This document discusses canine otitis, including: - Demodicosis is caused by an overgrowth of mites that normally reside on the skin. It can be localized or generalized. - Diagnosis is typically made via skin scrapings to identify mites. Treatment involves topical or oral miticides for a minimum of 3 months. - Otitis is very common in dogs and can be acute or chronic. Chronic cases are often poorly responsive due to perpetuating factors like ear canal changes. - Diagnosis involves cytology and treatment considers primary causes, secondary infections, and reducing inflammation. Chronic cases may require flushing under anesthesia and more aggressive, sustained treatment.

1. Tricky Infections
Linda Vogelnest BVSc MACVSc FACVSc
Specialist Veterinary Dermatologist

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Demodicosis
• Non-contagious host-specific mites
– normal flora in most mammals
• Disease:↑mite numbers
– immunosuppression, older age
– genetic T-cell defect (dogs)
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Demodicosis - Dogs
3 mite species
•D. canis – elongated mite (follicles, ear canals)
•D. cornei – short-tailed mite (stratum corneum)
•D. injai – long-bodied mite (sebaceous glands)
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Classical Demodicosis - Dogs
• Juvenile onset (<2-3yrs old)
• Genetic
• >95% totally resolve with tx
• Adult onset (>3yrs)
• Immunosuppression
– drug therapy [corticosteroids]
– hormonal diseases [hyperA,
hypoT4]
• ≤ 50% idiopathic
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Classical Demodicosis - Dogs
• Presenting Complaint
– Lesions: localised or generalised
• Alopecia (well- to poorly-demarcated)
• Scaling, crusting, weeping dermatitis
– Pruritus – mild/moderate to absent
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Long-bodied Demodicosis
 D. injai
 greasiness & scaling
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Demodicosis - Cats
• Rare
• 2 mite species
• D. cati – elongated mite (follicles)
• D. gatoi – stumpy-tailed mite (stratum corneum)
• Pathogenesis
– Immunosuppression
• drugs (steroids), FIV, underlying dz (neoplasia)
– D. gatoi may be contagious
• pruritic presentation!
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Demodicosis - Diagnosis
Skin scrapings
•deep (follicular mites)
•capillary ooze
•avoid friable skin
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Demodicosis - Diagnosis
• Less sensitive but easier tests
– Trichogram
– Squeeze Tapes
– Tape impressions
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Demodicosis - Diagnosis
Deep scrapings diagnostic:
•MITES = DEMODICOSIS (VERY rare from normal skin)
•NO MITES = NO DEMODICOSIS except:
– Sharpei - thick skin → difficult to extrude mites
– Pododermatitis
• may need to biopsy
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Demodicosis - Pitfalls
• Demodicosis present & not recognised
• scrapings not done (most often!)
• scrapings not deep enough (very rare)
• Demodicosis absent, but tx on suspicion
• despite negative skin scrapings
– biopsy if any doubt; DON”T trial tx
• Treatment – insufficient duration (&/or frequency)
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Demodicosis – Treatment Dogs
• Localised (1 to several small lesions)
– treatment not recommended
– mostly self-resolve in similar time to tx
• Generalised (whole body; large regions; >1 foot)
– intensive + sustained tx
– 50% may self-resolve (juvenile)
– underlying dz (adult-onset)
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Demodicosis – Treatment Dogs
• Treatment duration
= single most important factor of tx
• MUST continue beyond clinical resolution
• repeat scrapings (4 wkly)
– continue at least 4wks after 2nd
neg scrape
3-month minimum tx course
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Demodicosis – Treatment Dogs
1. Ivermectin = mainstay of tx
 Cattle injectable or sheep oral (Ivomec®)
 300-600ug/kg daily oral
 weekly injections?
 unreliable (unless self-resolving anyway!)
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Demodicosis – Treatment Dogs
1. Ivermectin
2. Doramectin
 slow-release, cattle inj (Dectomax®)
 variety protocols
 300-600ug/kg s/c wkly
 oral; eod
 less studied
 less efficacious? sub-optimal frequency?
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Demodicosis – Treatment Dogs
1. Ivermectin
2. Doramectin
3. Advocate® - imidacloprid + moxidectin
 Registered monthly
 Ineffective
 may be adjunctive weekly
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Demodicosis – Treatment Dogs
1. Ivermectin
2. Doramectin
3. Advocate® - imidacloprid + moxidectin
4. Amitraz (0.5g/L)
– cattle powder (500g/kg)/liquid (125g/L)
• care with dilution
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Demodicosis – Treatment Cats
Easier than dogs
–Ivermectin
• 200-300ug/kg eod (with care)
–Advocate® - wkly?
–Lime sulfur
• not available Australia
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QUESTIONS??
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Dermatophytosis
Pitfalls & Challenges
•Incorrect diagnosis
•Treatment challenges
– Catteries
– Pounds/shelters
•Zoonosis
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Dermatophytosis
HISTORICAL CLUES
•Species/Breed
– Cats: long-haired, Persians
– Dogs: Yorkshire/JRT
•Age
– Young or older/immunocompromised
•Environmental conditions
– Multiple pet households
– Humid climates
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Clinical Clues - Cats
• Head (face, pinnae)
– Well-demarcated asymmetrical alopecia
– Subtle patchy alopecia
– Miliary dermatitis
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Clinical Clues - Dogs
• Well-demarcated asymmetrical alopecia
• Extensive severe forms
– Yorkshire/Other Terriers: immunosuppression
• Kerions = highly inflammatory → nodules
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Well-demarcated Alopecia
Differentials?
1. Bacterial Pyoderma
2. Demodicosis
3. Dermatophytosis
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Dermatophytosis - Diagnosis
Cytology
•Trichogram
•Tape impression
– fungal spores, hyphae
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Dermatophytosis - Diagnosis
• Wood’s Lamp
– ~ 50% M. canis fluoresce
– warm up - 5mins
– easy to over-interpret:
• +ve = bright, iridescent green - hair shafts
– can help with monitoring resolution
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Dermatophytosis - Diagnosis
• Fungal culture
– confirms species/likely source
– samples
• hairs (periphery of lesions)
• surface scaling (scrape)
– in-house Fungassay
• lab more reliable for ID
• false –ve & +ve
• Skin biopsy
– helpful for uncertain cases/atypical cases
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Dermatophytosis - Treatment
• Young (<12 months)
– often spontaneously resolve 2-3 mnths
• Treatment important for:
– Extensive infections; older animals; immunocompromise
– Long-haired cats
– To hasten resolution & ↓ risks of contagion
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Dermatophytosis - Treatment
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Topicals
1. Rinse
•Enilconazole 0.2% (Imaverol®)
– q. 5-7d x 4wks min
•Lime sulfur 2% overseas (not available
Aus)
2.Cream (localised lesions)
•miconazole or terbinafine cream - 3-4wks min
3.Shampoo (adjunctive only)
•miconazole (Malaseb®)

