Faculty member leads team to create guidelines for equine allergic skin disease

Dr. Rosanna Marsella
Dr. Rosanna Marsella with her stallion, Alessandro.

For the first time ever, clinical consensus guidelines for equine allergic skin diseases have been published for the World Association for Veterinary Dermatology by a team led by Dr. Rosanna Marsella, a professor of dermatology with UF’s College of Veterinary Medicine.

The guidelines were published May 8 in Veterinary Dermatology.

Allergic skin diseases are common in horses worldwide, with the most common causes being insect bites and environmental allergens, the paper states. The study’s goal was to provide a review of the current literature and provide consensus on pathogenesis, diagnosis, treatment and prevention of these diseases.

“I was approached by the world organization, which wanted to have an open access document of consensus guidelines so that anyone could look at this long manuscript and see a summary of all studies and current recommendations for equine allergic skin diseases,” Marsella said. “We got the information from the most experienced dermatologists in the world. I was the chair of that group, which is how I ended up being first author on the study.”

While those contributing to the paper were dermatology specialists, the purpose of it being open access was to make the information available to equine veterinarians and anyone wanting to know the “state-of-the-art, best understanding” of certain allergies that affect horses, Marsella said.

“This work relates to any itchy horse,” she said. “Many times, veterinarians in practice may not know what is causing the allergy or what it is; they just know that you want to make that horse comfortable.”

By nature, consensus guidelines are aimed at practitioners, which is why they amount to a review, Marsella said. But the part of these guidelines that might surprise people is that “there are so many things we don’t know.”

“There are many things we do and say, but if you look at the literature to find out how well documented they are, you find very little evidence,” Marsella said.

“This shows the need for real studies to prove or disprove certain facts,” she added. “We have largely adopted things from humans and dogs, but when you look at the literature, there are very few controlled studies, so everything ends up being practice-based versus the result of a controlled study. So maybe that is a surprise and hopefully will be motivation for people to do more evidence-based studies so we can make some real progress.”

Horses are “in the dark ages” as far as progress in the area of allergic skin disease is concerned, she said, adding that while there had been many studies of certain diseases affecting horses, skin diseases were understudied despite the fact that horses can be euthanized due to skin disease because they can’t be ridden or are unmanageable trying to roll and scratch or get secondary infections.

“I’ve had horses with corneal ulcers or who have injured themselves rubbing,” Marsella said. “Some horses even leave Florida because they can’t survive in this environment. There is definitely a need for more research to help horses with skin disease. So maybe the surprise in these guidelines would be our ignorance.”

One project Marsella is excited about that she is currently studying involves the development of a biologic therapy that targets a molecule, known as IL-31, or interleukin 31, which mediates itch. Veterinarians already makes use a biologic in dogs, but no work in this area has previously been conducted in horses.

Marsella talks more about her research in this UF Vet Med Voice podcast.


As part of both the Institute of Food and Agricultural Sciences and the Academic Health Center, Veterinary Medicine is dedicated to advancing animal, human and environmental health through teaching, research, extension and patient care.


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