This has come up on one list, so I'm posting to several since it is bound to start making the rounds. Please feel free to forward or reprint in club newsletters.

The research team lead by Dr. Cathryn Mellersh at the Animal Health Trust in the UK has found a mutation responsible for most, but not all, cataracts in Aussies. The gene is dominant. Approximately 89% of the dogs in the study that had bilateral cataracts had at least one copy of the mutation. They are preparing a scientific article on their research for publication. Once that is accomplished they plan to develop a screening test breeders can use to determine the status of their dogs.

Cataracts have been difficult to avoid since they often do not develop until after the age at which a dog has been bred. When the test becomes available, all breeding dogs can be checked prior to producing puppies. The genetic status of close relatives of cataract affected dogs can be determined so owners will know if they need to watch for the development of cataracts in their dogs.

Since this is dominant, one parent of any affected dog must also carry the mutation and therefore will probably develop cataracts. I say "probably" because the age of onset is highly variable. Some dogs in the study with only a single copy of the mutation do not have cataracts, though will likely develop them if they live long enough. All dogs with two copies of the mutation had cataracts.

The research project is continuing. They hope to discover whether having two copies of the mutation causes dogs to develop cataracts at a younger age than those with only one copy. They would also like to figure out what is going on, genetically, with the cataracts that are not caused by this mutation. If you have an Aussie with any kind of cataract, please submit a DNA sample and data to the study. Information on how to do so is available on the ASHGI site (below.)

This test, once it is available, will be a big help toward reducing cataracts in the breed but you need to remember that roughly one Aussie in ten will have cataracts that are not caused by this mutation. You also need to guard against assuming that if one of your dog's pups develops cataracts and your dog has not, that it must be the other parent's fault. Your dog may still have the mutation. The only way you will know for sure is to test.

This variable age of development probably means there are other genes and possibly environmental factors that influence when a dog will actually get cataracts, but having a test for the mutation will solve a big part of this particular puzzle for us.

CA C.A. Sharp, Pres.
Australian Shepherd Health & Genetics Institute, Inc.
All Aussies All Genes All the Time
http://www.ashgi.org