January 2011, Issue 27

Transcription

1 Page 1 of 7 Having Trouble Viewing this ? Click Here You're receiving this because of your relationship with Aspen Meadow Veterinary Specialists. Please confirm your continued interest in receiving from us. You may unsubscribe if you no longer wish to receive our s. January 2011, Issue 27 What's New at AMVS Aspen Meadows Veterinary Specialists' (AMVS) first Continuing Education event of the year is an exciting one. In This Issue What's New at AMVS Otitis Externa Please join us this Thursday, Jan. 27 at AMVS (104 S. Main St. in Longmont) for a lecture and lab conducted by Dr. Matthew Rooney, Dr. Felix Duerr, Dr. Trent Gall and Dr. Jim Perry. This month's topic is The Orthopedic Exam: A Hands on Experience. Registration, appetizers and drinks are at 6:15 p.m. with the lecture from 6:30-7 p.m. followed by a lab that will last about an hour to an hour and a half. Space is limited and reserved for veterinarians only. Technician specific topics to be announced. Call to R.SV.P. by Wednesday, Jan. 26. In addition to our regular ER hours, AMVS is providing emergency and critical care services to your patients: Fridays, all day Otitis Externa AMVS is: PACE certified,

2 Page 2 of 7 By Jackie Campbell, DVM, Dermatologist 1. Otitis Overview 2. Dermatologic and Otoscopic Exam 3. Cytology LEED certified, and a zero-waste facility. 4. Topical Therapy 5. Systemic Therapy Introduction: Otitis externa is a common multifactorial disease, with prevalence of otitis externa in dogs ranging from 10% to 20%.1, 2 Primary causes of otitis externa include hypersensitivity disorders, otic parasites, foreign body such as plant, hair, or hardened secretions, glandular disorders, keratinization disorders and conformational defects.3 Otic flora acting as opportunists can secondarily complicate otitis. Common pathogenic bacterial species include Staphylococcus, Pseudomonas, Streptococcus, Proteus, Corynebacterium, and Enterococcus.1-3 The most common fungal pathogen to perpetuate canine otitis is Malassezia species, with rare isolation of Candida, and other saprophytic fungal organisms.3 Treatments for otitis externa in dogs are varied and include topical therapy with antibiotic, antifungal, or corticosteroid medications used alone or in combination. Otitis is often a recurrent issue for the pet. With each episode of otitis severity can increase, and the otitis may become refractory to previous therapies. The most critical point in the treatment of otitis is the realization that otitis is a clinical sign of underlying disease. The most common underlying disease trigger for otitis is a hypersensitivity disorder such as atopy or food allergy. With chronic otitis changes in the microenvironment of the ear canal take place. Changes to the ear canal include altered epithelial migration, cerumen gland hyperplasia, and increased numbers of a pocrine glands. These glandular changes are most notable in the American Cocker Spaniel and Labrador 4. Edema is also a feature of otitis and with chronicity stenosis, fibrosis, and eventual ossification of the ear canal are seen. A sequential and thorough approach to otitis is necessary to determine the underlying trigger and aid in successful treatment of otitis

3 News from Aspen Meadow Veterinary Specialists Page 3 of 7 and restore quality of life for the patient. Failure to diagnose and treat the primary and perpetuating factors concurrently will lead to treatment failure, recurrent disease, and chronic irreversible changes to the ear canal. History and physical examination are helpful in determining the underlying trigger for the otitis. For example, an acute onset with lack of other dermatologic lesions may support an otic foreign body. Recurrent episodes of otitis along with other dermatologic lesions such as pododermatitis or pyoderma support an underlying hypersensitivity. Food hypersensitivity should never be overlooked in cases of chronic otitis with a diet trial indicated. A novel protein diet is the gold standard for food trials and should be instituted for a minimum of eight weeks. Although hydrolyzed diets may be effective in some patients, a recent review by Olivry et al. (2010) found hydrolyzed diets were not sufficient for controlling symptoms in dogs with cutaneous adverse food reactions. A strict novel protein diet trial such as rabbit and potato is the gold standard. The otoscopic exam allows assessment of the ear canal, tympanic membrane, and identification of foreign body, otic parasites, mass, or ear canal changes. In some cases of severe otitis, the ear may be too painful at the initial visit to perform this step. normal tympanic membrane viewed via video otoscopy

