50. Diseases of the external ear in dogs and cats Flashcards

1
Q

Otitis externa?

A

Otitis Externa

Acute or chronic inflammation of the external ear canal

Predisposed: Dogs>Cats

Untreated acute otitis externa (OE) can lead to chronic otitis externa.

In response to this, the following may be seen:

§ Ceruminous gland hyperplasia

§ Epithelial hyperplasia

§ Hyperkeratosis

§ Follicular hyperplasia

The long term effect of these can lead to apocrine gland rupture,
sebaceous gland degeneration, auditory canal fibrosis, stricture or
calcification.
AETIOLOGY
Predisposing factors
§ Hanging auditory canal § Swimming
§ Narrow auditory canal § Stricture
§ Frequent bathing § ↑ Soft tissue
§ ↑ Cerumen from glands
Primary causes (those that cause acute OE)
§ Otodectes spp. § Sarcoptes spp.
§ Demodex spp. § Atopy
§ Endocrine disorders § Food allergy
§ Contact hypersensitivity § Foreign body
§ Keratinisation disorders § Tumour
§ Autoimmune disorders
Secondary causes (problematic along with the primary causes)
§ Bacteria § Irritative drugs
§ Yeast § Overcleaning
Perpetuating factors (those that maintain inflammation)
§ Skin oedema § Ulceration
§ Skin fibrosis § Thickened skin
§ ↓ Epithelial migration § Stricture
§ Otitis media (OM)
§ Ceruminous gland obstruction or dilation

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2
Q

Otitis externa treatment and diagnosis and disinfectants?

A

Disinfectants

Potentiates the effect of antimicrobials by destroying the bacterial

cell wall, ↓ resistance & dissolving the biofilm.

§ Chlorhexidine

Topical & systemic antibiotics, antimycotics, antiparasitics or

antiinflammatories may be used in combination with cleaning

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3
Q

Bacterial Otitis Externa?

A

BACTERIAL OTITIS EXTERNA

Secondary infection requiring primary/predisposing factors

Staphylococcus spp.

§ Erythematous inflammation; Pustules; Pus

§ Mild ear canal narrowing

§ Painful & sensitive

Pseudomonas aeruginosa

§ Reddened canal; dry, brown contents; Inflammed; Ulcers

§ Mild narrowing; Some creamy-brown discharge

§ Highly sensitive & painful

Streptococcus spp.

E. coli

Enterobacteriaceae spp.

Proteus spp.

DiagnosisCytology Coccoid/rod-shaped bacteria; Bacterial clouds; WBCs

Treatment

§ Cleaning (see earlier)

§ Antibiotics

§ Anti-inflammatories

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4
Q

Fungal Otitis externa?

A

FUNGAL OTITIS EXTERNA

Secondary infection requiring primary/predisposing factors

Malassezia pachydermatis

§ Thickened, wrinkled ear surface; Dark-brown discharge

§ Inflamed; Cobblestone pattern of skin; Canal stricture

§ Diagnosis – Cytology: Bowling-pin shaped fungi

Candida spp.

Microspora spp.

Treatment

§ Cleaning (see earlier)

§ Antibiotics

§ Anti-inflammatories

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5
Q

Parasitic ottitis externa?

A

PARASITIC OTITIS EXTERNA

Otodectes cynotis

§ Predisposition: Cats > Dogs; Young > Old

§ CSx: Intensive scratching & shaking

§ Black & crusty ear surface; Reddened & inflamed skin

§ Black-brown discharge; Very painful

Ticks

Demodex spp.

Treatment

§ Cleaning (see earlier)

§ Topical: Thiabendazole

§ Systemic: Selamectin; Moxidecting; Ivermectin

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6
Q

Foreign bodies?

A

Foreign bodies

Grass awn “fox-tail”– Most common

Seasonal; Outdoor pets; May predispose secondary factors

Clinical signs

Sudden onset; Unilateral

§ Pain § Shaking

§ Ear scratching § Head tilt

§ Bloody discharge § Pus

Treatment

§ Removal of foreign body

§ Cleaning (see earlier)

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7
Q

Masses in the dog?

A

Masses

IN THE DOG

Papilloma > Adenocarcinoma > Polyps

Predisposed: Old > Young

Owner may report: Smelly, bloody discharge; Severe middle-ear

symptoms over a chronic period

Examination

§ Possible visible mass; Narrowed ear canal

§ Bloody discharge; Debris & pus

§ Inflamed & irregular skin

§ Sensitive & painful

Treatment:

§ Total ear canal ablation (TECA)

§ Ventral bulla osteotomy (VBO)

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8
Q

Masses in the Cat?

A

IN THE CAT

Polyps (most common)

Predisposed: Young/middle-aged

May be unilateral or bilateral

Owner may report: Head tilt; Ear scratching; Respiratory symptoms

(stridor); Smelly discharge; Horner’s syndrome (see topic 1 & topic

40)

Examination

§ Visible polyp; Large amount of discharge (smelly; white)

§ Closed ear canal; Inflamed & irregular skin

§ Sensitive & painful

Treatment

§ Traction removal

§ Glucocorticoids for 2 weeks

§ Surgery

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