Mistletoe: A Treatment for Sarcoids?

Mistletoe might be a timeless excuse for stealing a kiss at Christmas, but Swiss researchers have found a more practical and innovative use for the plant: treating equine sarcoids, the most common skin tumors in horses.

The research team, led by Vincent Gerber, PhD, DVM, Dipl. ACVIM, ECEIM, FVH, of the University of Bern, in Switzerland, tested the effect of mistletoe extract, Viscum album, on 43 horses with sarcoids using either the extract or a saline placebo.

Sarcoids usually are benign and often cause little disruption in a horse's daily life. Under certain circumstances, however, these tumors can be a nuisance and a health risk, not to mention unsightly. If they appear in an area where tack or equipment might rub against them (for example, near the mouth where a bit would rest), they can crack and bleed frequently in addition to causing significant discomfort. Larger masses are even more troublesome, sometimes splitting and becoming infected by flies and maggots.

In an attempt to find a treatment for sarcoids, the scientists gave 1 milliliter of V. album extract (VAE) in increasing concentrations or saline subcutaneously three times a week over 105 days (15 weeks), and they observed 163 tumors closely for one year. The sarcoids partially or completely regressed in 41% of the horses treated with VAE compared to just 14% in the horses receiving saline.

"On the level of the individual tumors (as opposed to the individual patient), 67% of the sarcoids showed complete or partial regression in the VAE group, compared with 40% in the control group," said Gerber. "The curative effects were higher in verrucous sarcoids (flat, wartlike tumors)."

He added that no significant side effects were observed.

Although a viable treatment option, VAE must be injected under the skin three times weekly for several months. "Since the volume per injection is small, the horses don't seem to mind, but it is still a challenge for both the owner and the veterinarian to comply with this protocol," Gerber said.

Treatment with VAE might have a systemic effect, as well, meaning not only the injected tumors benefit from treatment: "If the treatment is successful, all tumors of a patient can regress," he added. "A disadvantage of the therapy was that the response was slow. In many cases therapeutic effects did not become apparent until after the end of the 15-week treatment period."

Gerber and his colleagues are still monitoring their study horses to assure they remain in remission.

The study, "Treatment of clinically diagnosed equine sarcoid with a mistletoe extract (Viscum album austriacus)" was published in the November-December 2010 issue of the Journal of Veterinary Internal Medicine. The abstract is available on PubMed.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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