4 News from Aspen Meadow Veterinary Specialists Page 4 of 7 bulging tympanic membrane viewed via video otoscopy Cytology samples should be obtained basaloid tumor viewed via video otoscopy directly from the ear cone used forotoscopic exam or via a cotton swab and assessed microscopically. Cytologyaids in the identification of secondary infections, usually identified due to the presence of white blood cells. There is little research on the number of yeast or bacteria present in normal and diseased ear canals, thus the identification of white blood cells, and the number of microorganisms present can aid in this distinction. Cytology is also useful in the identification of otic parasites such as Otodectes and even Demodex. Cytology is critical in both the initial diagnostic exam, and in monitoring treatment progress. Culture of the external ear canal in recurrent cases of otitis may be unnecessary as some bacteria will be reported as resistant to a particular antibiotic, yet topical treatment will be successful. Topical antibiotic therapy can typically achieve much higher MIC levels than those used for systemic therapy and susceptibility testing.

5 Page 5 of 7 The arsenal of treatments for otitis includes flushes, topical medications, systemic antibiotics, systemic antifungals, and systemic steroids. Many topical medications have diminished efficacy in the presence of debris. Therapeutic ear flushes aid in removal of debris, improve epithelial migration, and contain ingredients such as TrizEDTA, which weaken the bacterial cell wall to improve penetration of antibiotics for cell death. An in-hospital flush performed by the veterinarian can jump start therapy, and aids the owner in initiation of therapy. Flushing is important in therapy of otitis, but should not be rushed if the patient is painful on examination. For the painful patient, systemic steroids are necessary to control the inflammation and pain associated with chronic otitis. Once the patient is more comfortable with systemic therapy (typically three to five days) then flushing by the owner can be instituted. Topical otic medications are often combination products containing a steroid, antibiotic, and antifungal ingredient. If the tympanic membrane cannot be visualized ototoxicity is a concern and general avoidance of aminoglycosides is indicated. Topical fluoroquinolones are safe topically if the integrity of the tympanic membrane is in question. The author prefers a topical combination of baytril, dexamethasone, and miconazole in such cases. After the initiation of otic therapies, otic evaluation in 10 to 14 days is recommended and the tympanic membrane can typically be assessed at that time. If the tympanic membrane is ruptured then systemic antibiotics for six-week duration, combined with topical therapy is necessary and should be based on otic culture from the middle ear. Systemic antifungals may be indicated in cases of malassezia otitis associated with significant inflammation or if malassezia dermatitis is affecting other areas of the body. Therapy of fluconazole or ketoconazole at 5mg/kg/day for a 21-day treatment can be instituted in these cases. Systemic steroids are key in decreasing pain and inflammation and may even aid in reversal of the chronic changes associated with otitis including stenosis, glandular hyperplasia, and fibrosis. In general, other non-steroidal anti- inflammatory drugs are not indicated in cases of otitis. If significant pain is noted then the addition of tramadol can be made until the patient is more comfortable with therapy. The dose of systemic steroids is dependent on the degree of otitis and secondary ear canal changes. Video otoscopy is indicated in recurrent cases of otitis, with recalcitrant bacterial infection and allows complete flushing of the ear canal, removal of debris, culture of the external ear canal, assessment of tympanic membrane and culture of the middle ear if indicated. A total ear canal ablation and bulla osteotomy is indicated in cases of severe,

6 Page 6 of 7 irreversible stenosis, fibrosis and mineralization to restore patient health and quality of life. It is critical to identify the underlying cause of otitis, treat secondary infections, and treat the changes due to chronic otitis aggressively. Frequent rechecks of the patient are necessary to assess response to therapy and resolution of disease. Unfortunately, the ears are not as forgiving as the rest of the body, and early and prompt identification of the problem is necessary to impede the path to end stage otitis and necessary surgery. References 1. Cole LK. Otoscopic evaluation of the ear canal. In: Veterinary Clinics of North America Small Animal Practice, Ear Disease. Philadelphia: WB Saunders Co., 2004; 34: Angus JC. Otic cytology in health and disease. In: Veterinary Clinics of North America Small Animal Practice, Ear Disease. Philadelphia: WB Saunders Co., 2004; 34: Scott DW, Miller WH, Griffin CE. Diseases of Eyelids, Claws, Anal sacs and Ears. In: Muller and Kirk's Small Animal Dermatology. 6th ed. Philadelphia: WB Saunders Co., 2001: Gotthelf LN. Factors that Predispose the Ear to Otitis Externa. In: Small Animal Ear Diseases An Illustrated Guide, 2nd ed. Saint Louis: Elsevier Saunders, 2005: Thank you for your continued support. -Aspen Meadow Veterinary Specialists 104 S. Main Street Longmont, CO (p) (f) info@aspenmeadowvet.com

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