Veterinarski Glasnik (Jan 2005)
Pathogenesis of otitis externa and otitis media in dogs and cats
Abstract
Diseases of the outer and middle ear (Otitis externa and Otitis media) are a frequent clinical problem which is mostly approached in the wrong way. We believe that the approach to a diseased ear in dogs or cats by practicing veterinarians in our country is most often incorrect. Namely, the conventional approach to inflammation of the outer ear is narrowed down to cleaning the ear, usually with cotton wool and hydrogen peroxide, and then by applying ear drops for veterinary or human use over the next few days. A somewhat more conscientious approach implies treatment using antibiotics, topical and/or systemic, but based on an antibiogram. If the presence of a foreign body is suspected, the veterinarian will use an otoscope, and this is where the entire diagnostic approach in our conditions usually ends. Such procedures most often fail to resolve the problem, so that the disease recurs after a certain time or becomes chronic recurrent Otitis externa, which is one of the biggest problems in dog dermatology. Experience shows that veterinarians here are generally not familiar with the pathogenesis of outer and middle ear infection, and that this is the reason why they approach diagnostics and therapy in the wrong way. The most important thing is to have in mind that bacteria and fungi linked with a pathological process in the ear canal are merely opportunistic microorganisms, and never primary pathogens, themselves responsible for Otitis externa. Antibiotic or antimycotic treatment does not cure the basic disease which led to the inflammation, but only its consequences. A large number of factors involved in the inflammation of the outer or middle ear are traditionally divided into primary, predisposing, secondary, and underlying. The basis for the successful treatment of Otitis externa and Otitis media is the recognition, elimination or control of the primary factors (atopy, nutritive allergy, keratinization disorders, parasitic infestations). The predisposing factors should be observed in order to reduce the incidence of recurrence. The most frequent predisposing factor are hairs in the ear canal or on the concave side of pendulous ear conches. There are also frequent damages or excessive humidity in the canal as a consequence of irregular treatment of the outer ear. Among the predisposing factors are also abnormalities in the structure of the ear canal, such as stenosis which is often present in shar-pei-dogs. Secondary factors - bacteria and fungi, are in our conditions wrongly considered causes of ear inflammations. Their control leads to a clinical improvement, but not to the lasting cure of the process of this disease. Supportive factors are the main reason for the poor response to therapy. They are expressed as progressive pathological changes in the outer ear canal itself, changes in the tympanic membrane, and changes in the middle ear. The effect of therapy can be positive only provided the listed factors, which participate in the ear inflammation to a greater or smaller degree, are kept in mind and treated as such, but, unfortunately, this is often not the case.
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