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Dermatophytosis - Treatment
Systemic antifungals:
1. Itraconazole 5-10mg/kd sid; pulse (1wk on, 1wk off)
2. Terbinafine 30-40mg/kg sid; pulse (1wk on, 1wk off)
3. Griseofulvin – 25mg/kg bid with fatty meal; less reliable
Environmental decontamination - bleach
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Questions??
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Otitis
• Very common in dogs
• Acute disease
– Often relatively simple; poorly managed → chronic
• Chronic &/or severe disease
– Often poorly responsive &/or recurrent
• Good management plan
– relies on understanding dz pathophysiology
• 1°, 2°, perpetuating factors
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External Ear
• Pinna
• External ear canal
– Outer vertical portion
– Inner horizontal portion
– Modified skin, surrounded by cartilage (mainly) & bone (short tube)
→ external ear canal flexibility
• Tympanic membrane
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Middle Ear
• Air-filled
– Connects to pharynx (auditory tube)
– Closed by tympanic membrane
• Bony ossicles
– Transmit vibrations → inner ear
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External Ear Canal Disease
• Otitis externa
– Dog - extremely common: 15-20% dogs ≥ once
• Predisposing Factors – anatomy
– Pendulous pinnae
– Relatively hairy canal entrance
– Greater physical length
→ more poorly ventilated canals
• 1° Disease
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External Ear Canal Disease
1° Diseases
• Inflammatory: allergic, parasitic, endocrine
• Neoplasia: benign sebaceous/ceruminal gland
ATOPY
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Canine Otitis
Important factors:
1. Predisposing
2. Primary
3. Secondary
4. Perpetuating

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Secondary Factors
• Bacteria
– Cocci - Staph, Strept
– Rods - Pseudomonas, Proteus, E. coli, Klebsiella
• Yeast
– Malassezia pachydermatis

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Perpetuating Factors
• Chronic Inflammation →
– epi hyperplasia, hyperkeratosis
– dermal oedema, fibrosis
– ceruminal gland hyperplasia
– calcification
→ thickening, folding, stenosis of canals

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Perpetuating Factors
• Otitis media
– keratin plugs, cells & secretions
– reservoir of bacteria, yeasts
• Dog: common
– majority = extension from OE
• Cat: less common
– More often primary OM

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Tympanic Membrane
• Tympanic membrane alterations
– thickening, loss of transparency

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My Approach to Otitis
1. Consider history & clinical signs
2. Collect samples for ear cytology & assess canals
3. Otoscopic exam if possible
4. Treatment
a) Acute dz
b) Chronic/Severe dz

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Treatment: Acute Dz
1. History + CS - 1º factors
2. Cytology (every patient!)
– sample + assess canal/discharge
1. Otoscopic exam (if possible)
– foreign bodies, ear mites
1. Treat 2° bacterial/yeast infections
– TM rupture?
– doesn’t influence my tx choices!

