Equine sarcoids are the most common skin tumors of horses. Despite being such a common entity, relatively little is known about many features of sarcoid epidemiology or growth. In addition, due to the detection of Bovine Papillomavirus (BPV) DNA of 2 different types, BPV type 1 (BPV1) and BPV type 2 (BPV2), in equine sarcoids BPV has been suggested as the causative agent of sarcoid development. Recently, however, BPV DNA has also been detected in other skin conditions of horses; the significance of this is unclear. Multiple studies to learn more about sarcoids were undertaken.<p> To investigate the epidemiology of sarcoids in horses in Western Canada the records of five veterinary diagnostic laboratories were searched to identify submissions of sarcoids from horses. The submission record and diagnostic reports of 802 separate submissions of equine sarcoids were reviewed for age, breed, and gender of the horse and the number, location and clinical type of sarcoid. Based on these submissions, horses of a wide variety of ages and 23 different equine breeds were affected, within these breeds, Donkeys were overrepresented.<p> The presence of BPV was determined by Polymerase Chain Reaction (PCR). BPV was found in 74 of 96 (77.1%) samples, and using Restriction Fragment Length Polymorphism, BPV1 and BPV2 were identified in these samples. BPV2 was present in 59 (79.7%) of these. Unlike other areas in the world, in Western Canada, equine sarcoids are most commonly associated with BPV2.<p> A second study examined different clinical types of sarcoids to determine if there was differential expression of immunohistochemical markers associated with apoptosis, Cleaved Caspase 3(ClC3), and antiapoptotic factors, B-Cell Lymphoma 2 (Bcl-2) and Survivin. No differences in the expression of any of these markers regardless of BPV type were noted. Survivin was expressed in equine sarcoids of all types and increased levels of expression are associated with more aggressive clinical behaviour.<p> Finally, the location of BPV DNA was determined in both sarcoids and a variety of non-sarcoid inflammatory skin conditions of horses, as well as, normal skin. PCR for BPV DNA was performed on 86 skin biopsies from horses with non-sarcoid skin conditions, as well as, normal skin. BPV DNA was present in 41 of 86 biopsies. These positive samples, in addition to BPV positive sarcoid samples from the earlier study, were dissected into tissue compartments using laser microdissection followed by 2 forms of BPV DNA amplification, PCR and isothermal loop mediated amplification. BPV DNA was more often located in the epidermis of non-sarcoid skin conditions than in sarcoids. In addition, areas of inflammation within the dermis and epidermis were more likely to contain BPV DNA than non-inflamed areas. These results suggest that while BPV is commonly found in equine skin, the location where it is found differs between sarcoids and non-sarcoid samples. When BPV DNA was found in non-sarcoid samples, it was commonly associated with inflammation suggesting that microscopic damage to the epidermal barrier of the skin maybe an adequate predisposing factor to the development of sarcoids.

Equine sarcoids are the most common skin tumors of horses. Despite being such a common entity, relatively little is known about many features of sarcoid epidemiology or growth. In addition, due to the detection of Bovine Papillomavirus (BPV) DNA of 2 different types, BPV type 1 (BPV1) and BPV type 2 (BPV2), in equine sarcoids BPV has been suggested as the causative agent of sarcoid development. Recently, however, BPV DNA has also been detected in other skin conditions of horses; the significance of this is unclear. Multiple studies to learn more about sarcoids were undertaken.<p> To investigate the epidemiology of sarcoids in horses in Western Canada the records of five veterinary diagnostic laboratories were searched to identify submissions of sarcoids from horses. The submission record and diagnostic reports of 802 separate submissions of equine sarcoids were reviewed for age, breed, and gender of the horse and the number, location and clinical type of sarcoid. Based on these submissions, horses of a wide variety of ages and 23 different equine breeds were affected, within these breeds, Donkeys were overrepresented.<p> The presence of BPV was determined by Polymerase Chain Reaction (PCR). BPV was found in 74 of 96 (77.1%) samples, and using Restriction Fragment Length Polymorphism, BPV1 and BPV2 were identified in these samples. BPV2 was present in 59 (79.7%) of these. Unlike other areas in the world, in Western Canada, equine sarcoids are most commonly associated with BPV2.<p> A second study examined different clinical types of sarcoids to determine if there was differential expression of immunohistochemical markers associated with apoptosis, Cleaved Caspase 3(ClC3), and antiapoptotic factors, B-Cell Lymphoma 2 (Bcl-2) and Survivin. No differences in the expression of any of these markers regardless of BPV type were noted. Survivin was expressed in equine sarcoids of all types and increased levels of expression are associated with more aggressive clinical behaviour.<p> Finally, the location of BPV DNA was determined in both sarcoids and a variety of non-sarcoid inflammatory skin conditions of horses, as well as, normal skin. PCR for BPV DNA was performed on 86 skin biopsies from horses with non-sarcoid skin conditions, as well as, normal skin. BPV DNA was present in 41 of 86 biopsies. These positive samples, in addition to BPV positive sarcoid samples from the earlier study, were dissected into tissue compartments using laser microdissection followed by 2 forms of BPV DNA amplification, PCR and isothermal loop mediated amplification. BPV DNA was more often located in the epidermis of non-sarcoid skin conditions than in sarcoids. In addition, areas of inflammation within the dermis and epidermis were more likely to contain BPV DNA than non-inflamed areas. These results suggest that while BPV is commonly found in equine skin, the location where it is found differs between sarcoids and non-sarcoid samples. When BPV DNA was found in non-sarcoid samples, it was commonly associated with inflammation suggesting that microscopic damage to the epidermal barrier of the skin maybe an adequate predisposing factor to the development of sarcoids.

