Introduction
Dogs' ears come in various shapes and sizes, but they all share one unique characteristic - a long ear canal with vertical and horizontal components. This anatomic uniqueness of the dog's ear easily traps debris and increases a dog’s risk of ear infections.
Naturally, dogs shake and scratch their heads when something is inside their ears to get rid of it. Instinctively dogs shake their heads in response to sensations, it could be itchiness or irritation in their ears.
While shaking can solve simple problems like some water or an insect in the ear, continued shaking indicates that there could be something more inside the dog’s ear that needs to be addressed.
Medically, what causes head shaking and ear scratching in dogs?
Acute or chronic inflammation of the external ear is a more frequent cause of head shaking and ear scratching in dogs than in cats. It is one of the primary reasons dogs are presented to veterinarians.
The inflammation of the external ear is a condition called Otitis externa. It affects up to 20% of the dog population, and the disease is often caused by different combinations of primary, predisposing, and perpetuating factors.
Primary factors:-
These are diseases that affect the external ear canal directly, causing otitis. These include:-
Ear parasites (mites) such as Otodectes cyanotis,
Hypersensitivity disease [food allergy, atopic dermatitis, contact hypersensitivity]. Underlying hypersensitivity disease is the most common primary factor leading to otitis in dogs,
Endocrine diseases such as hypothyroidism, diabetes mellitus
Ear neoplasia (tumours/cancers) and
Foreign bodies, e.g. grass.
Predisposing factors:-
These are factors that alter the local ear canal environment and create an increased risk for the development of otitis externa. Several predisposing factors are involved in causing otitis externa. These factors include:-
Ear canals with excessive hair,
The haired concave side of ears,
Anatomical ear canal stenosis,
Increased cerumen (earwax) production in the ear canals,
Ear canal masses / Obstructive diseases (neoplasms/tumours/cancer) ,
Frequent ear cleaning,
Changes in external environmental temperature and humidity
Pendulous ears,
Moisture retention,
Washing, injury during manipulations,
Foreign bodies,
Prolonged antibiotic treatment,
Systemic conditions (immunosuppression)
A plethora of microbiota, such as bacteria, yeasts, and progressing pathological alterations (hyperplasia, oedema, fibrosis).
Perpetuating factors:-
Perpetuating factors do not initiate inflammation but exacerbate the inflammatory process and maintain ear disease even if the primary factor has been identified and corrected. The most common factors include:-
Bacteria such as Staphylococcus and Pseudomonas,
Malassezia yeasts
The presence of infection in the middle ear can also act as a perpetuating factor, leading to recurrent external ear infections.
Perpetuating factors are often the main reason for treatment failure in dogs affected by recurrent otitis externa.
How is Otitis Externa diagnosed?
Otitis Externa diagnosis is made in five steps which are:-
Clinical examination,
Direct examination of cerumen/earwax (erythematoceruminous otitis externa),
Bacterial culture and sensitivity testing (suppurative otitis externa),
Direct impression smears, cleaning and otoscopy, and
Diagnosis of underlying skin disease.
How is Otitis externa treated?
The successful treatment of the disease requires appropriate medications, including anti-inflammatory drugs, antifungal agents and chemotherapeutics with the sensitivity of the aetiological agents.
How is Otitis Externa Prevented?
The following are the few effective preventive measures that exist for otitis externa.
A thorough otic examination of all patients presented for a physical examination to help with the early detection of mild and early cases of otitis.
Thorough client education and detailed diagnostic work-up when dogs are presented with signs of otitis externa
Frequent follow-up examinations help prevent complications that may lead to chronic otitis, hearing loss, otitis media, and end-stage ear disease.