A CLINICAL AND EPIDEMIOLOGIC-STUDY IN RELATION TO EQUINE LEUKOCYTE ANTIGENS (ELA)

Associations between clinical parameters of sarcoids and the equine le ucocyte antigen system (ELA) were analysed for 120 Swedish horses. Med ian age of affected horses was 5.2 years, and the majority presented w ith solitary tumors between 2 and 5 cm in diameter and ventral abdomen was a predilection site. Clinical signs first appeared at a median ag e of 3.5 years, and sarcoids at different locations first appeared at different ages. Lesions at dif ferent sites differed in size, and mult iple tumors, early onset, long duration, and older age all had an asso ciation with large size. Clinical manifestations of sarcoids and the a ssociation between certain ELA-specificities and early onset (A5) and increased recurrence rates after surgery (W13), in addition to increas ed prevalence (A3W13), strengthen further that some horses are inheren tly predisposed to sarcoid growth. Unassociated with any clinical para meters, one third of the untreated horses became free of sarcoids due to ''spontaneous'' regression, perhaps as a result of immune responses against the tumors. Seventy percent of the horses were treated (mostl y by excision), and large size was the main parameter promoting treatm ent. Excision had no significant effect on possibly remaining sarcoids . Recurrence rate after first treatment was about 35%, with the majori ty of tumors recurring within 4 months. Early onset, long duration, la rge size, and localization to distal limbs all appeared to increase ri sk of recurrence. Early treatment, performed under general anesthesia in recumbency which permits wide excision and measures to avoid autoin oculation, significantly reduced recurrence rates.