I thought long and hard before answering this, it's hard to recall sad and bitter memories, but I will make this as short as possible so as not to bore you all.
In 1991 I lost my beloved Cassie to CL and let me assure you at the time, the BC Club of NSW was of no help to me at all and refused to name the TOP breeder of BC's of the time! As far as I am aware, Bill is correct, it is a disease that has mainly been found in Australian Show bred lines and some of these breeders are still breeding!!!
If you are truly interested Karin, I can give the breed line that a lot of theses cases have been found in. With the help of the NSW University of Vet Science, I did a lot of research at the time and still have some of the papers. The BC Club have the rest
All I cam say is, Thank God something positive is being done. I hope no one else ever goes through the torment my family and Cassie did.
Darien