Equine sarcoid is a common form of skin cancer that can afflict horses of all breeds and ages. The lesions contain DNA fragment that are derived from a Bovine Papilloma virus. It can be very persistent and frustrating to treat. There is little evidence that it is transmissible between horses or from other species although some form of vector may be involved initially. Different horses vary in their individual susceptibility and this cannot be predicted.
There are many treatments that have been used historically with little evidence backing them and some such as topical pastes remain hugely popular despite variable evidence for their efficacy. At B&W Equine Hospital we use a multimodal approach to treatment of soft-tissue skin masses (including sarcoids and melanoma) that is tailored to individual horses, based on the best current evidence. This can involve surgical debulking using a diode laser with energy protocols selected for the specific horse. This is often combined with adjunctive therapy with intra-lesional chemotherapy using cytotoxic drugs enhanced using Electrochemotherapy which potentiates the effects of the cancer drugs, or using slow releasing beads. Depending on the site and size of lesions some treatments (including electrochemotherapy) can only be done safely with the horse anaesthetised. Discrete lesions in certain sites and some follow up treatments can be done with the horse sedated on an outpatient basis.
There is a vaccine licensed against canine melanoma that has some benefit in reducing recurrence rates in horses. This can be administered by a veterinary specialist, with up to 4 doses at 1-2 week intervals being the normal protocol.