50. Diseases of the external ear in dogs and cats Flashcards
Otitis externa?
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
Otitis externa treatment and diagnosis and disinfectants?
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
Bacterial Otitis Externa?
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.
Diagnosis – Cytology Coccoid/rod-shaped bacteria; Bacterial clouds; WBCs
Treatment
§ Cleaning (see earlier)
§ Antibiotics
§ Anti-inflammatories
Fungal Otitis externa?
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
Parasitic ottitis externa?
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
Foreign bodies?
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)
Masses in the dog?
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)
Masses in the Cat?
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
