Otitis Externa is the medical term for an infection and inflammation of the external ear canal. Otitis is a very common malady of cats and dogs that causes a lot of distress to owners and discomfort to the pet.
Anatomy
The external auditory canal is the portion of the ear located between the pinna (ear flap) and the tympanic membrane (ear drum). The ear canal of the dog and cat is long and narrow. Halfway along its length, the ear canal turns from vertical to horizontal forming an “L” shape. Otitis externa is an ear infection and inflammation of the epithelial lining of the ear canal. If the infection moves past the ear drum into the middle and inner ear it becomes otitis media or interna.
Symptoms
Dogs and cats with otitis externa may have any of the following symptoms:
- Scratching of the ears and shaking of the head
- Ear flap and canals may be inflamed and ulcerated
- A waxy discharge from the ears that may be yellow to brown in color
- Ears may have a strong unpleasant odor
- Shies away from being petted on the head
- Head tilt or loss of balance
- Changes in hearing
Causes
Otitis externa is usually caused by an infection. A small number of yeast and bacteria are considered normal micro-flora of the skin and ears of dogs and cats. When this normal micro-flora is disturbed and over grows, an infection results. The most common opportunistic organisms that can cause otitis externa are Staphylococcus intermedius bacteria and Malassezia pachydermatitis yeast. Ear infections are not contagious between animals because infections are caused by an over growth of normal skin flora.
Diagnosis
A veterinarian can diagnose otitis externa by performing an otoscopic exam of the ear canal. An Otoscope allows a veterinarian to look down into the ear using magnification and light to evaluate the health of the external canal and tympanic membrane. When otitis is suspected, swab samples of the ear discharge should be taken from the ear to perform a microscopic cytological exam. Cytology helps to determine whether there are yeast, bacteria, or inflammation present in the ear. Occasionally samples of the ear discharge may be sent for culture to determine what species of bacteria or yeast are present and the organisms susceptibility to medications.
Treatment
Medical management with topical medicine is preferred for most pets with otitis externa. Treatment is usually a regiment of ear cleaning and topical ear ointment. Cleaning of the ears is very important for treatment of ear infections, especially if a lot of discharge is present. Ear cleaners contain cleansing and antiseptic agents that help to remove waxy discharge, disinfect the ear canal, pH balance, and decrease the moisture in the ear canal. Next, the ear canal is treated with a topical medication to control the over growth of bacteria or yeast. Most topical ear medication formulas contain a mix of an antibiotic, antifungal, and anti-inflammatory medications selected based on cytology results and severity of infection. Medication are ointments or drops that are applied directly into the ear canal to treat the infection. Finally, depending on the severity of the infection, a third component of treatment may be prescription oral medications for inflammation or infection.
If your pet has any symptoms of loss of balance or deafness, this may be a sign of a ruptured ear drum and otitis interna. Discontinue any ear cleaner and topical medications and call the clinic to schedule a recheck appointment.
Predisposing Factors
Some breeds of dogs have a predisposition to develop otitis externa because of small ear canals or long, floppy ear flaps that prevent air flow. Otitis externa is a common condition in breeds of dogs such as the Golden Retriever, Cocker Spaniel, and Labrador Retriever. Some activities such as frequent swimming or bathing, trap water in the ear canal and can predispose a pet to ear infections.
Occasionally, recurrent otitis externa is caused by an inflammatory allergy reaction. Allergens like pollens, mold, dust, cigarette smoke, and certain foods can cause chronic inflammation that can lead to ear infections. A pet with allergies may occasionally have inflammation of the ear canal without infectious agents present.
Older dogs may also have hormonal problems that depress the immune system. Diseases such as diabetes, hypothyroid, or poor adrenal gland function can predispose a pet to re-current otitis externa
Prognosis
The prognosis for otitis externa is excellent when diagnosed and treated early in the course of the disease is excellent. Most acute cases of otitis externa respond quickly to prescription medications. If left untreated, otitis externa can cause rupture of the ear drum and infection of the inner ear. Otitis interna can affect a pet’s sense of balance and can also cause deafness. Identifying and treating an ear infection early, while it is still in the external ear canal, will help prevent more serious inner ear infections that have a guarded prognosis.
