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Researchers at the University of Cambridge recently published their findings in Genes after identifying the genetic mutation that is causing progressive retinal atrophy (PRA) in English shepherd dogs. PRA is a group of inherited diseases causing progressive degeneration of the light sensitive cells within the back of the eyes. When it comes to PRA in dogs, they are born with normal vision but by the age of 4-5 they go totally blind with no treatment.
According to the release, by identifying the canines carrying this disease before they lose vision, this can be then used as a tool to guide breeding decisions to prevent the passing of the disease onto puppies.1 Historically, owners did not realize their dog had PRA until they were middle-aged, which means it could have been passed on to puppies if they had bred, making this a hard disease to control.
“Once the dog’s eyesight starts to fail there’s no treatment – it will end up totally blind,” said Katherine Stanbury, BSc, PhD, a researcher in the University of Cambridge’s Department of Veterinary Medicine and first author of the report.1 “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.”
The team discovered the genetic mutation causing the disease is recessive, meaning English shepherd dogs can only suffer this blindness if they inherit 2 copies of the gene. For breeding, if a dog only has 1 copy, this makes the dog a carrier and it will not develop PRA but can pass it onto its puppies. If 2 of these carriers are bred together, almost 1 in 4 puppies will be affected. Because dogs are ‘very inbred,’ many individuals are related, giving them a higher chance of being affected by recessive disease when compared to humans.1
The inspiration behind the study came after the team was contacted by a distraught owner of an English shepherd dog, who was diagnosed with PRA. This dog was working as a search and rescue dog but had to retire due to visual deterioration that caused total blindness.
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To complete the study, researchers put out a call for DNA samples from other owners or breeders, receiving 6 samples with PRA and 20 without. This gave them enough information to pinpoint the genetic mutation causing PRA using whole genome sequencing. With these findings, PRA can be completely eliminated from English shepherd dog populations quickly.1
The team is offering commercial canine genetic testing services to breeds to help them avoid breeding canines that will develop inherited diseases. These tests will now offer a DNA test for Progressive Retinal Atrophy in English Shepherds that can be bought for £48, a little over 61 USD. Anyone can buy these tests and all that has to be done is pet parents or veterinary professionals will need to swab the inside of the dogs mouth and send it back to the lab for testing.
“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,” explained Cathryn Mellersh, BSc, PhD, University of Cambridge’s Department of Veterinary Medicine, senior author of the report.
“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,” she concluded.1
This discovery is the 33rd genetic mutation causing an inherited disease in canines that the researchers found, and out of those 33, 23 cause eye diseases. These findings highlight the fact the health and wellbeing of canines has been compromised due to how they have been bred by humans.
The researchers believe that their work with dogs can help provide clarity of the human version of the disease as well as identify targets for gene therapy in the future.
Reference
New genetic test will eliminate a form of inherited blindness in dogs. News release. University of Cambridge. July 21, 2024. Accessed July 25, 2024. https://www.eurekalert.org/news-releases/1051683
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