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| − | ==Introduction==
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| − | Otitis externa is an '''acute or chronic inflammation of the external ear canal''', developing anywhere from the tympanic membrane to the pinna.
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| − | It is the most common disease of the ear canal in dogs and cats, and is much more common in dogs than in cats.
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| − | It can range from a mild to a severe disease and it sometimes extends to the middle ear.
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| − | ==Aetiology==
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| − | There are three areas which regroup the causes of otitis externa.
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| − | :'''Predisposing factors''' increase the risk of development of the disease.
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| − | :'''Primary factors''' directly cause the otitis.
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| − | :'''Perpetuating factors''' prevent the resolution of otitis externa once it develops.
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| − | ===Predisposing factors===
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| − | <u>Anatomy</u>: pendulous pinnae, hairy, stenotic canals, long, steeply-sloping canals
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| − | <u>Maceration</u>: wetting due to swimming, bathing/hosing, high humidity.
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| − | <u>Trauma</u>: usually from inappropriate cleaning
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| − | <u>Concurrent systemic disease</u>: pyrexia
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| − | <u>Tumours, polyps, cysts</u>: more common in cats
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| − | ===Primary factors===
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| − | <u>Parasites</u>: ''[[Otodectes cynotis]]'', ''[[Sarcoptes]]'', ''[[Demodex]]'', [[Trombicula autumnalis|''Neotrombicula'']], [[:Category:Ticks|ticks]]
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| − | <u>Fungi</u>: [[Dermatophytosis]]
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| − | <u>Allergies</u>: [[Atopic Dermatitis|atopic dermatitis]], diet, [[Contact Dermatitis|contact]]
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| − | <u>Foreign bodies</u>: grass seeds, grass awns,
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| − | <u>Abnormal epidermal turnover or sebum production</u>: [[Seborrhea|seborrhea]], endocrinopathy, nutritional problems, [[Sebaceous Adenitis|sebaceous adenitis]]
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| − | <u>Primary keratinisation defects</u>: [[Seborrhea|idiopathic seborrhoea]]
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| − | <u>Autoimmune disease</u>: [[Pemphigus Foliaceus|pemphigus foliaceus]]
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| − | <u>Miscellaneous</u>: [[Juvenile Pyoderma|juvenile cellulitis]]
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| − | ===Perpetuating factors===
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| − | <u>Bacteria</u>: ''S. intermedius'', ''[[Pseudomonas aeruginosa]]'', ''[[Proteus]]''
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| − | <u>Fungi</u>: ''[[Malassezia pachydermatis]]
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| − | <u>Topical treatments</u>: inappropriate use of topical treatments
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| − | <u>Progressive ear pathology</u>: ulceration, glandular hypertrophy and atrophy, thickened, folded canals
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| − | <u>Otitis media</u>
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| − | ==Clinical Signs==
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| − | The animal will present with a history of '''head-shaking and ear scratching''', either acute-onset and severe or chronic and intermittent.
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| − | The ears may show evidence of '''self-trauma, erythema, and primary and secondary lesions'''. There may be pinnal deformities and the ear canal may feel thickened on palpation.
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| − | The animal may present with an [[Aural Haematoma|'''aural haematoma''']] from head-shaking if it is severe.
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| − | There may be '''discharge''' coming from the ear which may be brown and waxy or purulent and green.
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| − | The animal may show signs of '''pain''' on clinical examination and may resent otoscopic examination unless it is sedated.
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| − | ==Diagnosis==
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| − | '''Signalment and dermatological history''' will provide some clues as to the cause of the otitis.
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| − | Examination of the ears will help determine if this is a chronic problem or not.
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| − | '''Otoscopic examination''' should be carried out to search for any primary factors which may have caused the otitis, such as a mass, foreign bodies or parasites.
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| − | The '''tympanic membrane''' should be examined for evidence of disease or rupture. The ear canal may have to be flushed and cleaned for this to be possible.
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| − | '''Cytological examination''' of an ear swab should be performed in all cases to determine the flora present in the ear. It is normal to find low numbers of cocci and yeasts such as ''M. pachydermatis'' in the ear canal, but increased numbers or the presence of rods indicating ''Pseudomonas'' infection indicate that culture and sensitivity should be performed on the sample.
