Simple Diagnosis and Treatment of Pruritic Otitis

Chapter 13 Simple Diagnosis and Treatment of Pruritic Otitis



Steven A. Melman, VMD


Most cases of acute otitis externa are pruritic. The pet is presented to the veterinarian for scratching at the ear, erythematous pinnae, head shaking, or pain when the ears are manipulated. The differential diagnosis for pruritus is extensive and is dealt with in other textbooks on dermatology.


This chapter contains a “rapid-fire” clinical approach to the treatment of the itchy pet with or without otitis externa. Using this approach, treatment for several different etiologic causes of pruritus are addressed at once. Not only does this regimen promise the best chance at fast and lasting relief from pruritus, but it also allows the veterinarian to make a rapid clinical diagnosis based on the response to the various elements involved in the trial. Protocols to treat most known types of ear problems, including Malassezia and bacterial (e.g., Pseudomonas) otitis, follow the discussion of treating pruritus.


Perhaps the most common etiology for acute otitis externa is hypersensitivity. The most common hypersensitivities encountered in small animal practice are flea allergy, food allergy, and atopy. Dogs with atopic dermatitis are presented to the veterinarian with a clinical history of pruritus of the feet, face, axilla, and ears. It has been estimated that as many as 80% of dogs with atopy have otitis externa and pruritic ears. In dogs and cats with food hypersensitivity, otic pruritus may be the only clinical sign. Flea allergy may contribute to overall pruritus, but rarely causes otic pruritus singularly.


If the clinician suspects atopy, then prior to starting this pruritic clinical trial, which involves the use of some corticosteroids, a pretreatment blood sample for in vitro allergy testing should be drawn. The blood should be spun and the serum frozen. Frozen serum can be submitted for in vitro allergy testing for as long as 60 to 90 days without affecting the results. Testing and therapy for atopy is both tedious and expensive. The treatment is lifelong. The following clinical trial affords clients proof that their pet is suffering from hypersensitivity, making the decision to test and hyposensitize easier.


Of course, a good physical examination and observational skills are not to be neglected in attempting to sort out the etiology of dermatologic disease. It is prudent to do skin scrapings, fecal analysis, heartworm testing, fungal culture, skin and ear cytology, and other tests as indicated by clinical common sense during the initial examination.


In addition, recheck visits and the observational skills of the client are crucial to securing an accurate diagnosis. Have the client keep a daily diary of the pet’s response using a scale of 1 to 10 to quantify the intensity of pruritus, erythema, pain, any discharge from the ear, and head shaking.



Clinical Treatment Trial for Pruritus


Here is an outline for the pruritic clinical trial. This clinical trial should be done in conjunction with topical ear treatment. Start all steps on day 1.


Before starting the trial, which involves the use of corticosteroids, take serum and freeze it. Allergy testing is variably adversely affected by the effects of prednisone.



Step 1: Shampoo Therapy


Of the approximately 116 million dogs and cats in the United States, 12% to 20% have allergy-induced skin problems that require frequent bathing, preferably with “hypoallergenic” shampoos.


Shampoo therapy has moved to the forefront as a component in the treatment of all but the rarest skin disorders. It involves the use of cleansing, moisturizing, antiseborrheic, degreasing, antiparasitic, antibacterial, antifungal, and antipruritic shampoos. Specific products and protocols usually are selected on the basis of the presenting morphologic characteristics such as dryness, oiliness, scaling, inflammation, and associated pyoderma.


Generally, the use of a milder, more elegant product before a coarser, more potent one increases compliance on the part of the pet owner and reduces the risk of side effects such as irritation. Under the circumstances of a short-term clinical trial, where concurrent infections with Staphylococcus and Malassezia may be present, use a shampoo that is strong enough to treat both yet mild enough to use for frequent bathing.


Various issues should be considered when selecting therapeutic shampoos to relieve pets’ specific symptoms.



Cleansers and Moisturizers.


