Derm Jeopardy: "I'll take annoying parasites for $400, Bob" (Proceedings)

Diseases of the ear represent a majority of cases observed in practice and often with accompanying integumentary involvement. The causes of the otitis have previously been classified according to anatomical location or etiological association. Other criteria of classification have been used to relate to ear disease. The causes of otitis externa are represented by predisposing factors, primary causes and the perpetuating factors. The following list provides specific reference to conditions that relate to each.

Predisposing Factors

Conformation

Stenotic canals

Hair in canals

Pendulous pinnae

Moisture

Canal obstruction by neoplastic growth or polyps

Systemic metabolic disease

Treatment effects

Trauma Irritants

Superinfections

Microflora imbalances

Perpetuating Factors

Bacteria: Staphylococcus spp., Proteus spp., Pseudomonas spp., Escherichia coli & Klebsiella spp.

Yeasts: Malassezia pachydermatis, Candida albicans

Otitis media

Progressive pathologic changes

        Hyperkeratosis

        Acanthosis

        Edema

        Epithelial folds/hyperplasia

        Hidradenitis

        Apocrine gland hypertrophy

        Fibrosis

        Calcification

Primary Causes

Foreign Bodies: plant awns, foxtails, hairs, etc.

Glandular disorders: apocrine hyperplasia, Parasites: ear mites, demodicosis, scabies mites

Microorganisms: dermatophytes/intermediate mycoses

Hypersensitivities: atopy, food, contact, drugs.

Keratinization disorders: Primary idiopathic & endocrinopathies, abnormal cerumen production.

Autoimmune Diseases: Pemphigus complex, bullous pemphigoid and lupus.

Viral diseases: Canine distemper

Glandular disorders: apocrine hyperplasia, sebaceous hyperplasia, altered secretions.

Neoplasia

Systemic disease

Autoimmune disease

Systemic infection Liver failure

An important aspect of treating otitis externa is determining the primary cause of the otitis. The accentuation of the perpetuating factors often results as inadequate recognition of the predisposing factors or as important the primary causes. The establishment of chronic infections often obscures the clinical features of primary causes observed in the ear because it may be difficult to resolve or control. It also has a strong likelihood of progression to otitis media. While culturing the case of chronic otitis externa may be indicated, in some instances it focuses all the attention on the perpetuating factors to the exclusion of the primary causes. The bacterial culture and susceptibility testing is often incorporated in the diagnostic plan with the exclusion of direct microscopic examination of material collected from the ear canal. Smears should always be included in the appraisal of otits externa. Infectious agents are the predominant perpetuating factors causing chronic otitis externa particularly in the early stages of the disease. The progressive pathological changes are potentiated by the infectious agents and further complicates the therapy as well as becoming yet another perpetuating factor.

The most common primary cause of otitis externa in the dog in Southeastern U.S. is allergy (atopy, food allergy or contact allergy to medications). Many other primary causes do occur and likewise eventually develop an infectious component. Treating only the infectious aspect and ignoring the underlying problem results in partial control of the problem. Suffice it to say that in some cases dealing with the infectious agent alone is a major challenge. A complete dermatological examination and history should be included to assist in the recognition of the primary cause since the integumentary disease is so often observed in association with ear disease.

Principles of Assessment

There are several major principles of clinical assessment for routine otitis externa that are often overlooked. Some of the relevant points are as follows:

1. Perform a complete examination of both the pinnae (often a significant component of the ear disease) as well as the ear canal. Evaluate both ears even if the primary complaint is relevant to only one ear.

2. Use sedation when possible particularly in the initial visits when there is apt to be abundant exudate and sensitive ear pathology making adequate visualization impossible.

3. Always perform ear cytology even if culture & susceptibility testing is to be performed. Rapid stains make this procedure very simple (e.g. Diff Quick). Utilize the Gram's stain kits for more precise recognition of bacteria.

4. Reevaluate the ear canal after it has been adequately flushed and cleaned. You are not always going to be in a position of seeing the tympanic membrane at the initial examination.

