Contributors: Rosanna Marsella, Ian Mason, David Scarff, David Godfrey

 Species: Feline   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading

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.
Print off the owner factsheet on Chronic otitis Chronic otitis to give to your client.Follow the diagnostic tree for Evaluating and Managing Otitis Externa/Media Evaluating and Managing Otitis Externa/Media.  

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:
  • 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

Presenting Problems

  • Aural pruritus/pain.
  • Pinnal or peripinnal lesions.
  • Otic exudate.
  • Head shaking.

Client History

  • Head shaking or scratching affected ear.
  • Otic exudate.
  • Pain on palpation.
  • Malodor.
  • Aural hematoma Aural hematoma 01 Aural hematoma 02Aural hematoma: close up Aural hematoma: head positioning.
  • Acute moist dermatitis of face.
  • Red, hot, swollen pinna.
  • Scale pinna.
  • Crusts pinna.
  • Prior treatment with neomycin Neomycin containing drops: contact hypersensitivity.
  • Bleeding from ears.
  • Head tilt.

Clinical Signs

Acute otitis externa

  • Erythema and swelling.
  • Vasodilation.

Later

  • Erosion/ulceraton leading to crust formation.
  • Otic exudate, nature dependent on cause (however, these are not sensitive distinguishing signs):
    • Dry coffee grounds, thick brown to black wax - Otodectes cynotis Otodectes cynotis.
    • Moist brown: cocci and yeast.
    • Purulent creamy: Gram-negative bacteria.
    • Ceruminous waxy yellow: keratinizing, glandular, chronic allergic.
    • Ceruminous or purulent exudate without signs of inflammation and grayish or pink mass in horizontal canal: nasopharnygeal polyp Nasopharyngeal polyp.
  • Pruritus or pain.
  • Pinnal lesions (erythema, swelling, scaling, crusting, alopecia).

Chronic otitis externa

  • Yellowish/brownish ceruminous otic exudate.
  • Hyperplasia.
  • Thicker, firmer, less pliable vertical and horizontal canal.
  • Mass in ear canals.
  • Pruritus and skin lesions in other body locations.
  • Systemic signs.
  • Aural hematoma Ear: aural hematoma.

Diagnostic Investigation

  • Other: Otodectes cyanotis Otodectes cynotis: female  Otodectes cynotis: adult male.
  • Initial symptomatic treatment based on history, examination and cytology may be required in order to allow adequate examination by otoscopy. Topical and systemic corticosteroid treatment for about a week is especially valuable to decrease pain, open up edematous ear canals and allow both more effective home cleaning and otoscopy and cleaning in the practice.
  • It is important that otoscopic examination is performed at some stage as part of identifying primary and perpetuating factors, eg presence of foreign bodies, canal narrowing and ear drum rupture.

Otoscopy/video otoscopy

  • Sedation is often required for otoscopic examination and in cats with painful and swollen ear canals it is often helpful, prior to scheduling the examination, to treat for 1-2 weeks with topical and/or systemic corticosteroids (when the ears are too painful for the owner to treat at home).
  • If the horizontal canal requires cleaning to visualize the eardrum general anesthetic is often required. Cats that are only sedated often continue to move when stimulated by cleaning this area.
  • Video otoscopy provides a much enhanced view of the horizontal canal and the ear drum and enables recording of lesions.
  • Evaluation of the ear drum is challenging:
    • Small tears may be difficult to see.
    • A plug of debris may be taken for an intect ear drum.
    • The medial wall of the middle ear cavity may be mistaken for the ear drum.
    • When the ear drum is ruptured or absent then a stream of air bubbles is expected to rise from the air-filled middle ear into the ear canal when it is filled with fluid (saline should be the fluid used during these evaluations).
  • Palpation of the ear drum with a soft feeding tube passed down an otoscope can be useful. When the ear drum is absent the end of the tube should fall out of sight in the middle ear cavity.

Microscopy

Bacteriology

  • Culture and sensitivity Bacteriology if: a) microscopy demonstrates white blood cells or rods in discharge. b) chronic otitis externa.
  • Cytology is more important than culture.
  • Cytology and culture often give conflicting results in which case cytology should be followed.
  • Culture should be taken from both the external (horizontal) canal and middle ear in cases of otitis media because different bacteria may be present in various parts of the canal.

Histopathology

  • If sometimes indicated:
    • Neoplasia, polyps.
    • Keratinization disorders.
    • Intraepidermal pustules: pemphigus complex.

Radiography

  • Otitis media   Ear: otitis media (right side) - radiograph VD .
  • Radiography is sometimes useful for evaluating the middle ear cavity but CT Computed tomography: head and MRI scanning are superior for imaging the middle ear and are indicated in cases where middle ear pathology is suspected or needs to be ruled out and when bulla osteotomy is being considered.

