Equine sarcoids are spontaneous, locally invasive tumours of the skin of horses, mules, and donkeys and are the most common equine neoplasm representing over half of all equine tumours. They are variable in appearance, location and rate of growth and although they seldom affect a horse’s usefulness (unless they are in a position likely to be abraded by tack) they are unsightly and may cause considerable discomfort to the horse.
They can occur anywhere on an animal’s body although areas exposed to trauma or skin damage seem more commonly affected, they may proliferate in size and number and may develop at other sites. Treatment is not always necessary but where required it can prove difficult and expensive and re-growth may occur after treatment. They are thought to be caused by the Bovine Papilloma Virus which may be spread by flies (the face fly Musca autumnalis) which act as vectors spreading the infectious agent between individuals.
Sarcoids are classified according to their appearance:
NODULAR SARCOIDS are firm spherical nodules found under normal looking skin, they can be variable in size and number and some can ulcerate and become fibroblastic.
VERRUCOUS SARCOIDS are slow growing wart like proliferations of the skin which are seen particularly on the face, groin and body.
FIBROBLASTIC SARCOIDS are fleshy proliferative growths which often ulcerate and are locally invasive and are seen on the eyelid, lower limbs, groin, coronet, and areas of trauma.
FLAT (OCCULT) SARCOIDS are single or multiple patches of hair loss which may contain nodules and often become locally aggressive, they are seen particularly around the mouth, eyes and neck.
MIXED SARCOIDS are transitional between verrucous and fibroblastic and become progressively more aggressive as more fibroblastic transformation takes place.
MALEVOLENT SARCOIDS are multiple and invasive tumours which spread along lymphatic vessels and lymph nodes, they are frequently the result of repeated trauma e.g. surgery to other types of sarcoid but not all malevolent sarcoids develop as a result of this
Treatment is always more effective if implicated as soon as possible after the sarcoid appears.
Treatments available include:
Application of a band or lamb ring to nodular sarcoids cuts off the blood supply causing them to shrink and drop off over a period of time. However there is a risk that the sarcoid will recur after treatment, occasionally in a more aggressive form as it is not always possible to get the root.
Application of creams –
Antiviral creams (such as aciclovir and imiquimod) have been used to good effect on some occult sarcoids. They often need application over a prolonged period of time but the benefit is they are unlikely to make the sarcoid worse and are cheap so often worthwhile trying as a primary treatment.
Bloodroot ointment can be used on small occult/verrucous sarcoids to good effect. It does cause some local irritation and swelling but this is transient, the cream can be applied by the owner.
Cytotoxic creams containing heavy metals and 5 fluorouracil are prepared by Professor Derek Knottenbelt and his team (formerly of Liverpool University). They are very effective at causing sarcoids to die and fall off but can cause quite severe swelling and damage to surrounding skin. It must be applied by a veterinary surgeon under strict routine and management conditions.
Injection of chemotherapeutic chemicals
Mitomycin C is an anti cancer drug which can be effectively injected into nodular and fibroblastic sarcoids by the vet causing them to regress. Again local swelling is to be expected and sometimes injections need repeating after a couple of months.
Iridium wires are inserted into the sarcoid to destroy it. As the treatment is radioactive the treatment can only be carried out at certain premises under strict regulations so is very costly but can be the only option for some sarcoids around the eyes.
Sarcoids can be a serious problem & take a variety of forms however with the right treatment approach they can be managed before they become too extensive.
There are many anecdotal reports of other treatments from applying toothpaste to piercing a black slug with the thorn from a hawthorn bush and squeezing the juices onto the sarcoid! However we strongly advise owners to stick with treatments from veterinary surgeons which have been scientifically proven to work rather than waste time and subject the horse to further distress with treatments that may do more harm than good.