Clinic and anatomic aspects of verification and monitoring of various types of equine sarcoid in the western regions of Ukraine

Abstract

Sarcoid is the most common skin tumor reported worldwide in equids, donkeys, zebras, and mules of all ages and sexes. The bovine papillomavirus (BPV) plays an important role in the pathogenesis of the disease. Globally, the incidence of equine sarcoid ranges from 12 % to 67 % of all skin neoplasms. Unfortunately, no attention is paid to the study of sarcoid epizootology in Ukraine. There are no reports on the clinical types of neoplasms, their pathohistological characteristics, and treatment methods. Our study aimed to describe the clinical manifestations of different anatomical types of equine sarcoid, ranging from small single lesions to multiple aggressive fibroblastic tumors, which were registered in horses from private farms and stables in the western regions of Ukraine during 2019–2022. According to its macroscopic features, sarcoid was divided into six clinical and anatomical types: hidden, verrucous, nodular, fibroblastic, mixed, and malignant. In general, 1012 horses were examined, of which 328 animals were clinically diagnosed with sarcoid. Neoplasms were localized in different parts of the body and belonged to different sarcoid types.The smallest number of neoplasms was detected in the area of the head around the eyes in the form of single nodules (2.3 %), on the neck (5.4 %),  and limbs (14.8 %). Most of the multiple focal sarcoid tumors were localized in the chest area (26.5 %) and in the area of the abdominal wall and groin (51 %). Both depigmentation and hyperkeratinization of the affected areas were the typical morphological features of all sarcoid types. Hidden sarcoid was characterized by lesions of the skin’s superficial layers with well-defined areas of alopecia. Verrucous sarcoid was mainly localized in the neck and groin areas with the formation of irregularly shaped and large skin thickenings characterized by damage to the deep dermis layers. The third type of sarcoid is nodular, which was visually manifested in the form of mobile spherical subcutaneous nodules of small sizes. They were usually localized in the groin, prepuce, inner thighs, and eyelids. Fibroblastic type is one of the most aggressive equine sarcoids. It is characterized by rapid growth with the formation of massive tumors on the leg with an ulcerated surface and marked vascularization. Mixed sarcoid combined verrucous, fibroblastic and nodular types with predominant signs a particular type of tumor. Malignant form of sarcoid was relatively rare but particularly aggressive. Tumors spread along the course of lymphatic vessels with the formation of nodes and ulcers. This sarcoid was detected only in two horses. In general, it should be noted that sarcoid is not a fatal neoplasm for horses. However, its location, size, and the possibility of progression to a more aggressive form commonly leads to deterioration of the exterior and culling of thoroughbred animals.