Progressive Retinal Atrophy in Felines
As a responsible breeder I feel that where ever possible is it our duty to actively take measures to eradicate genetic diseases. There has been a resurgence of the degenerative eye disease, Progressive Retinal Atrophy in recent years. This disease has been designated “rdAc”. A single nucleotide mutation in the gene called CEP290 produces a defective protein which is associated with this progressive retinal atrophy (PRA) in the cat. This seems to affect only certain breeds of cats at present however the breeds most prone to it at present are Siamese and their related breeds, of which the Tonkinese is obviously one. PRA does not only affect felines but also affects dogs and humans. PRA is however an inherited condition and therefore provides us with an opportunity to eradicate it.
PRA is characterised by the degeneration of the photoreceptors in the retina. These are the specialised cells which convert light into electrical nerve signals which are interpreted by the brain. There are two different types of photoreceptors in the retina – cones, which mainly deal with colour vision, and rods, which deal with black-and-white and low-light vision. Cats affected with this form of blindness have normal vision at birth. The first signs of the disease expressed by the cat are difficulty with night vision as the rod cells fail. This degeneration eventually leads to irreversible blindness by the age of about three to five years, and unfortunately, there is no treatment for this condition.
There are 3 states relating to PRA;
Normal: Non-Carrier – These cats are not affected in anyway and do not possess any copies of the defective gene.
Heterozygous: Carrier – These cats are not affected in anyway but carry one copy of the affected gene.
Homozygous: Affected – These cats carry two copies of the gene and will go on to develop the disease at around the ages of 3 to 5 years old.
We have taken steps to test all of our queens for this disease. All of which came back negative. Should any of our kittens go on the active register they will be tested for PRA along with coat pattern expression and only be allowed to go from us on the active register if they are Negative.