The Border Collie is a working and herding dog breed developed in the Scottish borders for herding livestock, especially sheep. Trapped Neutrophil Syndrome (TNS) is a hereditary disease in which the bone marrow produces neutrophils (white cells) but is unable to effectively release them into the bloodstream. Affected puppies have an impaired immune system and will eventually die from infections they cannot fight. The mutation responsible for TNS has been found in border collies in English working dogs, in show dogs that had originated in Australia and New Zealand, and in unrelated Australian working dogs. This indicates that the gene is widespread and probably as old as the breed itself. For a national competition, normally held between England, Ireland, Scotland, and Wales, trials run over a 400-yard course. International courses use a 400-yard course for the qualifying trials, but on the third and final day, trials are held in a course of 800 yards.