IN-DEPTH: DERMATOLOGY AND LUMPOLOGY


It is also important to know that in some cases, application of remedies of various natural and homeopathic types have resulted in considerable exacerbation of the tumors. This is probably more a property of the fact that the tumors have been interfered with rather than any directly harmful effect of the so-called remedy.


Prognosis


The prognosis is always very guarded and owners should be made aware of the possible serious com- plications, which can arise both from the disease itself and from the treatment. A diagnosis of equine sarcoid has a very serious effect on the value of the horse and the likely enjoyment that the owner will get out of it.


Summary


Whatever is said about the equine sarcoid in folk- lore and in the largely ill-informed lay press, it should undoubtedly be regarded as a form of skin cancer. It should therefore be treated with the re- spect deserving of any neoplastic state; early veter- inary consultation will help to ensure that the condition is held in check and not allowed to run rampant through the skin of a horse. Whenever a horse is found to have a sarcoid lesion, it needs to be put into the proper perspective. The condition is unpredictable and before a buyer purchases a horse they should be sure of the insurance implications and the likelihood that treatment will be required. A single small lesion may remain identical until the horse dies of old age but it could erupt at any time or it may herald the development of more lesions as time passes; the difficulty is deciding which is which. There is no clinical indicator which helps to predict which lesions will take on an aggressive form and which will not. It is clear that the fewer lesions that are present at any one time, the fewer it will get and this may link to the feeding habits of flies during summer months. Horses should be as sarcoid free as they can be over the summer months when flies are a problem. The condition is more related to surface feeding flies than to blood feeding flies since the latter do not ever visit open ulcerated sites. The prospects for successful treatment are far bet-


ter if the lesions are small, early, and the horse is under 4–5 years of age. None of the treatment methods are cheap and none of them are certain of success. Sarcoids around the face and on the legs are particularly dangerous in almost every aspect of the disease and owners should not be unduly sur- prised when any selected treatment fails to help, in fact the treatment could make matters worse. Fur- thermore, there is no current method for treating microscopic lesions—treatment is only possible for lesions that are visible. It is hoped that eventually there will be a way to make the immune processes of the patient recognize the presence of abnormal cells and reject them—this way every single cell could be detected and destroyed; there would be no


more sarcoids. This is some way off yet—if it were as simple as this there would be an answer to every cancer and disease in every species of animal. There is a desperate need for more effec- tive treatments and some form of prophylaxis if this disease is going to be eliminated from the horse population to avoid the welfare and cost implications. The correct choice of treatment method is critical.


The best possible method should be used for each individual lesion taking into account the type, ana- tomical location, duration, and previous treatment history, and owners’ resources. Each factor will in- fluence the decision but no method is universally effective. Resorting to homeopathic irrationality or other inappropriate interference is not what cancer deserves. Unless and until there is a wider appre- ciation of what the disease is and how it can develop into an irretrievable situation, horses will continue to be destroyed. There is no doubt that many sarcoid lesions can be treated by one means or another. As always, the successes are not the problem—it’s the failures. Failure of any treatment has to be viewed as a potential disaster since the prognosis for subsequent treatments falls dramatically (by around 40%). Any claims for 100% effective treatment should be viewed with considerable skepticism: either the cases are so carefully selected or the results are interpreted constructively. There is nothing more expensive than a cheap treat-


ment that does not work except of course an expensive treatment that does not work. A lack of research effort in equine oncology is possibly the most signifi- cant single factor that constrains oncologic advances. In spite of the ease of access and diagnosis, cutaneous oncology still receives little research effort or clinical interest.


Acknowledgments


Declaration of Ethics The Author has adhered to the Principles of Veteri- nary Medical Ethics of the AVMA.


Conflict of Interest The Author has no conflicts of interest.


References and Footnotes


1. Haspeslagh M, Vlaminck L, Martens A. The possible role of Stomoxys calcitrans in equine sarcoid transmission. Vet J 2018;231:8–12.


2. Jackson C. The incidence and pathology of tumours of do- mestic animals in South Africa: A study of the Onderstepoort collection of neoplasms with special reference to their histo- pathology Onderstepoort. J Vet Res 1936;6:1–9.


3. Knottenbelt DC. A clinical classification of the equine sar- coid. Clin Tech Equine Pract 2005;4:278–295.


4. Knottenbelt DC, Kelly DF. The diagnosis and treatment of periorbital sarcoid in the horse: 445 cases from 1974–1999. Vet Ophthalmol 2000;3:73–82


5. Knottenbelt DC. A suggested clinical classification for the equine sarcoid. Clin Tech Equine Pract 2006;4:278–295.


AAEP PROCEEDINGS  Vol. 65  2019 19


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