5. Repeat the first four steps on reevaluations

Direct smears from each ear should be prepared form both ears. I usually prepare to sets of slides initially for the purpose of performing the first slide with Diff Quick and holding the second in the event of performing a Gram's stain on it. Slides must be heat fixed before staining to avoid loss of the specimen during the process. The presence of yeast or coccal bacteria are easily recognized from the Diff Quick slide when examined under oil immersion. The observation of rods in a specimen stained with a Diff Quick or similar stain does not differentiate between Gram's positive or Gram's negative bacteria thereby requiring a rapid Gram's stain. This stain is available through Fischer Scientific or comparable laboratory supply sources. The examination of the specimen with Gram negative organisms suggest the presence of very unfriendly bacteria (pseudomonas spp., Proteus mirabilis, E. coli, Klebsiella spp., etc.) Bacterial cultures are routinely acquired from ear canals with exudate containing Gram negative organisms to acquire specific identification and most importantly susceptibility testing. Culture specimens are best sent to the microbiology laboratory in a tube of transport media (Port-a-Cult). If the otitis externa has recurrent or severe for greater than three months there is a great chance for otitis media. Cultures from both the external canal and deep cultures from the middle ear should be taken. The evaluation treatment of an animal with otitis media will usually require heavy sedation or general anesthesia. Following the determination of need for and acquisition of bacterial culture, the ear is ready for cleansing to achieve maximal otoscopic evaluation. Visualization of the tympanum is not possible often times, in the chronic case because of the extent of exudative accumulation in the ear canal. The first product used should be a cerumenolytic to help break down the waxy build-up in the ear or aid in the evacuation of the exudative material. This needs a 10 minute contact time to be effective. The ear should then be flushed with warm water or saline. The process may need to be repeated several times before satisfactory evacuation of material is accomplished. The use of a bulb syringe is usually necessary to achieve optimal success. Removal of fluid from the ear canal should be the next step. This is usually facilitated with the use of 12 cc syringe and a cut off end of a male urinary catheter or a "torn cat" catheter after the bulk of fluid is removed by a bulb syringe. This procedure is performed through a surgical otoscope or a video-otoscope

Principles of Treatment

Systematic treatment principles are often overlooked in the management of otitis externa but instead the hope is for one medication that will solve the problem, (at least for a limited period of time). Most cases of otitis require more than exam room evaluation and treatment. Outpatient admission is often excluded because of time or financial constraints and may represent a major limitation to satisfactory control. The ideal therapeutic approach is dependent on the results of both the direct inspection of the ear(s) (gross and otoscopic) and direct microscopic examination of otic material. In summary the following steps should be taken in the assessment and treatment of chronic otitis externa.

1. Direct smear of material collected from the ear canal as well as the inside of the pinna if suspicious lesions are present. Do not forget to "heat fix" the specimens before staining.

2. Perform otoscopic examination. If unable to accomplish, it may be necessary to wait for sedation. If the canal is full of debris and exudate, it may be necessary to continue through the cleaning procedure and attempt examination later.

3. Cerumynolytic application is necessary particularly if there is a ceruminous otitis with waxy build up in the canal/pinnae. Be familiar with products that have good cerumenolytic activity but also be aware of potential irritancy and restrictions. Allow at least 10 minutes for adequate time for drug action.

4. Cleaning and flushing should follow cerumenolytic treatment.

5. Drying through evacuation of the ear canal of irrigating solution or saline.

6. Treatment based on results of direct microscopy of material collected from the ear canal and culture results if performed.

Unfortunately, steps 2 - 4 are often omitted and therapy is initiated prematurely limiting the likelihood of resolution of the problem. If response is not noted with conservative treatment (i.e. minimal or no ear cleaning) the animal should then be hospitalized for more thorough ear cleansing and examination. Modifications of the approach to individual cases depend upon previous history and response to treatment, understanding all factors relevant to the disease, temperament of the animal and financial factors.

Cleaning

There a several important reasons that cleansing of the diseased ear is essential for optimal therapeutic response. The most obvious is merely the removal of barriers that do not allow proper penetration of the epithelial lining of the ear canal by the medication or produce the desired effect on the infective organisms or to have an anti-inflammatory effect. Many antimicrobials such as aminoglycosides are inactivated in presence of pus making its removal essential. The accumulation of exudate can further potentiate the irritation by the effect of toxins, degenerating cellular debris and metabolic by-products. Removal of foreign bodies are also a major reason for complete cleansing. Cleaning can be subcategorized in three areas: 1. mechanical 2. cerumynolytic 3. aqueous flushing

Mechanical cleansing

Removal of large accumulations of material with the aid of ear loops or cotton swabs help facilitate cleansing but should not replace it. Cotton swab applicator sticks are probably over used and can actually cause epidermal irritation and abrasion in the inflamed ear. Application of a cerumynolytic helps solubilize the material for easier removal and allows the use of products containing topical anesthetics if utilized. Cleaning solutions may include 2-4 % lidocaine solution. Cleaning the ear also removes the end products of inflammation including toxins, enzymes and other irritating substances.

