HERDA: Preventing The Heartbreak

(Editor's note: This is Part 3 of a series on one owner's experiences and struggles with a HERDA-affected horse. Start the series at Part 1: When HERDA Strikes.)

Robin Davison "did everything right" when she bought her registered Paint mare Quality Sensation (aka Penelope), including hiring a knowledgeable trainer as her guide and agent and scheduling a prepurchase exam. Penelope's HERDA was undiagnosed then, but Davison says in hindsight there were signs that the mare had the skin disease, which can be severe enough that euthanasia is required in some cases.

Checking for HERDA sores

Although Penelope passed a thorough prepurchase exam, the mare was diagnosed with HERDA shortly after Robin Davison purchased her.

"There were subtle things, like a three-inch lump on her topline that was mushy, not firm like in normal horses," explained Davison.

According to HERDA researcher Ann M. Rashmir-Raven, DVM, MS, associate professor of Large Animal Clinical Sciences at Michigan State University, there are several characteristics of HERDA to watch for when evaluating a horse to buy.

"To avoid purchasing a horse with HERDA, you have to consider all scars or soft, mushy areas along the horse's topline," said Rashmir-Raven. "Also, look for stretchy, disconnected-feeling skin in unusual locations, such as under the mane, over the jaws, and over the topline."

Rashmir-Raven cautioned that HERDA shows up in certain Quarter Horse, Paint, and Appaloosa bloodlines; any horse whose pedigree has Poco Bueno on either sire or dam’s side is a potential HERDA carrier, able to pass along the defect if bred.

“Unfortunately Poco Bueno most often shows up seven or eight generations back, so an extended pedigree is often needed. In addition, those with Poco Bueno crosses on both sides could potentially be affected with HERDA, and should be DNA tested prior to being purchased if less than three years of age,” she added.

Trainer and breeder Vicky Seidler of California-based Seidler Pleasure Horses feels that responsible breeders should be willing to run DNA tests on their stock, and that they should make responsible breeding decisions based on the results. A low-cost DNA test can identify whether a horse is a HERDA carrier, will be HERDA-affected (before the horse begins showing clinical signs), or is normal and a non-carrier.

Buyers should feel comfortable asking for information on the pedigrees of horses for sale, and even for test result information. "After you check the pedigree, if there's any Poco Bueno in the bloodlines, ask the breeder if they've tested for HERDA, and if they have any horses that are carriers," she said. "If they haven't tested, ask them if they will."
Owners and breeders aren't the only ones who need to identify HERDA and prevent it from perpetuating, according to Nena Winand, DVM, PhD, of Cornell University; veterinarians must play a role, too.

"Anytime a veterinarian is vetting the purchase of a horse with Quarter Horse ancestry (e.g., AQHA, APHA, ApHC registered horses, Quarter Ponies, and even grade horses) they should be on the lookout for signs of HERDA, advising their client of the DNA testing option," said Winand.

Establishing the HERDA status of a horse before purchasing can also prevent years of heartache, according to Davison.

"We're doing the best we can to keep Penelope safe and comfortable," she said. "But it's not a situation I'd wish on anyone."

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Lisa Kemp

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