Other

  • Many tests for primary causes may be indicated depending on the signalment and examintion findings.
  • Skin scrape for parasites Scraping: skin, eg Demodex, dermatophytes.
  • Elimination dietary trial for food allergy.
  • Intradermal skin test Intradermal skin test or serological allergy test Allergy testing to aid treatment of atopic dermatitis.
  • Biochemistry, hematology, urinanalysis and endocrine tests for diagnosing cysteic diseases and evaluating the cat prior to certain treatments. 

Brainstem auditory evoked response (BAER) hearing testing

  • It is helpful to establish the extent of hearing that remains in an ear Hearing tests.
  • Hearing is affected in otitis externa due to obstruction of the ear canal by tissue and debris, from concurrent otitis media and interna and by the use of ototoxic drugs.
  • The only value in retaining an ear canal is to enable hearing so once this is lost total ear canal ablation Ear: total ear canal ablation with bulla osteotomy Bulla osteotomy is indicated rather than continued medical treatment.

Biochemistry and hormone assays

  • Specific tests for endocrinopathies may sometimes be indicated:
    • Hyperadrenocorticism.
    • Hyperthyroidism.

Treatment

Initial Symptomatic Treatment

Unless the problem is acute and straightforward, extensive client education about the theory behind the PSPP system and their cat's prognosis will be be very helpful.
  • Eliminate obvious primary causes with a specific treatment, eg Otodectes, foreign body.
  • Eliminate secondary causes, eg treating with a topical antibiotic and/or antifungal for cocci, rods and/or yeasts.
  • Control predisposing and perpetuating factors, eg treating with a suitable corticosteroid for ear canal wall inflammation.
  • Ear canal cleansing with ceruminolytics for waxy ears or an antiseptic cleanser for purulent discharges (most are contraindicated if the tympanic membrane is ruptured, the exceptions are saline and squalene) using ear bulb syringe or syringe and feeding tube. This may be performed at home or in the clinic under sedation or general anesthesia as appropriate.
  • Cleaning removes debris and microbes. Antiseptic cleansers can eliminate more than 50% of infections without the need for antibiotics.
  • Dry the ear canal with drying agent (contraindicated if severely inflammed or ulcerated). Some cleaning products contain a drying agent.
  • Continuing cleaning is required to prevent further build-up of secretions and debris in cats with the perpetuating factor of inadequate epithelial migration - which is expected to be present in animals with chronic otitis externa even when the primary cause had been contolled. This ongoing cleaning may be required for months, years or life in these patients. The frequency will be case dependant and over-cleaning can also be a cause of otitis externa.
  • Many owners need help in learning how to perform effective ear cleaning Ear: cleaning and to apply medications.
  • Cleaning and medicating should be separated by at least an hour.

Topical ectoparasiticides

  • See also otic parasiticidals Therapeutics: parasiticide.
  • If parasites seen on otoscopic or microscopic examination.
  • Otodectes cynotis Otodectes disease: treat all in-contact cats, ferrets and dogs, whole body treatment may be required, continue treatment for at least 3 weeks.

Treatment of secondary infections

Topical antibacterials

  • Often required when bacteria and white blood cells are identified by cytology.
  • Some ear cleaners have antiseptic activity.
  • Bacteriocidal agents are preferred.
  • When Staphylococci are seen then neomycin, gentamicin, polymixin B, fusidic acid or a fluoroquinolone may all be effective. Enrofloxacin should be avoided in cats.
  • When rods are seen Pseudomonas spp should be suspected and culture is recommended. Concentrations of topical ear antibiotics are much greater (c1000 fold) than the concentrations in vitro so laboratory sensitivities may not be a good guide that a particular agent will be ineffective.
  • Agents usually safe in the presence of a ruptured ear drum:
    • Fluoroquinolones, aqueous gentamicin (Note: NOT the veterinary licensed gentamicins), silver sulphadiazine.
  • Agents often unsafe in the presence of a ruptured ear drum:
  • Topical polymixin B is highly effective against Pseudomonas spp, as long as exudate is not present (excellent cleaning also is required).
  • Solutions of fluoroquinolones, aqueous gentamicin or amikacin Amikacin designed for injection may be useful. Enrofloxacin should be avoided.
  • Some dermatologists use higher volumes of antibacterial products than recommended on the licenses.
  • TrizEDTA solutions enhance antibiotic activity.
  • Ear wicks are useful for clients that cannot apply medications frequently at home as they act as local reservoirs of the agents, but they do require general anesthetics for application and replacement every 3-10 days.

