1. **Introduction**
- The animal ear is multifunctional serving purposes beyond just hearing.
- Function: auditory perception balance communication and potential health indicators.
- Healthy ears influence environmental interactions communication abilities and overall comfort.
- Emphasis on the holistic nature of health with ears playing a significant role in an animal's overall wellbeing.
- The lecture aims to explore the importance of ear health in animals.
2. **Auditory function**
- Ears enable animals to detect sounds ensuring safety and communication
3. **Balance and equilibrium**
- The inner ear is crucial for balance and coordination
4. **Communication**
- Ears assist in interpretation and communication
5. **Disease prevention**
- Regular care is needed to prevent infections and complication.
6. **Overall comfort**
- Ear problems can cause discomfort and lead to harmful behaviours.
7. **The ear's health can be compromised by various ailments many of which have dermatological origins or implications.**
- The skin is the body's largest organ that:
- Acts as the primary barrier against external environmental factors.
- Protect internal structures and systems.
- The epithelial components of the ear and the skin share many characteristics such as disruptions or diseases affecting the skin can also affect the ears.
- A comprehensive understanding of the dermatological aspects of ear health is crucial for effective veterinary care.
8. **Anatomy and Physiology of the Animal Ear**
- Basic structure: External ear middle ear and inner ear
9. **External ear:**
- Composed of auricular and annular cartilage.
- The auricular cartilage of the pinna forms a funnel-like shape initiating the external ear canal.
- The canal has a vertical section (about an inch) that transitions to a horizontal section both containing auricular and annular cartilage.
10. **Middle ear:**
- Contains an air-filled chamber called the tympanic cavity.
- Houses three small bones for hearing known as auditory ossicles.
- Features a semi-transparent eardrum with two parts: Pars flaccida and Pars tensa.
- Components of the tympanic cavity:
- Minor epitympanic recess.
- Significant ventral bulla.
- Main tympanic bulla.
- The medial side showcases a ridge called the promontory which houses the cochlea.
- Behind the promontory is a round window with a delicate membrane.
- Above is an oval window with a diaphragm where the stapes bone connects.
- The auditory tube connects the nasopharynx to the front of the main tympanic cavity.
- Auditory ossicles amplify sound vibrations from the eardrum to the inner ear.
11. **Inner ear:**
- Located within the petrous section of the temporal bone.
- Encased in a bone-made maze.
- This bony structure contains another maze made of membranes.
- Contains sensory structures essential for hearing and balance.
12. **Definition and classification of otitis**
- Otitis externa
- Refers to the inflammation of the external ear canal including the pinna.
- Accounts for 10 to 20% of dog-related consultations.
- Classification of causes:
- Predisposing Factors
- Primary Factors Perpetuating and Secondary Factors
- Data from insured Australian dogs in 2016 and 2017 showed otitis externa had an incidence rate of 34.12 and 34.82 per 1000 dog years at risk respectively.
- Dogs may experience multiple escalating infections in their lifetime with potential microorganism resistance to treatments.
13. **Otitis media**
- Refers to the inflammation of the middle ear containing the auditory ossicles.
- Can result from untreated otitis externa or due to tumours polyps etc.
- In dogs:
- 16% with acute otitis externa and 52% with chronic otitis externa develop otitis media.
- Chronic otitis externa can progress to otitis media.
- Primary Secretory Otitis Media (PSOM) is notable in Cavalier King Charles Spaniels presenting symptoms similar to syringomyelia.
- In cats:
- 63% diagnosed with otitis media/interna showed no previous ear infection signs.
- Commonly associated with past respiratory issues or inflammatory growths.
- Rarely otitis media may follow otitis externa.
14. **Otitis interna**
- Refers to the inflammation of the inner ear where the cochlea and vestibular system reside.
- Can result from progressing otitis media or systemic infections.
- Symptoms include dizziness loss of balance involuntary eye movement (nystagmus) and hearing loss.
- Less common than otitis externa or media typically presenting as a complication of these conditions.