Cerumynolytics

Many products carrying labels suggesting claims of cleansing properties are no more than alcohol or pH adjusters (malic, acetic, lactic or other type acid) The active ingredients in these products have little to no activity on emulsifying waxes or lipids. Active ingredients with excellent cerumynolytic activity include dioctyl sodium/calcium sulfosuccinate , carbamide peroxide, urea peroxide, squalene, triethanolamine polypeptide elit condensate, and hexamethyltetracosane . Less effective, but certainly not to be overlooked, ingredients include propylene glycol, glycerin, and other oils. Cerumynolytics should not be used if the tympanum is not intact although squalene has least adversity in this situation (Cerumene, Vetoquinol). Some cerumenolytics may be very effective but if left in the ear cause irritancy. Unfortunately, many times, visualization of the tympanum cannot be accomplished until adequate cleaning has been performed. Removal of debris is important for proper examination. Ceruminolytics require time to work, usually 10-15 minutes. Unless used properly, their attributes are limited. Removal of as much exudate/solubilized wax as possible provides more effective flushing with an aqueous solution.

Aqueous Flushing

Flushing the ear canal is the next step toward complete cleansing. The easiest method is an ear bulb syringe or the use of a 12-20 ml syringe attached to either a torn cat catheter or pediatric feeding tube (may also cut a male dog urinary catheter to the desired length). Antiseptic solutions such as chlorhexidine may be included but may cause some irritation and would not be desirable with a ruptured tympanum. Warmed physiological saline is the best alternative for ulcerative or extremely irritated ears. Following repeated flushes, removal of all fluid should be performed to allow otoscopic exam of the canal and the tympanum. Suction devices with a Frazier suction tip or the more simplistic version consisting of a catheter and syringe. As previously described. Application of drying agents containing organic acids (acetic, malic, salicylic, lactic, boric or benzoic) +/- alcohol may be used to help dry the ear but if much irritation/ulceration is observed, strong alcohol products should be avoided. Otic products with Burrow's solution (BurOtic & BurOtic HC, Virbac) combines burrow's solution with acetic acid and provides both an astringent/drying and antibacterial activity. There are a number of products with combination of ingredients for cleaning such as propylene glycol, lanolin, glycerin, lactic acid, parametaxylenol and different drying agents and pH adjusters (acetic, malic, ascorbic or other weak organic acid) Malacetic Otic and Malacetic Otic HC, DermaPet®. Many of these products can be used for the maintenance treatment of chronic cases but may not be effective in the initial treatment because of lack of cerumenolytic components. Some may contain alcohol which aggravates an already irritated ear.

Treatment

Treatment products for infectious and inflammatory conditions are also variable. Most of these products contain glucocorticoid which has a distinct advantage in the treatment of the inflamed ear canal/pinna. In addition antimicrobials (antibiotic(s) &/or antifungals) are usually added. The vehicle may be either an oil base or aqueous. Crusty or dry, scaly ears are best treated with an oil base where moist lesions are best treated with solutions. The use of creams or other occlusive medications should not be used in ears that are moist and exudative. Glucocorticoid containing products will result in systemic absorption. Examination of product labels should be done routinely to recognize the type/concentration of steroid present. Excessive use of glucocoritcoid/antibitoic preparations can result in the superinfection by yeast. Antibiotics used in otic preparations are quite variable and usually beneficial. There is a tendency of many clinicians to utilize those with the greatest amount of antibiotic potential, such as aminoglycosides without trying more conservative approach first. Aminoglysides may actually cause ototoxicity and should not be used extensively. Common antibiotics used include neomycin, polymyxin B & gentamycin. Systemic antibiotics are reserved for cases of confirmed or suspected otitis media, Gram negative bacteria or resistant Gram positive bacteria. Systemic antibiotics are usually required for a prolonged period when treating an otitis media/interna. Total regimens have required 45-90 consecutive days. Determination of treatment endpoint may be very difficult even with the most sophisticated methods. Antifungal drugs are most important in the control of Malassezia pachdermatis or Candida species. The infection of dermatophytes may occasionally involve the pinnae or the canal.

The use of systemic glucocorticoids may be necessary when there is much exudates and the dog is painful. The use of specific treatment is of little value if the owner cannot administer the medication because of excessive discomfort. The use of oral glucocorticoid is preferential to parenteral administration for more controlled anti-inflammatory affect. Prednisone at 1-2 mg/kg administered daily for 10-14 days then tapered usually results in some reduction in tissue edema, decreased exudates and increased comfort level of the animal. Severely affected otitis would be best reevaluated at close intervals at the onset of treatment (7,10 or 14 days). There have been occassions when cases have been released on prednisone therapy without the systematic approach to ear cleaning and evacuation to promote the reduction of inflammation. There is a greater likelihood of more effective outcome in some of these situations.

