In cases of ear inflammation, your veterinarian will want to identify and correct the primary underlying cause as well as the perpetuating cause (e.g. bacterial infection). Diagnosis of atopy is based on history (age of onset, progressive worsening overtime), clinical signs (pruritus on face, feet and ears), exclusion of other pruritic diseases, intradermal skin test, and serology testing for allergen-specific IgE.
Food allergy is diagnosed by appropriate food trial in which a source of protein is selected based on the individual history and used for a minimum of two months. The food is then discontinued, and if signs clear up, the food will be given again to see if symptoms recur.
Diagnosis of a primary disease of keratinization is made based on history of very young age of onset, lack of pruritus (itchiness) at least initially, and skin biopsy.
Diagnosis of an underlying endocrine disease is based on clinical signs, compatible changes on CBC and chemistry panel and specific tests for either thyroid or adrenal function.
Diagnosis of ear mites is made by cytology and identification of mites under the microscope.
In most cases of chronic otitis externa/media bacteria are present. Although bacteria are not a primary cause of otitis, once the infection is established, they can cause significant inflammation and damage. Diagnosis is based on cytology of the exudate, bacterial culture and sensitivity. Aggressive treatment is warranted as resistance to antibiotic may easily occur especially in cases when Pseudomonas is cultured.
Any time that rods are detected on cytology, a bacterial culture/sensitivity test is warranted to investigate whether Pseudomonas is present and what the sensitivity is.
Thorough ear cleaning is a vital part of the treatment of chronic otitis. The reasons are multiple. The exudate is irritating and provides a good environment for bacteria and yeast to proliferate. In addition, the exudate may inactivate antibiotics and thus cause treatment failure.
When flushing an ear with a ruptured ear drum, the use of saline or 1:1 or 1:3 dilutions of 5 percent white vinegar are recommended. The fluid is discarded with every flush and suck cycle and the canal is filled again with clean saline. This is repeated multiple times using a fair amount of saline. The best results for deep ear cleaning or flushing are obtained with the patient under general anesthesia.
Cleaning cannot be done on very swollen, narrowed, ulcerated or painful ears. Such cases need to be treated symptomatically at first and cleaned at a later date when the inflammation has been reduced and the canals have opened. Systemic anti-inflammatory doses of prednisone for 10 days and topical glucocorticoids like Synotic® may be used to decrease inflammation, swelling and pain.
Pseudomonas infections are extremely frustrating and difficult to treat. Most effective treatments include:
Topical Polymyxin B. This medication is rapidly inactivated by the exudate and aggressive cleaning is an essential part of therapy.
Acetic acid (vinegar/water 1:1)
Silver sulfadiazine (1gm of silver sulfadiazine is mixed with 100ml of sterile water). 0.5 ml of the mixture is applied twice daily.
Pre-soaking the ear with edetate trisodium (tris-EDTA) 15 minutes prior to application of the antibiotic increases the efficacy of aminoglycosides.
Injectable enrofloxacin has been used topically with DMSO (1/1). The stability of this mixture has never been evaluated in controlled studies but in clinical situations it seems to be stable and effective for at least 7 days.
Systemic enrofloxacin or ciprofloxacin twice daily for a minimum of 2 months.
If Staphylococcus is the cause of infection, cephalexin or trimethoprim-sulfa are used.
Topical therapy is usually sufficient and miconazole and clotrimazole are the most commonly used ingredients. In rare cases of otitis media due to Malassezia, systemic treatment is necessary and oral ketoconazole (Nizoral) is used twice daily for 3 to 4 weeks. Side effects include anorexia, vomiting and diarrhea. In animals that have adverse reaction to ketoconazole, itraconazole (Sporonox®) may be used once daily. It comes in capsules or in a suspension.
Therapy for ear mites can be topical or systemic. Topical treatments include milbemycin (Milbemite®), ivermectin (Acarexx®) or thiabendazole (Tresaderm®) in the ears or selamectin (Revolution®) as a spot on treatment to be applied in between the shoulder blades. Treatment should cover the cycle of the mites, which is three weeks. One single application of milbemycin, ivermectin or selamectin is usually sufficient to eradicate the infestation.
Cytology and culture should be performed monthly throughout the therapy and before discontinuation of antibiotic therapy. Early identification of the underlying cause and aggressive treatment of the infection are the only ways to prevent more serious and permanent damage in the ear canal.