The Cape Mountain Zebra (CMZ) has been described as one of the most vulnerable mammals in the Republic of South Africa with current populations existing in isolated units. In recent years, South African conservation officials have noted the appearance of tumour like growths, similar to equine sarcoids, in some of these populations. The possibility that the existing populations, numbering around 1 500 animals in total, arose from a very small gene pool is very real, considering that in the early 1970’s there were only 35 breeding animals in the Mountain Zebra National Park. A genetic component to the susceptibility to sarcoid tumour development has been identified in horses. Researchers have found an association between susceptibility to sarcoid and certain heritable cell-surface proteins called major histocompatibility antigens. Studies have reported the possibility of high levels of inbreeding in CMZ in the Bontebok National Park (BNP). The non-territorial social organisation of mountain zebras allows the population to increase to a high density within a relatively short period of time. These observations, coupled with the fact that there are no confirmed reports of sarcoids in the relatively outbred Burchell’s zebra population in the Kruger National Park and the Hartmann’s mountain zebra populations in Namibia, strongly support the hypothesis that a correlation exists between inbreeding in zebra populations and expression of sarcoids. The small number of CMZ in BNP with an apparent high prevalence of suspected sarcoid tumours made this an ideal population to capture, identify and to study the skin tumour. The entire population of CMZ in the BNP was observed and sampled. A total of 15 CMZ was present in the Park at the time of the study. The individual animals were darted from a helicopter using M99, Azaperone and Hyalase after which a ground team moved in and covered their eyes and ears. Each animal was thoroughly examined for the presence of any tumours; the distribution was recorded on a body chart and sizes and appearance were recorded. Anatomical location on the body was divided into head and neck, ventral abdomen and limbs. Biopsies were taken from all of the zebras with sarcoid-like growths. The sarcoids were either surgically excised or a representative biopsy was taken by means of 6mm biopsy punches. The samples were collected in 10% buffered formalin for histological examination. The prevalence of sarcoid in CMZ in BNP was 53%. Of the affected animals, 50% had multiple tumours. The main predilection sites were on the trunk, followed by the limbs and then the head and neck. The severity of the lesions in one stallion was so extreme that it warranted euthanasia. The verrucous type, followed by much lower percentages of the fibroblastic and nodular types, dominated the clinical appearance. Lastly, the sarcoids examined showed either all or some of the typical epidermal and dermal histological features of equine sarcoid. A total of 7 of the affected CMZ were treated using four different methods. The sarcoids were surgically excised (n = 2), treated with intra-lesional 5-fluorouracil (n = 2), autogenous vaccine (n = 2) or autogenous vaccine combined with 5-fluorouracil (n =1). The zebras were immobilised for examination 18 months later. One animal that had been treated with intralesional 5-fluorouracil only had large numbers of verrucous and fibroblastic sarcoids. Her condition was so severe that she had to be euthanased. No signs of sarcoids could be found anywhere on the remaining 6 treated CMZ. This study confirmed that the growths in the CMZ in BNP population are indeed sarcoids and that many of them exhibit an aggressive nature. Sarcoid tumours is a disease that is considered multifactorial in aetiology and therefore other parameters such as immune status of tumour-affected populations and associated environmental variables warrant further investigation. / Dissertation (MSc (CACS))--University of Pretoria, 2006. / Companion Animal Clinical Studies / unrestricted