Scientists at the University of Cambridge have identified the genetic mutation responsible for progressive retinal atrophy (PRA) in English Shepherd Dogs. This discovery not only pinpoints the cause of this incurable blindness but also provides a genetic test to help eradicate the disease for good from future generations.

New Hope for Breeders

Progressive retinal atrophy is an umbrella term for a group of inherited diseases that lead to the degeneration of light-sensitive cells in the eye, resulting in blindness. Dogs with PRA are born with normal vision, but by the age of four or five, they lose their sight entirely. Currently, there is no treatment available.

“Once the dog’s eyesight starts to fail there’s no treatment — it will end up totally blind,” said Katherine Stanbury, a researcher in the University of Cambridge’s Department of Veterinary Medicine and first author of the report.

The team from Cambridge has developed a DNA test that can detect the mutation causing PRA. Breeders can now identify carriers of the disease before any symptoms appear. Consequently, informed breeding decisions can prevent the faulty gene from being passed to puppies.

Most dog owners are unaware their pet has PRA until the dog is middle-aged, often after it has already bred. This delay has made controlling the disease virtually impossible.

“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,” Stanbury said in a press release.

Addressing the Genetic Challenge

The mutation responsible for PRA is recessive, meaning a dog must inherit two copies of the gene to develop the disease. Dogs with one copy of the gene are carriers and can pass it on, but they do not suffer from PRA themselves. Given the high level of inbreeding among dogs, the risk of such recessive diseases is significantly higher in dogs compared to humans.

The research began after a search and rescue dog was diagnosed with PRA, prompting the owner to reach out to the University of Cambridge. The team collected DNA samples from both affected and unaffected English Shepherds and used whole genome sequencing to identify the mutation.

The research team now offers a commercial genetic testing service for breeders, which includes the newly developed DNA test for PRA. For £48 ($62), breeders can obtain a testing kit to screen their dogs before breeding.

“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,” said Dr. Cathryn Mellersh, senior author of the report.

The English Shepherd, popular in the United States and related to the Border Collie, is just one of many breeds affected by PRA. The disease also bears similarities to retinitis pigmentosa in humans, a condition that causes blindness. The research team believes their work on PRA could offer insights into the human version of the disease and potentially identify targets for gene therapy.

This discovery marks the thirty-third genetic mutation causing an inherited disease in dogs identified by the team, with 23 of these affecting vision. The research underscores the impact of selective breeding on canine health and the potential benefits of genetic testing in preserving the well-being of dog breeds.

The findings are published in the journal Genes.