14 Apr 2025
Scientists say earlier treatment for a vitamin deficiency could prevent eyesight deterioration if it is caught early enough.
Allister Webb
Job Title
Cathryn Mellersh. Image: University of Cambridge.
Hundreds of dogs could potentially be saved from blindness or even euthanasia following the development of a new DNA test.
Researchers said the breakthrough can allow earlier treatment of retinopathy with vitamin E deficiency (RVED) in English cocker spaniels and could eventually eradicate the condition from the breed altogether.
The test was developed through collaboration between the Canine Research Centre, which is part of the University of Cambridge’s vet school, and Dick White Referrals (DWR) near Newmarket.
James Oliver, DWR’s head of ophthalmology, said: “It’s exciting to think the work which has gone into this project could now mean that cocker spaniels who would have lost their sight due to RVED can now be prevented from going blind.”
Dogs with RVED go on to develop retinal degeneration, which can progress to blindness if it is not treated, because of low vitamin E levels. Some dogs can also experience balance issues or seizures that can lead to them being euthanised.
But following updated canine genome information, researchers discovered a mutation in the alpha-tocopherol transfer protein gene, which appears to be the cause of the disease.
Senior research associate Cathryn Mellersh said: “This gene is responsible for getting vitamin E into the blood stream.
“We now know that RVED is a recessive disease, meaning that affected dogs must have two copies of the faulty gene to develop low vitamin E levels and retinal degeneration.”
Although researchers had suspected a genetic cause, it has taken many years to identify it, with the support of vets and pet owners who had contributed DNA samples for analysis.
The discovery means that young dogs found to have RVED can be given supplements to reach normal vitamin E levels, preventing degeneration and sight loss if the disease is caught early enough.
Dr Mellersh said: “This DNA test is a rare example of one which not only can be used to identify dogs that are carrying the mutation, and thus reduce the frequency of the mutation in future generations, but also has the incredible benefit of providing a sight-saving treatment option for dogs with the disease.
“From the research we have done, we estimate that there could be several hundred cocker spaniels alive today that have two copies of this mutation, whose eyesight could be saved by this test.”
However, the test’s impact could extend far beyond the current population if breeders can be encouraged to have their dogs tested to prevent the birth of puppies that would be affected by it.
A study of the topic, published in the G3: Genes Genomes Genetics journal, found the mutation was present in all 30 dogs that where either known or suspected to have RVED.
It added: “With appropriate use of DNA testing, breeders will be able to eradicate RVED from the breed efficiently.”
The test is being made available through Canine Genetic Testing, with profits being used to facilitate research into other serious conditions in dogs.
