Otitis externa Flashcards
What owners see when their animal has an ear infection:
- Erythema on the ear pinna and in ear canal
- Excess exudate, edema, pain, malodour
- Head shaking, scratching
- Excoriation, dermatitis around ears, on face, aural hematomas
- (head tilt)
Otitis externa/hematoma
What skin disease causes ear margin alopecia?
sarcoptes scabiei
(vasculitis too but isn’t skin dz)
Primary causes of otitis externa (capable of causing otitis by itself). (4)
- Allergy (atopic dermatitis, food allergy)
- Parasites (Otodectes cynotis, Demodex spp, Sarcoptes scabiei)
- Foreign bodies (hair, grass awn)
- Immune-mediated, endocrine, autoimmune diseases
Causes of otitis externa can be:
* Primary
* Secondary
* Predisposing
* Perpetuating
Dog with allergic otitis:
Erythroceruminous otitis (ceruminous
otitis)
Ceruminous cystomatosis (top) and
inflammatory polyps (lower) in cats (these are NOT neoplasia)
These can be both primary and predisposing causes of otitis externa.
Ceruminous cystomatosis
Ceruminous cystomatosis is a benign, non-neoplastic condition affecting the ceruminous glands in the external ear canals of small animals, particularly cats.
It is characterized by the development of multiple cystic structures filled with a clear to brownish fluid, leading to otic discharge, recurrent otitis externa, and potential hearing impairment.
The exact cause remains unclear, but chronic inflammation and glandular hyperplasia are suspected contributors.
Diagnosis is typically based on otoscopic examination and histopathology. While benign, severe cases may require surgical intervention, such as total ear canal ablation, if medical management with cleaning and anti-inflammatory therapy fails.
Secondary causes of otitis externa. (2)
- Bacteria (cocci, rods) e.g. pseudomonas
- Yeast (malassezia)
Neutrophil involvement causes slimeyness/wetness.
Suppurative otitis
Neutrophil involvement causes slimeyness/wetness.
Predisposing factors for development of secondary otitis externa. (4)
- Anatomical (hairy or stenotic ear canals,
pendulous ears) - Excessive moisture (swimming, moist and
warm environment, long hair trapping moisture) - Obstructions (neoplasia, polyps, cysts)
- Excess or wrong cleaning, plucking hairs from ear canal (regular use of Nacl in the ears is no good, one off time is fine though).
Ear cleaning products are oily so they can actually dry out a wet ear canal. Put some in after a dog has gotten water in its ear canals.
Epidermal hyperplasia is from chronic otitis.
Name 4 Perpetuating factors for otitis externa.
- Epidermal hyperplasia
- Glandular hyperplasia
- Ear canal stenosis and ossification
- Otitis media
Why does canine hypothyroidism predipose to otitis externa?
In hypothyroid dogs, the immune response may become impaired, leading to an increased susceptibility to infections.
hair thinning, dry or flaky skin, and increased oiliness or wax production in the ear canal. The buildup of wax and debris can create an ideal environment for microorganisms
In hypothyroid dogs, the skin’s ability to shed dead cells and regenerate may be impaired, which can contribute to clogged ear canals
excess or abnormal ear wax due to hormone imbalance.
Anamnesis for otitis should include: (5+)
- Dermatological history!
- Is it the first episode?
- Hair cleaning at home? Prior treatments?
- Other dermatological problems?
- Life style of the dog – is it outdoor/indoor
dog, contact with other animals, swimming
etc.
Examination of an otitis patient should include: (5)
- Clinical examination (endocrine disease)
- Examination of the ears (pinna vs ear canal)
- Otoscopy (ear canal, tympanum, foreign bodies, neoplasias)
- Dermatological examination (allergies, autoimmune diseases)
- Examination of the cerumen (also cytology)
Microscopy in otitis cases is…
Essential in all cases! Even rechecks!
* Examination of unstained cerumen in oil
(cerumen+oil+low magnification)
* Stained cytology too (cerumen+heat +Diff-Quick+oil + large magnification)
Findings:
* Otitis externa + 3-5 cocci or malassezia
* No matter how many bacteria/yeast +
neutrophils/phagocytosis
* Rods - always a problem
neutrophils
eosinophils from a pemphigus case
rods
yeast
Bacterial culture and sensitivity testing in what otitis cases?
In case of Chronic, recurrent cases that don’t respond to typical treatment!
So if you had an otitis case so bad that you’re considering systemic AB.
Other possible diagnostics for otitis after microscopy: (5)
- Elimination trial
- Allergy testing
- Thyroid panel (plus other blood tests)
- Skin biopsy
- X-ray, MRI, CT
Treatment of otitis externa main points. (4)
- Finding the primary disease
- Eliminating the secondary factor
- Managing the predisposing factors
- Removing of perpetuating factors
Local treatment vs systemic treatment for otitis externa.
Local: EVERY POSSIBLE CASE should receive local tx
Systemic only when: parasites, corticosteroids for
stenotic and severely inflamed ears, otitis media, when owners can’t handle topical treatment - but that isn’t really a good reason for using systemic drugs when you shouldn’t.
Proper ear cleaning!
Showing and explaining to the owner how to treat and clean the ears!
