A review of equine sarcoid : Equine cutaneous tumours

Bovine papillomavirus (BPV) is perhaps the most extensively studied animal papillomavirus. In cattle BPVs induce benign tumours of cutaneous or mucosal epithelia, called papillomas or warts. Cattle papillomas are benign tumours and generally regress without eliciting any serious clinical problems in the host, but occasionally persist and provide the focus for malignant transformation to squamous cell carcinoma, as in the case of cancer of the urinary bladder and cancer of the upper alimentary canal. BPV is the only papillomavirus that jumps species: the virus also infects equids, and gives rise to fibroblastic tumours called sarcoids. Sarcoids very rarely regress, more often they persist and can be locally aggressive. These tumours are the most common dermatological tumour of equids worldwide. The purpose of this review is to discuss the biology of BPV, the biology of bovine tumours and equine sarcoids, and present the current understanding of BPV in tumour pathogenesis in its natural host, cattle, and in its heterologous host, equids. Finally, the use of anti-BPV vaccines as a therapy for equine sarcoids will be discussed. Only limited information on the clinical or pathological aspects of either bovine or equine tumours will be provided as this subject has been extensively addressed previously.

Sarcoids are the commonest form of equine skin tumour. Several therapeutic measures have been described but none is considered to be universally effective. Electrochemotherapy (ECT) is a new anticancer therapy that utilises electrical field pulses to induce increased cell membrane permeability to antitumour hydrophilic drugs, such as cisplatin. The increased intracellular concentration of the drugs has a significant therapeutic benefit. The procedure has not been previously reported in a large number of horses. To validate ECT as a novel alternative treatment for equine sarcoids. A retrospective study evaluating the efficacy of cisplatin ECT in the treatment of equine sarcoids was performed. Electrochemotherapy treatments were applied under general anaesthesia at 2 week intervals with or without prior excision or debulking. Electric pulses were directly applied to the lesions following intra-tumoural injections of an aqueous solution of cisplatin. One-hundred-and-ninety-four sarcoids on 34 horses, 2 ponies, 11 donkeys and one mule were treated with ECT. The 4 year nonrecurrence rate was 97.9% for animals (47/48) and 99.5% (193/194) for tumours. When ECT was used as a single treatment, a significant influence of tumour size (ρ= 0.55) on the number of treatments required for cure was shown. When prior surgery was performed, there was a significant influence (P<0.001) of the excision quality (complete or incomplete) and the healing mode (closed or open wound) on the number of treatments. The most common adverse effect was a slight oedematous reaction for lesions located on thin skin regions. Results demonstrate that ECT, with or without concurrent tumour debulking, is an effective alternative for treatment of equine sarcoids. © 2011 EVJ Ltd.

The purpose of this study was to determine the characteristics of occult, verrucous, fibroblastic, nodular and mixed equine sarcoids. Ten tumours of each type were examined histologically and analysed for the presence of bovine papilloma virus (BPV)- DNA. All tumours were positive for BPV - DNA and showed an increased density of dermal fibroblasts. Epidermal hyperplasia, hyperkeratosis, rete peg and 'picket fence' formation were only found consistently in the verrucous and mixed types and were often not present in occult and nodular sarcoids. Immunohistochemical staining for Keratins 10 and 16, Ki67 and p53 showed no important differences between the clinical types. It can be concluded that the presence of BPV - DNA and the increased density of dermal fibroblasts were the only common characteristics for all sarcoids of the different clinical types. The presence of other microscopic alterations was variable but could not be used in the differentiation of the clinical types based on histology. Copyright 2000 Harcourt Publishers Ltd.