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Sponsored by an educational grant from Ceva Animal Health clinician’s forum ™ Expert Views from a Roundtable on Atopic Dermatitis Dermatology Roundtable Part 1 Allergy & Topical Therapy: The Role of Skin Barrier Dysfunction & Infection Advances in elucidating the functions and dysfunctions of the skin coupled with emergence of antibiotic-resistant bacteria have changed the face of therapy for patients with atopic dermatitis. This discussion covers the latest strategies in effective management of this troublesome condition and their rationale. Dr. Thomas: Human medicine has seen an increase in the number of allergic patients over the past several years. Have you observed a similar trend? Dr. Angus: We’ve seen a transition in some breeds over the last 10 to 15 years, with the French bulldog leaping to the front of the pack as far as atopic dermatitis. I think that speaks to the fact that there are not only environmental factors but also genetic ones at play. Dr. Plant: It is difficult for somebody in specialty practice to assess prevalence as we tend to see the same allergic dogs repeatedly. But there probably has been some increase. Dr. Thomas: Have you seen an increase in other dermatologic conditions? Dr. DeBoer: I think we’re all seeing changes in pyoderma and in resistant organisms in general—more resistant staphylococci and Pseudomonas. The overuse of antibiotics has complicated all of our jobs a lot. Dr. Thomas: Do dogs and cats suffer from methicillin-resistant Staphylococcus aureus (MRSA) or MRSA-equivalent infections? 1 • clinician’s forum PARTICIPANTS John Angus, DVM, DACVD Veterinary Dermatologist Animal Dermatology Clinic, Pasadena, CA Douglas DeBoer, DVM, DACVD Professor of Dermatology University of Wisconsin-Madison School of Veterinary Medicine Madison, Wisconsin Valerie Fadok, DVM, PhD, DACVD Veterinary Dermatologist North Houston Veterinary Specialists Spring, Texas Jon D. Plant, DVM, DACVD Veterinary Dermatologist SkinVet Clinic Lake Oswego, Oregon MODERATOR Ursula Thomas, DVM, DACVD Veterinary Dermatologist Angell Animal Medical Center-West Waltham, Massachusetts Dr. DeBoer: That’s really an emerging topic. First, it’s very important that veterinarians and clients understand and use the terminology correctly. We should always make sure that clients understand that MRSA refers specifically to Staphylococcus aureus, the human staphylococcal strain, and that methicillin-resistant Staphylococcus pseudintermedius, or MRSP, is the animal strain that’s prevalent in dogs and sometimes cats. Dr. Angus: I would say over the last 10 to 15 years, the incidence of MRSA in dogs has remained relatively flat, while the incidence of MRSP has skyrocketed. Probably 40% of the patients I see are currently infected with MRSP. Dr. Fadok: We don’t culture much MRSA from dogs, but I culture quite a bit from cats. Usually Skin barrier dysfunction (left) is characterized by allowing entry of elements that would normally be prevented. those are very inflammatory lesions. Five years ago in Houston, we still had several options for dogs with MRSP, but now MRSP is reported as sensitive to only three antibiotics: amikacin, mupirocin, or rifampin. Mupirocin may not be widely used in general veterinary practice, but it has been in veterinary dermatology. I now use mupirocin only for methicillin resistant infections. Dr. DeBoer: One of the first implications of this resistance is that it’s changing our treatment. When a staphylococcal strain is methicillin-resistant, it’s resistant to all of the beta-lactam antibiotics, including all penicillins and cephalosporins. It may still be susceptible to other antibiotic classes, but it becomes necessary to do more culturing, which gets expensive. Dr. Plant: Aside from the public health concern about a dog with MRSP, it’s very challenging to the owner. Dr. Fadok: Another concern is our lack of knowledge about pyoderma treatment duration. If it doesn’t improve, should we treat it longer? If it’s not better in four weeks on cephalexin, will treating for 8, 12, or 16 weeks really make a difference? Dr. DeBoer: I agree, and especially if new lesions are appearing during antibiotic treatment: that’s a warning sign that something is wrong. Dr. Angus: I’ve really changed the way I’m prescribing. I actually go for much shorter courses than what I was taught in school. I always combine the antibiotic with a topical antiseptic like chlorhexidine, which accelerates the elimination of the wild-type Staph that is causing the pyoderma, but also hopefully provides some backup to the antibiotic so that we aren’t acquiring a methicillin-resistant infection. Dr. DeBoer: Practitioners also need to be aware of the transmissibility implications. If it’s MRSP, we know it’s not generally a human health hazard, but we don’t want that patient in areas of the clinic where it may be transmitted to other animals. On the other hand, if it’s MRSA, you can become colonized by touching your