• Dermatologic & Otic Diseases
• Infectious Diseases
• Veterinary Medicine
• Companion Animals

• Dermatologic & Otic Diseases
• Infectious Diseases
• Companion Animals

Most difficult problems in managing canine otitis are the result of inadequate treatment, chronic inflammation, or failure to identify and control the underlying cause. According to James O. Noxon, DVM, Iowa State University, Ames, Iowa, USA, 2 key concepts are important to appropriate management of otitis. First, appropriate standard-of-care topical therapy must be used and any infections cleared, not just suppressed. Second, long-term maintenance is necessary to prevent recurrence.

Otitis treatment involves thorough cleaning and administration of medication to the entire ear canal. Oil-based ointments penetrate the skin better than do aqueous solutions but should be based on a light oil so that the medication can reach the entire length of the canal. The amount of medication to apply depends on the size of the ear canal, which varies according to weight. According to Dr. Noxon, the volume recommended on most ear products is too low and is a major source of treatment failure. He recommended applying medication by volume (mL) rather than drops but cautioned that too much can cause systemic effects. Once-daily administration is sufficient for most conditions. To completely clear otitis, medication should be applied for 30 days.

After treatment is completed, the patient should be rechecked. Maintenance therapy involves client education and intermittent use of antiseptics, therapeutics, and mild glucocorticoids until the primary cause is identified and controlled.

Pseudomonas infections, ceruminous otitis externa, and hyperplastic ear changes can be difficult to treat. Pseudomonas should be strongly suspected when a single population of gram-negative rods is seen on cytology. The identification can be confirmed with culture and susceptibility testing. Antibiotics are the primary treatment for Pseudomonas infection (Table 1). Pseudomonas aeruginosa can form a biofilm in the ear, increasing resistance to treatment; in such infections, the concentration of medication should be increased [Pye CC et al. Vet Dermatol 2013]. Tromethamine edetate disodium dihydrate (Tris-EDTA) is synergistic with some antibiotics, clearing antibiotic-resistant Pseudomonas infections. Tris-EDTA significantly potentiates the bactericidal activity of silver sulfadiazine against multidrug-resistant P aeruginosa [Buckly LM et al. Vet Dermatol 2012 (abstr FC-20)].

Ceruminous otitis most often accompanies familial seborrhea and may involve various infectious agents. The ear wax thickens and is difficult to remove. Progressive hyperplastic changes occur. Treatment consists of cleaning and control of infections (Table 1). Hyperplasia (lichenification) promotes a microclimate favoring microbial growth and prevents distribution of topical medications. Swelling may be due to inflammation and edema or fibrosis, including cartilage ossification. Diagnostic evaluation includes palpation of the ear canals and bullae for calcification or fibrosis; pain indicates bullae involvement. Otoscopic examination and imaging studies can help determine the extent of involvement. Hyperplasia and any infections should be treated as described in Table 1.

Dr. Noxon concluded that most difficult otitis cases develop when there has been a breakdown in communication or a failure to strictly adhere to the best ear management practices. Thorough ear cleaning and control of infections are necessary.

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