Dermatology Goes to the Dogs, and Human Patients Benefit

Maureen Salamon

July 28, 2017

NEW YORK CITY — Atopic dermatitis (AD) in dogs is the strongest link between human and canine dermatology in offering a model for the investigation of mechanisms and therapeutics, an expert said here at the American Academy of Dermatology (AAD) 2017 Summer Meeting.

"The hair coat and wide distribution of atopic dermatitis on dogs makes topical therapy nearly impossible for most patients and has caused us to rely almost exclusively on systemic therapies," said Daniel Morris, DVM, MPH, from the University of Pennsylvania School of Veterinary Medicine in Philadelphia.

Dr Morris' remarks were part of a novel presentation on comparative dermatology between animals and humans and the One Health paradigm.

Rooted in the time when a single physician cared for all members of a household, including humans and animals, One Health fosters collaboration between various medical and scientific disciplines, including physicians and veterinarians.

"Once you start to identify the connections between humans and animals, it's possible to take a One Health approach and really start to come to some answers for some of our biggest problems in public health," said presenter Jennifer Gardner, MD, from the University of Washington and collaborating member of the UW Center for One Health Research in Seattle.

"It also allows us to look at the animal world as sentinels for human disease," Dr Gardner added. "It's the so-called canary in the coal mine that if we understand it, we can see what's coming down the line for us and hopefully intervene."

Atopic dermatitis in humans and dogs is a near-perfect match with similar prevalence and ages of onset early in life, presenter Charles Bradley, DVM, explained to an audience of about 75 attendees. In both species, the condition typically presents as "the itch that rashes" and is brought on by an interplay between genetic and environmental triggers.

Atopic Dermatitis

"With roughly 70 million dogs across 40 million households in the US, it's an incredibly common disease," said Dr Bradley, from the University of Pennsylvania School of Veterinary Medicine.

Veterinary medicine has been quicker than human medicine to develop interleukin-31 (IL-31) inhibitors that target AD-related itch in dogs, said presenter Brian Kim, MD, codirector of the Center for the Study of Itch at Washington University School of Medicine in St. Louis. In humans, there are no FDA-approved agents for chronic itch, he pointed out.

"IL-4 drugs like dupilumab may have broader implications for itch, and JAK-1 selective inhibition may be more effective than broad JAK blockade for itch," Dr Kim said. Approved in March 2017, the monoclonal antibody dupilumab (Dupixent, Sanofi/Regeneron) is the first-ever human biologic therapy available for moderate-to-severe atopic dermatitis.

Animal-human dermatology comparisons also included demodicosis. Common in dogs, the microscopic mites can also play a role in rosacea, blepharitis, alopecia, pityriasis folliculorum, and other human conditions, said presenter Dirk Elston, MD, from the Medical University of South Carolina in Charleston.

Dermatologists often spot the tiny spines of demodex mites sticking out from patients' skin, he said. Ivermectin is a common treatment in both animals and humans, but Dr Elston said sulfur "tends to be my most reliable for anything demodectic" in people.

/I think there's huge opportunity for collaboration between veterinarians and human medical doctors in discovering disease treatments and sharing best practices./

Similarities between human and animal dermatology cease when drug costs are considered, Dr Morris said, with veterinary agents typically much less expensive than similar human versions. But dermatologists should be aware that veterinary washes and other topical preparations are not regulated for human use and should not be administered.

Asked to comment on the presentation, AAD scientific assembly committee chair Jacob Levitt, MD, from the Mount Sinai School of Medicine in New York City, said he was struck by the high level of sophistication in veterinary medicine.

"The degree of science the veterinarians use in treating their animals is probably something that's underappreciated by human doctors," Dr Levitt told Medscape Medical News.

"I think there's huge opportunity for collaboration between veterinarians and human medical doctors in discovering disease treatments and sharing best practices," he added. "Animal models provide a preview for what's to come in human medicine and it's an interesting opportunity for medical specialists to have a sneak peek at future therapies by inviting veterinarians to their conferences."

Drs Morris, Gardner, Bradley, and Elston have disclosed no relevant financial relationships. Dr Kim serves on an advisory board for Celgene and is a consultant for Incyte and Regeneron. Dr Levitt serves on advisory boards for Amgen, Janssen Biotech, Genentech, Medac, Ranbaxy, Pfizer, Promius, and Castle Biosciences and is a consultant for Novartis.

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