face. The animal can serve as a reservoir for that very resistant human strain in the household, and the owner has to be informed of that. Dr. Thomas: What are key factors for the successful management of bacterial skin infections in dogs and cats? Dr. Angus: There is always an underlying cause in a bacterial skin infection. You can’t treat bacterial folliculitis as a diagnosis rather than a clinical sign. Dr. Fadok: It’s important to have a short-term plan for treating the active infection and a longterm plan devoted to preventing recurrence. But identifying the underlying cause is, ultimately, that key to success. ALLERGIC DERMATITIS & SKIN BARRIER DYSFUNCTION Dr. DeBoer: Many dogs have “mild” or atypical allergic disease, maybe resulting in recurrent inflammatory yeast otitis. Once the infection is gone, the dog seems comfortable, but the presence of the allergic disease causes the infections to come back. Those dogs need some kind of management for chronic allergic disease. This is our wakeup call. We have to get a grip on the underlying cause of these resistant diseases, and we have to implement effective topical therapy. Each time the infection comes back, we’re going to have to culture it. Otherwise we’ll lose the one or two antibiotics we have left. —Dr. Fadok Dr. Angus: Until we learned about epidermal barrier dysfunction as a key mechanism in the pathogenesis of atopic disease, we didn’t understand why dogs get so many skin infections. Now we understand that epidermal barrier defect is almost inseparable from the progression of atopic dermatitis with age and Staph coloniclinician’s forum • 2 For me, the “Aha!” moment that connected bacterial pyoderma and atopic disease in dogs was reading human research that showed diminishing ceramide levels in both lesional and non-lesional atopic skin compared with non-atopic skin. One of the factors implicated was sphingosine: zation on the skin. Early recognition of the role of staphylococci and yeast in atopic dermatitis should translate to aggressive management to reduce colonization of the skin. Topical emollients and ceramides and pro-ceramides should also be used to repair that epidermis. So we start to progress from a normal-looking dog to an armadillo in our West Highland white terriers and Scottish terriers. That lichenification appearance of the skin is a response pattern to what I suspect to be a really defective epidermal barrier. Dr. Thomas: Can you elaborate on the connection between the skin barrier and allergic dermatitis? WHY TOPICAL THERAPY? Dr. Angus: First, the stratum corneum is a very important permeability barrier. It prevents the exit of water, but also prevents entry of allergens and irritants, along with things like yeast and staphylococci. Second, studies have shown that the epidermis produces antimicrobial peptides that are important to preventing infection. I think of it as a permeability barrier and an antimicrobial barrier. Dr. Thomas: How can we measure if there is actually a defect in the skin? Dr. Fadok: We infer the presence of a defect based on hot, dry skin or excessive scale formation. A tool we traditionally used in research is assessment of transepidermal water loss. sphingosine levels Dr. Angus: One thing to look at is what happens to the skin when you create a defect in the barrier. You get increased epidermal turnover and more rapid proliferation of the keratinocytes. As the skin barrier worsens, it adapts by getting thicker. Atopic dog skin certainly looks different from normal skin, particularly if you have added in a couple of secondary infections. went down, Staph 3 Keys to Managing Bacterial Folliculitis colonization went up. 1. Not all pyoderma is bacterial, so confirm your diagnosis. Demodicosis, pemphigus foliaceus, dermatophytosis, and Malassezia dermatitis are all frequently mistaken for bacterial folliculitis. atopic patients had a two-fold reduction in epidermal sphingosine compared with nonatopic individuals. As —Dr. Angus 2. Bacterial skin infections always have an underlying cause. Treating only the infection without managing the underlying disease is like treating pneumonia with a cough suppressant. 3. A dog can never be bathed too often. Topical therapy is critical to not only resolving the current infection but also preventing relapse. Appropriate antibiotic therapy should be coupled with frequent bathing: two to three baths per week during active infections, and then once a week thereafter for prevention. 