XL Equine vet Dr. Aoife Byrne DrMedVet MRCVS discusses the rise in sarcoid cases, whether this is because they are becoming more common or clients now realise that if left untreated they can become more of an issue.
Where I work we treat sarcoids in a number of different ways, sometimes using a variety of treatment options, depending on the type, location and size of the sarcoid. We also have to take into consideration the temperament of the horse, the owner’s financial budget and the particular experience and preferences of the vet.
These include a variety of topical chemical creams and drugs which can be injected directly into the sarcoid (Chemotherapy), various surgical methods, including surgical removal and cryo-surgery.
In my experience the treatment which gives the highest success rate, is a chemotherapy cream provided by Professor Knottenbelt. This was the treatment I chose for a patient of mine called Albie. He had a number of various sarcoids types spread over his belly, groin & sheath areas. The cream required application for a total of five days spread over a course of 10 days. Then we waited. Some of the sarcoids responded very well and were gone with the first round of treatment. But some required a second round of treatment and then a third round. Albie’s owner was very patient as the whole process took over a year to complete and to complicate matters some treatment sites developed infection. But I saw Albie recently for his annual booster and checked him over thoroughly - so far he has had no recurrence and has had a successful summer competing at dressage.
Sarcoids are a very common type of skin tumour affecting male and female horses, ponies and donkeys. They affect all ages apart from young animals under about two years-old. Some animals appear to be genetically susceptible to developing sarcoids.
Sarcoids can occur at almost any site on the skin, although there are some regions that are more liable to their development such as the skin of the head and neck, between the front legs and in the groin area. Whilst they can spread within the skin, they do not spread to the internal body organs.
Sarcoids are likely to multiply on an individual horse and individual lesions may enlarge rapidly or slowly; especially when the sarcoid is traumatised or otherwise interfered with. Individual lesions frequently enlarge over time although they may remain static for many months or years. Nothing is known about potential triggers for exacerbation apart from the fact that trauma (either accidental or intentional) can trigger the development of the most aggressive forms from even the earliest mildest and smallest lesions.
Sarcoids can affect a horse in a variety of ways:
The sarcoid can become ulcerated and/or infected.
Sarcoids that develop at sites such as the eyelids and over joints and coronary bands can cause severe functional problems.
Cosmetic difficulties may reduce the owner’s enjoyment of the horse and may impair the relationship between the horse and the owner.
Location of the sarcoid can make it impossible to wear tack/rugs.
Sarcoids are ‘attractive’ to flies in the summer months and this can be highly distressing for the horse.
A horse with sarcoid(s) may be unsellable and is certainly worth less in a sale than it would be if it had no sarcoids; sarcoid is a common cause of loss of commercial value even in high performance horses.
Sarcoids may limit the working life of horses both in the short and longer term.
Types of sarcoid
There are six different types of sarcoid which vary in appearance and growth patterns, from flat flaky patches to large, ulcerated pedunculated growths.
1) Verrucose – Usually irregular patches of slightly raised, crusty or flaky skin.
2) Fibroblastic – Consist of red/yellow ulcerated, proliferating masses, that bleed readily and may be covered in a crusty discharge, attracting flies in the summer. They may become quite large and hang down from the body.
3) Nodular – Usually smooth, firm, fibrous lumps within or under the skin. They can be found individually or in groups.
4) Occult – A smooth, flat area of hair loss often with well-defined margins with relatively normal looking skin.
5) Mallignant – Widespread infiltration of different types of sarcoid covering a considerable area, with little evidence of normal skin, usually seen in genetically susceptible individuals.
6) Mixed – These contain any combination of the different types of sarcoid, occurring at the same location at the same time.
Sarcoids vary greatly in appearance, in some cases resembling warts, areas of proud flesh or even a patch of ringworm. To confirm a diagnosis of sarcoid, a tissue sample or biopsy can be taken and examined at the laboratory. However, sampling a sarcoid can stimulate it to grow, so they are often treated without taking a biopsy first and should always be treated promptly if a biopsy result confirms the presence of a sarcoid. Treating a sarcoid at the earliest opportunity increases the success rate and reduces the chance of further sarcoids developing.