Equine Sarcoids: Stuck between a rock and a hard place.
Sarcoids are known to be the most common skin tumour found in horses worldwide. The sarcoid is an aggressive fibroblastic tumour occurring in 6 recognisable forms, all of which have a high natural tendency for recurrence.
IN SHORT, SARCOIDS ARE NASTY BUSINESS!!
Sarcoids do not discriminate between equines, with all types of horses, ponies, and donkeys being susceptible to them. Sarcoids are even found amongst the Zebra population. They may develop at any age, but is often found between the ages of 2-10 years with them being more common in geldings. Sarcoids are best regarded as a form of skin cancer. Some forms are very locally aggressive with the condition limited to only the skin and tissue directly under it. Thankfully, they are generally benign and do not have a tendency to spread to the internal organs.
Sarcoids seem to develop in some defined anatomical locations, most commonly found on the animal’s head, groin and inner thighs, and the prepuce (foreskin) in geldings and stallions. This however does not mean that sarcoids follow the rules! As always, there are exceptions.
Large sarcoid on the prepuce of a horse.
As mentioned, there are 6 types of sarcoids – not all easily recognisable, which can make it difficult to diagnose by visual inspection alone; therefore a biopsy of it is a definitive diagnostic tool.
- Occult sarcoids: Usually appear as grey, hairless, often circular or roughly circular areas. These are most commonly found on the face, armpit and inside of the thigh/ groin.
- Verrucose sarcoids: These look scabby, warty and grey in appearance and can have small nodules within them.
An example of a Verrucose sarcoid around the eye. Treatment options are complicated because of the location of such sarcoids.
Verrucose sarcoid where the girth would normally sit- obviously this would need to be removed in order to ride the horse.
Typical Verrucose sarcoid
Picture courtesy of Manual of Equine Dermatology – Pascoe & Knottenbelt
- Nodular sarcoids: These are discreet solid nodules of various sizes and are commonly found under the skin located in the armpit, inside thigh and groin areas. They may be single or can be found in multiple bundles and often they have no skin involvement with the skin being able to move independently of it.
Nodular sarcoids on the sheath (above and below)
- Fibroblastic sarcoids: These are fleshy masses that generally have a wet, haemorrhagic (bloody) surface. They often occur at the site of an injury to the skin, most predominantly found on the limbs. They may develop rapidly from a milder form following trauma.
Fibroblastic sarcoids on the chest
- Mixed sarcoids: These are a variable mixture of two or more of the other types (Verrucose, Nodular and Fibroblastic).
Mixed with mostly nodular appearance sarcoids between the hind legs and on the sheath
- Malevolent sarcoids: These are by far the most aggressive type of tumour and they spread extensively with rope-like tumour tissue interspersed with nodules and ulcerating fibroblastic lesions.
Picture courtesy of Manual of Equine Dermatology- Pascoe& Knottenbelt
The In’s and Out’s
Any affected horse may have one lesion or several others hidden amongst the tissue. It is not known whether sarcoid tumours are transferred between horses, but what is known is that it has a very complex epidemiology.
Sarcoids are said to be related to Bovine Papillomavirus, have a genetic predisposition, and often strike when the immune system is compromised. It can be further aggravated by insect bites and injury sites. Virus-like genetic material has been isolated in a large portion of sarcoids but no specific virus particle has been found. In layman’s terms, sarcoids demonstrate virus like behaviour but cannot be classified as a virus. It is strongly recommended that strict fly control measures are implemented along with hygienic wound management and this is advised for affected and non-affected horses. One should pay close attention to injuries on horses that have sarcoids, and one should monitor these horses closely for any changes to the wound.
Sarcoids are notoriously difficult to treat, with there being several treatment regimes commonly used. We must state however that not one treatment is universally effective.
- Radiation gives the best results, with a near 100% effectiveness, however it is expensive, very restricted and not available in South Africa as yet.
- Homeopathic and natural medicines are entirely unpredictable and the success rate is not well documented. There is no scientific evidence that turmeric powder, either per mouth or directly on the lesion, is effective in any way.
- Surgical removal is a common method of treatment, but the rate of recurrence following surgical removal is high. Instead of surgical excision, ligation (putting an elastic band around the base of the sarcoid) may also be used.
- Cryosurgery (freezing) generally does not yield good results.
- Hyperthermia, electrocautery and laser surgery have been described to have limited success.
- Local/Topical medication, in particular Professor Derek Knottenbelt’s AW4-LUDES cream seems to be having the highest success rate when used on the right type of sarcoid.
- Vaccination trials do exist, but currently, there is no effective vaccine for sarcoids.
Treatment has been found to be more successful when lesions are treated early in the affected equine’s life, generally between the ages of 4-6 years. A horse that has any sarcoids is, by definition, predisposed to them and probably will remain so for life. No horse that has, or has had, sarcoids can be categorically considered “permanently cured”. This is with the exception of horses that “self-cure” at an early age. These horses can then usually be regarded as being “immune” to the disease.
An early diagnosis with prompt and effective treatment is the best overall policy. One needs to be aware that the commercial value of a horse, even with one sarcoid, is probably less on the open market than the same horse, without the sarcoid. If you are considering a horse with one or more sarcoids, you should be seriously taking the following into account:
- The horse will not be insurable with respect to the disease after purchase. This means that any treatment or complications related to the sarcoid will be excluded.
- Ongoing treatment is likely to be expensive, with repeated treatments being needed, at various intervals over the entire horse’s life.
- The value of the horse may be affected, and it may be difficult to sell the horse on at a later stage.
- Sarcoids can become a serious health issue and may evolve and become life threatening.
Again, and as mentioned before, it is important to have an accurate diagnosis before commencing any treatment protocol, sale agreement and insurance vetting.
Sarcoids cast a nasty shadow over an otherwise healthy, talented horse, however, with careful and consistent sarcoid management; these horses can continue to have successful careers in their chosen discipline.
A special thank-you must go to Professor Derek Knottenbelt- for without his detailed research and knowledge- we would not have been able to write this article.
Should you have any questions or concerns, feel free to call one of our Vet’s for advice on 082 459 0129, or if you want additional information on Sarcoids, please visit www.equinesarcoid.co.uk.