Progressive Retinal Atrophy (PRA) is an inherited condition that many dog breeds are predisposed to. It is characterised by bilateral degeneration of the retina, resulting in progressive vision loss and eventual blindness. Secondary cataract formation is also commonly seen in the late stages of the disease but removal of the cataracts is unlikely to restore sight as the underlying retinal degeneration is usually too advanced already.
To date, PRA in the dog is not a disease that can be cured and affected patients sadly have to adjust to blindness. In the Tibetan Spaniel, PRA is a late-onset condition which may not be showing clinical signs before the age of 6 or 7 years. However, an eye specialist may detect clinical signs during an ocular examination as early as from 3 years of age.
PRA is caused by a genetic defect – but multiple different forms of the genetic mutation exist between different breeds or even within the same breed. The geneticists at the Animal Health Trust have named a mutation causing PRA in the Tibetan Spaniel PRA3 to distinguish it from other mutations causing the disease. During their investigations, they found that approximately two thirds of the clinical cases identified with PRA in Tibetan Spaniels to be carrying the PRA3 mutation – which means, that one third of cases of PRA in the Tibetan Spaniel are caused by other conditions or genetic mutations that have not yet been identified.
For those wishing to have PRA3 DNA testing done the following labs offer the service:
- Combibreed purchased through the Kennel Club shop at a cost of £50, results go directly to the Kennel Club.
- Animal Diagnostics at a cost of £48;
- Pet Genetics Lab at a cost of £40;
- Genomia at a cost of $56 plus VAT
Other than Combibreed owners will have to send results to the KC themselves.
Prices correct as at October 2021
However, the DNA test should not replace the eye examination – and both should be used in synergy because:
- As explained above, genetic testing can only pick up approximately two thirds of dogs affected with PRA as one third of cases do not carry the PRA3 mutation. These dogs can only be identified on an ocular examination – and early detection of affected dogs is imperative to prevent these individuals to be bred from, keeping in mind that clinical signs of PRA may not be apparent to owners until well after the ‘breeding-age’ of the dog.
- Furthermore, a DNA test will only identify one very specific genetic mutation (one single eye disease) whilst an eye examination screens for a whole range of potentially inherited ocular conditions. The early detection of ocular abnormalities plays an important part in the surveillance of a breed for emerging inherited conditions. This is especially important in numerically small breeds – where there is a large shared gene pool and where an inherited condition could be widely disseminated into the breed before attention to its existence is drawn by clinical cases identified by owners and veterinary surgeons.
- Finally, an eye examination under the BVA/KC/ISDS scheme also provides an expert health check for your dog’s eyes and can yield information about other, non-inherited, diseases of importance.
If your eye specialist is concerned, he or she will refer you back to your own veterinary surgeon to arrange an appropriate treatment.
PRA Testing information - Added November 2021
A new canine genetic testing service, Canine Genetic Testing (CAGT) will open its doors for business on Monday November 22nd, 2021. The service, which operates from the Department of Veterinary Medicine at the University of Cambridge, offers a range of DNA tests for painful, blinding or otherwise debilitating inherited canine disorders. The CAGT team is passionate about providing high-quality customer service to offer accurate, breed-relevant, validated DNA tests that can be used to reduce the incidence of disease in breeds at risk. Prior to moving to the University of Cambridge some members of the CAGT team worked in the Genetic Testing Service at the Animal Health Trust, prior to its closure in July 2020, and bring with them considerable expertise in the field of canine genetics and genetic testing. When CAGT opens on November 22nd a range of validated DNA tests will be offered and the number of tests available will increase over the coming weeks and months.
As we are still in the early stages of development, we are currently only able to sell tests to customers based in the United Kingdom. We do plan to extend our services to customers outside of the United Kingdom as soon as possible. Visit their website at https://www.cagt.co.uk/
PRA Testing information - Added February 2022
The DNA test for PRA3 is called 'Progressive Retinal Atrophy Fam161A-Type' although the name may change to PRA3 to avoid confusion. The test costs £45. For those who are unsure this is the same people who developed the test.
Canine Genetic Testing is a new canine DNA testing service based in the Department of Veterinary Medicine at the University of Cambridge. Several members of the team used to be part of the Animal Health Trust Genetic Testing Service - which means they have heaps of relevant knowledge and expertise. CAGT operates alongside the Kennel Club Genetics Centre (KCGC), headed by Dr Cathryn Mellersh, but is administratively separate from it.
For the last few months, they have been working very hard to develop their service and they have now launched their website and are selling several disease-associated DNA tests. They currently offer one test for the Tibetan Spaniel, and they continue to work on developing and validating more tests. If there are any additional tests that you would like them to offer in the future, please do get in touch with them.