HERDA: A Daily Struggle

Horses afflicted with the skin disease hereditary equine regional dermal asthenia (HERDA, also called hyperelastosis cutis or HC) can develop external lesions from a variety of environmental factors. This includes everything from sunlight to contact with tree bark or fence boards ... even other horses; keeping their fragile skin intact can be a full-time job. (Editor's note: This is part 2 of a series on one owner's experiences and struggles with a HERDA-affected horse. See part 1: When HERDA Strikes.)

Treatment for Hematoma

Desitin is used to coat Penelope's leg to prevent serum burns while a large hematoma drains.

According to Ann M. Rashmir-Raven, DVM, MS, associate professor of Large Animal Clinical Sciences at Michigan State University, HERDA-afflicted horses have a genetic mutation that affects collagen, the primary protein found in connective tissue such as skin, bone, cartilage, and tendon. The result is fragile skin that tears and scars easily in response to very small stresses, such as contact with a saddle.

Robin Davison discovered in mid-2010 that her newly purchased registered Paint mare Penelope had HERDA. While devastated by the diagnosis, Davison was determined to give the mare the best quality of life she could.

"I've researched HERDA online and I've been in touch with some of the top research veterinarians in the country, and we've developed a routine that minimizes the risks while still allowing Penelope to be a horse," she said. Targeted nutritional management is also important.

"For these horses, it's important to provide adequate protein," said Rashmir-Raven. "We have evidence that cofactors in collagen formation, such as vitamin C and copper, might improve affected horses, as could supplementation with the amino acid lysine."

To help Penelope's skin stay healthy, Davison prepares daily supplement packets of flaxseed plus vitamins C and E that are included as top dressing on the mare's commercially prepared feed. Penelope also eats alfalfa and grass hays.

With a band of HERDA horses in her research program, Rashmir-Raven has developed additional management strategies.

"Sunlight restriction is the most important aspect of the management of these horses, with heat restriction being part of the goal as well," she explained. "I recommend that affected horses be stalled during the day, especially in summer, with a fan on them if it's hot."

While Penelope has had several episodes of skin lesions, Davison keeps her out of the sun as much as possible to prevent their recurrence.

"In the summer she's turned out with her fly mask on, which also provides UV protection for her eyes, and I have a UV sheet I can also put on her," she said.

As for lesions, Rashmir-Raven pointed out that smaller hematomas (pockets of blood from local trauma collected in tissues) frequently reabsorb on their own. "Larger ones generally need to be drained but should not be flushed," she said. "Serum scalding from draining fluid can affect even a normal horse, but you can protect a HERDA horse's skin by applying Desitin ointment in the fluid path."

Right now, everything is an experiment, according to Davison. "We're very lucky, because we caught it early and Penelope doesn't have the worst case." Still, the mare requires constant vigilance. "We have to watch her closely, because the situation can change at any time." 


Related Articles: Study: Consider Ocular Disease in Horses with HERDA

HERDA: DNA Tests Available for Disfiguring Skin Disease

HERDA: Skin Characteristics

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Lisa Kemp

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