Plant & Animal Genomes XV Conference

January 13-17, 2007
Town & Country Convention Center
San Diego, CA

Genetic Characterization Of Chronic Progressive Lymphedema In Draft Horses.

Amy E. Young¹ , Verena K. Affolter² , Hilde E.V. De Cock³ , Gregory L. Ferraro⁴ , Danika L. Bannasch¹

¹  Department of Population Health and Reproduction School of Veterinary Medicine University of California 1114 Tupper Hall Davis, CA 95616 USA

²  Department of Pathology, Microbiology and Immunology School of Veterinary Medicine University of California 1044 Haring Hall Davis, CA 95616 USA

³  University of Antwerp Department of Veterinary Medicine Campus Drie Eiken D.U012 Universiteitsplein 1 2610 Wilrijk Belgium

⁴  Center for Equine Health School of Veterinary Medicine University of California One Shields Ave Davis, CA 95616 USA

Chronic progressive lymphedema (CPL) in draft horses is characterized by swelling, thickening and firmness of the skin and subcutis on the lower legs caused by abnormal functioning of the lymphatic system. The heavy feathering on the legs predisposes horses to repetitive skin infections which enhance the chronic progressive lymphedema and often do not respond to treatment. Thick skin folds and large, painful nodules develop on the lower legs as the condition becomes more chronic. Symptoms progress throughout the life of the horse, ending in disfigurement and limited mobility of the limbs and often requiring euthanasia. Since severe symptoms do not present until later in life, affected horses are often bred prior to being diagnosed. CPL has been observed in several draft horse breeds. Belgian draft horses and Shires segregate the disease and Clydesdales appear to be fixed for the phenotype. To date, no Percherons have been diagnosed with CPL. It is likely that the disease has a common origin in the breeds affected. Blood and tissue samples from affected and unaffected horses from these breeds have been obtained and continue to be collected. Since severe symptoms often have a late age of onset and can be obscured by the heavy feathering on the lower legs characteristic of these breeds, deep tissue biopsies of the distal limbs are required after age eight to determine that a horse is unaffected. These samples will be used to determine the mode of inheritance and eventually identify the gene responsible for CPL in draft horses.