocker spaniels may develop glandular hypertrophy and German Shepherd Dogs are reported to have an increased predisposition. Working dogs and pet dogs that are exercised in rural areas are more likely to get grass awns and other vegetative foreign objects in their ears.

Signs
There are many signs including :

Reddening of the skin of the pinna
A visible, often smelly, discharge in the outer ear canal. This can be any colour from black, brown, red-brown, red, yellow, to off-white.
Head shaking
Scratching at the affected ear(s)
Drooping of the affected ear
Pain when eating (if complicating otitis media involves tempero-mandibular joint)
Holding the head to one side, (to the side of the affected ear)
Walking in circles
Fitting - if complicated by otitis media/interna

Complications
Bacteria and yeasts are common secondary infections (they are rarely a primary cause). Chronic otitis externa leads to thickening of the skin of the pinna, with hyperplasia, hyperkeratosis, fibrosis and calcification. Swelling of the tissues closes off the auditory canal leading to reduced natural ventilation.

If the tympanic membrane is diseased or ruptured otitis media may develop with osteomyelitis.

Diagnosis
Thorough examination of the external ear canal with an auroscope is necessary to identify the presence of a foreign object. To get good visibility may require cleaning the wax and debris out of the canal and a general is needed in some cases to get good visibility of the horizontal canal and tympanic membrane.

Other diagnostic tests that may be helpful include :

Cytological examination of the discharge in the ear canal
Culture an sensitivity testing of swabs taken from the canal
Biopsy and histopathological examination

Treatment
There are several forms of treatment :

Cleaning - use proprietory ceruminolytic product

Removes foreign material and objects
Removes excessive wax and other secretions as well as cellular debris
Flush with sterile physiologic saline solution

Polytherapy products are often used topically in the ear canal to treat otitis externa. These are usually given as oil-based drops or creams and include a combination of some or all of the following :
- Antibiotic
- Corticosteroid - glucocorticoids for their anti-inflammatory and antipruritic effects.
- Antifungal agent
Systemic antibiotics or corticosteroids have been reported to be helpful to treat otitis media.
In chronic otitis externa the external ear canal can become so narrow that the condition cannot be managed successfully with medications alone. In such cases surgical intervention may be needed -
- aural resection (opening of the lateral side of the vertical canal) or, in the worst cases
- vertical canal removal (ablation) or total removal of the external canal.
Bulla osteotomy is needed to treat persistent or recurrent otitis media.

Prognosis
Good if treated early. Guarded with chronic otitis externa ..can have a protracted course and .may result in surgery being needed.

Long term problems
Hearing loss. Recurrences are common