| 10/23/2002 The Root of a Devastating Skin Disorder in Belgian Horses is Identified - 10/19 Equine Research Magazine The genetic mutation responsible for causing Herlitz-Junctional Epidermolysis Bullosa (JEB)a devastating skin disease in which skin layers can't adhere to one another has been identified by University of Guelph Prof. John Baird, department of Clinical Studies, and researchers from the French Institute of Health and Medical Research (INSERM). They've developed a test for screening carriers of the mutated gene. Testing will soon begin for all colts born after January 2003 in the most affected breed, the Belgian. By testing future breeding stock for the breed, breeding practices can be managed so that carriers can be removed from the gene pool with the hopes of eliminating the disease within North Americašs population, says Baird. An estimated 30-35 per cent of Belgian horses in North America are JEB carriers. Baird became interested in finding the disease's cause after seeing its devastating effects in a Belgian foal brought to the Ontario Veterinary College several years ago. When a foal inherits the mutated gene from both parents, they lack a skin protein known as Laminin-5, which normally interacts with collagen to help connect the various layers of the skin. Affected foals suffer from painful skin sores and lesions, particularly in the fetlock, stifle and hock areas. JEB also affects the epidermal surfaces of organs, and causes mouth and tongue ulcers. Death usually occurs within one week of birth. The affliction was first described in the Ardenner breed (an ancestor of the Belgian) in the 1930s, by Swedish veterinarians. Suspecting it had a genetic cause but limited by lack of DNA technology pedigrees began to be recorded, so they could trace the disease. These pedigrees proved extremely useful to Baird. Extensive reviews allowed him to trace the ancestors of reported cases, and identify which animals were carriers. He determined that the mutation began in several well-used sires, starting in the late 1800s. These sires are ancestors for nearly all Belgians, and were mated with several other draught breeds as well, says Baird. Baird collected DNA samples of known carriers and sent them to Dr. Guerrino Meneguzzi, a geneticist with INSERM, who used the samples to identify the precise location of the mutation responsible for JEB. A simple, reliable test was then developed, which requires only hair (including the root, which contains DNA) be taken from the horses. The test involves the same procedure currently used to identify the genetic disorder Equine Hyperkalemic Periodic Paralysis (HYPP), which originated in the North American Quarter Horse population. Baird presented his findings to both the American and Canadian Belgian Horse Associations last summer. Genetic testing will soon be offered by the University of Californiašs Veterinary Genetics Laboratory in Davis under a license agreement. "This disease is not only a welfare concern, but it also costs the Belgian horse industry thousands in lost revenue every year," he says. "Hopefully by disallowing known carriers being used for breeding, this disease will be a thing of the past.˛ |
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