A Texas veterinarian is taking a novel approach to sarcoid treatment in horses--removing portions of the tumors, freezing the tissue in liquid nitrogen and implanting it in the same horse's body.
"This is basically a very archaic viral vaccination attempt," says Benjamin Espy, DVM, DACT, a private practitioner who adds that the technique has been successful in 12 of 15 documented cases so far. "We are trying to get the body to recognize the sarcoid as foreign and mount its own response. This is an autologous vaccine, meaning it's made from the same animal you give it to--a very common technique in other livestock species."
Sarcoids, the most common skin tumor of horses, are believed to be caused by the bovine papilloma virus. They can be treated with chemotherapy drugs, such as cisplatin, or removed surgically or with lasers.
However, Espy says, if any trace of a growth remains, the sarcoids will return: "If you take off a huge sarcoid and leave behind even a tiny portion by accident, there might be five, six or 10 billion virus particles in it, and the sarcoid will come back, possibly even worse because once they've been significantly disturbed, sarcoids can become very 'angry.'" An injectable sarcoid vaccine is under development, he says, but studies on its efficacy have been controversial.
Espy specializes in equine reproductive work (theriogenology), but several challenging sarcoid cases associated with equine genitalia have been brought to his practice over the years, which sent him looking for better ways of treating the tumors. "For instance," he says, "I had a stallion referred to me with a huge sarcoid on his sheath. There is only so much you can cut away in that area."
For his technique, Espy takes several pencil-eraser-size samples off the surface of a tumor and freezes them by immersing them in liquid nitrogen to kill the virus. Once the sections have thawed, Espy implants them along the crest of the neck. "I choose the crest because the skin is thin and the area relatively immobile so it heals quickly. Also, if there is a scar or white hair accumulation, the mane will cover it."
So far, says Espy, the technique has been as or more successful than conventional sarcoid treatments he has tried. The tumors typically regress between 90 and 120 days after treatment, but some have taken as long as 180 days to subside. None of the horses has had a recurrence, Espy says. The horse he has followed the longest is still sarcoid-free five years later.
Espy says that, after presenting a paper on the technique at the 2008 American Association of Equine Practitioners Convention, he was approached by several veterinarians who recalled a similar discussion at the 1975 convention in Nevada.
"It's logical, so I'm sure I'm not the first person who thought of it," he says, adding that his main goal was sharing information about an effective treatment. "I'm a repro guy; I'll leave it up to the dermatologists and pathologists to figure out and write the paper on exactly why this works, but I've seen that it does."
This article orginally appeared as "A Better Sarcoid Treatment?" in EQUUS 379, April 2009.