15. **Otitis externa frequently involves a series of interconnected factors (Rosser 2004):**
- Primary factors
- Direct triggers or elements that initiate inflammation of the external ear canal.
- Secondary factors
- Issues arising in an already compromised ear.
- Often become persistent or recurring if the root cause isn't addressed.
- Predisposing factors
- Processes or elements increasing the risk of otitis externa.
- Work in tandem with primary or ongoing causes to produce the clinical condition.
- Recognition and management are crucial for a holistic treatment approach.
- Perpetuating factors
- Do not initiate otitis externa but play a role in its continuation once established.
16. **III. Primary Causes of Otitis Externa (OE) in Dermatology**
- Allergies
- Leading cause of OE.
- Atopic dermatitis causes OE symptoms in 55% of affected dogs. For 3-5% of these dogs, it's their only symptom.
- OE is seen in up to 80% of dogs with food allergies and is the sole symptom in 25% of cases.
- A study by Saridomichelakis et al. (2007) identified allergic dermatitis as the primary OE cause in 43 out of 100 dogs. Of these:
- 12 had acute OE.
- 31 had chronic or recurring OE.
- Only 8 were diagnosed with atopic dermatitis; 2 had adverse reactions to food.
- 30 (69.8%) showed itching excluding around the ears.
- 42 (97.7%) had self-inflicted skin lesions.
17. **Parasites**
- Otodectes cynotis (ear mite) is responsible for over 50% of feline OE cases.
- Otodectes cynotis infestation leads to itching in 41.5% of cats and unusual ear secretions in 85.4%.
- Infestation rates: Young cats have the highest rate of singular infestation (10.38%); elderly dogs have the lowest (0.89%). Cats overall are more prone to infestations than dogs.
- Other parasites like Sarcoptes Notoedres Cheyletiella harvest mites and the spinose ear tick can also cause OE. Demodex mites can result in waxy ear infections.
18. **Autoimmune skin diseases**
- Conditions such as pemphigus foliaceus, pemphigus erythematosus, and discoid lupus erythematosus can affect the external ear canals.
- Seldom primary causes for OE, they usually accompany skin lesions elsewhere.
- Pemphigus foliaceus, a prevalent autoimmune skin condition in dogs, disrupts cell-to-cell binding causing pustules, crusts, and scales.
19. **Endocrine disease**
- Hypothyroidism in dogs can lead to skin issues resulting in OE.
- Skin changes include seborrhea, hair thinning, hyperpigmentation, reduced healing, and increased infection susceptibility.
- The dry skin from hypothyroidism can elevate wax production in the ear, fostering bacterial and yeast growth which can progress to OE.
20. **Epithelialization disorder**
- Idiopathic seborrhea:
- A keratinization disorder particularly evident in American Cocker Spaniels.
- Causes alterations in discharges from the ear canal's ceruminous and sebaceous glands and prolongs epithelial renewal time.
- Leads to an accumulation of keratosebaceous waste in the outer ear, promoting microbial growth.
- Sebaceous adenitis:
- A rare skin condition causing inflammation and damage to the sebaceous glands which produce skin oils.
- Most frequently affects breeds like Standard Poodles, Akitas, and Vizslas.
- Dry skin from this condition makes the ear canal susceptible to inflammation and infection.
- Lack of protective oils supports bacterial growth in the ear canal.
- Inflammation thickens the ear canal's skin, obstructing the natural drainage of earwax and increasing infection risk.
21. **Foreign bodies:**
- Items like grass seeds or burrs can become trapped in the ear, leading to intense irritation and inflammation.
- Signs include head shaking or ear scratching by the affected animals.
- Avoid letting pets roll in dirt or sand to prevent foreign object entry.
22. **Medication reactions:**
- Reactions to certain medications or topical irritants can trigger otitis externa.
- Substances such as alcohol may dry out the ear, causing discomfort.
- Solutions with a low pH disrupt the natural acidic balance of a dog's ear, favoring bacterial or yeast growth.
