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.

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, anti- seborrheic, 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.

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

ALL-VEGETABLE HYPOALLERGENIC DIET

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 181-pint plastic containers and freeze.

2. Rice (prepare as required)

2½ cups rice

5 cups water

¹/2 cup sunflower oil

1 tsp salt

Mix ingredients, bring to boil, reduce heat, and simmer until water is absorbed. Allow to cool.

3. Thaw 1 pint of vegetable puree and add to rice; mix thoroughly.

4. Feed ¹∕2 to ³∕4 cup per 10 lb body weight twice daily. Monitor weight weekly. Do not add meat supplements.

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

capsules. Most fish oils and all flaxseed oil do not contain the necessary EPA content.

Step 4: Corticosteroids

Administer a low-dose corticosteroid for 12 days (e.g., prednisone at 0.5 mg/lb twice a day). Use a declining dosing regimen that ends with 0.5 mg/lb every other day. The rationale is to break the pruritic cycle and observe whether the case is corticosteroid responsive.

Step 4a

A topical corticosteroid spray (Genesis, 0.015% triamcinolone, Virbac) has been helpful in reducing the pruritic cycle. Some cases require less to no further systemic corticosteroid supplementation.

Step 5

If the pet has pyoderma, use an antibiotic such as cephalexin at 10 to 15 mg/lb twice a day for a minimum of 21 days. If the ear is also infected with bacteria, use a fluoroquinolone such as enrofloxacin at 5 mg/lb twice a day or 10 mg/lb once daily. If Malassezia dermatitis is present, bathe with the acetic acid/boric acid shampoo as outlined in Step 1; antibiotic therapy usually controls the pruritus. On rare occasions, or when there is very severe involvement of the skin with Malassezia, oral ketocona­zole at 10 mg/kg once daily or itraconazole at 5 mg/kg once daily may be used. Duration of treatment varies, but treat for at least 2 weeks. Systemics such as itraconazole and ketoconazole do not work as effectively in the ear as they do in the skin. When treating Malassezia dermatitis that does not respond to topical and systemic antibiotic therapy, itraconazole is my preference because of its low level of toxicity and ability to persist in the epithelium.

Step 6: Ectoparasites

Treat scabies, other ectoparasites, and some endoparasites with a trial of ivermectin. In all breeds except Collies or their mixes, use ivermectin (Bovine Ivomec, MSD/AgVet), 0.1 to 0.2 ml per 10 pounds of body weight. Use every 7 to 10 days for four treatments. The extralabel use of this drug requires the informed consent of the client. Other methods of flea control are reported to control scabies. However, for the purpose of this trial, in order to be sure scabies is eliminated from the differ­ential diagnosis, the author prefers ivermectin.

Step 7: Endoparasites

Treat phantom endoparasites with a dewormer that kills whipworms.

Step 8: Flea Control

If not already on flea control, begin flea control program.