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Study Reveals Powerful Long-Term Impact Of DNA Tests On Dog Diseases

A new study has revealed that the number of pedigree dogs at risk of often painful and debilitating inherited diseases is being dramatically reduced by responsible breeders.

The research, carried out by scientists who work for the Kennel Club and the Animal Health Trust, examined the long-term impact of dog breeders using DNA tests to avoid producing puppies affected by inherited conditions. The study specifically examined DNA tests for eight diseases in eight breeds. Researchers discovered that approximately ten years after each DNA test became available, the gene mutations that caused the diseases had decreased in each breed by a staggering 90 per cent or more.

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Taking DNA sample with cheek swab - Credit: Animal Health Trust

The study examined data for diseases such as progressive rod cone degeneration (prcd-PRA), an irreversible and blinding condition that cannot be treated; Spinocerebellar ataxia, a neurological condition that leads to in coordination and loss of balance in puppies and primary lens luxation, a painful and blinding inherited eye condition.

The breeds analysed in the study were the Labrador Retriever, Parson Russell Terrier, Gordon Setter, Irish Setter, Cavalier King Charles Spaniel, Miniature Bull Terrier, Cocker Spaniel and the Staffordshire Bull Terrier.

Similar previous studies, that investigated the frequency of disease mutations over time, analysed smaller and more restricted datasets than the current study. This unique study was able to take advantage of the way that the Kennel Club records DNA test results in its registration database.

Currently the Kennel Club records and openly publishes the results of DNA tests for over 70 different inherited diseases, representing approximately 10,000 DNA tested dogs each year. In some cases, the Kennel Club is able to use DNA test results from a registered dogs’ parents to determine whether the offspring carries the specific mutation associated with a particular disease. This enables a breeder to know a dog’s “hereditary status”, a process that is carried out for around 60,000 dogs a year. It is these data that has allowed this newly published research to investigate the previously unseen impact that breeders can have on the health of a breed.

Dr Tom Lewis, Quantitative Geneticist & Genetics Research Manager at the Kennel Club, who co-wrote the study, said:

“The Kennel Club and the Animal Health Trust have a long history of working together to develop and promote vital new DNA tests for breeders. Our research shows the sizable impact that responsible breeders can have, and have had, not only on the dogs that they breed, but also on the generations of dogs that come after them. It emphasises the importance of continued research into inherited conditions and shows the impact a simple DNA test can have.

“Testing for genetic diseases is already common practice for many responsible dog breeders. These DNA tests reveal to breeders a dog’s genetic make-up, helping them to avoid unintentionally producing puppies with known painful and life-limiting diseases from mating two unaffected parents which are both ‘carriers’ of the disease causing gene variant.

“Our research highlights the fantastic work that has already been carried out by those breeders and breed clubs that have been utilising and promoting DNA tests for years, while similarly demonstrating why those who haven’t been health screening should be doing so. It also stresses why puppy buyers should only buy puppies from breeders who appropriately test their dogs, such as Kennel Club Assured Breeders, not only for the immediate health reassurances, but also for the health of the wider dog population.”

The study by Dr Tom Lewis and Cathryn Mellersh, Canine Head of Genetics at the Animal Health Trust, is entitled ‘Changes in mutation frequency of eight Mendelian inherited disorders in eight pedigree dog populations following the introduction of a commercial DNA test’ and has been published in the scientific journal PLOS ONE.

The conditions analysed in the study were: progressive rod cone degeneration (prcd-PRA), Early onset hereditary cataract (HC), exercise induced collapse (EIC), Primary Lens Luxation (PLL), Episodic falling (EF), Congenital Keratoconjunctivitis sicca and ichthyosiform dermatosis (dry eye and curly coat DE/CC), Rod cone dysplasia (PRA-rcd-4), Spinocerebellar ataxia (SCA).

To read a copy of the study click here. To find out more about the DNA tests available for Bearded Collies and other breeds visit www.thekennelclub.org.uk/dnatests

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