PRA-CORD1 – Progressive retinal atrophy
PRA-CORD1 is an eye disorder, which belongs in progressive retinal atrophy group of disorders. Progressive retinal atrophy (PRA) comprises autosomal recessively inherited diseases that lead to degeneration of retinal photoreceptor cells in dogs and other pets. In general, these diseases are characterized by disturbance of dark vision, visual field defects, and abnormalities in the electroretinogram, which can progress to blindness. It appears in both eyes simultaneously. The age of onset and rate of retinal degeneration varies between the different forms of the conditions. Some forms of PRA are common to multiple dog breeds, while others are recognized in just a single breed. PRA appears in most dog breeds, but also in mixed breed dogs. Almost all PRA disorders are recessively inherited, with exceptions of dominant and X-linked PRA inheritance in few breeds, such as Old English Mastiffs, Bullmastiffs, Siberian Husky and Samoyed.
Rods are important for vision in dim light, or also night vision and PRA with its rode degeneration leads to night blindness. In the researches, it is estimated that PRA causes death of around 95% of the dog’s photoreceptors. For dog owners or breeders, PRA is recognized by ”glow” or ”increased shine” in the eyes. The disease can progress, from initial stage of night blindness to advanced stage of PRA which causes full blindness in the dog. The advanced stage of PRA usually occurs within one year, since the appearance of the first symptoms.
PRA-CORD1 is a specific form of PRA, and it stands for cone-rod dystrophy-PRA. Unlike in other forms of PRA, in PRA-CORD1, the cones are affected first and the rods secondly. The cones are photoreceptors responsible for detecting bright light or colors, and the rods detect dim light and responsible for night vision. But nevertheless, PRA-CORD1 affected dog will lose its ability of vision with time and there is no cure currently available. The age of showing the first symptoms can vary greatly, from 6 months of age until 10 years of age.
PRA-CORD1 is inherited in an autosomal recessive pattern. In case of showing the signs of PRA-CORD1, the healthy parents of a cub with an autosomal recessive form of PRA-CORD1 are obligate heterozygotes, and therefore carry one mutant allele. Heterozygotes have no symptoms. At conception, each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
There is no cure for PRA, and only way to prevent it, is to breed dogs which are not carriers of the mutation. Defected genes for autosomal recessive disease can be passed for many generations without affected individuals occurring until two carriers are bred to one another. The only way to find out if there is a chance of getting an affected puppy is to do PRA-CORD1 genetic testing.