What they are:
Warts are a type of tumour and are the most common growths found in horses. They are raised grey or pinkish cauliflower-like growths that are usually fairly small (usually not much bigger than the size of a pea). They can appear alone or in groups, and the most common location in which to find them is on the muzzle or around the eyes. However, they have occasionally been seen to occur on the ears, lower legs and genitals. The growths appear to by symptomless in that they do not appear to cause any pain or discomfort.
Warts are caused by a virus, the equine papillomavirus, which can survive outside the body for weeks. Young horses under 18 months of age are the most valuable to infection, although warts can be found in adult horses.
Warts are usually harmless and do not need treating. However, if their location is problematic, they may need removal. If, for example, they are preventing a horse from eating or moving comfortably or they are being rubbed by tack, they probably warrant removal. Left alone, warts will typically shrink and ultimately disappear altogether, leaving no scars.
This process usually takes around four months in younger horse, as the immune system develops to tackle the virus, but in an older horse it can take more than a year for the horse’s immune system to clear the warts.
Warts that warrant removal can be cut out using a laser or cryosurgery (freezing the wart), but these processes are likely to leave scars. Drugs that stimulate immunity may also be helpful. However, if the warts do not clear or they grow to a larger size, get your vet to come and examine them, as some conditions, like sarcoids for example, can have an appearance very similar to that of a wart.
It is important to isolate affected horses from unaffected horses, especially younger horses. Any tack or shared equipment used on a horse with warts must be disinfected thoroughly before being used on another horse.