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Otitis externa
Introduction
- Inflammation of the external ear canal.
- Affects 2-6% cats.
- Cause: numerous causes, categorized by predisposing and perpetuating factors and primary and secondary causes. Otodectes cynotis is the primary cause in 50% of cases of otitis externa.
- Signs:
- Pruritus usually earliest symptom.
- Head shaking.
- Discharge.
- Diagnosis: clinical signs with aid of otoscopic examination is enough to diagnose otitis externa but further tests are required to identify the particular relevant predisposing and perpetuating factors and primary and secondary causes.
- Treatment: elimination or control of primary and secondary causes and predisposing and perpetuating factors is needed to control the acute signs and prevent recurrence or to control chronic otitis externa.
Presenting signs
- Pruritus with headshake or scratching affected ear.
- Otic discharge and malodor.
- Erythema, swelling, scaling, crusting, pain of affected ear.
- Acute moist dermatitis of the face.
- There are also often other signs applicable to the primary cause of the otitis, eg in allergy there may be pruritus elsewhere on theskin; and in epithelialization disorders there may be generalized seborrhea.
Pathogenesis
Etiology
- The PSPP model categorizes causes and factors involved with otitis externa into:
- Primary causes which are diseases that can affect a normal ear canal.
- Secondary causes which are diseases that only affect an ear canal that is already abnormal.
- Perpetuating factors are changes to the anatomy and physiology of the ear canal as a consequence of disease. They worsen with chronicity and, unless resolved, prevent resolution of clinical signs.
- Predisposing factors are abnormalities of the ear canal anatomy that pre-exist otitis externa and increase the chance of it occurring.
- Primary causes:
- Allergy - atopic dermatitis Skin: atopic dermatitis, adverse cutaneous reaction to food Food hypersensitivity, contact allergy Skin: allergic contact dermatitis, parasite bite allergy (flea Flea bite hypersensitivity, Otodectes cynotis).
- Autoimmune diseases - pemphigus foliaceous Skin: pemphigus folicaceous, erythema multiforme, vasculitis Cutaneous vasculitis.
- Endocrine disorders - hyperadrenocorticism Hyperadrenocorticism.
- Foreign bodies.
- Fungal infections - dermatophytosis Dermatophytosis, aspergillosis Aspergillosis.
- Parasites - Neotrombicula autumnalis Neotrombicula autumnalis infestation, Demodex spp Demodectic mange , Otodectes cyanotis Otodectes disease, Notoedres cati Notoedric mange, Sarcoptes scabei Sarcoptic mange, tick spp.
- Others - proliferative and necrotizing otitis, eosinophilic granuloma complex Eosinophilic granuloma complex.
- Secondary causes:
- Bacterial - especially Staphylococci, Streptococci and Enterococci spp.
- Yeast - Malassezia and Candida spp.
- Irritation from topical medications - persistent wetting, acids, propylene glycol, alcohol.
- Physical damage from cleaning.
- Perpetuating factors:
- Excessive production of secretions.
- Inadequate epithelial migration (self-cleaning of ear canal).
- Ear canal wall edema.
- Ear canal wall proliferation.
- Ear canal wall scarring.
- Tympanic abnormality - dilation or rupture.
- Apocrine gland abnormalities.
- Hidradenitis.
- Sebaceous gland hyperplasia Sebaceous gland: hyperplasia neoplasia.
- Calcification around the ear canal.
- Otitis media Otitis media.
- Predisposing factors:
- Conformation - narrow canal.
- Moisture in ear canal - humid climate.
- Ear canal obstruction - polyp, ceruminous cystomatosis Ear: ceruminous cystomatosis.
- Systemic catabolic state.
- Unnecessary overtreatment.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Angus J C & Campbell K L (2001) Uses and indications for video-otoscopy in small animal practice. Vet Clin North Am Small Anim Pract 31 (4), 809-828 PubMed.
- Crespo M J, Abarca M L & Cabañes F J (2000) Otitis externa associated with Malassezia sympodialis in two cats. J Clin Microbiol 38 (3), 1263-1266 PubMed.
- McKeever P J & Torres S M (1997) Ear disease and its management. Vet Clin North Am Small Anim Pract 27 (6), 1523-1536 PubMed.
- Rosychuk R A (1994) Management of otitis externa. Vet Clin North Am Small Anim Pract 24 (5), 921-952 PubMed.
- August J R (1986) Evaluations of the patient with otitis externa. Dermatol Reports 5 (2), 1-2 VetMedResource.
- Woody B J & Fox S M (1986) Otitis externa: seeing past the signs to discover the underlying cause. Vet Medicine 81 (7), 616-24 VetMedResource.
- Wilson J F (1985) A practitioner's approach to complete ear care. Dermatol Reports 4 (2), 1-8 VetMedResource.
- Griffin C E (1981) Otitis externa. Comp Contin Educ and Pract Vet 3, 741.
Other sources of information
- Miller W H, Griffin C E & Campbell K L (2013) Otitis externa. In: Muller & Kirk's Small Animal Dermatology. 7th edn. Elsevier Mosby, St Louis, p 741.
- Griffin C E (2010) PSPP System. www.animal dermatology.com
- Moriello K A & Mason I S (1995) Handbook of Small Animal Dermatology. Pergamon Press. pp 259-267. (Concise for quick reference.)
- Merchant S & Griffin C (1994) The 1994 Ear Care Symposium, Otitis Externa, the 21 Most Commonly Asked Questions.Veterinary Learning Systems Co Inc. (Practical advice on treatment.)
- McKeever P J (1993) In: Manual of Small Animal Dermatology. Eds P H Locke, R G Harvey and I S Mason. Cheltenham: BSAVA. pp 131-140. (Concise for quick reference.)
- Griffin C E, Kwochka K W & MacDonald J M (1993) Current Veterinary Dermatology: The Science and Art of Therapy.St Louis: Mosby Year Book3. pp 245-262. (Well presented dermatology text book with good treatment plans.)