Sarcoids are a the most common skin tumour in horses. They are very variable in appearance, shape, size, growth rate and their reaction to treatment. Sarcoids can be problematic to treat because of the unpredictability over how each will react to the treatment. Unfortunately sarcoids often recur after treatment and they can be aggravated by trauma and interference. In summer, they attract flies and can become open sores which don’t heal.
Sarcoids most commonly affect the chest, groin, sheath and around the mouth and eyes. These are places where flies typically congregate and insect transmission is thought to be involved sarcoid transmission. Geldings are more susceptible to sarcoids than mares. Young to middle-aged horses are most often affected and there may be a genetic predisposition. Once a horse has a sarcoid it is more likely to develop another. Although sarcoids are cancerous tumours they do not spread to the internal organs. Donkeys and even zebras also get sarcoids.