Sarcoids are a type of equine skin tumour that exist in the skin and the tissue layers immediately below the skin. They do not spread to internal organs. Unfortunately, we now recognise 2-8 % of horses in the UK have sarcoids. Interestingly, Europe seems to have a lower rate of sarcoids in their equine population. As sarcoids affect all equines, it means even some of the best competition horses have them and if sarcoids do not affect tack areas or vision, competitive careers should be unaffected. It seems sarcoids commonly develop between 2-10 years of age although they can occur at any time from a few weeks of age to geriatrics.
There appears to be a genetic predisposition that dictates which horses develop sarcoids when exposed to the disease. Lipizzaners seem to be very resistant to sarcoids; Arabian horses seem more susceptible. Despite the apparent genetic predisposition and familial links, it is unknown whether predisposition to sarcoid development is a heritable factor. Unfortunately, there are still so many unanswered questions with regard to sarcoids. It does appear that bovine papilloma virus (BPV) may be implicated in some way but it is certainly not the whole story. Sarcoids also seem to spread during the summer which we attribute to spread of a viral factor by flies, to susceptible skin tissue; either on the same animal or different animals. Most sarcoids appear on thin skinned areas that are often targeted by flies, such as head, belly, and groin. Sarcoids can also occur at wound sites so it should be considered if a wound is non-healing.