Otitis Externa – Where do you Start?
As a new graduate you will quickly realise dermatology cases represent a significant proportion of your daily consultations. Despite your desire to only perform heroic life saving surgery the skin case which the boss leaves for you in the middle of a hectic evening surgery is a mandatory feature of the new grad’s passage into that “experienced” vet quoted in the jobs columns.
Typically dermatology cases have allergic undertones and these numerous patients start to blur into one but then the “exciting” case crosses your threshold that sets you off on a mission searching through your tatty final year notes. Unfortunately the realisation of owners’ limited budgets halts you in your tracks and the patient ends up on a conservative therapy instead but occasionally your desires are met. That appreciative owner and happy patient make you realise funky orthopaedic surgery isn’t the only fun you can have being a vet.
So how does otitis externa fit into this spectrum of dermatological disease? Is it a simple issue of inadequate flea control in an allergic dog or is it a manifestation of an unusual autoimmune disease mentioned briefly in small print at the end of those notes? Remember common diseases are common... that young athletic cat presenting with crusty ear pinnae is not suffering from cold agglutination disease but a simple case of rabbit fleas acquired during its hunting antics.
Working up the case
Put simply the very first consultation is a matter of prescribing a broad spectrum ear treatment with a cleaner, if required. Most cases of otitis externa will be mixed bacterial populations and with broad spectrum antibiotics they should respond within the 7 days. Only if the otitis has an insinuation of chronicity or recurrence do you start to think more elaborately about the three factors of reinfection – Primary, Perpetuating and Predisposing (fig 1.). This does not mean the brain cannot be engaged in the first consultation as a basic history is vital for any ear case. Questions on flea control, running through grass meadows and whether swimming is regular part of the dog’s life are just some of the fundamental questions that should be asked. A thorough, yet quick, clinical examination comes with experience but soon, within a few minutes a physical inspection and medical history can be documented revealing many clues as to why the otitis externa case has been deposited on your consult table.
Fig. 1: Factors of reinfection
Deciding on topical with or without systemic therapies depends on the individual case. Initially the patient may benefit from a mix of topical and systemic progressing onto just topical preparations. Something you will realise very quickly is how much pain your patients are suffering. Otoscopy is often restricted by inflamed canals and violent objections by the patient. Never force an examination as all this is likely to achieve is a stressed patient that becomes fearful of aural examinations. Sedation for the purpose of examination is not a luxury but sometimes a necessity and must be explained to owners that this is for the benefit of the pet and not because you want to charge extra. Damage to inflamed canals is easily achieved by overzealous cleaning and scope insertion and may then compound the problem. If an ear canal is extremely inflamed and oozing purulent slime then a quick swab and ‘Diff-quik’ stain may reveal far more relevant information than trying to visualise a tympanic membrane. In chronic cases this should one of the first procedures carried out to determine what perpetuating factors may be present. Chronic pathology can permanently alter the anatomy compromising treatment outcomes. First sight of a predominance of gram negative bacilli or Malassezia should set the alarm bells ringing. Sensitivity testing for ears has recently come under scrutiny as doses used topically are massively more than the stated resistant break points and therefore results must be interpreted with care.
More recent ear treatments have potent steroid components designed to reverse the aggressive inflammation that can sustain an environment conducive to infection. In fact this inflammation is often the primary factor and control is instrumental in successful long term management. Explaining to the owner how to manage the disease is imperative as their compliance to treat the patient is crucial if a positive outcome is to be achieved. Ear treatments have come a long way over the last few years with locally acting potent anti-inflammatory steroids, broad spectrum antibiotics and short treatment courses. Asking an owner to count drops into a troublesome ear twice daily for fourteen days can be the reason for poor treatment success and recurrence. Infrequent application or inadequate dosing will potentially lead to resistant bacteria, continual disease and unhappy clients.
With the plethora of cleaners on the market it is often hard to decide which one to use. Basic considerations for choosing a cleaner include ability to dissolve wax, soothing action for itchy or troublesome ears and anti bacterial / anti-fungal activity especially if combined with EDTA. Most ear treatments will be more efficient in a cleaned ear canal and ALL POM-V treatments do state that excessive exudation may impede the function of the preparation.
If managed correctly using products designed to make life easier for owners most otitis externa cases will be treated successfully leaving both owners grateful and pets comfortable.
This article was provided by Virbac, manufacturers of EasOtic* and Epi-Otic.
*EasOtic contains gentamicin, miconazole and hydrocortisone aceponate. More information available from Virbac Animal Health, Woolpit Business Park, Windmill Avenue, Woolpit, Bury St Edmunds. IP30 9UP. 01359 243243.
This article was first published on VetGrad.co.uk in July 2015
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