Could a festive winter decoration provide the cure for equine sarcoids?
Sarcoids are the most common skin tumour of horses. They are difficult to treat, and may recur after treatment. A new therapeutic option has been suggested by a Swiss study, which found that an extract of mistletoe was an effective treatment.
The findings have been reported in the Journal of Veterinary Internal Medicine. Lead author was Ophélie Christen-Clottu of the Research Institute of Organic Agriculture, Frick, Switzerland.
The study compared the response of sarcoids to treatment with an aqueous extract* of the pine mistletoe (Viscum album ssp. austriacus) and a placebo.
Mistletoe contains compounds, like lectins and viscotoxins that have been shown experimentally to have cytotoxic and growth inhibiting properties and immune modulating activity. Extracts are used as an adjunct to treatment of cancer in human medicine.
The treatment consisted of injections of 1ml of mistletoe extract in increasing concentrations (from 0.1mg/ml to 20mg/ml) administered 3 times a week for 15 weeks. Control animals were injected with 1ml of saline at similar intervals.
The researchers monitored the location, number, and type of sarcoids present for a year after the start of the study. Neither they nor the horse owners knew which horses were treated with the mistletoe preparation or the placebo until the end of the study.
Fifty-three horses, with a total of 444 sarcoid lesions, were treated - with either mistletoe extract or placebo. Forty-two horses were treated as monotherapy and 11 horses were treated with mistletoe extract or placebo after selective surgical excision of some sarcoids.
Five of the treated horses developed mild oedema at the site of injection when the higher concentration injections were given. This swelling disappeared within a few days without treatment. No other adverse effects were noted.
At the end of the study, sarcoids were no longer visible in 9 of 32 mistletoe extract treated horses and 3 of 21 placebo control horses. This difference was not statistically significant. However, another 4 horses in the VAE group showed reduction in more than half of the sarcoids.
So, overall, 41% of horses in the treatment group showed complete or partial regression of the sarcoids - which was significantly different from the response in the placebo group.
The curative effects were higher in verrucous sarcoids than by other types of sarcoids. On advantage of VAE treatment is the systemic effect: if treatment is successful, all tumors of one horse can regress. The disadvantage of the therapy was that response to treatment was slow - being seen only after the end of the 15 week treatment period in many cases.
They conclude that mistletoe extract proved effective for treating clinically diagnosed equine sarcoid in this study. They suggest that it can be recommended particularly when excision may not be appropriate, for example for sarcoids around the eyes or for cases with multiple sarcoids.