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Treatment: Antimicrobials
• Best guided by cytology (100% cases)
• Bacterial culture may be helpful (5%)
– rods (uniform population) & many previous treatments
– can be misleading; must interpret in light of cytology
– not helpful if yeasts only, or mixed populations
a) Systemic – rarely needed; often unreliable alone
b) Topical – most effective; 3wk minimum

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Antimicrobials
1. Yeasts on cytology
– miconazole - Surolan®, Easotic®
– clotrimazole - Otomax®, Mometamax®
– nystatin - Canaural®, Topigen®

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Antimicrobials
1. Yeasts
2. Bacterial cocci
• polymixin B & miconazole - Surolan®
• fusidic acid - Canaural®

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Antimicrobials
1. Yeasts
2. Bacterial Cocci
3. Bacterial Rods (resistance more freq):
• gentamicin - Otomax®, Topigen®, Easotic®, Mometamax®
• enrofloxacin - Baytril otic®
• polymixin B - Surolan®
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Antimicrobials
1. Yeasts
2. Bacterial Cocci
3. Bacterial Rods (resistance more freq)
4. Combinations (rods + cocci &/or yeasts)
• Treat for rods first
• Culture rarely indicated
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Treatment: Acute Dz
Topical Treatment Principles
1. Drug choices – based on cytology
2. Volume/method administration !!!
3. Monitor cytology q. 2wks
• continue 1wk beyond cytological resolution

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Treatment: Acute Dz
1. Antimicrobials - mostly
2. Ear Cleaners
– rarely during tx (unless very productive ears)
– may institute regular preventative treatment plan
» Epi-otic®, Bayer Clean Ear®, Milo’s Ear Cleanser®
» PAW Gentle ear cleaner®
» Otoflush® (TrizEDTA)
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Treatment: Acute Dz
1. Antimicrobials - mostly
2. Ear Cleaners - rarely
3. Anti-inflammatories - mostly
• Important
• Most topical medicated drops contain
• not Baytril otic® or Ilium® ear drops
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Treatment: Chronic/Severe

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Treatment: Chronic/Severe
As for acute ear dz plus:
1. Flush (G/A) if copious/persistent discharge
– sterile saline, ~14g i/v catheter, 20ml syringe
– videoscope, 4g catheter through port – more effective
• myringotomy if TM intact/suggestion middle ear dz
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Treatment: Chronic/Severe
As for acute ear dz plus:
1. Flush (G/A)
2. Treat 2º infections aggressively
– bacterial culture MAY be helpful (if rods OR poor response)
– systemic antimicrobials more often
• yeasts - ketoconazole 5mg/kg bid or itraconazole 5mg/kg sid
• bacteria - based on cytology & c/s
– compounded topicals
• silver sulfadiazine/dex; ticarcillin/clavulinic acid/dex; enrofloxacin/dex
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Treatment: Chronic/Severe
As for acute ear dz plus:
1. Flush (G/A)
2. Treat 2º infections aggressively
3. Anti-inflammatories essential
– topicals often sufficient
• less potent: pred (Surolan®, Canaural®)
• more potent: betamethasone (Otomax®),
fluocinolone (Topigen®)
• most potent: mometasone (Mometamax®),
hydrocortisone aceponate (Easotic®)
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Treatment: Chronic/Severe
As for acute ear dz plus:
1. Flush under G/A
2. Treat 2º infections aggressively
3. Anti-inflammatories essential
– topicals often sufficient
– systemic (v. inflamed ears + prior to flushing if stenotic)
• pred 0.5-1mg/kg sid
• cyclosporine (severe hyperplasia e.g. Cockers)
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Treatment: Chronic/Severe
As for acute ear dz plus:
1. Flush under G/A
2. Treat 2º infections aggressively
3. Anti-inflammatories essential
4. Sustained treatment & repeat cytology VITAL
• 2wkly, until beyond cytological resolution
• min 6-8wks
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Treatment: Chronic/Severe
As for acute ear dz plus:
1. Flush under G/A
2. Treat 2º infections aggressively
3. Anti-inflammatories essential
4. Sustained treatment & repeat cytology VITAL
5. Investigate for underlying dz
• hypersensitivities, endocrinopathies
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Treatment: Chronic/Severe
Minimise recurrences?
1. Manage 1°/predisposing factors if possible
– swimming?
– hair removal?
1. Regular cleaning
– q. 1-2wks if tolerated
1. Pulse treatment (atopy)
– anti-inflam drops 1-2 times wkly
• e.g. Surolan® (↑ risk of antimicrobial resistance)
– best with vigilant owners
• e.g. silver sulfadiazine (Flamazine®)/dex compounded)
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Questions??
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