In this retrospective study, medical records from a referral hospital in the United Kingdom over a 6-year period were evaluated to determine primary underlying conditions associated with the development of Pseudomonas spp ear infections. For each of the primary diseases identified, age of onset and time from the initial diagnosis of otitis to development of Pseudomonas spp otitis were determined.
Sixty dogs met the outlined inclusion criteria; spaniels (particularly cocker spaniels), Labrador retrievers, basset hounds, West Highland white terriers, and German shepherd dogs were overrepresented. Mean age of onset of the first episode of otitis for all dogs was 50 months. The most common primary underlying conditions included allergic disease (atopic dermatitis in 41 dogs), masses (3 neoplastic, 5 benign), and endocrinopathies (6 hypothyroid, 1 hyperadrenocorticism). Autoimmune skin disease was diagnosed less frequently (3 dogs). Progression from the first episode of otitis to Pseudomonas spp infection occurred more rapidly in patients for which a mass or autoimmune disease was diagnosed (average, 10 months and 8 months, respectively) as compared with endocrinopathy (average, 19 months) and allergy (average, 28 months). This was attributed to the more severe inflammation observed in patients with masses or autoimmune diseases, which appears to lead to a more rapid switch in otic microbial population.