Topical glucocorticoids

  • Usually required.
  • Used for significant inflammatory primary causes or perpetuating factors, eg allergy, swelling, proliferative changes.
  • Also if there is glandular over-secretion as a primary cause or a perpetuating factor as they reduce glandular activity.
  • Injectable dexamethasone Dexamethasone used topically can be useful.
  • Some dermatologists use topical hydrocortisone aceponate Hydrocortisone off-label in ear canals.
  • Some dermatologist use unlicensed 1% prednisolone Prednisolone drops chronically.
  • Chronically, use the least potent formulation which will be effective as percutaneous absorption has been shown to occur leading to iatrogenic hyperadrenocorticism.

Topical antifungals

  • See also otic antifungals Therapeutics: non-bacterial infection.
  • If yeast identified by cytology in significant numbers (5-10/high power field or >10 if numerous bacteria and <5 if only yeast).
  • Or if yeast are present at lower numbers and are suspected to be significant.

Systemic antibacterials consider when:

  • Otitis media is present: Clindamycin Clindamycin may be effective for coccal infections and fluoroquinolones for rods (avoid enrofloxacin) Therapeutics: antimicrobial drug.
  • Severe otitis externa, eg Pseudomonas infection. But topical treatment alone will often be effective.
  • Chronic otitis externa where proliferative changes inhibit use of topical therapy. Cephalosporins may be effective for coccal infections and fluoroquinolones for rods (avoid enrofloxacin).
  • Acute otitis externa where pain inhibits use of topical therapy.
  • Antibiotics should be based on cytology and culture/sensitivity.

Systemic glucocorticoids when:

  • Marked inflammation or proliferative changes are present, eg for the first week or two of treatment when waiting for canal wall swelling to reduce to allow examination and perform cleaning.
  • Chronic otitis externa where proliferative changes inhibit use of topical therapy.
  • When compliance for topical therapy is poor.
  • When controlling atopic dermatitis as a primary cause.

Systemic antifungals when

  • Malassezia spp otitis media is diagnosed.
  • Owners are unable to administer topical agents.
  • Severe recurrent Malassezia spp otitis externa is present.

Systemic parasiticide treatment

  • Selamectin or moxidectin products can be used as treatments and also to rule out Otodectes cynotis and Sarcoptes scabei as primary causes.

Surgery

  • Lateral wall resection:
    • This is rarely helpful as it only aids control of lesions confined to the vertical canal.
    • Indicated if chronic disease is confined to the lateral wall.
    • It may be most helpful when used early in the course of problems in animals with congenitally stenotic canals.
  • Vertical canal ablation Ear: ablation - vertical canal:
    • Rarely helpful as it only aids control of lesions confined to the vertical canal.
  • Total ear canal ablation plus bulla osteotomy:
    • Stenosis of canal.
    • Tumors or polyps.
    • Chronic recurrent otitis externa despite full diagnostic work-up and appropriate treatment of primary and secondary causes and predisposing and perpetuating factors.
    • Especially if the ear is already deaf as this surgery inevitably causes significant deafness.

Monitoring

  • Worsening of symptoms: change medication (?irritant dermatitis Skin: irritant contact dermatitis or contact hypersensitivity Skin: allergic contact dermatitis).
  • Check for pruritus - shaking, scratching; discharge, odor and compliance to medication.
  • Repeat cytology on each examination.
  • Hematology, biochemistry, urinanalysis and ACTH-stimulation test ACTH-stimulation test to monitor side-effects if long-term systemic or topical glucocorticoids are used.

Subsequent Management

Treatment

  • Maintenance ear cleaning every 3-7 days +/- topical therapy.
  • Topical low potency steroid if ceruminous glands continue to over-produce exudate (eg hydrocortisone-containing solution) Hydrocortisone  +/- topical antibacterials and/or antifungals if secondary infection cannot be controlled by control of the primary cause and perpetuating and predisposing factors.

Monitoring

  • Subsequent history, clinical and otoscopic findings and cytology.

Outcomes

Prognosis

  • Good if acute and primary, predisposing and perpetuating factors eliminated or controlled.
  • Poor if chronic.

Expected Response to Treatment

  • Regression of clinical signs over days, weeks or months depending on the primary cause and perpetuating factors.

Reasons for Treatment Failure

  • Predisposing, primary and perpetuating factors not identified or treated, eg presence of otitis media, ear canal narrowed due to stenosis.
  • Inadequate cleaning.
  • Resistance to antibiotics, especially when Pseudomonas is present.
  • Cat does not allow treatment at home, If this is an issue consultation with a behaviorist/trainer may be helpful.

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 (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 (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.)

Other Sources of Information