Cataract test for Australian Shepherds

We are currently investigating the possibility of more than one genetic form of HC existing in Australian Shepherds. If your dog has been clinically diagnosed with cataract by a veterinary ophthalmologist we will test you dog free of charge if it's possible to receive a copy of the dog's eye examination. Also if your dog is over 8 years old and has no sign of eye disease we will test you dog free of charge if we can receive a copy of the dog's eye examination. Please email saija.ahonen@helsinki.fi for further details.

Researchers at the Animal Health Trust (AHT) found a mutation in HSF4 gene in Australian Shepherds. This gene defect causes hereditary cataract (HC) in the breed. More information is required of the clinical features of the cataract but posterior polar cataract seems to be the most common form of cataract found in Australian Shepherds.

HSF4 gene defect shows an autosomal dominant mode of inheritance. This means that the risk of developing cataract is increased if only one copy of the HSF4 gene has the mutation. Both parents of the HC-dogs do not therefore need to be the carriers of the mutation. The gene defect can also exist in both chromosomes but to develop the disease it is enough to get the mutations from one parent.

The most recent research done by the AHT in collaboration with the Canine Genomics Group in the University of Helsinki indicates that if the dog carries one or two copies of the HSF4 mutation it has 17 times higher risk to develop posterior polar cataract than the dogs that do not carry this specific mutation. It is also possible that there are still other unknown genes behind the risk of developing hereditary cataract in Australian Shepherds.

If a dog carries one copy of the mutations it will pass over the gene defect to approximately 50% of its offspring. If the dog has two copies of the mutation it will pass over the mutation to all of its offspring. Dogs that carry HSF4 mutations should not be used in breeding.

The test results are reported as follows:

NORMAL: The dog does not carry HSF4 mutation and therefore has no increased risk of developing posterior polar cataract.

HETEROZYGOTE: The dog carries one copy of the HSF4 mutation and because of the dominant inheritance has therefore 17 times higher risk of developing posterior polar cataract. Carrier dogs will pass over the defect to approximately 50% of their offspring.

HOMOZYGOTE: The dog carries two copies of the HSF4 mutation and therefore has 17 times higher risk of developing posterior polar cataract than a normal dog. The dog will pass over the gene defect to all of its offspring.

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References:

Mellersh C, McLaughlin B, Ahonen S, Pettitt L, Lohi H and Barnett K. Mutation In HSF4 Is Associated With Hereditary Cataract In The Australian Shepherd. Vet Opht, in press, 2009.