What is otitis externa?
Otitis externa is an infection of the external ear canal (outer ear infection) and is one of the most common types of infections seen in dogs.
Some breeds, particularly those with large, floppy, or hairy ears are more prone to ear infections (e.g., cocker spaniels, miniature poodles, Old English sheepdogs), but they can occur in any breed.
What are the clinical signs of an ear infection?
Ear infections cause pain and discomfort, and the ear canals are sensitive. Many dogs will shake their heads and scratch their ears, attempting to remove the debris and fluid from the ear canal.
The ears often become red and inflamed and may develop a bad odor. A black or yellowish discharge commonly occurs. In chronic cases, the ears may appear crusty or thickened, and the ear canals often become narrowed (stenotic) due to chronic inflammation.
The signs of ear infection are similar to the signs of ear mites: a black discharge, scratching, and head shaking. However, ear mite infections are more common in puppies and kittens. Adult dogs may occasionally contract ear mites from infected puppies or cats. Ear mites create an environment in the ear canal that often leads to a secondary bacterial or fungal infection.
Can I just treat these symptoms with over-the-counter ear drops?
No, your veterinarian must diagnose the exact cause of the problem to select appropriate treatment. There are several kinds of bacteria and at least one type of fungus that commonly cause ear infections. Knowing the type of infection present can better direct medication choice for the most effective treatment.
Sometimes, the problem is a foreign body, a polyp, or a tumor, and treatment with medication alone will not resolve these problems. Your dog must be examined to ensure the eardrum is intact. If the eardrum is ruptured, administration of certain medications can result in loss of hearing. Your veterinarian can detect a rupture by performing a thorough ear examination.
How are ear infections diagnosed?
Your veterinarian may examine the ear canal with an otoscope, an instrument that provides magnification and light. An otoscope gives a good view of the ear canal and allows your veterinarian to determine whether the eardrum is intact and whether a tumor or foreign material is in the canal.
If there is a lot of debris, discharge, or inflammation in the ear canal, it may not be possible to perform a thorough examination. If this is the case, or if the ears are extremely painful and your dog refuses to allow ear examination, sedation or general anesthesia may be necessary.
Your veterinarian may examine the material from the ear canal under a microscope. Microscopic examination is essential to choose the right medication to treat the inflamed ear canal. Culture and susceptibility tests are often used in severe or chronic ear infections to determine what microorganisms are present and to ensure your dog receives the right medication.
How are ear infections treated?
The otoscopic examination and cytology results tell the veterinarian how to treat your cat. If a foreign body is lodged in the ear canal, your dog can be sedated so it can be removed. Medication can be prescribed specifically for bacteria (antibiotics) or fungi (antifungals), and some medications combine antibiotics and antifungals with an anti-inflammatory agent.
It is important to identify any underlying disease that may have led to an ear infection. Allergies are involved in as many as 43% of ear infection cases, especially chronic or recurrent infections, and ear infections occur in 65% to 80% of dogs with food allergies. Hormonal issues like hypothyroidism can also lead to repeated ear infections. If your veterinarian suspects an underlying disease, they must diagnose and treat it, or your dog will continue to experience ear problems.
The ear canal may close when an infection becomes severe and chronic – a condition known as hyperplasia or stenosis. If the ear canal is swollen, it is difficult or impossible for medications to penetrate the horizontal canal. Some medications may help shrink the swollen tissues and open the canal in some dogs, but most cases eventually require surgery.
The most common surgery is a lateral ear resection, in which the vertical part of the ear canal is removed and the horizontal canal is cleared of swollen tissue. Removing the vertical canal is relatively easy but removing large amounts of tissue from the horizontal canal is more complicated. In some cases, it is necessary to remove the entire ear canal (total ear canal ablation), which may result in permanent hearing impairment.
What is the prognosis?
Nearly all ear infections in dogs that are diagnosed and treated can be successfully managed. However, if an underlying cause remains unidentified and untreated, the outcome is less favorable. Several recheck examinations may be needed before the outcome is successful.
Left untreated, ear infection can result in aural hematoma, in which blood vessels in the ear flap break, causing painful swelling that requires surgical treatment. Deep ear infections can damage or rupture the eardrum, causing an internal ear infection and even permanent hearing loss.