Cleansing and moisturizing shampoos are designed to do just what their names say. The mechanical process of bathing (even with water alone) helps remove scales, crusts, organisms, dander, loose hair, and other debris. All such shampoos should be pH-adjusted for dogs, which, despite breed variation, have the highest skin pH of any mammal (6.2 to 7.2), including humans.



Oils and Conditioners.


Moisturizing agents such as bath oils, conditioners, emollients, and humectants may be applied after bathing and rinsing to soften, lubricate, and rehydrate the skin. They can be used on a more regular basis on dry animals. When the patient has a concurrent infection, a “medicated” conditioner may add moisture as well as medication to the coat. One such example is MalAcetic Conditioner (DermaPet, 2% acetic acid and 2% boric acid), used after a shampoo.



Antiseborrheic Treatments.


Seborrhea is the term used for any skin disease involving dry (sicca) or greasy (oleosa) scaling. The term also encompasses disorders in the formation of keratin, a complex protein unique to the skin, hair follicles, and nails. Today, many experts prefer the term disorders of keratinization. This subject is covered in detail in a separate section of this book.


The epidermis turns over every 22 days in the normal dog. Epidermal turnover time in dogs suffering from idiopathic seborrhea, more common among Cocker Spaniels, may be as little as 3 to 6 days. This fast turnover creates a defect in the normal protective barrier, which may result in dry or greasy scales, comedones, alopecia, inflammation, crusts, pyoderma, and pruritus. Any of these conditions, in turn, may lead to skin damage. In these cases, it is important to slow the turnover process and treat the secondary problems.



Bathing Procedure.


Bathe the pet daily in a hypoallergenic or medicated shampoo, as described previously. If the pet remains itchy after these baths, an oatmeal shampoo or conditioner may help resolve mild pruritus. If pyoderma, Malassezia, or seborrhea oleosa is present, the owner may also use a shampoo that is degreasing and antiseptic every 2 or 3 days. The author prefers an acetic acid/boric acid shampoo (MalAcetic, DermaPet) followed by an acetic acid/boric acid conditioner. This unique combination kills bacteria and yeasts on the skin. Shampoo therapy should be used as a component of the plan for 3 weeks. If the pet improves symptomatically, the owner should continue bathing.



Step 2: Food Elimination Diet


Follow a strict food elimination diet for a minimum of 30 days (some food-allergic dogs may require 60 to 90 days to see a beneficial effect). Many diets that can be used for the food elimination trial are commercially available. They contain either uncommon, novel protein sources (venison, rabbit, duck, fish) or purified low–molecular-weight polypeptides. The author prefers to use a home-cooked vegetarian diet.



Step 3: Fatty Acid Supplementation


Supplement the pet’s diet with a high-quality fish oil supplement (omega-3 fatty acids) to help reduce the inflammation associated with pruritus. Antioxidants such as vitamin E should be included in the supplement because they are depleted more rapidly when there is fish oil (omega-3) in the diet. Because fish oil does not contain any protein, it will not interfere with the hypoallergenic diet. The current recommended dose is 1000 mg of fish oil containing 180 mg of eicosapentaenoic acid (EPA) per 10 lb per day as found in EicosaDerm (DermaPet) or generic fish oil capsules. Most fish oils and all flaxseed oil do not contain the necessary EPA content.




ALL-VEGETABLE HYPOALLERGENIC DIET


From Byrne K: Food allergy. In Melman SA, editor: Skin diseases of dogs and cats, Potomac, MD, 1994, DermaPet, Inc.



1. Vegetable puree (multiple batch)

Three undrained #1 cans of carrots, peas, green beans, and tomatoes, and greens (kale, dock, spinach, or mustard).


One 10 oz. package of chopped, frozen, broccoli.


Boil the broccoli in 2 cups of water until tender. Combine with other vegetables in a large kettle, mix, and puree until smooth. Fill 18 1-pint plastic containers and freeze.

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Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Simple Diagnosis and Treatment of Pruritic Otitis

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