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Dog: Otitis

General information

Other common/scientific names: ear infection, otitis externa, otitis media, otitis interna

Otitis is defined as inflammation of the ear and is commonly referred to as an ear infection. It is a very common medical problem in dogs. A dog’s external ear canal is shaped like an “L” with a vertical portion and a horizontal portion. Because of this structure, dogs are more prone to ear infections due to the fact that debris and wax must work its way upward rather than straight out. The tympanic membrane (ear drum) separates the external portion of the ear from the middle and inner ear. The inner ear is in close contact with the central nervous system (brain) and houses the vestibular system which is responsible for balance. While ear infections are rarely life-threatening, they can be very frustrating due to the difficulty in diagnosing and treating the primary cause. This can lead to numerous recurrences and lengthy, expensive treatments.

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Abb. GGT9P1RY: Schematic illustration of the outer ear, middle ear and inner ear.

Causes

Several predisposing factors can increase the risk of developing ear infections. They work in conjunction with primary causes and perpetuating causes. Predisposing factors include long, pendulous ears and excessive moisture from frequent swimming or bathing.

There are four primary causes or triggers of otitis which initiate the resulting inflammation and/or infection. These causes are:

  • Parasites: The most common parasite affecting the ear is ear mites or Otodectes sp. Other parasites which can cause ear infections are fleas, ticks and skin mites (Sarcoptes, Notoedres, Demodex, Cheyletiella spp).
  • Skin Allergies: Dogs can develop allergies to particles they inhale, come in contact with or ingest such as certain types of food.
  • Foreign Bodies: Foreign objects such as plant awns, dirt, sand and hair can lodge in the ear canal causing inflammation and infection. Tumors in the ear canal can also cause chronic otitis.
  • Autoimmune Diseases: Although rare, some autoimmune skin diseases can cause otitis.

Perpetuating factors do not cause otitis but these factors allow the condition to continue after the primary problem is resolved. These factors are bacteria, yeast and otitis media or infection of the middle ear.

Cardinal symptom

Scratching at ears

Symptoms

Clinical signs of otitis include scratching at ears, head shaking and painful ears. As the infection worsens, the dog may hold one ear dropped and a discharge and a foul odor is noticed. The inside of the pinna (earflap) may be red, swollen with scabs and crusts. With chronic otitis, the skin on the pinna becomes thickened, pigmented and scarred.

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Abb. GGBXY50W: Chronic Otitis.
This picture illustrates a red, swollen ear with thickened, pigmented skin.

If the infection reaches the middle or inner ear, these dogs may exhibit signs of vestibular disease such as a head tilt, lack of balance and nystagmus (unusual eye movements). Another complication of otitis is an aural hematoma. This results when blood vessels rupture in the earflap from vigorous shaking and scratching.

Diagnosis

A complete physical examination with special attention to both the ears and the skin should be performed. Many dogs also have concurrent skin disease such as allergies which can be the primary cause of otitis. If only one ear is affected, a foreign object, hair or a tumor should be suspected. However, if both ears are affected, allergies, parasites or an autoimmune disease may be the cause.

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Abb. GSR988TV: Foreign body sticking out of the ear

Because many dogs with otitis are extremely painful, sedation may be needed to perform a complete otoscopic examination. It is important to visualize the ear canals and tympanic membrane (ear drum) for the presence and degree of swelling, inflammation and exudate (discharge).

Laboratory tests are necessary for the proper treatment of otitis. These include cytologic examination of an ear swab to determine the existence of ear mites, bacteria, yeast or inflammatory cells. In recurring cases of otitis, additional laboratory tests may be needed. These include culture and sensitivity testing to determine the precise organism and the appropriate antibiotics or antifungal medication. In rare cases, a biopsy of the skin of the earflap may be necessary.

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Abb. GSR9BM6C: Ear mite, found in an ear swab.

Treatment

Treating the Primary Cause

The first goal of treating otitis is to determine the primary cause or trigger. Treatment will depend on this diagnosis. Ear mites, fleas and ticks can be treated with antiparasitics. Skin mites may indicate an underlying disorder and need to be treated with appropriate medication. Management of allergic conditions can help resolve associated otitis. Foreign objects and tumors may need to be removed under general anesthesia. An autoimmune disorder can be treated with specialized medication.

Treating the Perpetuating Cause(s)

Perpetuating causes (bacteria, yeast and otitis media) are the next concern when treating otitis. The resulting infection, excessive exudate and inflammation of the ear canal are treated with various combinations of ear cleaning, topical medications, systemic medications and surgical treatment.

Ear Cleaning

If the dog’s ear has a large amount of exudate (discharge) and wax, this material needs to be removed before treatment. Providing the dog is not too painful, the ears can be cleaned in the examination room with a bulb syringe. If the dog is extremely painful, medication can be dispensed for pain and swelling. The ear cleaning and flush may need to be performed under sedation if the dog is painful or the ear canal is full of debris and exudate. Depending on the dog, otic cleaning agents will be dispensed to be used by the owner at home.

Topical Medications

Topical ear medications are the foundation to treating the perpetuating factors of otitis. These medications commonly contain combinations of antibiotics, antifungals and anti-inflammatories and are applied directly to the ear. These can either be administered by the veterinarian or dispensed to the owner for continued treatment at home.

Systemic Medications

When the otitis is severe, recurring and/or involves the middle and inner ear, systemic medications usually in the oral form are also sent with the owner to administer to the dog at home. These include antibiotics, antifungals and anti-inflammatories.

Surgical Treatment

Some ear infections cannot be controlled by medications. The infection may be too resistant for treatment or the infection continually recurs. Perhaps the ear canal is so scarred and narrowed that external cleaning and topical medications are useless. In these cases, surgery may be indicated. There are two techniques used for dogs with chronic otitis: the lateral ear resection and the total ear canal ablation. The lateral ear resection is a conservative approach which removes the vertical portion of the ear canal. This allows for better cleaning and better canal ventilation. The total ear canal ablation, on the other hand, removes the entire ear canal and bones of the middle ear. The healthy tissue around the ear is sutured closed and allowed to heal. Because of the potential for nerve damage and other complications, a total ear canal ablation should be performed by a specialist.

Due to the tendency for otitis to become chronic, a recheck examination is need after 2-3 weeks to make sure the infection has resolved and the ear canals are healing.

Prognosis

Prognosis is good for mild otitis in which the primary cause can be identified and treated. In cases which become chronic and the underlying trigger cannot be determined or the dog is difficult to treat at home, the prognosis can be guarded.

Prevention

While some types of otitis cannot be prevented, it is recommended that your dog not be allowed to swim in lakes, ponds and rivers. Placing cotton in your pet’s ear when bathing can prevent excessive water and moisture from accumulating in the ear canal. Some veterinarians recommend pulling excessive hair from the ear canals while other veterinarians feel this can cause trauma to the ears and lead to otitis. Regularly cleaning your dog’s ears with a soft cloth or cotton balls can aid in preventing ear infections.

Tips

Ear infections can be frustrating since they have the ability to last for months and even years, they tend to recur and repeated treatments are costly. It is important to administer all medications and follow home care treatments as recommended by your veterinarian. Regular recheck examinations by your veterinarian are necessary to successfully treat otitis.

Update version: 4/24/2014, © Copyright by www.enpevet.de
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