7. Ear diseases (Otitis externa, media, interna) & skin adnexes

What is otitis externa?

Inflammation of the external ear canal distal to the tympanic membrane; the ear pinna may or may not be involved

What are some primary causes of otitis externa?

1. Allergy

2. Autoimmune diseases (pemphigus)

3. Endocrine disorders

4. Epithelialisation disorders

5. Parasites (Otodectes, Notoedres, Sarcoptes)

6. Viral infections (canine distemper)

7. Miscellaneous causes: foreign bodies like grass, overcleaning, and medication reactions

What do primary causes of otitis externa do?

Alter the ear environment, allowing secondary infections to develop

What are some secondary causes of otitis externa?

Bacteria (Staphylococcus, Pseudomonas) and yeast overgrowth (Malassezia)

What are some predisposing factors for otitis externa?

Abnormal ear anatomy (stenotic, hairy) and excessive moisture

What are some clinical signs of otitis externa?

Headshaking, odour, pruritus, pain on manipulation of the ear, exudate, and erythema

How can the type of cerumen help with diagnosis of otitis externa?

• Dark, dry cerumen = parasites

• Moist, yellow, odourous = bacterial

• Brown, waxy, acidic = yeast

• Yellow, oily = keratinisation disorder

How is otitis externa diagnosed?

History, clinical examination, and otoscopic examination

What should be assessed about the exudate in otitis externa?

Colour, consistency, and smell

What diagnostic tests can be performed on the exudate or crusts in otitis externa?

Cytology (Diff-Quick and microscopy), cultivation, and sensitivity testing

What other diagnostic tests can be used for otitis externa?

Skin scraping and biopsy (for abnormal masses or tumours)

What should you do if the eardrum is ruptured?

Avoid applying drugs directly into the ear canal (ototoxic); administer oral antibiotics or antifungals instead

What are the three steps of ear cleaning during otitis externa treatment?

1. Irrigation with a cleansing liquid (warm saline or emulsion),

2. Massaging the ear canal

3. Removing excess liquid and debris with cotton

What are some cleaning agents used for otitis externa?

Ceruminolytic agents (carbamide peroxide) or warm saline

What are some topical anti-inflammatory agents used for otitis externa?

Corticosteroids (betamethasone, hydrocortisone)

What are some topical antibacterial agents used for otitis externa?

Gentamicin, neomycin, enrofloxacin, and tobramycin

Which topical antibacterial agent is particularly effective against Pseudomonas?

Tobramycin

What are some topical antifungal agents used for otitis externa?

Imidazoles (ketoconazole)

What do some topical otic preparations contain?

A combination of glucocorticoids, antibiotics, and antifungals (e.g., Osurnia)

What are some antiparasitic agents used for otitis externa?

Pyrethrin, ivermectin, and selamectin

What are some drying agents used for otitis externa?

Acids with or without alcohol, salicylic acid, and EDTA

What is salicylic acid used for in otitis externa?

As a keratolytic agent

What is EDTA used for in otitis externa?

As an antimicrobial and antibiofilm agent

What are some topical antiseptics used for otitis externa?

Acetic acid and chlorhexidine

What are some surgical treatments for otitis externa?

1. Lateral wall resection (Zepp's procedure)

2. Partial ear canal ablation

3. Total ear canal ablation (TECA)

When is lateral wall resection indicated?

Chronic otitis externa isolated to the upper ventral canal

When is partial ear canal ablation indicated?

Otitis externa, hyperplasia, tumour, or trauma isolated to the ventral canal

When is total ear canal ablation indicated?

Severe otitis externa restricted to the ventral and horizontal canal or ear canal calcification

What procedure is often performed with total ear canal ablation?

Tympanic bulla osteotomy

When must the tympanic bulla be removed?

In TECA (total ear canal ablation) for severe otitis media

What is otitis media?

Inflammation of the tympanic membrane, malleus, incus, stapes, tympanic bulla, and tympanic cavity

What are the common routes of infection for otitis media?

Extension of otitis externa and haematogenous spread

What are some clinical signs of otitis media?

Head shaking, rubbing or scratching the affected ear, head tilting or rotation, facial nerve paralysis (ear droop, lip droop, ptosis), and Horner's syndrome (miosis, ptosis, enophthalmos, protrusion of the nictitating membrane)

What is the treatment for otitis media?

Broad-spectrum antibiotics (amoxicillin with clavulanic acid, enrofloxacin) and potentially total ear canal ablation with tympanic bulla osteotomy for severe cases

What is otitis interna?

Inflammation of the cochlea, semicircular canals, and vestibules

What are some causes of otitis interna?

Untreated otitis media and tumours

What are some clinical signs of otitis interna?

Head tilt, circling, nystagmus, vomiting, and ataxia (signs of peripheral vestibular syndrome)

What is the treatment for otitis interna?

1. Broad-spectrum antibiotics (amoxicillin with clavulanic acid, enrofloxacin).

2. Tympanic membrane ruptures typically heal within 4 weeks.

3. Treatment of tumours (radiation/chemotherapy). Hearing may recur even after deafness

What are parts of the skin adnexa?

Sweat gland, sebaceous gland, hair follicle, and nails

What are examples of diseases of the skin adnexa?

1. Sebaceous adenitis

2. Supracaudal gland hyperplasia

3. Claw infections

What is sebaceous adenitis?

Inflammation of sebaceous glands with overproduction of sebum, often genetic

What is the treatment for sebaceous adenitis?

Anti-seborrheic shampoo, cyclosporine, and antibiotics

What is supracaudal gland hyperplasia?

Overproduction of sebum and androgen causing a bald spot on the tail of male dogs

What are some causes of claw infections?

1. Secondary bacterial or fungal infections

2. Endocrine disorders

3. Allergies

4. Autoimmune disorders

5. Neoplasia

What is the treatment for claw infections?

Treating the underlying cause, removing loose claws, long-term systemic antibiotics, antifungals (itraconazole), and chlorhexidine soaks

What is onychogryphosis?

Abnormal, excessive development and curving of your dog's claws. Seen in leishmaniasis.

Why is it important to check the tympanic membrane in otitis externa?

 Check if infection has spread, if it's ruptured etc

What should be done if the tympanic membrane is ruptured in otitis externa?

• a thorough ear flushing, usually under sedation

• Oral antibiotics & antifungal medications are used in many cases

• Systemic corticosteroids - beneficial if severe inflammation & pain

• Some patients will require surgery - severe, irreversible changes of the outer ear with concurrent middle ear infection

• Most ruptured eardrums heal without surgery within 3-5 weeks.

What quick test can you use to determine if otitis externa is caused by bacteria or yeast?

Smear & stain w/ diff quick