Progressive retinal atrophy, or PRA, is a group of inherited diseases that lead to blindness in dogs, affecting over 100 different breeds. The progressive condition causes canines to lose their vision by age 4 or 5 and currently has no cure, but a new genetic test may be a step forward in eliminating it entirely.
In a study published July 20 in the journal Genes, a team of scientists out of the University of Cambridge pinpointed the gene that causes PRA in English shepherds and created a DNA test to identify it. They’ve now made that test available for U.K. pet owners and breeders to purchase.
“Once the dog’s eyesight starts to fail there’s no treatment — it will end up totally blind,” first author Katherine Stanbury said in a statement, adding: “Now we have a DNA test, there’s no reason why another English shepherd dog ever needs to be born with this form of progressive retinal atrophy — it gives breeders a way of totally eliminating the disease.”
There’s a touching story behind the research. The team began looking into the genetic mutation after receiving a call from a “distraught” pet owner whose English shepherd had been diagnosed with PRA. Prior to losing its sight, the pup had been working as a search and rescue dog. Researchers then put out a call for other owners of the breed to send in DNA samples from their dogs.
They received samples from six English shepherds who had PRA and 20 who didn’t, enabling them to identify the genetic mutation. In these dogs, that mutation is recessive, meaning both parents must pass it on to their offspring for the pup to have PRA. Different genetic mutations are responsible for it in different breeds, however, and some may be dominant rather than recessive, meaning only one parent needs to pass it on for it to affect a puppy.
Per the Cornell University College of Veterinary Medicine, PRA deteriorates the light-sensitive rods and cones in dogs’ retinas, often first affecting night vision before causing total blindness. Some of the breeds commonly affected include poodles, labradors, golden retrievers, English and American cocker spaniels, and papillons.
Because the condition is degenerative, owners and breeders sometimes do not realize that pups are affected until they’re a few years old, and may have already bred the dogs.
“An owner won’t necessarily notice their dog has got anything wrong with its eyes until it starts bumping into the furniture. Unlike humans who will speak up if their sight isn’t right, dogs just have to get on with things,” said senior author Cathryn Mellers.
She added: “For the price of a decent bag of dog food, people can now have their English shepherd tested for progressive retinal atrophy prior to breeding. It’s about prevention, rather than a cure, and it means a huge amount to the people who breed these dogs. They no longer need to worry about whether the puppies are going to be healthy or are going to develop this horrible disease in a few years’ time.”
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