Equine Sarcoid Treatment: An Ultrasound Trial and One Owner’s Story

The first time I saw the sarcoid on Gage's neck, it didn't look like much. It was a flat patch of skin on my Thoroughbred gelding, and it bothered me far more than it bothered him.

So I treated it. With my veterinarians instruction I started with XXTERRA, a paste made from bloodroot and zinc chloride that is sold for sarcoids. The patch became angry and inflamed, and the flat surface turned into a raised nodule. Next came BCG injections. BCG is an immune-stimulating treatment, and its job is to provoke the horse's own immune system into attacking the tumor.

It did exactly that, and it was not pretty. Gage's body began to reject the tumor. It looked as if the tissue was being eaten away and pushed out from underneath. Pus oozed from the site. I cold hosed it every day. Eventually the nodule was hanging from his neck by a stem of tissue, and my vet cut it off.

What was left behind was a hole where the tumor had been. It looked awful. I kept cold hosing, and slowly the flesh filled in and evened out. In the end it healed flat again. The skin stayed hairless, but it never grew, never bled and never oozed again. We watched it for changes and never treated it again.

The whole process took more than six months. Along the way it became painful for Gage, and he developed a secondary infection.

A new approach on trial for equine sarcoid treatment

I thought about Gage when I read about a mare named Pea. Pea is a nine-year-old Hanoverian and the first horse treated in a clinical trial at the Virginia-Maryland College of Veterinary Medicine at Virginia Tech. The trial is testing histotripsy, a non-thermal focused ultrasound technique, as a treatment for equine sarcoids.

Histotripsy was developed at the University of Michigan for human cancers. It uses focused ultrasound to create a cloud of tiny bubbles that mechanically breaks down the targeted tissue. Virginia Tech's team had already used it on soft-tissue sarcomas in dogs and cats.

The trial is led by Dr Sophie Bogers, an assistant professor of large animal surgery, working with the biomedical engineering lab of Eli Vlaisavljevich in the College of Engineering. It is funded by the Focused Ultrasound Foundation.

The team had to make some changes for horses. Human histotripsy uses a water bath, which doesn't work on a standing horse, so they switched to a gel-based coupling pad like the ones used in routine ultrasound. "We do ultrasound on horses all the time, and equine practitioners are very comfortable with ultrasound," Bogers said.

Pea's owner, Kelly Kuykendall, brought her from North Carolina to have a tumor on her belly treated this spring. Pea was awake and standing for the procedure. "She just stood there, was very happy. She didn't seem to feel or dislike the histotripsy," Bogers said.

The next morning, surgeons removed the tumor as planned, and the team confirmed the tumor tissue had been destroyed. Pea went home by lunchtime. In this phase of the trial, each treated sarcoid is surgically removed afterwards so the researchers can study it.

Still early days

The researchers are careful about what this means. One horse has been treated, and the team does not yet know whether histotripsy stops sarcoids from coming back. Bogers needs four more horses to complete this phase of the study, which is enrolling horses with sarcoids on the trunk, abdomen or neck.

"Sarcoids have long been a clinical frustration for veterinarians and owners, alike," Bogers said when the trial launched in May. Speaking to Virginia Tech News in September, she put it plainly: "There is no 'one-fix-for-all' solution for sarcoids."

Sarcoids are the most common skin tumor in horses. They are linked to bovine papillomavirus and a horse's genetic susceptibility, and they can come back after treatment. A gentler option that works on a standing horse, without days of oozing and bandaging, would be a real step forward.

Living with it

I wanted to treat it because it was a cosmetic blemish. That was vanity, and Gage paid for it. After it healed, I accepted that a blemish was not worth the health of my horse.

Veterinary guidance supports leaving some sarcoids alone. In the University of Minnesota's Large Animal Surgery notes, Dr Erin Malone writes that sarcoids which are not growing, ulcerated or traumatized are often best left untreated. Trauma, including a biopsy, can trigger some types to grow more aggressively.

Today my Mustang has two flat sarcoids on his neck. I'm leaving them alone and watching them closely. If they ever change, start to grow or become angry, I'll call my vet.

For my own horses, unless a sarcoid is growing in a bad spot, like the eye, inside the ear or around the private parts, where it gets in the way of daily movement and activities, I leave it alone and keep watching it.

Every horse and every sarcoid is different. This is one owner's experience, not veterinary advice. If you have a horse with a sarcoid, definitely discuss it with your vet.

In Virginia, Dr Bogers still needs four more horses to finish this phase of the trial. We plan to watch it closely and hope to see positive results. A treatment that works on a standing horse, with a short hospital stay, would have spared Gage months of cold hosing.