SCOTTISH scientists have discovered a DNA mutation linked to breathing problems in popular breeds of dog and it is hoped their find could in future help breeders avoid producing affected pups.

Such breathing difficulties are most often associated with flat-faced breeds, such as French bull dogs and pugs.

However, a team from Roslin Institute at the University of Edinburgh’s Royal (Dick) School of Veterinary Studies found the mutation is also carried by Norwich terriers, which have proportional noses.

Their finding raises the possibility of genetic tests being developed which could help vets identify those animals at risk.

French bulldogs are the most popular dog breed in the UK, but underneath their prized features can lie a life-threatening health problem.

The breed – and others such as English bulldogs and pugs – is commonly affected by a condition called bracycephalic obstructive airway syndrome (BOAS) which leaves the animals gasping for breath. Scientists had thought the only explanation for their breathing problems lay with their short faces, but Norwich terriers suffer from a similar breathing problem called upper airway syndrome, despite having proportional noses.

The Roslin team analysed DNA from more than 400 Norwich terriers, while vets carried out clinical examinations of the dogs to check their airways for signs of disease.

Researchers pinpointed a DNA mutation in a gene called ADAMTS3, which is not linked to skull shape and has previously been found to cause fluid retention and swelling.

The mutated version of the gene was also common in French and English bulldogs.

According to the team, this could help explain why some dogs of these breeds develop breathing problems, as well as complications following surgery to treat them.

Scientists say their findings will enhance our understanding of breathing problems in dogs.

They suggest that fluid retention in the tissue that line the airways could make it more likely that dogs with the mutation will develop breathing problems.

The study, published in PLOS Genetics, also involved experts from the Royal Veterinary College and the University of Bern in Switzerland.

Dr Jeffrey Schoenebeck, from the Roslin Institute, who led the study said: “BOAS is a complex disease.

“Although skull shape remains an important risk factor, our study suggests that the status of ADAMTS3 should be considered as well.

“More studies are needed to dissect the complex nature of this devastating disease.”

The Hospital for Small Animals at the Royal (Dick) School of Veterinary Studies hosts a specialist clinic called BREATHE, specifically for dogs with upper airway problems.

Vets there use a range of cutting-edge technologies to care for affected animals, including whole body scans and a specialist tool that monitors lung function, called a plethysmograph.

Dr Jon Hall, a senior specialist surgeon who leads the BREATHE clinic, said: “This discovery is a step change in our understanding of upper airway problems in dogs, which we hope will allow us to identify dogs at greater risk of catastrophic airway swelling before it happens.”