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.

Oboljenja spoljašnjeg i srednjeg uha (Otitis externa i Otitis media) jesu čest klinički problem kome se, uglavnom, pristupa na pogrešan način. Smatramo da je pristup obolelom uhu pasa i mačaka u našoj tzv. maloj praksi najčešće pogrešan. Naime, klasičan pristup upali spoljašnjeg uha svodi se na čišćenje uha najčešće vatom i hidrogenom, a zatim na ukapavanje tokom nekoliko narednih dana kapi za uši za upotrebu u veterini ili humanoj medicini. Nešto savesniji pristup, takođe, podrazumeva antibiotski tretman, topikalni i/ili sistemski, ali na osnovu antibiograma. Ako postoji sumnja na prisustvo stranog tela, veterinar će da se posluži otoskopom i tu se ceo dijagnostički pristup u našim uslovima najčešće završava. Ovakve procedure najčešće ne mogu da reše problem, tako da se bolest posle izvesnog vremena vraća ili pretvara u hronični rekurentni Otitis externa, što je jedan od najvećih problema u dermatologiji pasa. Iskustvo ukazuje da naše kolege ne poznaju patogenezu infekcije spoljašnjeg i srednjeg uha i da je to razlog zbog koga dijagnostici i terapiji pristupaju na pogrešan način. Najbitnije je da se ima u vidu da su bakterije i gljivice vezane za patološki proces u ušnom kanalu samo oportunistički mikroorganizmi, a nikada primarni patogeni sami po sebi odgovorni za Otitis externa. Antibiotskim ili antimikotičnim tretmanom ne leči se osnovna bolest koja je izazvala upalu vć} samo njene posledice. Veliki broj činilaca uključen u upalu spoljašneg i srednjeg uha tradicionalno se deli na primarne, predisponirajuće, sekundarne i potpomažuće. Osnova za uspešno lečenje Otitis externa i Otitis media jeste prepoznavanje, eliminisanje ili kontrolisanje primarnih faktora (atopija, nutritivna alergija, poremećaji keratinizacije, parazitska infestacija). Predisponirajuće faktore treba uočiti da bi se smanjila učestalost rekurencije. Najčešći predisponirajući faktori su dlake u kanalu uha ili na konkavnoj strani penduloznih ušnih školjki. Takođe su često prisutna oštećenja ili preterana vlaga u kanalu kao posledica nepravilnog tretmana spoljašnjeg uha. U predisponirajuće faktore ubrajaju se i abnormalnosti u građi ušnog kanala poput stenoze često prisutne kod šar peja. Sekundarni faktori – bakterije i gljivice se u našim uslovima pogrešno smatraju uzrokom zapaljenja uha. Njihovim suzbijanjem dolazi do kliničkog poboljšanja, ali ne i do trajnog izlečenja bolesnog procesa. Potpomažući faktori jesu glavni razlog slabog odgovora na terapiju. Očituju se kao progresivne patološke promene samog kanala spoljašnjeg uha, promene timpanične membrane i promene u srednjem uhu. Samo ukoliko se navedeni faktori koji manje ili više učestvuju u upali uha imaju u vidu i kao takvi leče, efekat terapije može da bude pozitivan, što nažalost često nije slučaj.