Compounding otic medications is a common practice and is often helpful to get resolution of the perpetuating infectious agents present in the otitis externa. There are many formulations that are currently in vogue and this list is not meant to be a treatise on all the versions but to represent several that have been helpful in routine therapy. Malassezia otitis: there are several products available that are manufactured for this condition but I have found a compounded otic solution to be more precise in the treatment and provide better results. Miconazole nitrate is a very effective antifungal and is available in two products useful in making formulations. Conofite is a 1% solution which may be combined in a 1:1 ratio with a vehicle such as a Burrows solution. Compounding either with a vehicle or other solution in a 1:1 ratio provides a very effective treatment. EpiOtic (Allerderm/Virbac) provides a good base for the combination of either miconazole solutions. The use of CortAstrin (Vedco) adds the additional enhancement of hydrocortisone and Burrow's solution. Some use Conofite directly but limits the volume available to treat with. The treatment of the inside of the pinnae which usually have demonstrable lesions of malassezia and is very important to include. The use of T8 Keto (DVM Pharmaceuticals) has been useful in treating ears with malasezzia with the ketoconazole combined with Tris EDTA. TrizUltra+Keto (DermaPet) contains 0.15% ketoconazole in a Tris EDTA solution and Malacetic Ultra Otic contains ketoconazole, hydrocortisone and malacetic

Gram Negative bacterial otitis: Fluroquinolones are commonly compounded for this problem usually incorporating injectable enrofloxacin. One simple formulation consists of 6.6 mis of Baytril (22.7 mg/ml) with 23.4 ml of water or propylene glycol to make a .5 % solution. The combination of enrofloxacin and silver sulfadiazine is available in the product Baytril Otic and combines the antimicrobial effectiveness of both agents for treating resistant Gram negative bacteria. Another formulation uses 6.6 mis of Baytril with 24 mis of a 1:1 ration of 1% miconazole nitrate and vehicle. Another formula includes 2 ml of enrofloxacin, 12 ml of an acetic acid/boric acid ear cleanser with 6 mg. of dexamethasone. The use of TrisEDTA is always helpful as a pre-rinse before the administration of antimicrobials to enhance their efficacy when dealing with a gram negative organisms. This product is commercially available and can be purchased from compounding pharmacies in 500 ml or liter quantities. Manufactured products containing Polymyxin B are also useful for treating Pseudomonas infections and other Gram negative organisms. A manufactured product (Cortomycin) contains polymyxin, neomycin and 1% hydrocortisone. Silver sulfadiazine cream may be mixed with a vehicle ranging from a 1:10 dilution to a 1:1 dilution.

The compounding of Timentin® (Ticarcillin Clavulanate) is often helpful in the treatment of resistant Pseudomonas otitis. A volume of 5 ml of saline or water is added to the 3.1 gram vial of powder making about 6 ml of solution. Then 1.0 ml. aliquots are removed with one syringe used to place the 1.0 ml of solution in a dropper bottle with 20 mis. of saline. The solution is dispensed for administration twice daily and maintains stability for 1 week in the refrigerator. The remaining 5 syringes are placed in the freezer where they are stable for up to 3 months. Each week, another is thawed to be diluted with 20 mis. of saline to be placed in the dropper bottle following discarding the existing solution and cleaning the container. This provides six weeks of therapy. Be sure to leave some space in the syringes before freezing for expansion. Treatment of any Gram negative infection of the ear should be based on bacterial culture and susceptibility.

Summary

Diagnosis and treatment of ear disease can be a real challenge particularly if the condition has been chronic. Surgical therapy should be reserved for cases that have significant conformational changes to their ear canal or requires exposure for more appropriate medical therapy. An aggressive medical approach should always precede the decision for surgery. Recognition of underlying disease is often overlooked with the result of major surgical expenses and persistence of the otitis externa. Many conditions will not be cured. Maintenance therapy may be necessary. Home flushing can be helpful especially for cases with ceruminous otitis externa, keratinization defects or allergic diseases. Proper instruction and determination of intact tympanum are essential. Reduction of the inflammation and discomfort is usually necessary before the owner will be able to utilize the flushing procedure. Flushing is best done at bath time. Many of the products that have mild cleaning activity but are predominantly used for acidifying the ear canal work well as a maintenance regimen for routine use.

Principles of Nasty Ear Management

1. Infectious otitis is a secondary occurrence and a perpetuating factor and needs resolution.

2. Identification and treatment of an underlying or co-existent problem is important in all cases of chronic recurrent otitis. Use a systematic approach to the diagnosis and treatment

3. Always base therapy upon results of otic smears and bacterial cultures when obtained. Thoroughly clean and dry the ear canal before commencing treatment.

4. Systemic therapy is usually indicated in otitis media cases but may be beneficial in chronic cases of non-Gram negative otits externa and Gram negative problems excluding otitis media.

5. Maintenance ear flushing every 7-14 days is helpful to avert recurrent infection in cases of chronic otitis externa