3 • clinician’s forum Dr. Thomas: How important is topical therapy for the management of these complicated skin diseases? Dr. Fadok: It’s absolutely critical that we teach owners the importance of bathing their dogs with skin disease. Often I think there are old misconceptions that bathing will damage the coat or the skin, but we didn’t always have the quality products we have now. If an owner is willing to bathe multiple times a week, great— but now we have a topical product for every client. We’ve got sprays, mousses, and for focal lesions wipes and spot-ons. I think that’s of great value. Dr. Angus: Many clients will only use antiseptic shampoo during the active infection, and then go back to their regular grooming routine once every six to eight weeks. But with chronic allergic skin disease, continuing to bathe that dog once a week is a very important. Dr. Plant: Actually, 20 years ago, we really did view topical therapy as a kind of adjunct therapy. But there were many times where I’d treat a patient with pyoderma with antibiotics and think the owner is probably not going to bathe this big plush-coated dog in January when it’s snowing outside. So I’d skip the bathing, thinking the antibiotics will do the job. I’ve really turned around 180 degrees. Topical therapy has become really important with the advent of antimicrobial-resistant Staph strains. A lot of times, owners don’t realize the importance of the topical therapy until they stop doing it. Dr. Angus: It’s vital that we engage with our clients to understand what obstacles they’re facing to the therapies that we recommend. You can’t tell somebody in their 80s with an Akita to bathe their dog twice a week and expect that they are going to be able to comply. Provide solutions. Tell the client: Bring your dog to us and we can provide that service. “Well, it costs too much.” We could package ten baths and charge you for seven. We also We’re discovering that atopic dermatitis is a group of diseases that may vary substantially from breed to breed. It explains in part why it’s so difficult to treat. —Dr. DeBoer have mousses and sprays that are certainly better than doing nothing. Dr. Fadok: I usually bathe them there before they go home, and it’s great. Dr. Thomas: For which dermatologic conditions do you strongly encourage your clients to use topical therapy? Dr. Angus: Directly applying therapeutics to the skin allows us to use these topicals like a drug instead of relying solely on systemic therapy. The condition that comes to mind most readily is MRSP. I’m now convinced that bathing is not just an adjunctive therapy, it’s essential to helping them get better. Sometimes we’re left with something like amikacin injectables as the only rational systemic antibiotic. I would much rather bathe that dog. A less-common disease where I frequently use topical therapy is demodicosis. The act of bathing and cleaning the skin, getting the crust off, opening up the hair follicles, and draining the skin can be very important. Less commonly, sebaceous adenitis responds very well to topical therapy. Dr. DeBoer: Is it sufficient to get a topical product of any kind onto the skin, or is it necessary to have the detergent action of the bath? Dr. Fadok: Initially, a bath is critical because the sudsing helps to remove the crusts and matted hairs and things that tend to accumulate on the skin. But if we do that in our clinic, we take the onus off the client. Then we can send them home with a topical antiseptic, or if we’re not treating an infection, a topical lipid. Then we could follow up with a spray or a mousse. 5 Common Underlying Causes of Bacterial Folliculitis • Demodicosis • Endocrine skin diseases including iatrogenic or endogenous Cushing’s disease, or hypothyroidism • Poorly controlled flea allergy dermatitis • Atopic dermatitis associated with either environmental or food allergens or both I’ve really turned • Other allergic skin disease around 180 degrees. Topical therapy Dr. Fadok: There’s a bewildering array of topicals available. If you’re going to buy an antiinfective shampoo, get one with lipids, a good veterinary product that contains chlorhexidine. Dr. Angus: One of the reasons we all use chlorhexidine shampoos is because it’s the one product that has residual antiseptic activity. Dr. DeBoer: I agree, chlorhexidine! However, we have to recognize that there’s no evidence that 4 % chlorhexidine is better than 2 %. When you’re selecting a chlorhexidine shampoo, look at its emollient capabilities, barrier repair, and how well it lathers. We want to select products clients are going to enjoy using on their pet. Dr. Angus: If they’re coming back to get more, that’s self-reinforcing. You do need to have more than one product on your shelf, because invariably you will get that one in a thousand bad reaction. And sometimes chlorhexidine isn’t the answer. The product that the veterinarian has the most confidence in is the one clients are going to use, because that will come across. SELECTING A TOPICAL PRODUCT Dr. Thomas: How do you choose the right product for the condition? has become really important with the advent of antimicrobial-resistant Staph strains. —Dr. Plant Tips for a Good Bath • Use tepid or cool water • Use mild grooming shampoo first if coat debris is plentiful • Begin medicated shampooing of affected areas; then proceed to rest of body • Aim for 10 minutes of contact time with the skin • Rinse affected areas last Copyright 2015 Educational Concepts LLC, dba Brief Media CAN0215006 clinician’s forum • 4