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| − | '''Biopsies''' should be taken from any mass observed.
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| − | '''Radiography''' of the bullae is indicated if the otitis is chronic and middle or inner ear infection is suspected.
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| − | If an '''allergy''' is suspected, various tests such as intra-dermal allergy testing could be performed in order to provide a long-term means of control.
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| − | ==Medical Treatment and Control==
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| − | Underlying '''predisposing, primary and perpetuating factors''' should be corrected.
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| − | '''Hair''' can be removed from the ear canal to improve ventilation and access for treatment.
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| − | '''Efficient cleaning''' of the ear is important, and the initial clean may have to be done under general anaesthesia in the clinic. Further treatments should be done at home before any medicated topical treatments are given.
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| − | '''Medical therapy''' may be useful:
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| − | :'''Oral corticosteroids''' can be given for a short period at a high dose to open constricted canals and improve topical treatment efficacy.
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| − | :If there is a bacterial otitis, '''oral antibiotics''' are useful.
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| − | :If ''[[Otodectes cynotis]]'' is detected, a general topical or systemic '''antiparasitic''' is indicated as this parasite can invade sites other than the ear.
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| − | :Many '''topical treatments''' are available for otitis externa cases. These usually provide a '''combination''' of anti-bacterial, anti-fungal, anti-parasitic and anti-inflammatory agents.
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| − | Duration of treatment should continue until the infection is resolved.
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| − | Animals should be examined and '''cytology swabs taken every week''' until there is no cytological evidence of infection. This usually takes '''2-4 weeks''' for acute cases. Chronic cases may take months to resolve and therapy may have to continue for the rest of the animal's life.
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| − | <u>Prevention:</u>
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| − | Ears should be '''cleaned''' before every treatment, and then regularly cleaned twice a week indefinitely.
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| − | '''Astringents''' can be used for dogs who are used to swimming to minimise maceration. Hairs can be regularly '''plucked''' from the inside of the ear to improve ventilation.
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| − | ==Surgical Treatment==
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| − | Treatment of otitis externa should always be '''medical initially'''.
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| − | '''Palpation''' of the ear canals and '''radiographs''' will help determine if there are chronic changes to the ear canals such as calcification.
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| − | ===Lateral Wall Resection===
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| − | This can be performed at an early stage to increased '''drainage and ventilation''' of the external ear canal.
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| − | It should be used in cases where otitis has recurred despite appropriate medical management.
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| − | The '''horizontal canal must be intact''' for this surgery to be effective, and irreversible canal stenosis and end-stage otitis can lead to failure of the procedure.
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| − | ===Total Ear Canal Ablation and Lateral Bulla Osteotomy===
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| − | This involves the '''complete removal''' of all external ear tissue except the pinna, and also removal of infected tissue within the middle ear.
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| − | It is a '''salvage''' procedure that should only be performed in otitis externa cases that are chronic and endstage.
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| − | It can also be performed if otitis externa is still present following a lateral wall resection.
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| − | {{Learning | |
| − | |Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis02565.asp Otitis externa]<br>[https://www.vetstream.com/canis/Content/Disease/dis02285.asp Otitis media]<br>[https://www.vetstream.com/canis/Content/Disease/dis02604.asp Aural hematoma]<br>[https://www.vetstream.com/canis/Content/Technique/teq00146.asp Total ear canal ablation]
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| − | <br>[https://www.vetstream.com/canis/Content/Technique/teq00679.asp Bulla osteotomy]
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| − | |flashcards = [[Small Animal Dermatology Q&A 19]]
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| − | }}
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| − | ==References==
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| − | Merck and Co (2008) '''Merck Veterinary Manual''' ''Merial''
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| − | Harvey, R. (2001) '''Ear diseases of the dog and cat''' ''Manson Publishing''
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| − | {{review}}
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| − | {{OpenPages}} | |
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| − | [[Category:Dermatological Diseases - Dog]][[Category:Dermatological Diseases - Cat]]
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| − | [[Category:Expert Review - Small Animal]]
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| − | [[Category:Integumentary System - Mite Infections]]
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