- Ingredients like propylene glycol in some products can irritate sensitive dogs.
23. **Ear canal neoplasia and polyps:**
- A significant cause of otitis in dogs and cats.
- Neoplasia can lead to benign or malignant tumors in the ear canal, resulting in obstructions and inflammation.
- Polyps, non-cancerous growths, can also arise in the ear canal, causing similar issues.
- Both disrupt the ear's natural environment, creating conditions conducive to bacterial and yeast infections.
- A detailed ear canal examination is essential for early identification and effective management of the condition.
24. **IV. Secondary Factors**
- Microbial infections
- Bacteria or yeast in otitis externa cases are opportunists, not primary pathogens.
- Even if infections don't recur post-treatment, they should be seen as a one-time disturbance to the external ear canal.
- Recurring infections indicate a need to determine the root cause.
- If not addressed, bacteria and yeast can grow resistant to treatments, potentially becoming immune to all antimicrobial agents.
25. **Bacterial infections**
- Staphylococcus spp.:
- Includes species like S. pseudintermedius, which is a Gram-positive bacteria linked to various infections in dogs (skin, ear, urinary, etc.)
- While commonly found on the skin, some strains can become opportunistic pathogens in compromised ear environments, leading to acute or chronic otitis externa.
- Methicillin-resistant Staphylococcus aureus (MRSA) is a strain resistant to multiple antibiotics, complicating treatment.
- Pseudomonas aeruginosa:
- A significant Gram-negative bacteria in otitis externa.
- Notable for strains resistant to multiple drugs.
- Produces a characteristic foul odor.
- Known for biofilm production, which challenges treatment.
- Biofilm
- Recognized as a significant virulent factor in chronic infections.
- Enhances bacterial resistance to treatments.
- Protects bacteria from both the immune response and direct medication.
- Described as a protective layer or "slime" produced by bacteria.
- Comprises components such as:
- Extracellular polysaccharides.
- Structural proteins.
- Nucleic acids.
- Particularly influential in infections caused by Pseudomonas.
- Identified in approximately 40% of Pseudomonas samples.
- Requires higher antimicrobial concentrations for effective treatment due to its presence.
- Study by Fernandez et al. (2006):
- Evaluated 53 dogs with otitis externa admitted to ZSU/UVP.
- Most common bacterial agents identified:
- Pseudomonas aeruginosa: 22.22%
- Proteus mirabilis: 13.89%
- Staphylococcus aureus: 12.50%
- Staphylococcus epidermidis: 8.33%
- Escherichia coli: 5.56%
- Staphylococcus coagulase-negative: 5.56%
- In the control group (healthy patients):
- Most common bacteria: Bacillus spp., Staphylococcus epidermidis, and Staphylococcus coagulase-negative each at 16.67%.
- Cytology tests showed Malassezia pachydermatis present in 69.8% of the samples.
26. **Fungal Infections**
- Malassezia pachydermatis:
- Predominant yeast associated with otitis externa.
- Found in 20% to 50% of healthy ears.
- Present in up to 72% of infected ears (as per August 1988).
- A normal skin inhabitant, but it can overgrow in the moist environment of an inflamed ear.
- Causes pruritus and emits a distinct yeasty odor.
- Often observed alongside allergic skin disease.
- Other fungal organisms occasionally identified in affected ears include:
- Candida spp.
- Aspergillus spp.
- Microsporum
- Trichophytum spp.
- Sporotrhrix schenkii
- Paecilomyces.
27. **V. Predisposing Factors**
- Ear conformation and hair growth
- Breeds predisposed due to ear shape and size
- O'Neill et al. (2021) study findings:
- Designer breeds had 1.63 times higher odds of developing otitis externa compared to crossbred dogs.
- Dogs with pendulous ear carriage had 1.76 times the odds, and those with V-shaped drop ear carriage had 1.84 times the odds.
- Poodle and Spaniel types had 1.91 and 1.24 times the odds respectively
